# Bicycle Mechanics - same gear inches?

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View Full Version : same gear inches?

Plow13
04-03-08, 11:49 PM
is a 42-22 pretty much the same as a 35-18

SweetLou
04-04-08, 12:21 AM
I have no idea what size wheels you are running, so I can't give you the gear inches. But if you were running 26" then it would be 49.6 gear inches for the 42-22 and 50.6 for the 35-18

sivat
04-04-08, 01:04 AM
Assuming the same size tire, the 35/18 will feel slightly harder, but not much.

Bill Kapaun
04-04-08, 01:17 AM
2% IS pretty much the same.

Plow13
04-04-08, 09:45 AM
oops! i am running 700x32c...but yea its the same tire size...Just trying to get some info on some gear changes i am going to making in the future

HillRider
04-04-08, 09:56 AM
Gear-inches = (chainring teeth/cog teeth)*wheel diameter. For both 27" and 700c wheels, the usual wheel diameter value used is 27.

In your example a 42/22 would be (42/22)*27 = 51.5 gear-inches and a 35/18 would be (35/18)*27 = 52.5 gear-iches so the difference is about 2% which is negligable.

You can use this equation for any gear combination you are interested in comparing.

CdCf
04-04-08, 10:02 AM
For any two sprocket combos giving the same gear ratio, the one with the bigger sprockets will be heavier, but will also provide greater chain engagement, improving efficiency and safety slightly.

San Rensho
04-04-08, 10:50 AM
Essentially equivalent gearing. You will not be able to tell the 1" difference in gearing between the two.