MCHardmanUK
03-10-2006, 09:03 AM
The Theory Behind Frames
Abreviations (Acreditted to burbsrider)
T/T - Top Tube
C/S - Chainstays
H/T Angle - Headtube Angle
S/T Angle - Seattube Angle
BB - Bottom Bracket
W/B - Wheelbase
Toptube Length
Longer is for taller people since they need more room and dont want to hurt there backs. shorter is for shorter people who need something there size so they can ride to there fullest ability. but there is alot of personal preference to. a taller person may perfer a short frame so they can land those technical tricks and a short person may want a bigger bike so the have lots of room to pull big tricks without being cramped up.
Chainstay Length
Longer chainstays create a more stable back end that are ideally suited to the taller rider whos extra height will naturally create the leverage for the front end to pop up, short rider beware getting the front end up will be hard work as your fighting physics. Also the rider that likes to gap far and ride trials will benefit from a frame with a longer chainstay.
Shorter chainstays create a twitchier back end that comes up very easily and can easily be looped out especially if you are a tall person as your extra height creates excess leverage and therefore a frame with a longer chainstay is recommended. Also shorter chainstays are ideally suited to the shorter rider as they naturally create less of a leverage angle and the rider that likes tech based riding as well as the rider that likes to spin,tallwhip etc...
Head Tube Angle
Steeper means easeier spins and nose manuals.also means the tt feels longer.like 20.5 on a 75 ht will feel like a 20.75 on a 74.5. ht generally vary between 74 and 75. i have seen a 73 on proper frames before though. steeper may seem unstable at first and i wouldnt reccomend it for those bombing huge gaps or riding trails. A very steep headtube will make the bike feel sketchy and unstable sometimes, especially on hard landings, and if you happen to land front wheel first it will be very hard to control the bike.
Seattube Angle
A steep seat tube like 71 means easier seat pinching and a farther back bb. but it can sometimes get in the way during some tricks. laid back angles like 69 means a farther up bb which make the tt seem shorter and the seat will be harder to pinch.
BB Height
Higher means quicker turning and easier manuals. also means less smashing of the sprocket. lower means more stability but manuals may feel weird since your feet are almost level with axle so the balance point is much higher. it will also affect your back position and how high your bars feel. lower bb means less bending over for your bars. tall guys beware.it generally ranges from 11.3 to 12
BB Type (Acreditted to Terrible One's Website)
There are 4 types of BB's used in BMX and there are:
US - Was the industry standard for many decades has the largest diameter BB shell and the bearing cups are pressed in with the bearings poping into the bearing cups. The heaviest of the BB options but by far the strongest in terms of allowing the biggest possible bearings to be used. Recommended if you want a hassle free BB setup and you ride hard.
Mid - Quickly becoming the new industry standard, does away with the BB cups found in the US BB but uses the same size bearings that have a pop in fit directy into the BB shell. As strong as the US BB but 1/3 of the weight recommended for any type of riding. The only downsides are that if your BB shell is deformed in any way wil most likely rendor your frame useless and they are only compatable with 19mm axles.
Spanish - Essentialy the same pop in fit as Mid BB's but smaller in diameter but are avaliable in 2 sizes for: 1) 19mm axles and 2) 22mm axles.
Euro - The smallest diameter BB shell as a thread cut into itand you screw your BB into the BB shell. Has very small bearings which can be subseptable to wearing and crushing over a short period but this is a very light option recommended for light street, park trais and racing.
Headset Type
There are three types of headset:
1" - Most commonly found on Race frames and very very very very old frames.
1-1/8" - Just like the US BB design in that the headset cups are pressed into the headtube and these cups house the bearings and a compression bolt is used to tighten the whole front end together.
Internal/Intergrated - Just like the MId and Spanish BB designs in that the bearings are pop fitted into the headtube. Again this design does away with headset cups just like the Mid and Spanish BB's did away with the BB cups and in the end the same probems are associated with this headset design as are with the BB design of which it orientated from.
Wheelbase
Wheelbase is the distance between the front and rear axles, which is directly effected by frame geometry, especially tt and cs length, but also headtube angle. The longer the wheelbase the more stable the bike is, but the less maneuvarable it will be.
Frame Materials
The most common materials used to make frames from are as follows:
Hi-tensile Steel
4130 Chromoly
OX Platinum
Reynolds 853
Sanko Japenesse Tubing
T45Hi-tensile Steel - Steer clear of framesmade from Hi-tensile steel it is a very cheap and weak tubing and is only found on cheap nasty frames.
4130 Chromoly - Basically 4130 is a mixture of different metals. The 4130 is a code of the American Iron & Steel Institute and defines the approximate chemical composition of the steel. The "41" denotes a low alloy steel containing nominally 1 percent chromium and 0.2 percent molybdenum (hence the nickname "chromoly"). The "30" denotes a carbon content of 0.30 percent. In addition, as normal constituents of plain carbon and low alloy steels, there will be around 0.2-0.5 percent silicon, 0.5-1.0 percent manganese, and well under 0.1 percent of each of a dozen or so other elements whose presence is unavoidable, in a few cases deliberate, and generally not harmful. The remaining 97-98 percent is iron (Fe).
OX Platinum - True Temper's OX PLATINUM Series is based on state of the art steel metallurgy. The metallurgists at True Temper began with an aerospace grade of air hardening steel and modified it to enhance its properties for light weight bicycle frames. The ultimate tensile strength exceeds 195,000 psi. Air hardenable steels are desirable for high performance welded steel frames. At the edges of the molten weld pool, as the metal freezes, an unavoidable microscopic notch is formed. This is a stress concentrator that magnifies the actual stresses of riding by a factor of 4 to 6 times. The weld is relatively small and cools so quickly that metallurgical changes occur creating localized hard and brittle areas, if the alloy is not specifically designed to avoid this. Air hardening steels are metallurgically designed so that as the steel cools and solidifies from the molten state in air, the steel hardens to an even higher strength. The metallurgists must control the alloying elements so that the hardened steel is also tough and able to absorb impacts, rather than brittle and subject to fracturing. True Temper not only solved these problems, but went further: Most heat treated steels tend to anneal, or soften, when heated between about 1000°F and 1500°F. TIG Welding, which heats the joint up to the melting point, must heat the part of the tube adjacent to the weld up into this annealing range, thus locally weakening the tube. This drop in strength has no effect on every day riding, but it does reduce the potential long term fatigue life and, in a crash, can lead to buckling of the frame. OX PLATINUM is very resistant to this annealing. Thus an OX PLATINUM frame will survive crashes better, and also have a much better fatigue life. When used on silver brazed lugged frames, OX PLATINUM neither air hardens nor anneals. Your frame is at 195,000 psi strength throughout, with no weaknesses! The PLATINUM Series alloys are ideal for both lugged and lugless frame construction! If an OX Platinum tube fails, for any reason, True Temper Sports, Inc will replace it at no charge.
