[G-spot]

well I'm new to this and have a Transition trail or park that I use for pump track/BMX track, 4X and want to start DJing, so my Question is I have a 28X14 gear on the bike would that be fine for what I want or should I try something else? I have a friend who said I should go to a 28X12 or 13. Just wanted to see what some other people say?

 

[sittingduck]

28/14 is a bit light. I run 28/12, but that's a bit heavy.... It's more of a personal preference. Ride it for a while and you should be able to figure it out.
Divide the large number by the small one to get your actual gear ratio. This will let you compare different combos subjectively.

 

[Bikael Molton]

too light.
I ride 28-12, but you might want to try 28-13 first.

 

[JGill]

26-12 works perfect for me

 

[Dirtjumper999]

28-12

 

[jerseydirt]

28-13

 

[cmc]

the formula is front teeth divided by rear teeth X wheel size should equal roughly 55 gear inches)

55 gear inches is the classic bmx gear ratio because the standard race gear was 44/16, and 44/16= 2.75 X 20 = 55. as the gear inches number goes up, it gets harder to pedal but you go faster.

SHORTCUT: with 26" wheels, double the rear cog + 2 to get what your front sprocket should be. so....

26/12
28/13
30/14
32/15
34/16

 

[G-spot]

Thanks everyone

 

[v-digit]

30:13 was a good one when i wasnt running 25 upfront.

 

[sittingduck]

SHORTCUT: with 26" wheels, double the rear cog + 2 to get what your front sprocket should be. so....
26/12
28/13
30/14
32/15
34/16

Close, but as they get bigger, the gear gets lighter.
26/12 = 2.1666666666666666666666666666667
28/13 = 2.1538461538461538461538461538462
30/14 = 2.1428571428571428571428571428571
32/15 = 2.1333333333333333333333333333333
34/16 = 2.125

 

[cmc]

Close, but as they get bigger, the gear gets lighter.
26/12 = 2.1666666666666666666666666666667
28/13 = 2.1538461538461538461538461538462
30/14 = 2.1428571428571428571428571428571
32/15 = 2.1333333333333333333333333333333
34/16 = 2.125

true. i called it a "short cut" b/c it is easier math to get close to 55 gear inches. most people seem to be scared of formulas and calculators. apparently you're not !

 

[sittingduck]

true. i called it a "short cut" b/c it is easier math to get close to 55 gear inches. most people seem to be scared of formulas and calculators. apparently you're not !

Yes sir, I do like me some figures and calculations.
http://sheldonbrown.com/gears/
This site even lets you factor in your crank arm length for gear inches....
28/12 on a 26x2.35 tire with 175mm cranks is 61.6 gear inches. :biggrin:

 

[cmc]

Yes sir, I do like me some figures and calculations.
http://sheldonbrown.com/gears/
This site even lets you factor in your crank arm length for gear inches....
28/12 on a 26x2.35 tire with 175mm cranks is 61.6 gear inches. :biggrin:

I can see how crank arm length affects torque. But, not sure that it affects gear inches: For one full 360 degree rotation of your cranks (however long they are), how far does your bike move? You could do the same calculation without having any cranks attached and just rotate the spindle 360 degrees.

 

[sittingduck]

I can see how crank arm length affects torque. But, not sure that it affects gear inches: For one full 360 degree rotation of your cranks (however long they are), how far does your bike move? You could do the same calculation without having any cranks attached and just rotate the spindle 360 degrees.

You're probably right... I think the crank length might be there for the other various calculations that are on that calculator.
Smaller cranks do feel like they are more "spinny" though.

 

[Savage_Animal]

26-12 works perfect for me

Thats what I got too its pretty nice.

 

[EGGS]

25-9 on a bmx ....

36-16 on a big bike

 

[G-spot]

well I've decided to go with a 28X13 set up.28X13 =a 56 gear ratio

 

[UiUiUiUi]

sorry to resurrect this but what crank length are you running on single speed dirt jump bikes?

 

[Zenkis14]

20" BMX = 25x9
26" DJ = 32x15

 

[Bikael Molton]

175mm

sorry to resurrect this but what crank length are you running on single speed dirt jump bikes?

 

[sittingduck]

I think 175 is probably the most common size.

 

[cmc]

sorry to resurrect this but what crank length are you running on single speed dirt jump bikes?

i prefer 180... but i'm 6'1" with long legs, and always run XL/XXL frames. 175 is probably better for a medium height rider and a short bike.

 

[pnj]

170. bmx and 26

 

[basikbiker]

used to run 28:13 but spins out to easy, so now rockin a 30:13 on 26's bytheway