chain skipping

slideshow bob

I have an 8 speed Deore rear mech and recently giving trouble after long and reliable service. Problems started sometime after I replaced the cable, but maybe unrelated. Chain started to skip from time to time. I've replaced the chain and the problem is slightly worse. I adjusted the cable tension, had the LBS adjust it too and that helped, but didn't eliminate the problem.

I've stripped, cleaned and lubed the mech and jockey wheels. I've lubed the cable. There is a little play in the mech, but not much. Minor improvement, but that might be imaginary after all the time I've put in. Still skips under pressure, but never on the bike stand.

How do I tell if the jockey wheels need to be replaced? Or the cassette needs replacing? Or if the mech is approaching end of life? Or other possible solutions?

DirkVoodoo

Well, if you have looked at all those areas, time to start looking elsewhere.

Have a proper look the freehub body. What type of wheels?

colm_gti

Is there any lateral play in the jockey wheels? You can get away with some lateral play, but if there is more lateral play in the top wheel than the bottom wheel your chain will skip. You can buy new jockey wheels for ~€20 and they're dead easy to fit.

Search google for photos of a worn cassette to see if yours looks anything like theirs.

If your jockey wheels are ok, your cassette is ok, your chain is ok and cable is new and indexed properly, I'm at a loss as to what it could be and await the expert advice

DirkVoodoo

colm_gti wrote: »

Is there any lateral play in the jockey wheels? You can get away with some lateral play, but if there is more lateral play in the top wheel than the bottom wheel your chain will skip. You can buy new jockey wheels for ~€20 and they're dead easy to fit.

Jockey wheels are designed to have more play in the upper wheel, it's a guide wheel and if it doesn't have more lateral movement than the lower one, the chain won't shift smoothly.

EDIT: I realise this is entirely dependent on which one you are calling the "top" wheel. If it's the guide pulley, then I'm right. If it's the tension pulley, then you may have a point!

I still think freehub, game on!

slideshow bob

DirkVoodoo wrote: »

Well, if you have looked at all those areas, time to start looking elsewhere.

So I'm not sure how to tell if the jockey wheels need replacing. The bushings seems fine, they are straight, run free and have no sign of damage. No visible signs of wear if this is anything to go by.

I'm not sure how to check cassette wear reliably. The teeth on the cassette are asymmetric when new anyway, so what tells me if they've worn to the point of replacement, apart from skipping with a new chain?

DirkVoodoo wrote: »

Have a proper look the freehub body. What type of wheels?

Airline 1 wheels on a hybrid bike. They have been really great over thousands of kms. Never had to true them. I'm not sure what to do to "check the freehub body". What to look at/look for?

smacl

slideshow bob wrote: »

Still skips under pressure, but never on the bike stand.

Put the bike on a turbo with a highish level of resistance and get someone else to pedal while you watch what's happening on the back wheel. Might give you some better clues.

dfin

sounds like your old chain was worn which will also cause wear on your cassette. a new chain will seem worse at first as the old chain has caused its own wear pattern on the cassette and your new one will not match. best to change cassette and chain together.
if you can tolerate the slip for a while your new chain will eventually "wear in" to the old cassette but it would be very frustrating until then.
sounds like its not related to the cable as that would cause it to jump gears, not slip and you mentioned the problem got worse with the new chain.
best of luck with it, I left mine so long once I had to replace chain cassette and front ring together

Seaneh

Yeah, I instantly thought it sounds like the cassette.

If you changed the chain and it's even worse now than it's definitely the cassette if you ask me.

smacl

Seaneh wrote: »

Yeah, I instantly thought it sounds like the cassette.

If you changed the chain and it's even worse now than it's definitely the cassette if you ask me.

Most probably. Should also happen more in regularly used sprockets if this was the case.

joxerjohn

Maybe another thing to check is if the derailleaur hanger is bent. It may have had a knock. Not usually too critical on 8 speed but will cause gear jumping problems on 9/10 speeds. Looking at it from the rear on the turbo as suggested will confirm if it is out of alignment.

ashleey

Seaneh wrote: »

Yeah, I instantly thought it sounds like the cassette.

If you changed the chain and it's even worse now than it's definitely the cassette if you ask me.

Coming to this late but what chain did you change to?

