Bike Maintenance - chains

[daveh]

I run a 12 speed Cube e-mountain bike for commuting (approx 3000 miles a year). It chews through chains and cassettes.

I've just tried to change the chain (it will be chain number 3 on this cassette). The old chain was up to 0.75 on the wear gauge. Had the bike up on the stand. Removed old chain, fitted new chain after giving it all a bit of a clean. New chain is CNM8100 120 link shimano XT 12 speed chain from Merlin Cycles. Its slightly short, 120 links compared to previous chain which was 126 links with 3 or 4 links removed.

Problem new chain drops off the front ring as soon as you move to the smallest two cogs on the rear cassette and this is just on the stand. Wasn't expecting the short chain to be a problem on the small cogs, thought it might be a problem on the largest cogs on the cassette, but I never use more than 8 or 9 of the 12. Was using the 120 chain so I didn't have to fiddle around with chopping out three or four links.

Why the problem - is it because the chain is too short or is it the wear on the cassette/chain/front chain ring is too much for the new chain or is the new chain dodgy (it was 50% of RRP)? If it goes in to the bike shop for a service its likely to be a new chain, cassette and possibly front chain ring. I was hoping to get another chain use out of this cassette before getting it serviced.

Thoughts on what to do?

[servodude]

I run a 12 speed Cube e-mountain bike for commuting (approx 3000 miles a year). It chews through chains and cassettes.

I've just tried to change the chain (it will be chain number 3 on this cassette). The old chain was up to 0.75 on the wear gauge. Had the bike up on the stand. Removed old chain, fitted new chain after giving it all a bit of a clean. New chain is CNM8100 120 link shimano XT 12 speed chain from Merlin Cycles. Its slightly short, 120 links compared to previous chain which was 126 links with 3 or 4 links removed.

Problem new chain drops off the front ring as soon as you move to the smallest two cogs on the rear cassette and this is just on the stand. Wasn't expecting the short chain to be a problem on the small cogs, thought it might be a problem on the largest cogs on the cassette, but I never use more than 8 or 9 of the 12. Was using the 120 chain so I didn't have to fiddle around with chopping out three or four links.

Why the problem - is it because the chain is too short or is it the wear on the cassette/chain/front chain ring is too much for the new chain or is the new chain dodgy (it was 50% of RRP)? If it goes in to the bike shop for a service its likely to be a new chain, cassette and possibly front chain ring. I was hoping to get another chain use out of this cassette before getting it serviced.

Thoughts on what to do?

I'd expect the derailleur to cope with one link less easily on the smaller sprockets

First thing I'd check is that the chain is on in the right direction (if it has a direction! fancy 12spds sometimes do)

Then that the rear wheel is where it should be in the frame (a mispositioned nut or washer can throw the chainline)
Then that the derailleur is adjusted correctly

If everything is set up where it should be - then I'd be looking at the front cog for wear
I've worn one down to a sharktooth once, and because of how components wear together it shows up when you change the chain

good luck
-sd

[redsturgeon]

This is a strange one. I assume there is no sort of chain guide to the front chain ring so it is purely the off centre nature of running the small rear sprockets that is the problem. I guess you could try switching back to the old chain to see if things are normal that would isolate the new chain as the only problem. I have never heard of directionally specific chains but who knows these days.Then I can only assume it is a case of new chain old chain ring causing the problem which is not unheard of. Only remedy then is new front chain ring.

I guess running 12 speeds means much slimmer components that have a lot of heavy lifting to do on an e=bike. I love the way my old 5, 6, 7 and even 8 speed bike's gears seem to run forever before needing parts replacing.

Your e-bike is probably a lot more capable though.

John

[daveh]

I run a 12 speed Cube e-mountain bike for commuting (approx 3000 miles a year). It chews through chains and cassettes.

I've just tried to change the chain (it will be chain number 3 on this cassette). The old chain was up to 0.75 on the wear gauge. Had the bike up on the stand. Removed old chain, fitted new chain after giving it all a bit of a clean. New chain is CNM8100 120 link shimano XT 12 speed chain from Merlin Cycles. Its slightly short, 120 links compared to previous chain which was 126 links with 3 or 4 links removed.

Problem new chain drops off the front ring as soon as you move to the smallest two cogs on the rear cassette and this is just on the stand. Wasn't expecting the short chain to be a problem on the small cogs, thought it might be a problem on the largest cogs on the cassette, but I never use more than 8 or 9 of the 12. Was using the 120 chain so I didn't have to fiddle around with chopping out three or four links.

Why the problem - is it because the chain is too short or is it the wear on the cassette/chain/front chain ring is too much for the new chain or is the new chain dodgy (it was 50% of RRP)? If it goes in to the bike shop for a service its likely to be a new chain, cassette and possibly front chain ring. I was hoping to get another chain use out of this cassette before getting it serviced.

Thoughts on what to do?

