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I have a Giant TCR road bike and replaced the crankset a few weeks ago. The first time I've done that job but it seemed simple enough.
I've ridden it twice since and all seems fine but I noticed when cleaning it afterwards that the chain won't shift onto the largest sprocket at the back. I'm not sure how long that's been the case as both rides since replacing the cranks have been flat so I had no need to use that gear combination.
I can adjust the limit screw and see if that cures it, but I'm mystified as to why I would need to randomly adjust a limit screw on a rear mech that was previously set correctly. All cables, inners and outers are fine.
Should I just adjust the limit screw and get on with my life or investigate further?
I.e. is it more likely that the drive side crank perhaps isn't fitted properly and I should re-visit that, than I would need to randomly adjust a rear mech limit screw for seemingly no reason? (drive-side cranks/chainring look and feels fine though).
I'm sure I would have tested the full range of gears after fitting the new crankset but honestly don't remember.
Has your chainring size increased or decreased?
No, cranks/chainring etc all like-for like.
The limit screws were set correctly less than 2 months ago so even if its possible that they could drift over time (and I'm not sure they ever really do?) I deffo don't think they would drift or loosen over the course of a handful of rides.
Is it actually hitting the limit screw? If you've got a bit of exposed cable try giving that a pull in addition to shifting in case the cable has slipped or the outer has given a bit.
no, likely to be just a coincidence.
Are you sure it's the B screw that needs adjusting?
Cheers both- good point on the limit/B screws, I will investigate further. I can't get the bike in the stand til later but will have a proper look then.
If its not normal to need to adjust rear mech after replacing the cranks I'll investigate the rear mech further and consider it a coincidence, as Cynic-al says.
Could the crankset have spacers in a different position putting the chainrings further outboard?
New chain, old cassette?
I don't recall seeing any spacers so as far as I know they are not in the equation.
Yep got a front mech and shifting on the front chainrings is fine and same as always- there was no adjustment to the front mech at all.
Yes, its a new chain on old cassette- could that be it?
I don't think cassette has loads of miles on it but I didn't replace it along with the the chain and crankset..
It could be. Either try the old chain, or just ride more and see if it works better when stretched. Playing with the limit screw is worth trying, to allow the mech to give the chain more of a shove (that the old one didn’t need when stretched). Doesn’t sound like a chainline issue, given the like for like swap and front mech trimming not needing adjustment.
Interesting, thanks all!
I'll investigate the rear mech when I can it into the stand and if nothing is obviously wrong at least I can hopefully just adjust the limiter and be content that its likely the new chain/old cassette combination.