Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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Originally Posted by radshark
The owner took out a Park chain tool and told me it measure ".75" and the chain needed to be replaced. I expected as much.
But then I was informed the cassette need to be replaced as well. That didn't seem right to me. I asked for the chain to be replaced but decided to delay the replacement of the cassette.
, you can always replace the cassette later if necessary.
The wear rate of cassettes is almost entirely determined by the condition of the chain. As the chain "stretches" the pitch no longer matches the sprockets and it begins to wear them at an accelerated rate. That's why it's important to replace chains before this happens.
There's no magic wear point, but experience dictates that those replacing chains at roughly 1/2% (1/16"/12") stretch enjoy good cassette life, and those who wait until 1% do very poorly, and have a good chance of needing a new cassette with the first chain replacement.
At .75% chain stretch, and especially when determined by a chain checker which tends to read high, I'd expect the cassette to be OK, though it could be toast, especially if you did most your riding on the same sprocket.
In any case I never
replace a cassette until I've determined that it won't run acceptably with the replacement chain. That's the acid test. If the old cassette runs with the new chain, it's fine.
If not, it isn't, and you'll have to replace it after all. Note: the greatest cassette wear will be on the smaller sprockets that you use the most so it may run better in some gears than others. It's up to you to decide what you'll accept as OK, unless it skips.
BTW- there's never any harm to the new chain caused by running it on an old cassette. Chains wear on their own schedule regardless of the condition of the sprockets they're running on. In the chain drive industry they say "chains wear sprockets, but sprockets don't wear chains.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance
Last edited by FBinNY; 05-02-10 at 03:38 PM.