Changing cassette without changing v. large chain ring
I bought my road bike second hand (with paperwork from the seller to prove he ordered it new rather than stole it) and according to that paperwork it has:
- Tiagra double 4500 9 speed chainset 170 39/52 on the front; and
- Tiagra 9 speed hg50 12-23 on the back.
I was aware at the time that this was highly geared setup and it is fine for my commute but if I go to the hills on the weekends I am finding that I get into my lowest gear far too quickly (even accounting for the fact I need to do more training).
My questions are:
1. I understand that an 11-30 cassette would be too big for a road bike or I would at least have to a larger rear mech cage - Is that right?
2. If I change to a 12-27 would I have to change: (a) the rear mech cage anyway? and/or (b) the chain?
3. If I change to a 12-27, is a low ratio of 1.44 low enough for a weekend rider to enjoy riding in the hills (box hill etc.) or do I need to bite the bullet and change the chainset? (I would rather not at this stage if I can avoid it given that a new cassette plus tools to fit it myself is about £30 vs over £100 for the chainset and I probably couldn't fit it myself).
Grateful for any input.
Top 1000 Contributor
I fitted a 30 tooth rear cassette on both mine and my wife's bike (from 25 tooth) both fitted with low end Shimano group sets and did not have any problem with the cage clearance, I did not even need to make an adjustment to the mech. Made a huge difference in the climbs around the Chilterns. A 30 is the absolute limit and in some cases may not fit, you need to try it. A 27 tooth should be no problem. I would say though that if you do fit a 30 then make sure you don't use it in the big rings front and back as the cage will be pulled forward a lot if you don't fit a slightly longer chain