Chain unseating, does this chainring look worn?

[Tom _M]

Put a (rather overdue) new cassette, chain and cables on and has a started unseating from big front chainring (to inside) sometimes when doing starting efforts like pulling away from lights, junctions. Trying to work out the cause and struggling. All indexes okay. Chain seems fine, though was off eBay so can’t discount it being a fake one. Other thought was of front ring was getting a bit worn and causing it?

[johnpsanderson]

When chainring teeth are very worn they become hooked like sharks teeth, which doesn’t look to be the case with those yet. But I would think it likely it’s down to the different wear between the parts that you’re now having trouble.

[OutInTheShed]

The teeth do look a bit worn, and the derailleur looks a bit high up the seat post?

[leyorkie]

Check your chain wheel by pulling the chain to see if there’s any movement.
Normally this is to check for chain wear but as you have fitted a new chain you know that’s ok.
Looking at the chain wheel pull the chain at the 3o clock position there should not be any movement with a new chain, if there is then the teeth are worn.

[Tom _M]

Thanks. Position of front mech not been moved and was okay before, so not so sure if is height. Can take a more clear pic though. Didn’t think teeth were too ‘sharks’ but as chain/cassette were new then makes me wonder. Chain that came off was a good 1% stretched.

[gazza285]

Chains wear, but they don’t stretch.

[OutInTheShed]

gazza285 said:

Chains wear, but they don’t stretch.

They get longer (under tension) due to the wear in every joint.
You can call that 'stretch' or not, it's semantics.

[Lotobear]

It's worn but not terminally. However I think it's a bit remiss to replace the chain and cassette and not put a fresh chainring on as well.

[gazza285]

OutInTheShed said:

gazza285 said:

Chains wear, but they don’t stretch.

They get longer (under tension) due to the wear in every joint.
You can call that 'stretch' or not, it's semantics.

Nothing has been stretched, it is not semantics, to say a chain has stretched is an incorrect statement.

[OutInTheShed]

gazza285 said:

Nothing has been stretched, it is not semantics, to say a chain has stretched is an incorrect statement.

bks,
It's been made longer.
That is one meaning of the verb 'stretch'.

[911hope]

Lotobear said:

It's worn but not terminally. However I think it's a bit remiss to replace the chain and cassette and not put a fresh chainring on as well.

Normally get through many chains and cassettes per chainring.

[911hope]

Tom _M said:

Put a (rather overdue) new cassette, chain and cables on and has a started unseating from big front chainring (to inside) sometimes when doing starting efforts like pulling away from lights, junctions. Trying to work out the cause and struggling. All indexes okay. Chain seems fine, though was off eBay so can’t discount it being a fake one. Other thought was of front ring was getting a bit worn and causing it?

The troughs in the chainring look elongated and the teeth will get very sharp quite soon.

The old chain will have lengthened, due to wear in the joints between the links.

Having put a new chain one, the chain pitch per link is shorted than the pitch per chainring tooth. So under drive the force is distributed between fewer chainring teeth. This pressure can cause the chain to rise up the teeth and become unseated. It also accelerates wear of the teeth.

[Lotobear]

911hope said:

Lotobear said:

It's worn but not terminally. However I think it's a bit remiss to replace the chain and cassette and not put a fresh chainring on as well.

Normally get through many chains and cassettes per chainring.

Indeed but that chainring is about ready so, for the price of a new one, it seems daft not to have a complete new drivetrain and re set the clock.

[911hope]

Lotobear said:

911hope said:

Lotobear said:

It's worn but not terminally. However I think it's a bit remiss to replace the chain and cassette and not put a fresh chainring on as well.

Normally get through many chains and cassettes per chainring.

Indeed but that chainring is about ready so, for the price of a new one, it seems daft not to have a complete new drivetrain and re set the clock.

Agreed

[Tom _M]

Have seen can get Shimano RS510 chainrings cheap. Look similar and have same BCD, so any reason why would not fit onto 105 chainset? Can't remember model number, but circa 2015/16 I think

[addey]

BCD is the only important metric, so yes that should work. And number of teeth obviously if you want to keep the same gearing (and chain!)