32T - 20T in 29er = 32T - XX? in 26er . Thanks.....- Mtbr.com

# Thread: 32T - 20T in 29er = 32T - XX? in 26er . Thanks.....

1. ## 32T - 20T in 29er = 32T - XX? in 26er . Thanks.....

32T - 20T in 29er = 32T - XX? in 26er .

Thanks.....

2. 18t

3. 32/20 = 1.6
29" = 73.66cm
73.66 * 3.14 = 231.30 cm = Distance covered by 1 rotation of 29" wheel
231.30 cm * 1.6 = 370.08 cm = Distance covered by 1 rotation of 32/20 crankset on 29" wheel

To cover 370.08cm per 1 rotation of crankset on 26" wheel
26" = 66.04 cm
66.04 * 3.14 = 207.37 cm = Distance covered by 1 rotation of 26" wheel
370.08 / 207.37 = 1.78 = Gear ratio required on 26" to cover the same distance as 32/20 on 29"
32 / 1.78 = 17.98 = 18 = Rear gear to achieve 1.78 gear ratio with 32t chain ring.

4. I actually like using the gain ratio as it seems to take crank arm length into account. This, seems to me, is a better scale of the power it will take to turn the pedals over. I use Mike Sherman's page which will give many other calculations as well. Mike Sherman's Bicycle Gear Calculator

Quick and fast rule when addressing the gear range most SSers will use is about a tooth in the rear per wheel size. 26 to 650b= +1t, 26 to 29er= +2t, 29er to 650b= -1t, etc. And, 2t up front is similar to 1t in the rear. Confusing yet?

5. MATH IS FUN!

Ring Tooth count X Wheel Diameter

Divided by

Cog tooth count

Magic gear inch calculonomy

6. Here's the calculator I use, you can load it on your PC or run it from the web:

Rabbit, a singlespeed and fixed-gear cycling calculator

7. Thanks for the inputs.
Your guys are good in Math.

8. Originally Posted by 4nbstd
32/20 = 1.6
29" = 73.66cm
73.66 * 3.14 = 231.30 cm = Distance covered by 1 rotation of 29" wheel
231.30 cm * 1.6 = 370.08 cm = Distance covered by 1 rotation of 32/20 crankset on 29" wheel

To cover 370.08cm per 1 rotation of crankset on 26" wheel
26" = 66.04 cm
66.04 * 3.14 = 207.37 cm = Distance covered by 1 rotation of 26" wheel
370.08 / 207.37 = 1.78 = Gear ratio required on 26" to cover the same distance as 32/20 on 29"
32 / 1.78 = 17.98 = 18 = Rear gear to achieve 1.78 gear ratio with 32t chain ring.
You way over did that since everything cancels out except the difference in the wheel diameters. It's actually much simpler:

559/622 = 0.90
Comparing bead seat diameter of 26 inch to 29 inch for more accuracy since 26 and 29 are nominal measurements. Assumptions: tires are the same size and aspect ratio, chainring is the same size.

0.90 x 20 = 18

9. Originally Posted by Thor29
You way over did that since everything cancels out except the difference in the wheel diameters. It's actually much simpler:

559/622 = 0.90
Comparing bead seat diameter of 26 inch to 29 inch for more accuracy since 26 and 29 are nominal measurements. Assumptions: tires are the same size and aspect ratio, chainring is the same size.

0.90 x 20 = 18
Ya, but your answer will only get partial mark. You have to show your work for full mark.

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