Chain Length ???

Huddster1

Hi All, I have just changed my crank-set on my Specialized Allez road bike 53-39 teeth to an FSA mega exo 50-34.Everything went smooth until i test rode the bike and have now encountered the problem of the chain rubbing the top chain ring when i'm in the lower gears on the cassette (last 2). Would i need to shorten the chain to try and eradicate the problem or go for the other option of purchasing a narrower chain to give more clearance ??? Your suggestions would be greatly appreciated !

ChrisSA

You should change into the top ring!

If you're on small-small then the chainline will be out.

nicklouse

as above sounds like you are using gears that you should not be using.

on most set ups you can not use all the rear cogs while just using the inner front ring.

Wheelspinner

Welcome to the down side of compact crank gearing..

I tried one, and soon realised I was doing a LOT more shifting to avoid the crossed chain problem. Only way to minimise that was to use a different cassette, which defeated the purpose of the compact in the first place.

The compact gave me nice low gears for hills, anda still-decent top speed since I rarely attempted 53/12 anyway, but otherwise I didn't get on with it that well.

Went back to the standard 53/39 instead.

John.T

Altering chain length would make no difference. It is the greater difference between the chain rings that causes it. As said avoid using the extreme cross over gears. 50/19 is the same gear as 34/13 so that should be the point to change rings. If you are climbing and need to go lower from 50/19 then get on the small ring before you run out of gears. You soon learn to judge the road ahead as to which gear set you should be using.
Use this calculator to see what ratios you actualy have and which are duplicated. There are more duplications with 53/39 than 50/34 which is both an advantage and a curse on both. Compromise is needed.
http://sheldonbrown.com/gears/