Chain slip on top gear only

Tacks

Hoping that someone can help ...

My chain keeps slipping once I shift into my top gear. It is absolutely fine on all the other cogs in the cassette and will shift into and out of top gear perfectly well too. The chain is new and not too loose. The cassette is Shimano 105 and not very old - am thinking that the fact that all the other cogs work well means that the cassette is not knackered but might be wrong!

Any tips for solving it or is it simply a case of shelling out for a new cassette?

Thanks

getprg

The chain is new and not too loose. The cassette is Shimano 105 and not very old

In which case neither is likely to be causal - if it is "slipping" it sounds like the chain is hunting for the next gear - do you know which direction it is hunting - up or down?

If hunting up for cog 9 then it could be a number of possibilities eg a dirty rear mech not fully returning to "resting" (ie fully extended position), worn or bent cable also preventing return to resting position, poor indexing adjustment (this can be the case at cog9/10 even though other gears 1-8 index ok) or bent rear hanger.

If hunting for phantom cog 11 (yes I know 105 doesn't yet have 11 speed) it could be the stop adjustment.

nicklouse

top gear? the smallest cog?

if yes then check that the chain is not contacting the cassette lock ring. they are not all the same size and using a too large one can cause this issue.

Tacks

Thanks for the responses!

It's a 10 speed 105 cassette and I've just replaced the gear cables to see if that would solve the problem. I've also replaced the mech hanger as the old one was bent a tiny bit but that too didn't solve it. The shifting from 9 to 10 and back again is absolutely fine when the bike is in a bike stand; it seems to be when I put pressure on the pedals when I'm out on the road

I did upgrade my wheels a couple of months ago and the cassette needed an extra spacer put on the hub before the cassette to ensure that it didn't move. Not sure if that would have anything to do with it?

Will have a look at the lock ring and see if that's affecting it

Cheers

nicklouse

Tacks wrote:

Thanks for the responses!

It's a 10 speed 105 cassette and I've just replaced the gear cables to see if that would solve the problem. I've also replaced the mech hanger as the old one was bent a tiny bit but that too didn't solve it. The shifting from 9 to 10 and back again is absolutely fine when the bike is in a bike stand; it seems to be when I put pressure on the pedals when I'm out on the road

I did upgrade my wheels a couple of months ago and the cassette needed an extra spacer put on the hub before the cassette to ensure that it didn't move. Not sure if that would have anything to do with it?

Will have a look at the lock ring and see if that's affecting it

Cheers

what wheels? yes the 105 requires the shimano 10sp spacer to be fitted first on a shimano patten body. you did then reset the stop screws and tension?

Tacks

The new wheels are Fulcrum Racing 5 set. And I stuck a shimano 1mm spacer on before the cassette. I've adjusted the high low screws but haven't adjusted the tension although the jockey wheels are clear of the cassette. Perhaps they're not close enough? What's the guide for correct adjustment?

Thanks for your help

drlodge

Not too familiar with Shimano cassettes, but could it be that the smallest sprocket is on the wrong way round? The ramps would try and make the chain lift up.

nicklouse

Tacks wrote:

The new wheels are Fulcrum Racing 5 set. And I stuck a shimano 1mm spacer on before the cassette. I've adjusted the high low screws but haven't adjusted the tension although the jockey wheels are clear of the cassette. Perhaps they're not close enough? What's the guide for correct adjustment?

Thanks for your help

spacer is correct.

if you adjusted the High and low screws there is normally a requirement to adjust the tension. (cable tension)

adjusting the B screw (for jockey wheel clearance is not needed unless you have change cassette size. and often things work fine anyway.

amaferanga

Does this happen on both chainrings or just the big or just the small?

Tacks

Largest chainring and smallest sprocket at the back.

Cheers

keef66

You can't put the sprockets on backwards, the spline pattern doesn't allow it.

I still think it sounds like Nicklouse's suggestion of the wrong lock ring. How many teeth is the smallest sprocket? IIRC you need a different lock ring for 11T

Tacks

Thanks very much for the replies and advice. I think that it might well be the lock ring touching the chain - it certainly looks like it is. Funny thing is that it is the lock ring that came with the cassette but I wonder if putting the spacer on the hub for this new wheel has meant that the lock ring is getting in the way. Anyway have just ordered a couple of different lock rings for shimano 11T cassettes with the hope that one of them solves it!

Thanks again,

Tacks