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Old 02-21-06, 09:11 AM   #1
thatguy
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What's scratching my chainstay?

On my two road bikes I've noticed lots of scratches developing (and getting worse) on the drive-side chainstay. It's right in the pedal/shoe area and below the little plastic cover they put on to protect it from the chain. The deeper ones go through the paint. I certainly don't notice any contact when I'm pedaling, but I can't rule it out. The non-drive-side is spotless. Should I be concerned about this? I hate to be scratching up my new bike.

See pic:
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Old 02-21-06, 09:49 AM   #2
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You may not notice it but there certainly is some contact with the heel of your shoe while pedalling. Try using pedals with little or no float.
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Old 02-21-06, 10:02 AM   #3
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It doesn't look like your shoe could do that. Not that close to the chainring in isolated small spots. Don't you lean that part of the bike against a bike rack or similar regularly, say, when locking up? Or it could be the chain, but it would have to flop around like crazy for that.
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Old 02-21-06, 10:29 AM   #4
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IMHO, I agree that it could be your shoe.

Just stick a 'Lizard Skin' over that area or as was recommended earlier, get a pedal with reduced float.
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Old 02-21-06, 11:52 AM   #5
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I can't imagine how your shoe could be contacting the chainstay in that location. It looks like chainsuck on the big ring to me, but it's odd that you'd have the same problem on two bikes at the same time. If it is chainsuck, you'll need chains and chainrings.
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Old 02-21-06, 11:54 AM   #6
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Too close to the chainring for heel (and probably shoe) contact. Most likely the chain.
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Old 02-21-06, 11:58 AM   #7
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I must concede that those up and down marks in a semi-sinesoidal pattern do look like they're caused by the chain. If it were a shoe, the marks would be vertical-parallel.
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Old 02-21-06, 12:21 PM   #8
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So if I understand correctly, the chainring is lifting the chain up to where it makes contact with the frame? That seems like quite a distance. Is there something I can do to prevent this? A shifting/pedaling technique? I don't see how anything could be mechanically wrong, it's performance/shifting has been flawless.
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Old 02-21-06, 12:36 PM   #9
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Like I said, if it's chainsuck you need a new chain and chainring.
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Old 02-21-06, 12:52 PM   #10
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naa, just reduce speed at bumps/potholes & another vote for a road neoprene sleeve.
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Old 02-21-06, 06:42 PM   #11
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Quote:
Originally Posted by thatguy
So if I understand correctly, the chainring is lifting the chain up to where it makes contact with the frame? That seems like quite a distance. Is there something I can do to prevent this? A shifting/pedaling technique? I don't see how anything could be mechanically wrong, it's performance/shifting has been flawless.
It's probably not the chainring lifting the chain. It's more likely the chain coming down to slap the chainstay.
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Old 02-21-06, 10:42 PM   #12
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It's probably your chain when your in your small ring and small cog and it is just bouncing up and down. It's common when you transport the bike in a car. As far as the shoe possibility goes unless you wear a size 36 or a size 5 there is not way it is coming from your heel because it would be farther back on the chainstay by the derailleur.
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Old 02-21-06, 10:50 PM   #13
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my bet is the chain. Strap an used bike inner tube over it to protect your frame.
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Old 02-21-06, 11:13 PM   #14
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Not ordinary chain slap it isn't.

And you would know if you had chain suck, it makes the crank set come to a sudden stop as the chain winds up. And even if it didn't come to a stop, it make lots of noise so you would know about it all right. And not on both bikes - that would be quite strange.

I wonder of you are leaning the bikes against each other or against a rough wall or heater or whatever that is scratching up the frame? Most people get off the left side, and lean the bike up against its right side when parking it.
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Old 02-21-06, 11:26 PM   #15
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Originally Posted by jur
I wonder of you are leaning the bikes against each other or against a rough wall or heater or whatever that is scratching up the frame? Most people get off the left side, and lean the bike up against its right side when parking it.
I guess most people do tend to do that. I'm opposite but then again I'm also left-foot chocolate.

As far as the chainstay scratches go. I'm inclined to believe it's from chainslap while in the inner ring. What kind of setup are you running? Double? Triple? What kind of rear derailleur cage do you have? Long? Medium? Short? Have you checked your chain sizing to make sure it's not too long? Regardless, I'd reccomend a Lizard Skin neoprene wrap.
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Old 02-22-06, 12:18 AM   #16
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it is my belief that chainsuck is causing your problem, when the chain sticks to the chainring when shifting and sneaks in between the bottom of the chainstay and the chainring. like dirtdrop said, you need to replace the chainring/chain
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Old 02-22-06, 02:38 AM   #17
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One question that should settle things: Are the marks shown in the pic dirty grease from the chain? If so, then it must be something like chain suck (although it would be one helluva coincidence this happens on both bikes at once) or an extreme form of chain slap, but that's still bottom on my list. Chainsuck could happen when running cross-chained (small-small). That's bad for the drive train. I hope you don't do this?
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Old 02-22-06, 07:43 AM   #18
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The Butler did it, in the Library, with the Candlestick.
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