Reynolds 853 - Reynolds 853 is a high strength, 210,000 psi, heat treated, air hardened steel alloy. Careful control of the alloying elements combine to give these tubes enhanced mechanical properties surpassing other materials currently available. The main advantage of Reynolds 853 is its ability to air harden after joining, a characteristic not shown by other chrome molybdenum / manganese molybdenum materials presently on the market. When building frames using either TIG welding or high temperature brazing, above 1600 degrees, the joints increase in strength as the frame cools to room temperature. Lug construction is the preffered method of joining 853. It allows a much larger area to be heated than tig welding which concentrates the heat to a very small area at the weld. This completely goes against the “AIR HARDENING” building philosophy of the material and adds nothing to the strength of the joint. It is however a much cheaper joining method, requiring less time and skill to perform. Due to the superior mechanical properties of 853 tubing, there are several benefits which will translate directly to the cyclist. The wall thickness of 853 has been reduced to 0.4 mm, a full 0.1 mm thinner than Reynolds other top of the line 753 tubing. This translates into a frame weight of under 3 pounds 5 ounces for a 56 cm frame (less fork). Because of the added hardness of this alloy the chances of denting the tubing are no greater than that of present materials being employed. The final significant advantage is the increased stiffness of the frame and its ability to transmit all of the cyclist power into forward motion. The oversized 853 tube set, with its oval chainstays represents the ultimate in power transmission. Aside from the 853 OS tubeset, conventional diameter sets are available which will allow for a more comfortable ride, while still retaining most of the benefits associated with 853 oversize.
Sanko Japenesse Tubing- Also will be refered to as full Sanko Japenesse tubing. Japan is well known for their steel manufacturing. Sanko is a company from there which is famous for their high quality products. The tubing we are using is made expecially for the bicycle market. It isn't double butted, but we can use thinner tubing since it's stronger (Material strength (kg/mm2) and is of a higher quality than normal Taiwanese steel.
T45 - T45 is a combination of Carbon, Manganese and Steel, and is one of the strongest and highest quality tubes available, and to top it off it's made in England. T45 is used a lot in the aerospace and motorsport industries because of it's superior strength to weight ratio over other steel tubing.
Tensile strength: (max pressure the tube takes before cracking)
-45 to 58 tons per sq inch
Torque load: (max pressure the tube takes before twisting)
-2255 tons per sq inch
Yield strength: (max pressure the tube takes before bending)
-620 tons per sq inch
Chromoly tubing also requires heat treating after any welding or brazing, where T45 does not require any heat treatment whatsoever. T45 is simply a stronger and higher quality tube than 4130 Chromoly.
The Theory Behind Bars
Postioning the Bars
The positioning of your bars and how far they point forward or back will have a significant affect on how the bike will handle. There are an infinitive amount of positions but they fall into three groups: Mexican - Bars are pointed backwards or behind your fork legs or front axle.
Chicago - Bars are pointed forward, past your fork legs or front axle.
Othordox - Bars are perfectly inline with your fork legs or front axle.WARNING: Having your bars postioned too far forwards or backwards is dangerous and could result in the bars slipping in the stem and the aftermath won't be nice.
Bar Width
As far as bar width is concerned the desired width will be down to personnel preference but should ideally be equal to the width of your shoulders to get maximun stability and control.
Bar Height
Bars come in various height rises these days and can range from anything between 4-8.5 inches. Im not too sure on how bars affect the handling of the bike but I assume and correct me if I'm wrong but the taller you are the more height rise you need. All I do know is that ike every other BMX part its personal preference and you may not follow these 'rules'.
Bar Sweep
Up Sweep -
Back Sweep -
(Acreditted to rusty shackleford)
The Theory Behind Forks
Pegs
Pegs come in two sizes 10mm and 14mm, they usually come with anti roll pins, which are basically bolts that screw into the peg and slot in the dropouts of the frame or fork to stop the pegs from spinnign and undoing themselves. You can run any combination of pegs, its whatever suits you.
WARNING: Only use pegs on forks hat have 14mm dropouts, the only exception is if the fork manufacturer says that pegs are OK to be use dof forks with 10mm axles.
Forks
Steerer tubes come in two sizes: 1 Inch
1-1/8 InchWARNING: Check what size the headtube on your frame is as the stem and fork steerertube need to be the same. They will be either of the two options above and all must be the same inorder for it to fit together and function properly and safely.
There are three types of fork:
Street/Park/Dirt - Medium weight fork made from 4130 that comes with optional proction for grinding, quite thick walled that tries to create the best of strong yet light.
Flatland - Often come in a 0 degree offset and no rake, tin walled Aluminum or 4130 that comes with 10mm dropouts to save weight.
Race - Light weight fork, made from very thin walled Aluminum or 4130, that comes with 10mm dropouts to save weight.
The Theory Behind Stems
There seems to now be three types of stem design on the market:
Toploader - Stem clamps onto the bar vertically.
Frontloader - Stem clamps onto the bar horizontally.
Monobolt - Stem clamps onto the bar using a single bolt to expand a set of wedges, that simaltanously clamps both the stem to the bar and the steerertube.The only difference design wise is how stems bolt together whether it be a top/front loader with 4 bolts or 6 in some cases or with a single bolt and wedge design. The only real significance I can see is that the less bolts used to do the stem up the more evenly distributed the presure is over the bolts and stem. Put simply less bolts equals more clamping force and more evenly distributed pressure across the stem-bar and stem-steeertube interface.
