Changed rear wheel on road bike and now the gears are out

[IntegraTypeR]

Hi all,

I've just fitted a new set of Shimano RS80s to my bike (replacing the previous Mavic Aksiums) and now the rear shift is quite erratic. I switched over the cassette from the previous rear wheel at the same time. Are there any fundamental reasons why switching wheels like this would cause this kind of problem? I'm finding that the rear shift is struggling to shift onto the top and bottom gears (shifting between the other gears seems fine). I've tried quarter turns of the barrel adjuster on the derailleur (in both directions) just to check if it's a cable tension issue, but that tends to make it work ok when shifting in one direction, but then causes problem in the other direction. I've double checked that the wheel is correctly seated and it appears to be straight.

Thanks for any advice you can give

Ian

[Ian Lancs]

IntegraTypeR said:

Hi all,

I've just fitted a new set of Shimano RS80s to my bike (replacing the previous Mavic Aksiums) and now the rear shift is quite erratic. I switched over the cassette from the previous rear wheel at the same time. Are there any fundamental reasons why switching wheels like this would cause this kind of problem? I'm finding that the rear shift is struggling to shift onto the top and bottom gears (shifting between the other gears seems fine). I've tried quarter turns of the barrel adjuster on the derailleur (in both directions) just to check if it's a cable tension issue, but that tends to make it work ok when shifting in one direction, but then causes problem in the other direction. I've double checked that the wheel is correctly seated and it appears to be straight.

Thanks for any advice you can give

Ian

Fitted the cassette spacers (if any) the right way round?

[IntegraTypeR]

Ian Lancs said:

Fitted the cassette spacers (if any) the right way round?

I'm 99% sure I took the cassette off and put it on in the same order but I can double check (I changed it a few days ago and my memory isn't all that good!). If you do fit them the wrong way round, what effect does that typically have on the position of the sprockets either side? can it make them further apart, or closer together?

In the past when I've changed wheels I've not had this problem, so I was wondering if the new wheel should be 100% compatible with the old one - i.e. it should not be expected that I would have to make gear adjustments when switching them over.

Thanks

[paulmon]

My Fulcrums came with a spacer that had to be fitted but the shimanos didn't have one so maybe the spacer isn't required. Even so my gears were out slightly and I had to reindex them. There is a really good how to index gears guide somewhere on the web. Probably worth a look.

[shalmaneser]

The gears will almost certainly need re-indexing, as different wheel will have slightly different offsets, and as you've found it only needs to be slightly out for the gears to be poorly indexed.

You'll also probably need to adjust the limit screws.

[IntegraTypeR]

Oh dear

I just found a spacer that was still on the old wheel (on the inside position of the freehub so I missed it when I lifted the cassette off). Perhaps I should have moved that over with the cassette! I really hope it's simple user error and I'm very happy to look stupid if it's as simple as putting that spacer on.

Let me go try - thanks for all the advice so far

[IntegraTypeR]

Yep, that was it - changing smoothly now. I also re-read the installation guide and found a small box that says you need a spacer for a 10 speed cassette. It's quite impressive how that 1mm offset makes the gear change behave so badly - now I can understand how just the tiniest knock to the mechanism can screw up your gear change.

Never have I been happier to be an idiot

Thanks again

[Matt London]

I find that my gears need a bit of tweaking when I swap to and from Rs80's and other wheels. Yes I do use the spacer