Whats happened to my rear gears?

[Dr Murdoch]

Ive just stripped down my rear derailleur and front crank, cleaned off all of the gunk and re-fitted. I've also put on a new chain.Its a ten speed cassette.

Unfortunately now I cannot get the rear shifting properly. It works fine from the lowest (biggest) gear down to 9, but when i try for 10, it slips and jumps between 9 and 10, before finally settling for ten. No amount of adjustment on the cable solves the problem, it only adversley effects the rest, notably gear 1.

Could it be the chain length? It was too long, so I took some links out and the derailer takes up the tension when the rear and the front are on the smallest.

[Bacon Is Proof]

Could be a new chain/worn cassette combo causing the issue.
If it's not getting far enough over on the last sprocket but fine on the rest, have you tried winding out the limit screw at all? Wouldn't take much.

[Dick Sternum]

New chain on a worn cassette would be my guess.

[Dr Murdoch]

Thanks chaps.

Ive never needed to change a rear cassette before, but I'm willing to try. Do I need to get any specific tools? And is it a pain in the ass?

Regarding the limit screw, is that the one that pushes on the frame?

[FredClogs]

If it worked before you cleaned it and now doesn't it's unlikely that something been worn out by cleaning it. Relubricate the chain then index the rear deuralier from scratch, there's a ton of youtube vids that'll show you how.

[fizzwheel]

Or alternatively if you put the old chain on does the problem go away ?

I would not fiddle with the limit screw, if it was fine before you changed the chain its unlikely in my opinion that the limit screw not being adjusted properly is the cause of your problem

I'd agree with the others new chain on worn cassette is the likely cause of your problem

[Justin S]

Dr Murdoch said:

Thanks chaps.

Ive never needed to change a rear cassette before, but I'm willing to try. Do I need to get any specific tools? And is it a pain in the ass?

Regarding the limit screw, is that the one that pushes on the frame?

Thats the B tension screw. That adjusts the chain tension by pulling the rear mech backwards. I would undo the gear cable and see that the mech drops down to the smallest sprocket. Then spin the cranks and push the mech to the largest sprocket and see that it sits there. Then re fit the cable. Remember that the mech mustnt have a tight cable when on the smallest sprocket, as it the shifter has an tension shift for the 1st to 2nd shift.
If you havent changed any parts and it worked before then I suspect its something small like this.

[Dick Sternum]

When fitting a new chain I normally lay the new one next to the old and size it as close as possible, bear in mind that the old chain will likely have stretched and will therefore be longer. If in doubt, count the links.

To remove the cassette you'll likely need a cassette removal tool (some are designed to be used with a socket set whilst others have a handle built in) and a chain whip. It's a bit fiddly as you need to use the chain whip to stop the cassette spinning whilst undoing the lock nut with the removal tool, but it's easy enough. Also be sure to get the correct type of removal tool as some cassettes (Campagnolo) need a different one, but if you're not running Campag a Shimano one will likely be fine.

Park tools have a load of good guides on pretty much all areas of maintenance including indexing. The limit screws control how far in (towards the frame) and out the rear mech moves and will normally be together on the body of the mech somewhere.

https://www.parktool.com/blog/repair-help/cassette...
https://www.parktool.com/blog/repair-help/rear-der...

DS

[J886ATV]

Dick Sternum said:

New chain on a worn cassette would be my guess.

This I'd believe if shifting is an issue in the middle of the cassette. Reckon my 9 & 10 sprockets get less than 10% use, so can't believe they will be worn

[moonigan]

Dr Murdoch said:

Thanks chaps.

Ive never needed to change a rear cassette before, but I'm willing to try. Do I need to get any specific tools? And is it a pain in the ass?

Regarding the limit screw, is that the one that pushes on the frame?

Chain whip and cassette lock ring tool are the only special tools you need. This assumes you have socket set or preferably torque wrench. You need to the chain whip to undo the lock ring to stop the cassette spinning on the hub. Depending on the make/model of cassette you will have a number of spacers that need to go back in the same order they came off and you might also have a spacer on the hub. 15 mins work tops.

P

[Dr Murdoch]

Thanks for the replies.

My current cassette is an 11-34 Tiagra, I was hoping to upgrade to 105 or Ultegra, but it appears that the closest match is 11-30?.

If I go with this, what adjustments will be required on the derailleur?

[Wilmslowboy]

Dr Murdoch said:

Thanks for the replies.

My current cassette is an 11-34 Tiagra, I was hoping to upgrade to 105 or Ultegra, but it appears that the closest match is 11-30?.

If I go with this, what adjustments will be required on the derailleur?

No adjustment should be required, but if you do a lot of climbing you might mis your 34.

Ideally you should check your chain for stretch, normally best to replace a chain with a cassette.

[gazza285]

Chains wear, but they do not stretch.

[HiAsAKite]

gazza285 said:

Chains wear, but they do not stretch.

Really ?.. why do we have chain stretch tools such as this https://www.chainreactioncycles.com/mobile/park-to... which measure increase in length between links?

I thought a symptom of wear, is stretch or increase on length..

[Justin S]

They measure how much the roller on the pin has worn and the links dont stretch, they basically wear.
http://pardo.net/bike/pic/fail-004/000.html

[HiAsAKite]

Justin S said:

They measure how much the roller on the pin has worn and the links dont stretch, they basically wear.
http://pardo.net/bike/pic/fail-004/000.html

Ok- learn new thing every day :-)

[Wilmslowboy]

Justin S said:

They measure how much the roller on the pin has worn and the links dont stretch, they basically wear.
http://pardo.net/bike/pic/fail-004/000.html

Ok, fair point.

The impact is the same, sloppy chain, that lengthens (....could be said to have stretched )

[Justin S]

Wilmslowboy said:

Justin S said:

They measure how much the roller on the pin has worn and the links dont stretch, they basically wear.
http://pardo.net/bike/pic/fail-004/000.html

Ok, fair point.

The impact is the same, sloppy chain, that lengthens (....could be said to have stretched )

Its just the way its always been said as 'stretched chain' but actually its the wear between the pins and the inner part of the links. I know we all wish we had muscles big enough to stretch a chain, but even though now chain side plates are very thin , in comparison to an 1/8 inch chain, as an example , stretching them would be a disaster for all who can

[anonymous-user]

Justin S said:

I would undo the gear cable and see that the mech drops down to the smallest sprocket. Then spin the cranks and push the mech to the largest sprocket and see that it sits there. Then re fit the cable. Remember that the mech mustnt have a tight cable when on the smallest sprocket, as it the shifter has an tension shift for the 1st to 2nd shift.

I was going to say this too. I'd do this first before buying tools and cassettes. If its not dropping in to 10th I'd be amazed if a new chain on an old cassette caused it, because the derailleur and cable aren't under tension to do it. They're not "lifting" the chain up to a sprocket with more teeth, which is typically where you get issues.

[Dr Murdoch]

Op here for an update.

I fitted a new cassette, but the same issue remained of the chain doing a hokey-kokey with the smallest sprocket on the rear.

So I played around with the adjuster screw that pushes against the frame. BINGO!

Well sort of, I think. The chain drops down the cassette and on to the respective sprockets with on click on the lever. My only slight issue/cocncern, and it is slight, is that the chain seems to drop on to the smallest sprocket, rather than 'glide' on to it like the others.

Should I be concerned? Is it easy to fix? If it isn't, then I can live with it.