Tiagra Rear Mech Compatibility Cassette Question

jam05

Hello all

My girlfriend has a 2011 Trek Lexa SL like the one in this link:

http://road-bikes.findthebest.com/l/356 ... ek-Lexa-SL

She wants to have an easier gear for going up the hills. Is it possible to put a different cassette that can enable her to do this? - at the moment it's a 11-26 9 speed cassette on a 50/39/30 triple crankset. The derailleur is a Shimano Tiagra.
Would a 11-30t be too much for the rear mech?

Alternatively, would it be better to go for a granny ring at the front?

If anyone can help, I'd be very grateful.

Cheers

James

markos1963

It should be fine as they would be using a long cage rear mech for the triple chain set anyway. I have a Tiagra set up(10sp) on my tourer and that runs 30/30 with no problems(apart from the fact I never use it!)

gozzy

Look up the shimano tech doc for 9 speed tiagra, 4400 I think it is, that will tell you the rear mech capacity. I would hazard that it'll be 28t but you'll probably find you can push it to 30. You might need to alter the chain length slightly.

keef66

She already has what many would regard as a granny ring at the front. Fitting a smaller chainring than 30t you'd probably find you're exceeding the range of the front mech and shifting would suffer. I'd try a 30t cassette first. As mentioned already, you may need a slightly longer chain, and adjustment of the B screw to make sure the upper derailleur pulley doesn't foul the largest sprocket.