The Theory Behind Everything Drivetain (Acreditted to flatline)
Gear Ratios
Ideally you are looking to achieve a gear ratio of around 2.75 but this not a set in stone, everything still depends on what your stlye of riding is. If you prefer slower, tech moves then a lower gear ratio is maybe more for you, or you might prefer going fast and hitting big things, inwhich case a higher gear ratio is probably more for you. Just don't go too crazy. High - A gear ratio is one that is harder to pedal, but gives you a HIGH top speed. Low Acceleration/High Speed. This gear ratio is ideal for downhill bmx tracks or some trail riding.
Low - A gear ratio is one that is easier to pedal, but you have a LOW top speed. High Acceleration/Low Speed. This gear ratio is ideal for flatland or technical mini-ramp riding.
Gear Ratio = Number Teeth of Front Cog/Number of Teeth of Front Cog
Micro Gearing: Disadvantages and Advantages Smaller gear systems result in smaller clearences between the brake post and the chain. (assuming you have chainstay brakes) To counter this, many people will buy new U-brake (Fly U-Brake) that has a overall lower stack height therefore freeing up valuable space between the chain and brake post. Others tend to cut their brake posts off completely and run brakeless. Any gearing below 30/11 will usually hit the top of the brake post without the brake on it.
For every tooth lost from the front sprocket the top run of chain will move down closer to the chainstays (or brake boss) by 0.08” ie.3 teeth causes a drop of about ¼(quarter).
Having fewer teeth in the sprocket and fewer on the driver, cog, freewheel, will require that the load be placed onto the teeth of these components to greatly increase. So instead of having the load being placed on 8 or 9 teeth like on a 16 tooth freewheel, it must be placed on only 4 or 5 teeth like that of a 9 tooth driver. The result is haveing a drivetrain that wears out quicker, is less durable, and isn't as strong as that of a higher gearing system. Not to say these forces of load placement and/or strength are in great measures, but enough to take into consideration.
Similar to the teeth on the sproket and drivers, the chain takes a blow from the smaller drivetrains. The chain has to carry the load of propeling the bike not only in fewer links, but a greater load all together. A chain will wear out faster on a "micro" gearing setup than a drivetrain with say a 39/14 gear setup. That being said, you WILL have to replace chains more often.
Cassettes may cost more than a flip/flop (freewheel) hub. And are typically louder. (although many people consider that to be a plus)
Some people might hate on you because either you can afford to have a micro gearing system, they may think you are a trend whore, or because they just don't like the whole idea in general.Advantages of Micro Gearing It can easily be seen as a way to free up a few extra ounces. Having less metal for a sprocket, less chain, and a smaller driver or cog in the rear all contribute to a lighter gearing system.
If you do a lot of grinding on your bike or do lots of tricks that require a higher clearance in the crank area, you may also benefit from having a small sprocket.
Having a smaller sprocket is also harder to bend. Bigger sprockets bend easier from grinding or landing on rails/copings and stuff like that. The leverage on a big sprocket at the teeth in a sideways movement is much greater than that of a small 4" tall 25t Sprocket
It also in my opinion looks better and cleaner having a micro gearing just because the sprocket and driver are small.
Crank Type
There are three types of crank: 1 Piece - These come on low budget bikes and please change them to 3 piece as soon as you can, they are prone to bending, snapping, you cant adjust them to get a perfect chainline and are generally a load of rubbish.
3 Piece - Widely considered the best type of crank on the market, these cranks consist of a left-hand arm, a right-hand arm and an axle. You put the axle through the bearing in the BB shell and then the arms are atatched either side of the BB shell on the axle that is sticking out. You use spacers that are normally provided with the cranks to aline your cranks to give a perfect chainline and then you do the bolts up.
2/1/2 Piece - These are still in development but Fly and Odyssey are currently testing prototypes. They are consist of the same two arms and axle as 3 piece but this time only one side of the cranks has a bolt screwed into it that pulls the cranks together.
Crank Length
The length of your cranks will affect your gear ratio a fraction due to the different leverage ratios different length cranks have on the pedalling motion. Longer - Will make pedalling easier
Shorter - Will make pedalling harder
Chain Tensioners/Tugs
Chain tensioners come in 10mm and 14mm and they go on the rear hub axle and atatch in between the dropout. They are used to position your rear wheel where you want it i the dropout to get an even chain tension. They also stop your wheel form working its way forward in the dropouts. Chain tensioners are not essential pieces of kit but they do offer the rider the knowledge that with them on your wheel will not be moving on its own accord. You onyl really need one chain tensioner and ideally it should be placed on the driveside.
Chain Compatibility
There are effectively 3 sizes of BMX chain:
3/32 - Thinnest is the narrow racer-size used on race bikes
1/8 - Standard is the size which comes on most bikes
3/16 - Thickest is the new FAT motorcycle type commonly used for street riding.You can mix and match sprocket/chain/freewheel sizes as long as the chain you use is that size or larger.
The Theory Behind All Things Wheels
Wheel Building
There are four common lacing patterns used for building wheels: Radial - Weakest lacing pattern that is currently used, only to be used for racing.
2X - Not very strong, recommended for racing or as a front wheel build if your smooth
3X - Strong but not the strongest can be used perfectly fine for most riding and rider types.
4X - Strongest lacing pattern that is currently used.In general the lower the crossing pattern you chose to build your wheel the less rotational weight - so radial built wheels will have the least rotational weight whereas 4x built wheels will have the most rotational weight.
To work out the size of spokes you need for your wheel build you will need to know the ERD (Effective Rim Diameter), various dimensions of your hub flanges and the lacing you want to use, whether it be radial, 2x, 3x or 4x.
WARNING: Never use different holed rims or hubs to build a wheel the spoke tension will not be distributed evenly throughout the rim or hub flanges and it will lead to a big mess.
WARNING: If you don't know what you are doing or are not confident enough to build a wheel don't, take it to a shop and get a qualified wheelbuilder to do it for a small price.
Spoke Length Calculators
BEST SPOKE LENGTH CALCULATOR EVER (http://www.thehousebmx.com/Spoke.html) - Simply the best spoke calculating tool out there, so simple and easy to use, pick your hub, rim, number of spokes and lacing and thats it.
Beyond Bikes Spoke Length Calculator (http://www.beyondbikes.com/bb/tech/?section=spo) - Very basic and easy to use.
Senet Spoke Length Calculator (http://users.senet.com.au/~mitchell/misc/html/spoke.htm) - Very basic and easy to use.
