Compact chainsets

[Deleted User]

I realy can't think of any reason why you wouldn't be able to use a 12-27 (assuming you're on shimano). That would work fine with a short-cage rear mech too.

Only issue is if you were on campy, and then you'd be switching to a 13/29 (i'll leave it to a campy fan to advise on any need for a new mech). I guess that the shop may have been concerned at you loosing the top end by dropping from an 11 to a 13. If this is the case I'd suggest using teh 13/29 for traning (and learn to spin on the descents) and then swap to the 11-25 for race day when you're on flatter courses.

popsider

Campag officially you'll need a medium cage mech for a 29 sprocket - unofficially other people reckon they've used a 29 with no problem - but you may need to lengthen the chain of course.

If you use Campag then why not get a cheap compact - I think that's a better option than riding about with a cassette with a 29 on it because of the gaps between the sprockets - though for training you may not mind it.

Agree with D74 there is no reason why you shouldn't use a 12-27 your bike shop have got that wrong - maybe if you have Campag they just meant campag don't do a 12-27 so you'd have to go to 29 which officially you shouldn't with your mech.

Unknown

I have Shimano ultegra components on the bike, I suspect it may have something to do with that. The shimano site also says I cannot use the 12-27... stupidly I have forgotten why not. The LBS chap did tell me...

[Deleted User]

The plot thickens. Would be fascinated to know why, as I ran a 12-27 for 8000 miles on the commute which is full ultegra 9 speed (now a 12-25) and a 12-27 on my race bike (full 105).

Ratbag

I've got Ultegra 9 speed and I use 12-27. Which is making me wonder whether I still should think about a compact or just get out and do more hills!!!

Unknown

I feel real stupid now for not remembering the reason why, it was plausible at the time. Then again, I am not particularly technical...

Will ask what my new LBS thinks of it...

popsider

You can definitely use a 12-27 - shimano do say you it's OK for a short cage mech - unless your chain was very short for your 11-21 and they were saying it wouldn't wrap the 27 on the big front ring without a new chain.

popsider

say you!?? Say "that" is what I mean.

[Deleted User]

There are some frames that won't take an 11 tooth as the chain catches, but I can't seee why not a 12.

Unknown

Nothing to do with the chain, I needed a new one anyway, as the old one was too short.. something to do with the derailleur perhaps?

Damn, stupid memory... :-( LBS will have to give the answer...