# Bicycle Mechanics - Gear inches .... question

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View Full Version : Gear inches .... question

merckxxx
07-23-07, 12:47 PM
I am about to start riding a compact crankset.. (after quite a few years on a standard 52-39)

I will a have a 50/34 chain ring with 11-23 cassett 10 spd..

in terms of gear inches... what is the equal gear in a 39 chainring to a 34 -23 (34 chain ring and 23 cog).

it seems to me ..that a 39- 26 gear would have about the same gear inches as a 34 23 but I a math idiot.. who knows what would be the closest to the 34-23?

caloso
07-23-07, 12:50 PM
http://www.sheldonbrown.com/gears/

55-11
07-23-07, 01:09 PM
I am about to start riding a compact crankset.. (after quite a few years on a standard 52-39)

I will a have a 50/34 chain ring with 11-23 cassett 10 spd..

in terms of gear inches... what is the equal gear in a 39 chainring to a 34 -23 (34 chain ring and 23 cog).

it seems to me ..that a 39- 26 gear would have about the same gear inches as a 34 23 but I a math idiot.. who knows what would be the closest to the 34-23?

34-23 = 39.91 gi

39-26 = 40.5 gi

39-27 = 39.0 gi ....basically

gmason
07-23-07, 01:20 PM
I like this one: http://www.panix.com/~jbarrm/cycal/cycal.30f.html

vpiuva
07-23-07, 01:49 PM
Now since you're keeping the same gear inches but on smaller cogs you can wear the drivetrain out faster. Usually people go to compacts to obtain lower gear inches.

55-11
07-23-07, 01:52 PM
Now since you're keeping the same gear inches but on smaller cogs you can wear the drivetrain out faster. Usually people go to compacts to obtain lower gear inches.

+1... I was going to add this fact to my response, but... I didn't want to steal your thunder, v.

merckxxx
07-23-07, 05:20 PM
Now since you're keeping the same gear inches but on smaller cogs you can wear the drivetrain out faster. Usually people go to compacts to obtain lower gear inches.

Thank you for your insight.. and extremly important, and riviting, social comentary on the motivations of people who ask questions here..

Another reason people sometimes go to compact cranks are ..... because they come pre-equipped on bikes that have a great price on them .... and sometimes purchasers have realy old bikes that have completly worn out drive trains and are beyond... salvage, and / or, safe use..

when that person sees they have a cassett that has 10 speed instead of 7 (like they might have had on their old 52-39 machine) ..... they are happy to have sooooo many more.... gears.. to choose from..

and wearing out that new ....drive train is exactly what they endend to do .... as fast as possible!!!!

merckxxx
07-23-07, 05:22 PM
I like this one: http://www.panix.com/~jbarrm/cycal/cycal.30f.html

Thanks..... that is exactly what I was looking for. I knew this kind of a calculator had to exist somewhere I just didnt know where to find it...