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Chain Drop issue need help

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Chain Drop issue need help

Old 07-06-09, 07:29 PM
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BrooklynRoadie
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Chain Drop issue need help

Im having an issue that I just cant seem to resolve...

My bike is an 07 Tarmac Pro w/ 50/30 FSA Compact Crank

Last year I had a serious crash as a result of my chain dropping while sprinting

I was standing up and sprinting hard and the chain just jumped right off...
After the crash I replaced the chain and was told by my LBS that my front chain ring is fine and does not need replacement.


Im out riding tonight and im climbing up a hill while standing ...low cadence and just powering up a hill and the chain dropped again. Luck for me I was able to keep my balance and come to a safe stop...


What could be causing this issue???

The shifting has been fine and doesnt feel like i need an adjustment at all.
Im ready to order a new crank,cassette and chain just to play it safe

THANKS!
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Old 07-06-09, 07:33 PM
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maybe your front derailer is not adjusted correctly or,

I had one slightly bent tooth on my big ring that caused the same exact problem.

The bent tooth was barely noticeable.
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Old 07-06-09, 07:37 PM
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Does this happen when you shift? If so, does it happen when down shifting?

Does it only happen under strong power? Have you checked your chain for tension? Is it too loose?
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Old 07-06-09, 07:43 PM
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Originally Posted by gigemaggs99 View Post
Does this happen when you shift? If so, does it happen when down shifting?

Does it only happen under strong power? Have you checked your chain for tension? Is it too loose?
Only happens when im putting down alot of power... EG low cadence , uphill or a hard sprint...
Ive had issue before where I would hear it make a loud POP, but the chain drop last summer almost got me killed and kept me off the bike for 2 months, so im ready to throw everything in the driveline in the trash. Its very disheartening to be worried every time you try to put down some power that you might drop the chain.

The front derailleur seems perfect to me...no issue with upshift or downshift

Thanks for the quick replies
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Old 07-06-09, 09:09 PM
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Is it dropping to the inside or outside? Only on the small ring or from either?

If it only drops from a specific chainwheel, then I'd replace that one and see what develops. If it is dropping to the outside only, I'd change the big chainwheel and check the derailleur limit screw. Ditto for the inside only.

If it continues then I'd change the cassette because a bad skip could potentially cause the same problem under high power output if it skipped at exactly the right moment.

You shouldn't need a new crankset but from now on I'd suggest replacing the drivetrain yearly since you are racing and training on it.
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Old 07-06-09, 09:15 PM
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Originally Posted by Rob P. View Post
Is it dropping to the inside or outside? Only on the small ring or from either?

If it only drops from a specific chainwheel, then I'd replace that one and see what develops. If it is dropping to the outside only, I'd change the big chainwheel and check the derailleur limit screw. Ditto for the inside only.

If it continues then I'd change the cassette because a bad skip could potentially cause the same problem under high power output if it skipped at exactly the right moment.

You shouldn't need a new crankset but from now on I'd suggest replacing the drivetrain yearly since you are racing and training on it.
It drops to the outside only... Im not racing on it, but I do ride hard every day im out...

Im gunna order a new chainring,chain, and rear cassette and see what happens

Thanks!
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Old 07-06-09, 10:05 PM
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When was the last time you replaced your chain and cassette? How often do you replace each? My bets are on a chain skip in the rear that causes the initial problem, then the chain derailing after the chain slip. It's pretty hard to spontaneously lose the chain to the outside when just pushing the pedals (i.e. not shifting).
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Old 07-06-09, 10:16 PM
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Originally Posted by Brian Ratliff View Post
When was the last time you replaced your chain and cassette? How often do you replace each? My bets are on a chain skip in the rear that causes the initial problem, then the chain derailing after the chain slip. It's pretty hard to spontaneously lose the chain to the outside when just pushing the pedals (i.e. not shifting).
I would vote for this too. If you not doing any shifting it isn't the front derailleur. To just drop because you are putting more power down would either be chain jumping due to a worn cassette or a bent big ring. I know that putting more power down will cause a worn cassette to cause the chain to jump. Luckily mine did not drop, but it was still scary.
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Old 07-07-09, 12:39 AM
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Originally Posted by Paniolo View Post
I would vote for this too. If you not doing any shifting it isn't the front derailleur. To just drop because you are putting more power down would either be chain jumping due to a worn cassette or a bent big ring. I know that putting more power down will cause a worn cassette to cause the chain to jump. Luckily mine did not drop, but it was still scary.

+1 Worn drive trains can behave quite nicely as long as you don't shift gears. Also, make sure the F DER is dialed in. Maybe do that first.
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Old 07-07-09, 06:44 AM
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Could be one bent tooth. You can usually tell by looking at all the teeth and it'll be the shiniest one. I had a bent tooth that was giving me horrible chain suck. when I shifted down from big to small, the chain would jump off the big to the right. Destroyed a FD in the process. How it was happening I don't know.

But I found the tooth and took care of it and now it doesn't do it anymore.
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Old 07-07-09, 06:50 AM
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I would also check the height of the derailleur in relation to the chainrings. With compact rings, the derailleur needs to be moved lower on the braze on mount (or the clamp moved down the seat tube) than with a 53 tooth outer ring.
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