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Serious Question about Chain Stay Damage

Old 05-29-14, 04:52 AM
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Binky
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Serious Question about Chain Stay Damage

Maybe I'm missing something obvious....

I have seen a lot of older and newer 10-speed road bikes that have various amounts of cosmetic damage to the paint on the top of the right chain stay from where the chain has impacted the stay.

I'm not talking about singular impacts but evidence that the chain has hit the stay frequently enough to blast the paint off.

How does this happen ??

If the chain is pulled tight across the top part of the loop while the rider is peddling, and held tight by the derailleur spring tension while coasting... when does the chain become slack enough to impact the stay ??



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Old 05-29-14, 05:09 AM
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Chain bouncing forces > spring tension when coasting. Especially on bumpy roads.
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Old 05-29-14, 06:34 AM
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the problem is sticky freewheels, the chain is sitting on the chainstay when the rider stops coasting and starts pedaling
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Old 05-29-14, 08:38 AM
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Or chain drop that occurs when the front derailleur isn't properly adjusted.
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Old 05-29-14, 09:01 AM
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Or when you remove the rear wheel for servicing or transport of the bike.
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Old 05-29-14, 09:21 AM
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Binky, There doesn't need to be a problem on a bike for this to happen. In my experience it happens when coasting or braking and occurs most frequently on my mountain bike.

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Old 05-29-14, 09:40 AM
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Chain slap is a common "problem", especially on mountain bikes. When on smaller sprockets the chain passes above the chain stay with limited clearance. Chains a re relatively heavy and have high inertia, so when the bike hits a bump the chainstay rises and slaps the chain.

About the only way to prevent chain slap is to keep pedaling so as to keep the upper loop under high tension. However most people coast over bumps so chain slap happens.
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Old 05-29-14, 12:44 PM
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Common and unattractive, but immaterial and easy enough to cover up with a chainstay protector decal.
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Old 05-29-14, 09:12 PM
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Originally Posted by bradtx View Post
Binky, There doesn't need to be a problem on a bike for this to happen. In my experience it happens when coasting or braking and occurs most frequently on my mountain bike.

Brad
Mountain bikes, yes !! I can see how it might happen on mountain bikes - especially bouncing on or through really rough terrain, but not on a road bike, especially one that only sees smooth pavement.

What put me in mind of it was a perusal of a Aquila Strada Max from the early 1990s that my wife dragged home from a garage sale last weekend: It was filthy and had been hanging like Nosferatu for over a decade and the chain stay under the chain was perfect. Not even a flea bite.

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Old 05-30-14, 04:34 AM
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Bink, Going by brake track wear, that's a low mileage Aquila. Nice find by your wife!

I've on occasion found evidence of chain slap (lube on the chain stay protector) during a post ride check and can't remember any significant bumps. This may even happen when the bike is strapped onto the car rack?

Brad

PS The wide 3M vinyl electrical tape makes for a decent chain stay protector.
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Old 05-30-14, 07:08 AM
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Think about it: one good hard bump while coasting and you can wind up with a dozen or so marks in the chainstay paint from the bottoms of the links. Hardly a derailleur bike of any kind comes in without these marks. No big deal. There are myriad devices sold to prevent the damage.
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Old 05-30-14, 08:12 AM
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The problem is common enough that many bikes come with a clear plastic cover on the drive side chainstay to protect the paint and there are aftermarket protectors also available. As noted, well ridden bikes, even road bikes, with no signs of chainstay scratches are rare.
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Old 05-30-14, 11:01 AM
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That black sticker piece on top of the chainstay is there to Do that, To be more chip resistant than the Paint.


maybe the size of it is Not big enough for your desires , if so you can go find a bigger one ..
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