WheelPro Spoke Length Calculator (http://www.wheelpro.co.uk/spokecalc/) - Very basic and easy to use.
DTSwiss Spoke Length Calculator (http://www.dtswiss.com/spokescalc/welcome.aspx?language=en) - Quite advanced use if you know what your doing.
Damon Rinard Spoke Length Calculator (http://www.damonrinard.com/spocalc.htm) - There are two version: Spocalc Express - Very basic easy to use
Spocalc - Very advanced use if you know what your doing this ones a nightmare to use if your a novice.Wheelbuilding Guide
G-Sport Wheel Building Masterclass (http://www.gsportbmx.co.uk/custom/wheel_build/wheels.html)
Rims
Seeing as your wheels come into contact with the floor the lighter they are the better as this decreases the roling resistance, but don't go too light, you don't want to end up with a exploding wheel.
Rims come in four drilling sizes: 28 - Designed for racing, not recommended for street unless your super smooth.
32 - Designed for racing but can be used for light street.
36 - Should be used as a front rim for pretty any type of riding, only to be used on the rear if your smooth.
48 - Used as a front or rear rim for street use, ideal if your a bit of a fatty or just ride hard and fast and crash a lot.Rims come in four rim surface finishes: Black anodised
Black Duralectra
Machined
Chrome If you are looking for the best stopping power than I suggest you buy a Chrome rim or if you really want a black rim and can afford it then a Duralectra rim as the rim surface finish does greatly improve the stopping power of a brake. Please remeber that your brakes need to be properly set up to achieve there maximun braking potential.
Hubs
There are four types of hub:
Fix Freewheel Standard - The hub is very basic in design and is the cheapest, it has a threaded part on the left or right to screw a freewheel on.
Flip Flop - The hub is very basic in design and is the cheapest, it has a threaded part on the left and right to screw two different sized freewheels on.
Cassette - This is the most expensive of all the hubs and the freewheel mechnism is built into the hub body. You will need this type of hub to run mirco gearing.
Freecoaster - This is the most complex of all the hubs with the freewheel mechanism built into the hub body as well as another mechanism that allows the hub to dis-engage when pedalled backwards. This is ideally suited to flatland riding but is becoming more popular in street and park riding. These hubs can be quite expensive and the engaement is very slow, they have a tendency to break more often than other types of hub and in most cases they are not designed for hard, agressive riding and the axles break a lot.
Freewheels
If you have a Flip Flop or Freewheel hub then you will also need to buy a freewheel that simply screws onto the threaded part of these hubs. There are two thread types: Metric - Accepts 13 and 14 tooth freewheels.
Imprrial - Accepts 15+ tooth freewheels.
Tyres
There are two groups of tyres: Knobbly
SlickIf you plan on riidng street and park then you would be better off running slic tyres with a high PSI rating or possibly a slic in the rear with a high PSI rating and a nobbly tyre up front. If you are riding Dirt then you should really be running knobbly tyres or atleast a set of slics with a little more tread than usual.
PSI Rating - This is amount of air you shouldinflate your tyres to, it is important that you pump your tyres up to the PSI rating printed on your tyres sidewallsand don't exceeed it astyres will pop off rims and there will be a mess.
Tyre Sizing - The most common appraoch is to run a bigger tyre in the front than in the back as you wil need the extra grip here and bigger tyres mean mre air volume that can absorb the impacts put upon your wrists. This isn't a rule just a guideline and its personel preference what size tyres you like to run.
(Acreditted to odsycalvin)
Spokes
There are three types of spoke: Plain guage
Double Butted
Straight PullSpokes come in different thicknesses or guages to give it its technical name: 10
11
12
13
14
15I suggest buying quality spokes, there not really that expensive but you will notice they build a better wheel, have better tension and keep there tension longer. Stay away from titanium spokes as they don't build a good wheel, they flex, undo often, snap, don't save much weight and are way overpriced.
Nipples
Nipples are what go on through the holes in the rim and thread onto the ends of the spokes to increase or decrease the tension. Nipple come in all shapes and sizes and you must make sure that the nipples you buy are the right size for the guage of spoke you are buying. Stay away from coloured aluminium nipples as they will rounded real easy, just stick to the basic braze ones.
The Theory Behind All Things Braking
Brake Levers
There are two types of lever: One finger - often very short lever blade, designed to brake using just your index finger.
Two finger - often have a medium to long lever blade designed to brake using two fingers or more if you are so inclined.Brake levers come in many different shapes and sizes but they all do one thing an one thing only, brake. Decide whether you like one of two finger braking and buy the appropriate lever for your needs. Longer elvers offer more leverage and lock better with less effort, whereas shorter levers are better for feathering and require a lot more effort to lock the wheel up.
Brake Calipers
Most BMX frames designed for Street, Park, Dirt, Flatland and Vert riding come with U-brake mounts positioned either under the Seatstays or on the Chainstays. Race orientated frames are the only places your likely to see V brake mounts on the top of the Seatstays.
With the ever growing popularity of Chainstay brake mounts brought about by the increased braking performance they bring due to physics and applied forces and Micro Gearing [25:9, 24:9, 23:8] manufacturers have had to redesign the brake caliper to get around the problem of chain clearence and inparticular chains rubbing on brake calipers. The answer is lower profile brake calipers coupled with angled chainstays, which together greatly increase the distance between the chain and brake calipers by lowering the brake caliper stack hieght. So if you have Chainstay brake mounts and want to run Micro Gearing then be warned, you will most likely need a low profile brake and a frame with angled chainstays otherwise you will have to settle for 30:11 gearing with a brake caliper thats not low profile and even that may be pushing it. If you have Seatstay brake mounts or brakeless you have nothing to worry about, you are free to run whatever gear ratio you like.
Brake Pads
Pads come in two compounds: Hard
Soft Pads come in four rough sizes: Narrow and long
Narrow and short
Wide and long
Wide and short
Brake Cables
There are two types of brake cable: Straight - With a straight cable brake setup you run a single brake cable from your lever to your calipers.
Gyro - With a gyro seup you run two gyro cables from the lever to the calipers.
Brake Modifications
The only brake modification I know of and have heard of is the 'Spoke Mod' this is where you replace the straddle cable with a Odyssey London Mod or a headset spacer with three holes drilled in it and use two spokes, one for each brake caliper to improve braking and also to be able to adjust each brake caliper individually.
