Chain slipping over cogs

Saruman

Can anyone give me an idea of what the issue could be here?
I was getting a slipping chain when peddling so I replaced the chain with a new one and got the same thing. I even took an extra link off the chain just in case but it had the same result.

The cassette is as tight as it can be and doesn't appear to be slipping.

I took a video here which shows what happens.

It looks like the chain comes off the teeth and continues on. It happens on every gear combination by the way, even the lowest combination (smallest front, largest back) which I never actually use so the teeth can't be worn.

My suspicion is the derailleur is failing. I have come off the bike a few times and I had to replace my limit screws as they were damaged.
When the bike is hanging, everything is perfect and all shifts work seamlessly. It's only when I'm physically on the bike and pushing that it happens. It started out happening when I was setting off from a stop but it's now unusable.


Here's an image of the rear cassette for reference.

secman

Teeth on the block dont look worn, what arecthe teeth like on the big ring ? Are they pointed ? The indexing might need adjusting.

JJayoo

Hmmm I had a similar thing happen, when put on the stand bike shop guy could turn pedal and fly through gears no problem but when cycling it would slip and the peddals would spin with no resistance.

Went to two different bike shops, went loads replacing bits with no fix.

Eventually I spotted the issue, the middle chainring, think that's the name, somehow got dented. So as I changed from the highest gear down the chain would sometimes get stuck in-between the two chain rings instead of actually fitting on, this meant that I could still cycle as it was turning the wheel but if I started to cycle hard it would slip from between the two chain rings and the peddals would spin freely sending me flying.

Did you bring me take a fall before you noticed this issue? The dint on mine was very suital

07Lapierre

How old is the cassette?

Can’t tell from the photo how many sprockets...is it 8,9 or 10 speed?

Is the chain the correct size for the cassette?

secman

Chain seems to have a bit of slack on it ?

magicbastarder

i was going to say they do look a bit worn. does it happen on all sprockets at the back?

con747

The chain is clearly slipping on the rear cassette in your video so the teeth are worn.

Wishbone Ash

Are you sure the chain is the correct size (i.e. width?). It looks like the chain is narrower than the sprockets and therefore isn't engaging with the teeth properly.

con747

If you look closely at the couple of gears above the one it's on at 9 o'clock to 10 o'clock, the teeth are worn nearly flat.

magicbastarder

some teeth are ramped like that anyway for smoother shifting.

07Lapierre

I suspect the chain and cassette are quite old and worn. Putting a new chain on won’t solve the problem if the cassette is also badly worn.

magicbastarder

this is a comparison of the gap between teeth of one of the middle rings, vs a gap on the second biggest one. there seems to be a clear difference.

ED E

07Lapierre wrote: »

How old is the cassette?

Can’t tell from the photo how many sprockets...is it 8,9 or 10 speed?

Is the chain the correct size for the cassette?

Its Tourney so has to be 7/8 speed I think.


Agree, cassette is probably EOL.

Saruman

It's an 8 speed cassette. New chain is an 8 speed and cut shorter than the one I took off.

The bike is almost 2 years old.
I've just worked out though that I cycle about 14km every single day for the most part so over 2 years, that's going to end up between 9000 and 10000 kilometres.
Probably well past time to replace the cassette and drive chain ring. I'm surprised it has lasted as long as it has since it's only a €300 Halfords bike, Carerra Subway One.

A Carerra Subway is decent for the money if it's the one without the suspension. Ideal bike for short runs and having to be locked up on the street/risky spots etc

Saruman

Cheers everyone, the Subway has served me well over the last 2 years so I'll fix it up.

I've ordered the new gear which I believe is all compatible.
Sticking with an 8 gear system as it's enough for this bike, I am giving it a minor upgrade.
Going for:

• Shimano Altus RD-M310 rear derailleur (Formerly Shimano Tourney TX RD-TX800)
• Shimano CS-HG41-8 Cassette 8-speed (no real upgrade, was a CS-HG31-8)
• Shimano Altus FC-M311 Crank Set 3x7/8-speed (formerly SR Suntour CW-XCC-T208-PB 28/38/48T)
• Shimano PD-EF202 Flat Pedal

I also ordered 2 chains to be safe:
Shimano CN-HG71 Chain 6/7/8-speed
SRAM PC 870 PowerChain 8-speed

The Clarke chain I just put on is probably grand as a spare but I shudder to think of the damage I may have caused while testing it like in that video.

I don't "need" new pedals but feck it, I might as well.
I'll keep the current front derailleur which seems to be fine and I couldn't get stock in Bike24 of the equivalent Altus model.

Unfortunately I had to order from Bike24 in Germany, except for the derailleur which Halfords had, I'd have preferred to just get it all from Halfords or another shop but stock seems to be a bit iffy after Brexit perhaps.

07Lapierre

If your changing the chain,cassette, derailleur and pedals, you might as well replace the gear (and brake) cables aswell.

Saruman

It's all easier said than done. Looks like whoever fitted the original crank/chainset somehow over tightened the cranks on both sides.
The result is, the cranks are no longer square so the crank puller can't make it through. I tried on one side but it just started stripping threads.





So the result is, the end piece of the crank puller can't make it through to the square spindle on the other side.

Oh and looking at images of the original crank set, they look identical to the new Shimano, proper square and the tool fits correctly into the new ones.

cletus

Saruman wrote: »

It's all easier said than done. Looks like whoever fitted the original crank/chainset somehow over tightened the cranks on both sides.
The result is, the cranks are no longer square so the crank puller can't make it through. I tried on one side but it just started stripping threads.





So the result is, the end piece of the crank puller can't make it through to the square spindle on the other side.

Oh and looking at images of the original crank set, they look identical to the new Shimano, proper square and the tool fits correctly into the new ones.

I could be way off, but they look like they were machined like that. The rounded corners look like relief cuts, and the curved section contacts the face of the square taper

Saruman

No I don't think so, original photo of the part number shows them square.

Got them off by using Dremel to cut away the crushed bits and made it square again.

Saruman

Got everything on and test cycle works fine, no slipping. Just need to adjust the limits etc tomorrow.
Thanks for everyone's help. I'll get a new bike anyway but this can now be my basic commuting/shopping bike.