Mine was skipping in the smallest cog only and I tried all the usual adjustments. It turns out that the removable link (mine is Wipperman) on many chains is often directional. I had mine the wrong way round and so it was rubbing on the cassette lock ring and causing a skip. I turned it round and now the skip has gone. On that reasoning, a stiff link cause also be a problem for you.

http://forums.competitor.com/topic/9437

doozerie

Yet another thing to check is whether the upper jockey wheel is too close to the cassette, this distance is adjustable via the B-screw on the derailleur. If it gets too close the upper jockey wheel will make contact with the cassette teeth and can cause the chain to skip. This will likely happen in some gears only, not all gears, but is usually easy to spot by just watching the positing of the derailleur while changing gear with the bike in a work stand or turbo trainer.

Another possible cause is cross-chaining, where the angle on the chain is too severe as it runs from an outer/inner ring on the front to an overly inward/outward cog at the back. In that case there is no problem, as such, you just need to be careful to use gears which don't result in an excessively crossed chain. I'm not sure though whether a used cassette + new chain would be more prone to skipping when cross-chained, so if cross-chaining didn't cause issues before I'm not sure it is any more likely to do so now with a mix of new and used parts. It's something to bear in mind though and is easy to confirm or rule out as the cause just by avoiding such gears.

slideshow bob

Thanks for all the replies - they've all been helpful. I've adjusted the B screw, checked the removable link (SRAM 8-speed and not directional AFAIK), checked for stiff links, checked the hanger, removed and refitted the jockey wheels just to be sure to be sure...

I wonder if DirkVoodoo is onto something with the freehub? The cassette wavers a tiny bit when freewheeling (not sure how to describe this) but has done this for years (at least since the first cassette replacement and I'm on my fourth), and didn't affect it before.

I've looked at the cassette - see pics.





Hard to tell, but there's possibly more wear on the middle sprockets (3-6) so maybe I let the chain wear a little too much? No such signs on the chainrings thankfully.

A replacement cassette seems to be the next step, and there's one on the way. Usually get the LBS to do this but I'll give it a go myself this time since I've recently acquired the tools for the job.

petethedrummer

Check your derailler hanger is securely screwed to your frame. Mine wasn't for a while there.

doozerie

The general advice, such as it is, for determining the state of a cassette is to look for teeth that have a shark fin -type of shape. Some of the teeth on your cogs from 2 to 6 look a bit like that but, to be honest, I've always found it very hard to gauge by eye and I got it wrong recently myself when I determined that my used cassette was okay only to find it jumping once I fitted a new chain. I've seen one tool that is supposed to measure wear on a cassette but from memory it only worked on a very limited number of cassette types/sizes and it was relatively pricey so I didn't look into it any further. The ultimate test is fitting a new cassette, which I guess you'll be in a position to do soon.

As for the freewheel wavering, if you are referring to what I think you are (a small wobble in the cassette when the wheel is freewheeling?) then that is fairly normal in my experience. Your freewheel could still be the issue of course, they do have a limited lifespan. I've found in the past that when any of my freewheels reached the end of their useful life the initial sign of this was the freewheel slipping a notable amount at a time (more than you'd get if the chain slipped by the length of one or two links), though this depends on the design of the freehub, and luck, to a certain extent.

route66

slideshow bob wrote: »

Thanks for all the replies - they've all been helpful. I've adjusted the B screw, checked the removable link (SRAM 8-speed and not directional AFAIK), checked for stiff links, checked the hanger, removed and refitted the jockey wheels just to be sure to be sure...

I wonder if DirkVoodoo is onto something with the freehub? The cassette wavers a tiny bit when freewheeling (not sure how to describe this) but has done this for years (at least since the first cassette replacement and I'm on my fourth), and didn't affect it before.

I've looked at the cassette - see pics.


<SNIP>



Hard to tell, but there's possibly more wear on the middle sprockets (3-6) so maybe I let the chain wear a little too much? No such signs on the chainrings thankfully.

A replacement cassette seems to be the next step, and there's one on the way. Usually get the LBS to do this but I'll give it a go myself this time since I've recently acquired the tools for the job.

The middle sprockets certainly look to be "hooked" and visibly narrower that the smaller ones at the front of the show. The lower gears (at the back) are a little fuzzy in the shots and hard to see. I'd say the cassette should sort the problem.

dquirke1

When a new chain makes things worse, It's almost always a worn cassette.

You can see the middle few sprockets are fairly badly hooked in the photo too
Nothing for it but a new cassette...

Raam

Save yourself some heartache, buy a new cassette and chain. The bike will feel like new.

Use the old cassette as ninja stars and the chain can be made into some nice bracelets for your significant other.

slideshow bob

Was cassette right enough. Running sweetly now. Thanks to all.