Abreviations (Acreditted to burbsrider)
T/T - Top Tube
C/S - Chainstays
H/T Angle - Headtube Angle
S/T Angle - Seattube Angle
BB - Bottom Bracket
W/B - Wheelbase
Toptube Length
Longer is for taller people since they need more room and dont want to hurt there backs. shorter is for shorter people who need something there size so they can ride to there fullest ability. but there is alot of personal preference to. a taller person may perfer a short frame so they can land those technical tricks and a short person may want a bigger bike so the have lots of room to pull big tricks without being cramped up.
Chainstay Length
Longer chainstays create a more stable back end that are ideally suited to the taller rider whos extra height will naturally create the leverage for the front end to pop up, short rider beware getting the front end up will be hard work as your fighting physics. Also the rider that likes to gap far and ride trials will benefit from a frame with a longer chainstay.
Shorter chainstays create a twitchier back end that comes up very easily and can easily be looped out especially if you are a tall person as your extra height creates excess leverage and therefore a frame with a longer chainstay is recommended. Also shorter chainstays are ideally suited to the shorter rider as they naturally create less of a leverage angle and the rider that likes tech based riding as well as the rider that likes to spin,tallwhip etc...
Head Tube Angle
Steeper means easeier spins and nose manuals.also means the tt feels longer.like 20.5 on a 75 ht will feel like a 20.75 on a 74.5. ht generally vary between 74 and 75. i have seen a 73 on proper frames before though. steeper may seem unstable at first and i wouldnt reccomend it for those bombing huge gaps or riding trails. A very steep headtube will make the bike feel sketchy and unstable sometimes, especially on hard landings, and if you happen to land front wheel first it will be very hard to control the bike.
Seattube Angle
A steep seat tube like 71 means easier seat pinching and a farther back bb. but it can sometimes get in the way during some tricks. laid back angles like 69 means a farther up bb which make the tt seem shorter and the seat will be harder to pinch.
BB Height
Higher means quicker turning and easier manuals. also means less smashing of the sprocket. lower means more stability but manuals may feel weird since your feet are almost level with axle so the balance point is much higher. it will also affect your back position and how high your bars feel. lower bb means less bending over for your bars. tall guys beware.it generally ranges from 11.3 to 12
BB Type (Acreditted to Terrible One's Website)
There are 4 types of BB's used in BMX and there are:
US - Was the industry standard for many decades has the largest diameter BB shell and the bearing cups are pressed in with the bearings poping into the bearing cups. The heaviest of the BB options but by far the strongest in terms of allowing the biggest possible bearings to be used. Recommended if you want a hassle free BB setup and you ride hard.
Mid - Quickly becoming the new industry standard, does away with the BB cups found in the US BB but uses the same size bearings that have a pop in fit directy into the BB shell. As strong as the US BB but 1/3 of the weight recommended for any type of riding. The only downsides are that if your BB shell is deformed in any way wil most likely rendor your frame useless and they are only compatable with 19mm axles.
Spanish - Essentialy the same pop in fit as Mid BB's but smaller in diameter but are avaliable in 2 sizes for: 1) 19mm axles and 2) 22mm axles.
Euro - The smallest diameter BB shell as a thread cut into itand you screw your BB into the BB shell. Has very small bearings which can be subseptable to wearing and crushing over a short period but this is a very light option recommended for light street, park trais and racing.
Headset Type
There are three types of headset:
1" - Most commonly found on Race frames and very very very very old frames.
1-1/8" - Just like the US BB design in that the headset cups are pressed into the headtube and these cups house the bearings and a compression bolt is used to tighten the whole front end together.
Internal/Intergrated - Just like the MId and Spanish BB designs in that the bearings are pop fitted into the headtube. Again this design does away with headset cups just like the Mid and Spanish BB's did away with the BB cups and in the end the same probems are associated with this headset design as are with the BB design of which it orientated from.
Wheelbase
Wheelbase is the distance between the front and rear axles, which is directly effected by frame geometry, especially tt and cs length, but also headtube angle. The longer the wheelbase the more stable the bike is, but the less maneuvarable it will be.
Frame Materials
The most common materials used to make frames from are as follows:
Hi-tensile Steel
4130 Chromoly
OX Platinum
Reynolds 853
Sanko Japenesse Tubing
T45Hi-tensile Steel - Steer clear of framesmade from Hi-tensile steel it is a very cheap and weak tubing and is only found on cheap nasty frames.
4130 Chromoly - Basically 4130 is a mixture of different metals. The 4130 is a code of the American Iron & Steel Institute and defines the approximate chemical composition of the steel. The "41" denotes a low alloy steel containing nominally 1 percent chromium and 0.2 percent molybdenum (hence the nickname "chromoly"). The "30" denotes a carbon content of 0.30 percent. In addition, as normal constituents of plain carbon and low alloy steels, there will be around 0.2-0.5 percent silicon, 0.5-1.0 percent manganese, and well under 0.1 percent of each of a dozen or so other elements whose presence is unavoidable, in a few cases deliberate, and generally not harmful. The remaining 97-98 percent is iron (Fe).
OX Platinum - True Temper's OX PLATINUM Series is based on state of the art steel metallurgy. The metallurgists at True Temper began with an aerospace grade of air hardening steel and modified it to enhance its properties for light weight bicycle frames. The ultimate tensile strength exceeds 195,000 psi. Air hardenable steels are desirable for high performance welded steel frames. At the edges of the molten weld pool, as the metal freezes, an unavoidable microscopic notch is formed. This is a stress concentrator that magnifies the actual stresses of riding by a factor of 4 to 6 times. The weld is relatively small and cools so quickly that metallurgical changes occur creating localized hard and brittle areas, if the alloy is not specifically designed to avoid this. Air hardening steels are metallurgically designed so that as the steel cools and solidifies from the molten state in air, the steel hardens to an even higher strength. The metallurgists must control the alloying elements so that the hardened steel is also tough and able to absorb impacts, rather than brittle and subject to fracturing. True Temper not only solved these problems, but went further: Most heat treated steels tend to anneal, or soften, when heated between about 1000°F and 1500°F. TIG Welding, which heats the joint up to the melting point, must heat the part of the tube adjacent to the weld up into this annealing range, thus locally weakening the tube. This drop in strength has no effect on every day riding, but it does reduce the potential long term fatigue life and, in a crash, can lead to buckling of the frame. OX PLATINUM is very resistant to this annealing. Thus an OX PLATINUM frame will survive crashes better, and also have a much better fatigue life. When used on silver brazed lugged frames, OX PLATINUM neither air hardens nor anneals. Your frame is at 195,000 psi strength throughout, with no weaknesses! The PLATINUM Series alloys are ideal for both lugged and lugless frame construction! If an OX Platinum tube fails, for any reason, True Temper Sports, Inc will replace it at no charge.
