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Old 03-20-10, 01:19 PM   #1
Alcyon
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I keep breaking cranksets

I weigh about 230lb. and I often stand up on the pedals when riding. This is now the second time I've had this problem: the teeth on the cog wear down and break off and then when I'm pushing in a high gear the chain will slip and jerk my feet around. It's like $50 or something to replace both the crankset and the rear gears, which the bike mechanic told me I have to replace together... First of all, is that B.S.? And is there a crankset you'd recommend that's a little tougher and might stand up to the torque? I don't really use anything but the middle chainring and I wouldn't mind getting a leg guard for the outside ring either, anything you'd recommend? I have a Kona Dew Deluxe, by the way.
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Old 03-20-10, 01:30 PM   #2
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Odds are that he is at least partially B.S-ing you. True, chains wear, and cassettes wear. but as the chainring(up by the crank) have so many more teeth to share the load, the chainring(s) will usually outlast several cassettes. And a cassette can often outlast several chains unless you've waited too long to replacec it.
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Old 03-20-10, 01:44 PM   #3
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I go through middle chainrings on my Ultegra triple as fast or faster than the cassette, just because I tend to stay in the middle and move the chain around in back, spreading the wear. YMMV

Terminology: you're not breaking cranksets, you're wearing out chainrings.

Before you wear out a chainring, you're wearing out chains. Lube your chain a lot more often. Every 100 miles is good and after every time you ride in the rain. Use a good bike chain wet lube. Clean off excess lube and gunge with a rag after lubing.

Check your chain for wear and replace it before it's worn out. That will cost money, but so do chainrings and cassettes.

The mechanic is technically wrong - you don't have to replace them together. You just have to replace what's slipping and replace the chain at the same time. Then if the other end slips with the new chain, you'll have to replace it, too, but you won't know that until you replace the chain. It's just easier for him to replace the ring, chain, and cassette all together and have it all work when it leaves his shop. Otherwise it might not.
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Old 03-20-10, 02:00 PM   #4
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50 bucks ain't bad.

I pay way more than that just for an XT rear cassette.

Btw, how long does it take you to wear out the set?
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Old 03-20-10, 02:05 PM   #5
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$50 to replace the crankset/chainring AND cassette? Including labor? That's pretty doggone inexpensive.

And teeth are actually breaking off on your cassette? What are you riding?

Also, how many miles have you been getting on your drivetrain between replacements? And in what kind of weather? And in what manner and how often do you clean your chain?

FWIW, I've gone down from 240 down to 200 since last summer (back up to over 210 over the winter) and in probably 4-5,000 miles or so I've gone through about three or four chains and am about to replace my cassette. And my chainrings are still fine. And despite all the standing on the pedals that I've done I've never broken a tooth of any gear.
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Old 03-20-10, 03:29 PM   #6
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The teeth may look broken, but they're not. They're made that way.

Not to say that your (probably middle) chain ring isn't worn out. They do that over time, but unless you have a riveted crankset, you don't have to replace the crankset, just the ring.


It would be nice if you would tell us what bike you're talking about, and what components are on it. We know more about you than we do about the bike.

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Old 03-20-10, 05:20 PM   #7
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Why not just stop standing on the pedals? Use a lower gear instead -- that's why they're there.
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Old 03-20-10, 05:42 PM   #8
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Quote:
Originally Posted by Carbonfiberboy View Post
I go through middle chainrings on my Ultegra triple as fast or faster than the cassette, just because I tend to stay in the middle and move the chain around in back, spreading the wear.
To both you and the OP I'd recommend that you try to use the large chainring a bit more. If you're in the middle ring and one of the smaller cogs in back then there's probably a similar gear that you can use with the large ring and one of the medium-size cogs. For a given pressure on the pedals you'll be generating less chain tension if you use the large ring instead of the middle, so that will reduce the rate of wear. And you'll be spreading the wear out among more parts so you won't have one of them failing so often
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Old 03-20-10, 05:44 PM   #9
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Yes, use the large chainring and larger cassette cogs more often. There's often quite a big of duplication in the gear-ratios and the only time I use the small ring is to get into the lowest 4 gears.
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Old 03-21-10, 04:03 AM   #10
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Rofl. The OP think he's strong enough to break teeth off chainrings. Hilarious. Here's what's happening

1) Chainring/chain/cassette wear
2) Drivetrain skips

Drivetrain needs to be replaced, end of story.
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Old 03-21-10, 07:02 AM   #11
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thanks for informations.
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Old 03-21-10, 07:17 AM   #12
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The metal used to make chainrings varies hugely in quality. I have sawed through old rings and the hacksaw glides through standard quality parts but it has a tough time getting through the higher grades.
The best replacement rings are probably by Specialities-TA.
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Old 03-21-10, 08:11 AM   #13
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Quote:
Originally Posted by Carbonfiberboy View Post

Terminology: you're not breaking cranksets, you're wearing out chainrings..
If he's tearing up cranksets that don't have replaceable rings then what is it?
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