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Strange Chainring Slips

Old 12-13-06, 07:02 PM
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jsmog
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Strange Chainring Slips

Greetings,
I recently rebuilt my 21 speed Trek, got it powdercoated, the whole shebang. I've adjusted both front and rear derailleurs and they shift well when the bike is at rest. The front 3 chainrings, cranks and chain are new; I didn't replace the cassette but it didn't look too worn (the previous owner replaced the wheels, so they were not as worn as the chainrings). Here's the strange thing:

The RD shifts as before, always a bit clunky (7 rings and a bit tight). Now, however, under load the chain pops in 2nd gear on the front, especially when the RD is set to 5th or 6th gear. Unfortunately this is the cruise setting for my bike. I called my shop and apparently they didn't recognize my voice, they suggested new chainrings! I'm wondering if the cassette needs replacing, although it doesn't make sense...all the slips and pops are in the front. It doesn't slip completely into 1st or 3rd, but it does make it difficult to get up to speed, and I'm anticipating breaking the new chain. I've given the FD a careful look and it's not interfering with the chain in any gear. Ideas?

PS If you need frame powdercoating in the LA area: www.stevesplating.com in burbank, Steve's Plating, they'll clean off your old frame and recoat it for $100 cash.
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Old 12-13-06, 09:07 PM
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Im assuming your talking about the middle ring of a triple crank and 5 or 6 th in the rear being you smaller (higher) cogs. Check the chain line fron the rear cog to the front chain ring my guess would be that you have too severe of an angle and the chain is catching on the new teeth of the big ring and trying to shift. With a triple chainring in frt you shoul be able to get gear ratios close to what you want on the big ring in front and the larger cogs in back. Hope this helps
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Old 12-13-06, 09:14 PM
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It doesn't take much wear for a cassette, particularly the most used cogs, to skip with a new chain.
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Old 12-13-06, 09:56 PM
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GEt a new cassette.
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Old 12-13-06, 10:23 PM
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Previous owner may have gotten a new wheel but kept the old cassette. This is a very common problem with a new chain and an worn cassette. The old cassette will also cause the new chain to wear out faster. You may also have to replace the middle ring on the front, too.
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Old 12-14-06, 05:10 AM
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I think he said it was slipping in frt though?
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Old 12-14-06, 06:54 AM
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Just curious but how do you tell if the chain is slipping from the front definitely? Do you ride with your head hanging down over the cranks?! Sounds like a new cassette job to me if everything else is new. Chain line would have to be so far out to cause jumping I just can't really see it being that far out if it's so new.
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Old 12-14-06, 06:57 AM
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Originally Posted by svt4cam
I think he said it was slipping in frt though?
Very easy to misdiagnose.
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Old 12-14-06, 07:08 PM
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Originally Posted by HillRider
It doesn't take much wear for a cassette, particularly the most used cogs, to skip with a new chain.
+1

I tried the same thing. I replaced the chain & front chainrings, but kept the casette, since it "looked" OK. Then the chain started skipping on the rear. I bought a new casette (+ another chain) and the skipping stopped.

I compared the new sprockets (at least the loose ones) with the old ones while they were off the bike. The difference in the two was barely perceptible holding them up together - but the chain could tell.
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Old 12-20-06, 09:05 PM
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Yeah, yeah

Yeah, I looked at the old cassette again, it still looked fine, even held up against a new (which was not easy to find, a 7 spd. 12-28) but that apparently was it.

Originally Posted by byte_speed
+1

I tried the same thing. I replaced the chain & front chainrings, but kept the casette, since it "looked" OK. Then the chain started skipping on the rear. I bought a new casette (+ another chain) and the skipping stopped.

I compared the new sprockets (at least the loose ones) with the old ones while they were off the bike. The difference in the two was barely perceptible holding them up together - but the chain could tell.
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Old 12-21-06, 08:45 AM
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Cheapest thing first,I would try and put your chain on the large ring up front and the small one on the back.Then tighten the cable and then try adjusting it.Good luck.
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