Bicycle Mechanics - compact crank, gear compatability (noob)

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA
hopsing08
08-13-09, 04:26 PM
My question is I got a Rival comapact crank; 50/34T and a Shimano Ultegra 12-25T cassette. (as i have heard many times that shimano cassettes are a little more quiet.) Is this setup good? did i lose too much top end or with my gearing did i completely negate my compact? i researched to compact part but i guess i just trusted the guy at the bikeshop to know what cassette would go well with it.
i do climb alot though and i want to make sure that my cassette compliments my Compact crank. thank you for your time and patience.

idcruiserman
08-13-09, 06:10 PM
No way to answer that question. Put it on your bike and try it out. I use 11-23 with my compact crank.
hopsing08
08-13-09, 06:21 PM
No way to answer that question. Put it on your bike and try it out. I use 11-23 with my compact crank.

11-23 is the one i see most commonly. i just wanted to make sure that my 12-25 is good. i know there are some gear heads out there.

Al1943
08-13-09, 06:26 PM
You probably made the best choice.

Al
DaveSSS
08-14-09, 06:42 AM
This takes some simple math to analyze. Your 50/12 is a bit higher gear than a 53/13, so you've lost most of the top gear that a lot of bikes have. The lowest gear is just abit higher than a 39/29, so you've got more low gear than a typical 39/27.

12/50 x 53 = 12.7

25/34 x 39 = 28.7

Using a 50/34 with an 11-23 doesn't do a thing for the gearing range, compared to a 53/39 with a 12-27, but it does reduce the big cog jumps at 21-24-27.
hopsing08
08-14-09, 10:24 AM
So essentially with the setup that I have, I lost a little top end speed but I did gain a little extra for climbing. Since I wont be sprinting for stage wins I'm sure I wont miss the top end.

Thanks DaveSSS and Al1943 for your input.
urbanknight
08-14-09, 11:18 AM
^ Correct.

Should you feel the need to change anything in the future, this is a great resource.

http://www.sheldonbrown.com/gears/