Snapped Chain requires new cassette?

JuliaT

Active Member
Location
London
Hi all,

During my commute this morning my chain snapped. I took the bike to the shop as I had no tools or knowledge on how to replace it (specially in the middle of the street and having a meeting in the morning).
The guy in the bike shop told me that, as I through away the snapped chain he would have to change the cassette. That they have to be replaced together... if not I will have problems with the new chain...

I am a beginner so I have no idea... My question is... is this for real or is he trying to scam me? If I have to change the cassette I will do it, no problem, but this sounds weird to me...

Thanks!
 

ianrauk

Tattooed Beat Messiah
It's all dependent on what mileage the chain and cassette have done and what condition they are in.
If it's a relatively new cassette and chain with little mileage then a new chain might work with the old cassette. If they have done a good few miles then a new chain may not mesh with the old cassette causing the chain to skip and jump.
 

bigjim

Guru
Location
Manchester. UK
Depends how worn the old chain is. The chain has usually had to be pretty badly worn to require a cassette change. Also a chain snapping is not a sign of a worn chain. It's quite a rare occurrence. Were the gears skipping before the chain broke? I'd be tempted to fit just the new chain. You will soon know if the cassette needs changing as the gears will start skipping about. So. he's wrong. They don't always have to be changed together at all. Change chains early enough and cassettes will outlast quite a few chains.
 

johnblack

Senior Member
You don't have to, but if your chain and cassette are the same age and the chain is worn, changing the cassette isn't a bad idea, it shouldn't cost a great deal, depending on what groupset your using obv.
 

Ian H

I am an ancient randonneur, & I stop often for tea
Location
East Devon
Cassettes wear as the chains wear, and fitting a new chain to an old cassette will often result in the chain slipping on some sprockets. Did he ask you how far you'd ridden on the current chain/cassette, or measure the wear on the snapped chain?
 

MichaelW2

Veteran
If you change your chain before it becomes to worn, you can use the old cassette. Further wear will result in sharks teeth profile wear in the cassette. The old chain will work but a new chain will slip across the cogs when under higher tension.
Probably best to change both together on any chain used for more than a year of daily riding.

The advanced riders solution to a broken chain is to carry a special link that can be fitted and removed without tools, although you prob need a special chain tool to remove bits of broken link.
The link comes free with most modern chains.
 

vickster

Legendary Member
I always get the two changed together. Saves me time and hassle in the long run and the cassettes on the bikes that get ridden most are under £25 online. Order together, hand over to LBS, job done. Once a year if that once the chain is properly worn and beginning to skip. Costs about £50 all in
 

Paulus

Started young, and still going.
Location
Barnet,
Generally yes, it is best to replace a worn chain and cassette at the same time. You can sometimes get away with only the chain, but at some point the chain will start to slip on the cassette and then you will have to replace it anyway.
 
OP
JuliaT

JuliaT

Active Member
Location
London
Depends how worn the old chain is. The chain has usually had to be pretty badly worn to require a cassette change. Also a chain snapping is not a sign of a worn chain. It's quite a rare occurrence. Were the gears skipping before the chain broke? I'd be tempted to fit just the new chain. You will soon know if the cassette needs changing as the gears will start skipping about. So. he's wrong. They don't always have to be changed together at all. Change chains early enough and cassettes will outlast quite a few chains.
I honestly don't know how used they are/were, I bought the bike second hand last year and during the service they told me they were fine. This year in the service they told me the chain might need to be changed at the end of the season. The gears were not jumping, actually they worked beautifully (in my opinion). I guess I will follow your advise, leave the old cassette and if it starts skipping and jumping will replace it. Thanks!
 
OP
JuliaT

JuliaT

Active Member
Location
London
You don't have to, but if your chain and cassette are the same age and the chain is worn, changing the cassette isn't a bad idea, it shouldn't cost a great deal, depending on what groupset your using obv.
I honestly don't know how old any of them is, as bought it second hand. But he told me the difference was from 20 (chain) to 80£ (chain and cassette)
 

Paulus

Started young, and still going.
Location
Barnet,
I honestly don't know how used they are/were, I bought the bike second hand last year and during the service they told me they were fine. This year in the service they told me the chain might need to be changed at the end of the season. The gears were not jumping, actually they worked beautifully (in my opinion). I guess I will follow your advise, leave the old cassette and if it starts skipping and jumping will replace it. Thanks!
An old worn out chain can still work fine with a worn out cassette, as they wear out at the same time. If the cassette is shark toothed a new chain, which has perfectly round pinions will not fit the teeth on the cassette.
 
OP
JuliaT

JuliaT

Active Member
Location
London
Cassettes wear as the chains wear, and fitting a new chain to an old cassette will often result in the chain slipping on some sprockets. Did he ask you how far you'd ridden on the current chain/cassette, or measure the wear on the snapped chain?
He did ask, but I have no idea and he couldn't measure it bcos the old chain is in a bin where it broke... I guess he was giving me a safe advise
 
OP
JuliaT

JuliaT

Active Member
Location
London
If you change your chain before it becomes to worn, you can use the old cassette. Further wear will result in sharks teeth profile wear in the cassette. The old chain will work but a new chain will slip across the cogs when under higher tension.
Probably best to change both together on any chain used for more than a year of daily riding.

The advanced riders solution to a broken chain is to carry a special link that can be fitted and removed without tools, although you prob need a special chain tool to remove bits of broken link.
The link comes free with most modern chains.
That's quite interesting! I'll check how to do that in case this happens again. Thanks!
 

vickster

Legendary Member
I honestly don't know how old any of them is, as bought it second hand. But he told me the difference was from 20 (chain) to 80£ (chain and cassette)
£60 extra for cassette and fitting sounds a lot? What groupset is it?
If you only change the chain, you may hasten it’s demise on a worn cassette but up to you. It’ll just mean another £20 potentially but you could the. source the parts cheaper online and ask a shop to fit (mine only charges another fiver if I get the parts)
 
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