Tiagra Rear Mech Compatibility Cassette Question

jam05 Posts: 41
edited September 2013 in Workshop
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.




  • markos1963
    markos1963 Posts: 3,724
    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
    gozzy Posts: 640
    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
    keef66 Posts: 13,123
    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.