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New Chain causing skipping on cassette - will this work itself out or is it unsafe?

Bicycles Asked by Dan Catlin on June 15, 2021

I just installed a new chain on my 2002 Trek 2200 Road Bike. The old chain was a Shimano 9 speed that I installed 18 months and about 5000 miles ago. It had stretched modestly and was full of winter cruft/grime. The new chain is a SRAM 9 speed, my first time using the gold snap ring system. I followed instructions and made sure I have the same link count as the chain that came off the bike. The cassette was new with the old chain, so it has about 5000 miles on it and doesn’t appear to have significant wear. After installation and a clean/wipe/lube/wipe, I took it for a 15 mile easy ride at about 15-16 mph. It shifts perfectly and I didn’t have to make any adjustments to either derailleur. Three times, however, when putting it under stain (once on a modest hill climb, once starting from a stop sign in a fairly big gear, and once on an acceleration coming out of a sharp turn) it skipped several teeth and caused my foot to slam down hard. On the hill, it actually hurt as I had my weight off the saddle (not really standing) and I came down hard on the inside of my thigh. I think all three were on the right side (power train side) pedal stroke, and I don’t think they were all in the same gear. I’m pretty sure it was the rear cassette that skipped, not the front chainring, but it did happen really fast each time. I will also say that it’s not like these were the only three times I put substantial pressure on the pedals in the ride – I wasn’t going hard, but I wasn’t being tentative or anything. Also, in case it’s relevant, it was cold, about 40 degrees F or about 4 degrees Centigrade.

My question: Is this going to get me hurt, or will the new chain ‘settle in’ over a few rides? I searched here and pretty much got confirmation of what I had previously thought, that you always get a new chain when you get a new cassette, but you should be able to get a few chains out of each cassette. Thanks!

5 Answers

Over time an old chain and cassette wear together, so you don't notice the wear until it gets really bad. When you replace the chain while leaving the old cassette the tooth profile is no longer correct and the new chain will skip off of the teeth, especially under load.

Unfortunately it won't get better and the only recourse is to replace the cassette as well. In the future you can save money by changing the relatively inexpensive chain more often as the cassette wears faster with an elongated chain.

More info: http://sheldonbrown.com/chains.html

Answered by Rex Kerr on June 15, 2021

You might need to get your derailleur adjusted; the new chain would be shorter than the previous chain and one might have bumped the derailleur upon installation.

Answered by Mimi Flynn on June 15, 2021

If you change your chain you must change the cassette or you're looking for problems.

The chain basically molds the cassette and when you put a new one on, it's fresh but the cogs are shaped by your old worn out chain.

So the new chain will not work well with the old, worn cassette.

Answered by roy on June 15, 2021

After 15000 miles on the same 9 speed chain, same cassette, and same chainrings on a Jamis Aurora 2010, my chain starting skipping when up off the saddle. One day the skipping caused me to flip forward onto my helmet/shoulder/left hip. I'm an advocate of always wearing a helmet now. I suspect I'd have a broken eye socket if I had no helmet. I too thought the skipping was on the rear cassette. But I was wrong. I first just changed the chain. Problem got worse. Then changed the cassette. Problem same. Did some closer testing and found when on the smallest chainring there was no skipping. Changed the two largest chainring and the problem was fixed. When purchasing a chainring you'll need to know the bcd (bolt circle diameter). It should be marked on the large chainring.

Answered by Joe Centurion on June 15, 2021

I have the same issue having changed the chain and cassette. The chain moves between the biggest cogs at the back when in the smallest at the front. Its also came off twice on first ride. Bike shop now says straighten hanger, adjust cable and derailler then replace jockey wheels. Says chain rings look okay. Have you tried those solutions?

Answered by James909 on June 15, 2021

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