I'd expect the derailleur to cope with one link less easily on the smaller sprockets

First thing I'd check is that the chain is on in the right direction (if it has a direction! fancy 12spds sometimes do)

Then that the rear wheel is where it should be in the frame (a mispositioned nut or washer can throw the chainline)
Then that the derailleur is adjusted correctly

If everything is set up where it should be - then I'd be looking at the front cog for wear
I've worn one down to a sharktooth once, and because of how components wear together it shows up when you change the chain

good luck
-sd

I tried switching the chain round, didn't seem to make a difference. I've got a longer chain, I'm going to chop that down to the correct size and try that if I get time at the weekend. At the moment I just put the old chain back on and its working fine. I was hoping to get another chain use out of the cassette, if that doesn't work I'll just run this old chain until it gets too bad and get the bike shop to change chain, cassette and front chain ring when I get it serviced. Front chain ring teeth don't look too bad shape wise, but there is definitely some wear of the teeth. Front ring has done 9500miles and the cassette 3500miles. Previously I had to change the front ring at 7000miles, but I left the first chain on too long so may have worn the front excessively with that chain as the front ring is supposed to last much longer than the cassette.

[servodude]

I'd expect the derailleur to cope with one link less easily on the smaller sprockets

First thing I'd check is that the chain is on in the right direction (if it has a direction! fancy 12spds sometimes do)

Then that the rear wheel is where it should be in the frame (a mispositioned nut or washer can throw the chainline)
Then that the derailleur is adjusted correctly

If everything is set up where it should be - then I'd be looking at the front cog for wear
I've worn one down to a sharktooth once, and because of how components wear together it shows up when you change the chain

good luck
-sd

I tried switching the chain round, didn't seem to make a difference. I've got a longer chain, I'm going to chop that down to the correct size and try that if I get time at the weekend. At the moment I just put the old chain back on and its working fine. I was hoping to get another chain use out of the cassette, if that doesn't work I'll just run this old chain until it gets too bad and get the bike shop to change chain, cassette and front chain ring when I get it serviced. Front chain ring teeth don't look too bad shape wise, but there is definitely some wear of the teeth. Front ring has done 9500miles and the cassette 3500miles. Previously I had to change the front ring at 7000miles, but I left the first chain on too long so may have worn the front excessively with that chain as the front ring is supposed to last much longer than the cassette.

That does sound like the cog might have worn then
When I was choosing my commuting e-bike I went for a heavy transmission with internal gearing and still go through a chain every 3000 miles or so - and the rotating bits are BMX thick

[ukmtk]

I normally replace the chain & cassette at the same time.
Well my mobile mechanic does!
I happily cycle but leave the technical stuff to the professionals.
I get the bikes serviced once a year (or if there is a noticeable problem).
The mechanic tells me what needs replacing.
I'm astonished at how smart he is - he'll spin a wheel and say "that's a dodgy bearing".
He built my Gridd gravel bike - I got the frame from Wiggle a few years back - it came with nice forks.

[Gerry557]

It does sound like you have worn the rest of the drive train especially if putting the old chain back on works. I have to admit swapping chains and running 2 or 3 at a time and swapping them out.

I have also suffered similar issues and it normally requires changing all the drive train. Its also probably worth changing the bottom bracket at the same time.

[daveh]

I normally replace the chain & cassette at the same time.
Well my mobile mechanic does!
I happily cycle but leave the technical stuff to the professionals.
I get the bikes serviced once a year (or if there is a noticeable problem).
The mechanic tells me what needs replacing.
I'm astonished at how smart he is - he'll spin a wheel and say "that's a dodgy bearing".
He built my Gridd gravel bike - I got the frame from Wiggle a few years back - it came with nice forks.

Trouble is a 12 speed chain is between £36-£50 depending on the grade* and a cassette is over £100. When I first got the bike I just ran it until the chain wasn't changing properly and then took it to the bike shop and they changed both chain and cassette and brake pads and serviced it for £259 and that was after 3770 miles of use. Next couple of services much the same happened except the mileage in between was only 2137miles and 2776 miles. The bike shop recommended I change chains at 0.5 wear and that I would then get three chains per cassette. That's roughly what I've been doing, but that means I'm only getting about 1300 miles per £36 chain and 4700miles for the cassette**. The more expensive (£50) chain did nearly 2500miles. I was hoping to get a third chain on the present cassette, but I've not tried a longer chain than the one that didn't work because before I found time to do it the bike snapped a spoke under braking and its now going into the bike shop next week.

*There does seem to be a difference as I got more miles out of the more expensive change before it reached 0.5 on the wear gauge - though by the time I got round to swapping to the new chain it was 0.75 on the wear gauge.

** I know it doesn't add up, but the bike shop only changed the chain at the service and the 4th chain was very rough (mismatch between new chain and worn cassette). I'd done several hundred miles before they could fit it in to change the cassette as I'm doing 150 miles a week commuting.

[ukmtk]

Last week I had a new cassette + chain on the Gridd bike: £76 + £35 labour.
The hand built Mercian steel (gravel) only has Shimano 105 kit (11 speed) - same as the MTB (9 speed triple) [it's an old hardtail].
The Gridd bike has the pricier Shimano GRX groupset (11 speed double).

It dawned on me that the pricier Shimano stuff was no better as far as engineering was concerned - just lighter materials - which are pointless for most cyclists.

[ukmtk]

I used to commute 3 days/75 miles per week on the MTB to/from Derby.
I invariably set off at 06:15 from home.
I carried a laptop + change of clothes in a backpack.
Most of the ride until I hit the outskirts of Derby had no street lights so I need good lighting in winter (3 back + 2 front).
I rode Specialized Crossroads Ex tyres - the ones with the ridges down the middle.
I hardly used the MTB off road - I just wanted to ensure I had no punctures in the dark - I never did!
I probably changed cassette + chain once a year at most.