Gearing

  • Discuss Gearing in the BMX Bike Tech forum in area BMX-Forum Community; what gearing do people run and what for? im interested in learning how you work gearing out, and to what purpose you use it for. im interested in... ...
  • Tags dirt jump
K

kam_holmes

New Member
Gearing post #1
what gearing do people run and what for? im interested in learning how you work gearing out, and to what purpose you use it for. im interested in getting a gear with more acceleration for use on the ramps.

views please people! :p
 
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infantry43RIDER

Guest
Gearing post #2
30-11 is what i run...

the norm would be running a lower gear for flatland and stuff like that but yea...it doesn't really matter what gear you use and for what as long as you are comfortable with the gearing that you have.

look on danscomp.com gear ratio and they will give you a list if you are interested.
 
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XIII

Guest
Gearing post #3
33-13T (little bit lower...i like it)
 
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Mr_Shrapnel

New Member
Gearing post #4
ok gearing is quite simple and you will cover it in GCSE design and technology. it goes like this: a sprocket (or gear) has teeth. when two (or more) sprockets are joined together via a chain, you will get a gear ratio. this is simply calculated by a simple formula, which is the number of teeth on the driver sprocket divided by the number of teeth on the driven sprocket.
the standard gear ratio which the vast majority of people use is 2.75. this is achieved by running a 44-16 set up (44t on the front - or driver sprocket, 16t on the freewheel - or driven gear).

as i just said the standard gear ratio which most people use, and find the best is 2.75, however this does not mean that you only need to run a 44t-16t set up to get this ratio. if you run a smaller driver gear eg 36t, and run a smaller driven gear eg 13t you will get a similar ratio to the 44-16 set (2.76), and you will have the advantages or a small gearing eg light weight, and out of the way.

the general rule is that the greater the gap between the number of teeth on the driver gear compared to the driven gear will give you a higher gear ratio, eg 44-13 = 3.38. likewise the smaller the gap between the number of teeth on the driver gear compared to the driven gear results in a smaller gear ratio eg 39-16 = 2.43.

the greater the gear ratio number, means that you will get a higher top speed, but a lower acceleration due to the fact that it will be harder to pedal.
the lower the gear ratio number, results in a lower top speed, but a higher acceleration due to the fact that it will be easier to pedal and cause a greater number of chain links to move over the driven gear in a short space of time.

to keep a gear ration similar to that of a 44-16 use these combinations.

44-16
39-14
36-13
33-12
30-11
28-10
25-9
 
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sentaafEQpovar

Guest
Gearing post #5
u think you could clear a 40 ft gap with 54/9 going full speed on smooth cement off a 10ft jump?
 
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trailkillerje

New Member
Gearing post #6
im riding a 44-17 for dirtjumping i love this gear its perfect. also i have a 36t for park riding but still a 17t freewheel
 
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XIII

Guest
Gearing post #7
you couldn't make it up to hte top of the ramp with a gearing like that? the 54-9 was it?

44-17 is too hig.
 
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trailkillerje

New Member
Gearing post #8
44-17 is good for my local jumps i cant use it on every dirtjump i ment it was perfect for me as where i live but i have 5 differents sprocket 44t 36t 44tbent bad, 42t,39t, all of them gifts and 2 freewheels 17t and 16t
 
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federal_rider12

New Member
Gearing post #9
i ride 36-16 everyone says you cant get speed with that or it sucks because its such a low ratio but its just great for me i can get lots of speed with it and not be panting when im done and its a huge plus because if there is a ramp with not enough space to get speed with running a 44-16 ratio(includes everything Mr_Shrapnel said) but i could do it with the quicker acceleration and i dont have the money to buy a cassette hub but then my chain wouldnt clear the brake so im sticking with my 36-16 its great!!!! and no matter what anyone says its not a gearing that gets you no speed at all
 
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sentaafEQpovar

Guest
Gearing post #10
actually it does lower your op speed... but maybe u dont need your top speed... higher gearing i think would be great for dirt jumps, ie, small free wheel with 44t or even more, cuase then your top speed wold be hella fast, and if u had a really long straight away before your jumps or a nice downhill, then there wouldnt really be much problem
 
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Mr_Shrapnel

New Member
Gearing post #11
federal_rider12 said:
and no matter what anyone says its not a gearing that gets you no speed at all
that is just retarded, try telling that to any mechanical engineer. of course its to do with the gearing! obviously it is to do with the rpm and crank leverage too, but the gear ratio is integral to a bikes performance, especially a bmx.

rememmber this thread when you change over to a 2.76 ratio. you will, you will.......
 
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kam_holmes

New Member
Gearing post #12
thanks everyone for you input, Mr_Shrapnel, great piece, thank-you. think ill be going for a lower gear ratio
 
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federal_rider12

New Member
Gearing post #13
what im saying is yes it does lower your speed and you have much quicker acceleration but still i can get really good speed i can get as much as i need and with the 44-16 it took me alot more power to pedal and longer to get speed but ive never needed to get flying and never will because i dont race you may think that staying with a 44-16 ratio is the best thats what i thought before so thats why i was going to get the 39t chainwheel and get that 15t freewheel, which would be closer, but i decided to go with the 36 and its much better then what i thought so i say 44-16 ratio isnt the best for me
 

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