Reynolds 853 - Reynolds 853 is a high strength, 210,000 psi, heat treated, air hardened steel alloy. Careful control of the alloying elements combine to give these tubes enhanced mechanical properties surpassing other materials currently available. The main advantage of Reynolds 853 is its ability to air harden after joining, a characteristic not shown by other chrome molybdenum / manganese molybdenum materials presently on the market. When building frames using either TIG welding or high temperature brazing, above 1600 degrees, the joints increase in strength as the frame cools to room temperature. Lug construction is the preffered method of joining 853. It allows a much larger area to be heated than tig welding which concentrates the heat to a very small area at the weld. This completely goes against the “AIR HARDENING” building philosophy of the material and adds nothing to the strength of the joint. It is however a much cheaper joining method, requiring less time and skill to perform. Due to the superior mechanical properties of 853 tubing, there are several benefits which will translate directly to the cyclist. The wall thickness of 853 has been reduced to 0.4 mm, a full 0.1 mm thinner than Reynolds other top of the line 753 tubing. This translates into a frame weight of under 3 pounds 5 ounces for a 56 cm frame (less fork). Because of the added hardness of this alloy the chances of denting the tubing are no greater than that of present materials being employed. The final significant advantage is the increased stiffness of the frame and its ability to transmit all of the cyclist power into forward motion. The oversized 853 tube set, with its oval chainstays represents the ultimate in power transmission. Aside from the 853 OS tubeset, conventional diameter sets are available which will allow for a more comfortable ride, while still retaining most of the benefits associated with 853 oversize.
Sanko Japenesse Tubing- Also will be refered to as full Sanko Japenesse tubing. Japan is well known for their steel manufacturing. Sanko is a company from there which is famous for their high quality products. The tubing we are using is made expecially for the bicycle market. It isn't double butted, but we can use thinner tubing since it's stronger (Material strength (kg/mm2) and is of a higher quality than normal Taiwanese steel.
T45 - T45 is a combination of Carbon, Manganese and Steel, and is one of the strongest and highest quality tubes available, and to top it off it's made in England. T45 is used a lot in the aerospace and motorsport industries because of it's superior strength to weight ratio over other steel tubing.
Tensile strength: (max pressure the tube takes before cracking)
-45 to 58 tons per sq inch
Torque load: (max pressure the tube takes before twisting)
-2255 tons per sq inch
Yield strength: (max pressure the tube takes before bending)
-620 tons per sq inch
Chromoly tubing also requires heat treating after any welding or brazing, where T45 does not require any heat treatment whatsoever. T45 is simply a stronger and higher quality tube than 4130 Chromoly.
The Theory Behind Bars
Postioning the Bars
The positioning of your bars and how far they point forward or back will have a significant affect on how the bike will handle. There are an infinitive amount of positions but they fall into three groups: Mexican - Bars are pointed backwards or behind your fork legs or front axle.
Chicago - Bars are pointed forward, past your fork legs or front axle.
Othordox - Bars are perfectly inline with your fork legs or front axle.WARNING: Having your bars postioned too far forwards or backwards is dangerous and could result in the bars slipping in the stem and the aftermath won't be nice.
Bar Width
As far as bar width is concerned the desired width will be down to personnel preference but should ideally be equal to the width of your shoulders to get maximun stability and control.
Bar Height
Bars come in various height rises these days and can range from anything between 4-8.5 inches. Im not too sure on how bars affect the handling of the bike but I assume and correct me if I'm wrong but the taller you are the more height rise you need. All I do know is that ike every other BMX part its personal preference and you may not follow these 'rules'.
Bar Sweep
Up Sweep -
Back Sweep -
(Acreditted to rusty shackleford)
The Theory Behind Forks
Pegs
Pegs come in two sizes 10mm and 14mm, they usually come with anti roll pins, which are basically bolts that screw into the peg and slot in the dropouts of the frame or fork to stop the pegs from spinnign and undoing themselves. You can run any combination of pegs, its whatever suits you.
WARNING: Only use pegs on forks hat have 14mm dropouts, the only exception is if the fork manufacturer says that pegs are OK to be use dof forks with 10mm axles.
Forks
Steerer tubes come in two sizes: 1 Inch
1-1/8 InchWARNING: Check what size the headtube on your frame is as the stem and fork steerertube need to be the same. They will be either of the two options above and all must be the same inorder for it to fit together and function properly and safely.
There are three types of fork:
Street/Park/Dirt - Medium weight fork made from 4130 that comes with optional proction for grinding, quite thick walled that tries to create the best of strong yet light.
Flatland - Often come in a 0 degree offset and no rake, tin walled Aluminum or 4130 that comes with 10mm dropouts to save weight.
Race - Light weight fork, made from very thin walled Aluminum or 4130, that comes with 10mm dropouts to save weight.
The Theory Behind Stems
There seems to now be three types of stem design on the market:
Toploader - Stem clamps onto the bar vertically.
Frontloader - Stem clamps onto the bar horizontally.
Monobolt - Stem clamps onto the bar using a single bolt to expand a set of wedges, that simaltanously clamps both the stem to the bar and the steerertube.The only difference design wise is how stems bolt together whether it be a top/front loader with 4 bolts or 6 in some cases or with a single bolt and wedge design. The only real significance I can see is that the less bolts used to do the stem up the more evenly distributed the presure is over the bolts and stem. Put simply less bolts equals more clamping force and more evenly distributed pressure across the stem-bar and stem-steeertube interface.
