mac

Very rarely have I noticed any shifting/slipping of my derailleurs. However, on my 2nd to last ride, when I was pedaling hard, especially up a mountain, I noticed my rear derailleur kept shifting/slipping. I was so bad I took my bike in for a tune-up.

On my last ride this morning (commute to work), the rear derailler continued to shift/slip on the flats and as I was climbing a mountain the front derailler started to shift/slip as well. Finally, the chain snapped off - I broke one of the links! So I had a 1+ hour walk home to try to think of what the problem would be.

I took it back to the bike shop and they replaced the chain. They suspect that one or more gears/teeth on my rear cassette might be worn. I'm not sure how that would explain the front derailler slipping this morning. If I have time this evening, I'll take my bike for a test ride to see if the new chain fixed my problem or not.

Any suggestions from you guys what it might be?

• 2005 Cannondale T2000 Touring Bike
• 2,800+ miles on same chain before it snapped
• total bike weight ~ 50lbs
• me < 200 lbs

MudPie

I'd vote the old chain had a jacked-up link. This link was causing the mis-shifts and finally broke.

Now, I'm not too sure what a jacked up link might be. Perhaps a damaged side plate, caused by some sort of impact to it (say chain was in big ring, and you smacked a rock) which damaged a link. Or a pin started working itself out (the pin could catch on parts and cause mis-shifts) and finally broke.

I carry a SRAM Powerlink in my Camelbak to repair busted links on chains. I've replaced three links on trail (all other riders) in my many years of riding.

operator

At your weight and your mileage, probably chain wear. Did you keep the chain to measure for wear? The more worn a chain is the more likely it is to break under load.

mac

No, I had my LBS dispose of it. Well I went for a 30-mile ride this evening around the mountains and I think it was just the chain. Only once did I have some gears shift/slip, but I adjusted the cable tension on-the-fly and it went away. Sheesh, I'm glad I wasn't on tour in the middle of nowhere when my chain snapped. How can you tell when your chain is going bad? Once I started having shifting problems the chain snapped within 20 miles.

Bill Kapaun

My guess would also be a damaged or stiff link.
Maybe the chain had already lost one sideplate and was warning you?