New chain and cassette - Chain Still Slipping

[DaveG]

I have a pretty standard commuter bike with nine speed cassette and do about 15 miles a day.

I started getting problems with the chain slipping when in top gear, and put this down to wear so replaced the chain and cassette, but it is still slipping and is, if anything, worse than before. It is worst in top gear, but it has slipped in any of the top four gears.

Using dots of paint I have confirmed that:
1. the chain is definitely slipping on the cassette cogs.
2. It is not slipping on the gear set.
3. The cassette is all moving as one.

I have cleaned and lubricated the cable and mech. The mech doesn't have any obvious signs of excessive wear or damage, the stops are set correctly and it indexes correctly. I've read differing views as to the effect of worn jockey wheels, but mine appear to be ok anyway.

This is driving me potty, any advice would be very much appreciated.

Thanks very much!

 

[chris-suffolk]

Does the derailleur B-screw need adjusting? Could be you aren't engaging enough teeth to get bite, especially on the small cogs.

 

[SheilaH]

Have you checked your chainwheel for wear? Is the chain sitting on top of teeth rather than meshing?

 

[chris-suffolk]

Have you checked your chainwheel for wear? Is the chain sitting on top of teeth rather than meshing?

Guess he has, as he said it slips on the cassette and not the gear / chain wheel

 

[I like Skol]

Is the chain definitely the right 'speed' to match the cassette? Might be running a 6/7/8 spd chain on a 9 or 10 speed cassette?
Also, is it possible that the freehub is slipping occasionally?

 

[sittingbull]

Maybe check the new chain with a chain gauge?

It really shouldn't be necessary but I have read one review where a new chain was poorly manufactured and was already on the wear limit for replacement.

 

[DaveG]

Hello All, thank you for your suggestions.

The middle and top chainwheels are worn, but it's definitely not slipping on there. I even got it to slip on the granny gear which isn't worn at all.
The B screw is at the maximum adjustment.
I wondered about the freehub, but with my trusty dot of paint it definitely showed that the chain is slipping on the cassette,

I'm pretty confident it is a 9 speed chain, though when I offered the new one up to the old one, it was about half a link shorter over 114 links. I put this down to stretching of the old one, was that right?

I don't have a chain measure, but I think I might invest in one.

 

[weareHKR]

The B screw has a specific role to play with the derailleur setting... please watch the attached video for ease of understanding.
How to adjust the...

 

[Ajax Bay]

Roughly how far do you think you have done on the chainset? I assume the chain and cassette are still almost 'as new'.

 

[DaveG]

I've done less than 20 miles on the new set.

I'm wondering whether the new set is a red herring as the problem was occurring on the old set too. I assumed that it was just down to chain wear but maybe it was something else.

Thanks weareHKR for the video. I'm sure the B screw is adjusted correctly now, but it has had no effect on the problem.

When in top gear, the resting position of the mech means that there is a gap of about 15mm between the feed wheel and the gear. Looking at other bikes, they all seem to sit with the feed wheel closer so more of the chain is engaged.

Just as an experiment, I just tried pulling the mech closer with a cable tie and I didn't get any slippage at all. But I also couldn't change gear

There is no way I can see of adjusting the mech to sit closer, so I am now wondering if it could somehow be the mech that it is at fault, though as I said there is nothing obviously wrong with it.

Thanks again for the help.

 

[slow scot]

I had a very similar problem on a bike a year ago. After trying everything, with no luck, I replaced the outer cable which takes the rear derailleur cable into the rear mech. Problem solved! The outer cable had a slight kink which was barely noticeable, but was enough to cause the chain to jump around on the cogs.

 

[craigwend]

Could it be your rear mech / hanger / frame is out of alignment?

 

[Ajax Bay]

it was about half a link shorter over 114 links. I put this down to stretching of the old one, was that right?

If the previous chain was the correct length, but elongated, then 'yes' that's the same number of links in the new chain.
I know you've said that you've checked that the new chain is jumping on the new cassette, same as the old chain was jumping on the old cassette, BUT
the symptom (once the chain/cassette combo cause is eliminated) points to one or more worn chain rings.
Rear mech malalignment may result in skipping to a different sprocket (as will poor indexing and 'cable issues'), not the symptom described in the OP.

 

[sittingbull]

Both the previous chain and the new one are slipping and are 114 links. I mostly ride a triple with a longish chain and still have to remove around half a dozen links from a new 114 link chain.

Do you know if the previous chain was the original?

Have you "sized" the new chain around the big front - big rear combination (without passing through either mech)?

I believe the length should be the first link at which it could be connected, plus 2

 

[DaveG]

Hello All, thanks again for all the suggestions and advice.

The good news is it is now sorted. I went back to the shop which sold me the chain and cassette, and after half an hour of him saying "it's the mech alignment / hub / cable / chainset etc" and me disagreeing, he eventually swapped the cassette for a different brand and hey presto, works perfectly.

When I bought the cassette, they only had unbranded ones (which were cheaper than the Shimano I was replacing), so I will never know if it was just poor quality, or if I had a duff one.

Whatever the case, I guess the lesson is to start with the most obvious cause first. I can only assume that the previous slipping was due to wear after all.

Back to chipping away at that lockdown bulge now.