The Theory Behind Everything Drivetain (Acreditted to flatline)
Gear Ratios
Ideally you are looking to achieve a gear ratio of around 2.75 but this not a set in stone, everything still depends on what your stlye of riding is. If you prefer slower, tech moves then a lower gear ratio is maybe more for you, or you might prefer going fast and hitting big things, inwhich case a higher gear ratio is probably more for you. Just don't go too crazy. High - A gear ratio is one that is harder to pedal, but gives you a HIGH top speed. Low Acceleration/High Speed. This gear ratio is ideal for downhill bmx tracks or some trail riding.
Low - A gear ratio is one that is easier to pedal, but you have a LOW top speed. High Acceleration/Low Speed. This gear ratio is ideal for flatland or technical mini-ramp riding.
Gear Ratio = Number Teeth of Front Cog/Number of Teeth of Front Cog
Micro Gearing: Disadvantages and Advantages Smaller gear systems result in smaller clearences between the brake post and the chain. (assuming you have chainstay brakes) To counter this, many people will buy new U-brake (Fly U-Brake) that has a overall lower stack height therefore freeing up valuable space between the chain and brake post. Others tend to cut their brake posts off completely and run brakeless. Any gearing below 30/11 will usually hit the top of the brake post without the brake on it.
For every tooth lost from the front sprocket the top run of chain will move down closer to the chainstays (or brake boss) by 0.08” ie.3 teeth causes a drop of about ¼(quarter).
Having fewer teeth in the sprocket and fewer on the driver, cog, freewheel, will require that the load be placed onto the teeth of these components to greatly increase. So instead of having the load being placed on 8 or 9 teeth like on a 16 tooth freewheel, it must be placed on only 4 or 5 teeth like that of a 9 tooth driver. The result is haveing a drivetrain that wears out quicker, is less durable, and isn't as strong as that of a higher gearing system. Not to say these forces of load placement and/or strength are in great measures, but enough to take into consideration.
Similar to the teeth on the sproket and drivers, the chain takes a blow from the smaller drivetrains. The chain has to carry the load of propeling the bike not only in fewer links, but a greater load all together. A chain will wear out faster on a "micro" gearing setup than a drivetrain with say a 39/14 gear setup. That being said, you WILL have to replace chains more often.
Cassettes may cost more than a flip/flop (freewheel) hub. And are typically louder. (although many people consider that to be a plus)
Some people might hate on you because either you can afford to have a micro gearing system, they may think you are a trend whore, or because they just don't like the whole idea in general.Advantages of Micro Gearing It can easily be seen as a way to free up a few extra ounces. Having less metal for a sprocket, less chain, and a smaller driver or cog in the rear all contribute to a lighter gearing system.
If you do a lot of grinding on your bike or do lots of tricks that require a higher clearance in the crank area, you may also benefit from having a small sprocket.
Having a smaller sprocket is also harder to bend. Bigger sprockets bend easier from grinding or landing on rails/copings and stuff like that. The leverage on a big sprocket at the teeth in a sideways movement is much greater than that of a small 4" tall 25t Sprocket
It also in my opinion looks better and cleaner having a micro gearing just because the sprocket and driver are small.
Crank Type
There are three types of crank: 1 Piece - These come on low budget bikes and please change them to 3 piece as soon as you can, they are prone to bending, snapping, you cant adjust them to get a perfect chainline and are generally a load of rubbish.
3 Piece - Widely considered the best type of crank on the market, these cranks consist of a left-hand arm, a right-hand arm and an axle. You put the axle through the bearing in the BB shell and then the arms are atatched either side of the BB shell on the axle that is sticking out. You use spacers that are normally provided with the cranks to aline your cranks to give a perfect chainline and then you do the bolts up.
2/1/2 Piece - These are still in development but Fly and Odyssey are currently testing prototypes. They are consist of the same two arms and axle as 3 piece but this time only one side of the cranks has a bolt screwed into it that pulls the cranks together.
Crank Length
The length of your cranks will affect your gear ratio a fraction due to the different leverage ratios different length cranks have on the pedalling motion. Longer - Will make pedalling easier
Shorter - Will make pedalling harder
Chain Tensioners/Tugs
Chain tensioners come in 10mm and 14mm and they go on the rear hub axle and atatch in between the dropout. They are used to position your rear wheel where you want it i the dropout to get an even chain tension. They also stop your wheel form working its way forward in the dropouts. Chain tensioners are not essential pieces of kit but they do offer the rider the knowledge that with them on your wheel will not be moving on its own accord. You onyl really need one chain tensioner and ideally it should be placed on the driveside.
Chain Compatibility
There are effectively 3 sizes of BMX chain:
3/32 - Thinnest is the narrow racer-size used on race bikes
1/8 - Standard is the size which comes on most bikes
3/16 - Thickest is the new FAT motorcycle type commonly used for street riding.You can mix and match sprocket/chain/freewheel sizes as long as the chain you use is that size or larger.
The Theory Behind All Things Wheels
Wheel Building
There are four common lacing patterns used for building wheels: Radial - Weakest lacing pattern that is currently used, only to be used for racing.
2X - Not very strong, recommended for racing or as a front wheel build if your smooth
3X - Strong but not the strongest can be used perfectly fine for most riding and rider types.
4X - Strongest lacing pattern that is currently used.In general the lower the crossing pattern you chose to build your wheel the less rotational weight - so radial built wheels will have the least rotational weight whereas 4x built wheels will have the most rotational weight.
To work out the size of spokes you need for your wheel build you will need to know the ERD (Effective Rim Diameter), various dimensions of your hub flanges and the lacing you want to use, whether it be radial, 2x, 3x or 4x.
WARNING: Never use different holed rims or hubs to build a wheel the spoke tension will not be distributed evenly throughout the rim or hub flanges and it will lead to a big mess.
WARNING: If you don't know what you are doing or are not confident enough to build a wheel don't, take it to a shop and get a qualified wheelbuilder to do it for a small price.
Spoke Length Calculators
BEST SPOKE LENGTH CALCULATOR EVER (http://www.thehousebmx.com/Spoke.html) - Simply the best spoke calculating tool out there, so simple and easy to use, pick your hub, rim, number of spokes and lacing and thats it.
Beyond Bikes Spoke Length Calculator (http://www.beyondbikes.com/bb/tech/?section=spo) - Very basic and easy to use.
Senet Spoke Length Calculator (http://users.senet.com.au/~mitchell/misc/html/spoke.htm) - Very basic and easy to use.
WheelPro Spoke Length Calculator (http://www.wheelpro.co.uk/spokecalc/) - Very basic and easy to use.
