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Crankset Slippage Under Load

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Crankset Slippage Under Load

Old 09-02-15, 09:04 PM
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Crankset Slippage Under Load

Hello all,
I recently acquired a second-hand, like-new carbon fiber road bike with full ~2010 SRAM Red groupset with the exception of a SRAM Force Yaw front derailleur. I recently (as in within the past two days) had everything adjusted and tuned up -- I've taken the bike on no more than four or five rides, and the person who owned it before me did nothing more than that either. The parts are all effectively new. However, halfway through my ride this afternoon, I was in the large gear on the crankset and the third or second-smallest on the cassette, and while trying to pedal at a decent cadence, the chain or crankset seemed to slip, as if the chain were skipping a link or something. Knowing that none of the parts have more than 200 miles on them, what could the problem be? I have read that it may be due to loose bolts on the crankset, but I'd hate to go all the way to my LBS and find out the problem was something that I could've easily fixed at home for little to no cost. Thanks in advance!
Danny
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Old 09-02-15, 09:12 PM
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If nothing is worn, it sounds more like a rear derailleur adjustment. I think if the chainring bolts were really loose, you'd know it. Of course it's easy enough to simply check them.
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Old 09-02-15, 09:17 PM
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A worn rear cassette will skip with a new chain. How do you know the cassette only has 200 miles on it? The rear derailleur could be misadjusted and that will be easy to spot by eyeballing the chain as it leaves the rear cassette and travels to the first derailleur pulley.
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Old 09-02-15, 10:01 PM
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To respond to both of you, the rear derailleur has been adjusted twice in the past week by my LBS on two separate occasions to fix two separate problems. I don't think the rear derailleur has touched anything since then -- I've been in no crashes, and I don't even think I've leaned the bike up against anything. I see no reason the rear derailleur should be misadjusted, though I understand how that could be the source of the problem.
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Old 09-02-15, 10:12 PM
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I just had this problem recently, but the chain would actually get thrown off of the front ring under heavy loads (though it would slip beforehand, as well). Turned out to be a couple of worn and bent teeth on the front chainring. I replaced the crankset, and all is good again.

Although your components are relatively new (mine had about 15k miles when it occurred), check the integrity of the front rings (trueness of the ring itself, as well as the teeth).
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Old 09-02-15, 10:13 PM
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Its amazing how many 5-10 year old used bikes seem to only have 200 miles on them
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Old 09-02-15, 10:38 PM
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Originally Posted by rms13
Its amazing how many 5-10 year old used bikes seem to only have 200 miles on them
I understand what you're getting at -- however, by both my observation and the observation of my LBS, the parts are in like-new condition. I've had bent teeth on bikes before and the problem was visibly obvious. I've seen nothing of the sort regarding my current bike and problem.
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Old 09-02-15, 11:17 PM
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Originally Posted by dannyboy2233
I understand what you're getting at -- however, by both my observation and the observation of my LBS, the parts are in like-new condition. I've had bent teeth on bikes before and the problem was visibly obvious. I've seen nothing of the sort regarding my current bike and problem.
It's very difficult to detect worn teeth on the cassette. Get a new one and change it out. You'll need a new one at some point anyways and it's a simple test.
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Old 09-03-15, 04:43 AM
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As mentioned, newer chain on older cassette is the main culprit. Less likely is a problem with the freehub.
Does it only happen in specific gears ??
Sometimes you can live with it and the chain will "break in" to that cassette after a bit. Depends on how bad it is and your patience level.

P.s. Post in the mechanics forum next time.
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Old 09-03-15, 05:39 AM
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Something to check would be spacers behind the cassette if applicable. I recently test rode some 11 speed wheels on my bike that required spacers behind my 10 speed cassette but everyone assumed it needed one spacer when it actually needed two. With only one spacer I kept getting the feeling of slippage under power, put both spacers in and problem solved.
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Old 09-03-15, 06:05 AM
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If all else is good, and it showed up on the smallest cogs:

Check for a tight link in the chain. Just handle the slack side of the chain, and make sure everything flexes easily. Pay attention to your missing link, to make sure that it is the right size for the chain.

It may be a very slight tweak to a barrel adjuster, like 1/8th of a turn. If it happens again, I would turn the rear barrel 1/8 turn clockwise. If that makes it worse, go 1/4 turn CCW. DO NOT PLAY WITH THE LIMIT SCREWS!!! They do nothing mid cassette.
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Old 09-03-15, 08:21 AM
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Originally Posted by RollCNY
If all else is good, and it showed up on the smallest cogs:

Check for a tight link in the chain. Just handle the slack side of the chain, and make sure everything flexes easily. Pay attention to your missing link, to make sure that it is the right size for the chain.

It may be a very slight tweak to a barrel adjuster, like 1/8th of a turn. If it happens again, I would turn the rear barrel 1/8 turn clockwise. If that makes it worse, go 1/4 turn CCW. DO NOT PLAY WITH THE LIMIT SCREWS!!! They do nothing mid cassette.
+1
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Old 09-03-15, 08:38 AM
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worn cog



test each cog by standing and mashing, when you find the culprit,


buy individual cogs here....

https://www.universalcycles.com/shop...hp?category=40

Last edited by bt; 09-03-15 at 09:12 AM.
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Old 09-03-15, 09:06 AM
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If you are really adverse to spending money ride it carefully for a couple of weeks. If it is a worn cassette (most likely) the chain will wear in. Replace the cassette on the next chain replacement. Do this too many times and you will be replacing chain rings.
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Old 09-03-15, 09:33 AM
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Originally Posted by dannyboy2233
To respond to both of you, the rear derailleur has been adjusted twice in the past week by my LBS on two separate occasions to fix two separate problems. I don't think the rear derailleur has touched anything since then -- I've been in no crashes, and I don't even think I've leaned the bike up against anything. I see no reason the rear derailleur should be misadjusted, though I understand how that could be the source of the problem.
Well I can think of at least one reason
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Old 09-03-15, 12:22 PM
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As others have said - worn cassette. Second hand is second hand. I wouldn't trust any 5 year old used bike someone claimed to have only 200 miles on certain parts.

New cassette + new chain = fixed bike.
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Old 09-03-15, 12:26 PM
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I also think the most likely cause is a worn cassette/chain. Replace them both and I'd bet the slippage goes away.
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