Gearing equivalents?

[haloblack]

ANy one have any practiced theories on gearing equivalents? That is to say, if I run a 34x20 on a 26" bike, what woudl I run on my 29"? I currenly am running 32x20 on my Karate Monkey. It seams great, but we have lots of long, steep climbs in so cal and Im wondering if my gearing in a smige to tall. Or Im a smidge to weak...hmmm. :confused:

[hophead]

I hope I'm figuring this out correctly.

Here it goes:

A 29" wheel has a circumference that is about 9% more than a 26" (depends on tire size too , of course) so you want a gear ratio that is about 9% less than you are currently running. A 34:20 equals a ratio of 1.7:1. Less 9% is 1.55:1 which is about a 32:21(1.52:1) or 34:22(1.55:1).

[wooglin]

I hope I'm figuring this out correctly.

Here it goes:

A 29" wheel has a circumference that is about 9% more than a 26" (depends on tire size too , of course) so you want a gear ratio that is about 9% less than you are currently running. A 34:20 equals a ratio of 1.7:1. Less 9% is 1.55:1 which is about a 32:21(1.52:1) or 34:22(1.55:1).
Dang. Thats some math. I just add two teeth on the back.

[davkatreb]

What's that in gear inches?

[riderx]

Use gear inches and use the same on both bikes. For instance, I run 2:1 on my 26" (34x17) which is 52". When I built the 29", 36x20 worked out to be the same.

[riderx]

A 29" wheel has a circumference that is about 9% more than a 26" Using diameter I get a 11.5% larger wheel. Diameter is used in gear inches, so I figure this is the way to calculate it. Could be wrong though.
My math:
A 29" wheel is 3" larger than a 26" wheel.
3/26 = ~11.5%

[hophead]

Using diameter I get a 11.5% larger wheel. Diameter is used in gear inches, so I figure this is the way to calculate it. Could be wrong though.
My math:
A 29" wheel is 3" larger than a 26" wheel.
3/26 = ~11.5%
Oops, your right. I got my numerator and denominator backwards. Your way is easier too.

[haloblack]

Holy moly I feel dumb. OK, so based on the 11.5% diameter, what are we looking at for the equiv of a 34x20 on a 26" bike?

Im thinking 32x22? Thats seems crazt low though...O I wish I would have gone to school instead of ditching and riding my bike!

[lensmire]

Go to this site and all the math is done for you.
http://vps.arachnoid.com

[lensmire]

My bad, at the home page, go to bicycles on drop down menu. http://vps.arachnoid.com/bike/

[riderx]

Holy moly I feel dumb. OK, so based on the 11.5% diameter, what are we looking at for the equiv of a 34x20 on a 26" bike?

Im thinking 32x22? Thats seems crazt low though...O I wish I would have gone to school instead of ditching and riding my bike!Using Wooglin's way (which seems to be a good rule of thumb) you would want 34x22. Using gear inches that is 44.2 (your 26") vs. 44.8

[tryandgetme]

I'll probably use the TLAR approach followed by TDFRYBTMAI approach, repeating as neccicary: That Looks About Right, That Dosent Feel Right Yet Better Throw Money At It,