DTSwiss Spoke Length Calculator (http://www.dtswiss.com/spokescalc/welcome.aspx?language=en) - Quite advanced use if you know what your doing.
Damon Rinard Spoke Length Calculator (http://www.damonrinard.com/spocalc.htm) - There are two version: Spocalc Express - Very basic easy to use
Spocalc - Very advanced use if you know what your doing this ones a nightmare to use if your a novice.Wheelbuilding Guide
G-Sport Wheel Building Masterclass (http://www.gsportbmx.co.uk/custom/wheel_build/wheels.html)
Rims
Seeing as your wheels come into contact with the floor the lighter they are the better as this decreases the roling resistance, but don't go too light, you don't want to end up with a exploding wheel.
Rims come in four drilling sizes: 28 - Designed for racing, not recommended for street unless your super smooth.
32 - Designed for racing but can be used for light street.
36 - Should be used as a front rim for pretty any type of riding, only to be used on the rear if your smooth.
48 - Used as a front or rear rim for street use, ideal if your a bit of a fatty or just ride hard and fast and crash a lot.Rims come in four rim surface finishes: Black anodised
Black Duralectra
Machined
Chrome If you are looking for the best stopping power than I suggest you buy a Chrome rim or if you really want a black rim and can afford it then a Duralectra rim as the rim surface finish does greatly improve the stopping power of a brake. Please remeber that your brakes need to be properly set up to achieve there maximun braking potential.
Hubs
There are four types of hub:
Fix Freewheel Standard - The hub is very basic in design and is the cheapest, it has a threaded part on the left or right to screw a freewheel on.
Flip Flop - The hub is very basic in design and is the cheapest, it has a threaded part on the left and right to screw two different sized freewheels on.
Cassette - This is the most expensive of all the hubs and the freewheel mechnism is built into the hub body. You will need this type of hub to run mirco gearing.
Freecoaster - This is the most complex of all the hubs with the freewheel mechanism built into the hub body as well as another mechanism that allows the hub to dis-engage when pedalled backwards. This is ideally suited to flatland riding but is becoming more popular in street and park riding. These hubs can be quite expensive and the engaement is very slow, they have a tendency to break more often than other types of hub and in most cases they are not designed for hard, agressive riding and the axles break a lot.
Freewheels
If you have a Flip Flop or Freewheel hub then you will also need to buy a freewheel that simply screws onto the threaded part of these hubs. There are two thread types: Metric - Accepts 13 and 14 tooth freewheels.
Imprrial - Accepts 15+ tooth freewheels.
Tyres
There are two groups of tyres: Knobbly
SlickIf you plan on riidng street and park then you would be better off running slic tyres with a high PSI rating or possibly a slic in the rear with a high PSI rating and a nobbly tyre up front. If you are riding Dirt then you should really be running knobbly tyres or atleast a set of slics with a little more tread than usual.
PSI Rating - This is amount of air you shouldinflate your tyres to, it is important that you pump your tyres up to the PSI rating printed on your tyres sidewallsand don't exceeed it astyres will pop off rims and there will be a mess.
Tyre Sizing - The most common appraoch is to run a bigger tyre in the front than in the back as you wil need the extra grip here and bigger tyres mean mre air volume that can absorb the impacts put upon your wrists. This isn't a rule just a guideline and its personel preference what size tyres you like to run.
(Acreditted to odsycalvin)
Spokes
There are three types of spoke: Plain guage
Double Butted
Straight PullSpokes come in different thicknesses or guages to give it its technical name: 10
11
12
13
14
15I suggest buying quality spokes, there not really that expensive but you will notice they build a better wheel, have better tension and keep there tension longer. Stay away from titanium spokes as they don't build a good wheel, they flex, undo often, snap, don't save much weight and are way overpriced.
Nipples
Nipples are what go on through the holes in the rim and thread onto the ends of the spokes to increase or decrease the tension. Nipple come in all shapes and sizes and you must make sure that the nipples you buy are the right size for the guage of spoke you are buying. Stay away from coloured aluminium nipples as they will rounded real easy, just stick to the basic braze ones.
The Theory Behind All Things Braking
Brake Levers
There are two types of lever: One finger - often very short lever blade, designed to brake using just your index finger.
Two finger - often have a medium to long lever blade designed to brake using two fingers or more if you are so inclined.Brake levers come in many different shapes and sizes but they all do one thing an one thing only, brake. Decide whether you like one of two finger braking and buy the appropriate lever for your needs. Longer elvers offer more leverage and lock better with less effort, whereas shorter levers are better for feathering and require a lot more effort to lock the wheel up.
Brake Calipers
Most BMX frames designed for Street, Park, Dirt, Flatland and Vert riding come with U-brake mounts positioned either under the Seatstays or on the Chainstays. Race orientated frames are the only places your likely to see V brake mounts on the top of the Seatstays.
With the ever growing popularity of Chainstay brake mounts brought about by the increased braking performance they bring due to physics and applied forces and Micro Gearing [25:9, 24:9, 23:8] manufacturers have had to redesign the brake caliper to get around the problem of chain clearence and inparticular chains rubbing on brake calipers. The answer is lower profile brake calipers coupled with angled chainstays, which together greatly increase the distance between the chain and brake calipers by lowering the brake caliper stack hieght. So if you have Chainstay brake mounts and want to run Micro Gearing then be warned, you will most likely need a low profile brake and a frame with angled chainstays otherwise you will have to settle for 30:11 gearing with a brake caliper thats not low profile and even that may be pushing it. If you have Seatstay brake mounts or brakeless you have nothing to worry about, you are free to run whatever gear ratio you like.
Brake Pads
Pads come in two compounds: Hard
Soft Pads come in four rough sizes: Narrow and long
Narrow and short
Wide and long
Wide and short
Brake Cables
There are two types of brake cable: Straight - With a straight cable brake setup you run a single brake cable from your lever to your calipers.
Gyro - With a gyro seup you run two gyro cables from the lever to the calipers.
Brake Modifications
The only brake modification I know of and have heard of is the 'Spoke Mod' this is where you replace the straddle cable with a Odyssey London Mod or a headset spacer with three holes drilled in it and use two spokes, one for each brake caliper to improve braking and also to be able to adjust each brake caliper individually.