thefsb

Recently my bicycle has developed an unpleasant noise while pedaling in the smaller sprockets, either in the large or small chainring. It's an irregular click/clunk noise. It started just a couple of weeks ago and quite suddenly. It appears to be caused by the outer plates and/or pins of chain links catching against the teeth of the next largest sprocket as the chain comes off the top of the sprocket.

Set up is Specialized Tarmac Pro, Neuvation wheel, SRAM OG-1070 12-26 cassette, SRAM PC-1070 chain, Dura Ace crank and rings.

I checked that he chain has unmeasurable stretch, the freehub and cassette are properly in alignment, neither der nor hanger are bent, der pulley wheels spin clean and free, and shifting performance is perfect. A mechanic at an LBS confirmed all these points.

I took some photos to show the issue:

https://www.flickr.com/photos/9688232...7617695889604/

Chain-1.jpg and Chain-crop-1.jpg show a decent gap between the chain and next larger sprocket, as you'd expect. Chain-2.jpg and Chain-crop-2.jpg show the chain touching a tooth of the next larger sprocket. I've observed that the loudest clunks happen when I can see the chain not disengaging from a tooth for a moment and then snapping off. It can be enough to set the spokes of the rear wheel ringing.

But how can this be happening? It almost seems as though the chain got wider but I've never heard of such a problem. And I'd expect that only if there were also measurable chain stretch, which there is not.

Any thoughts?

Tom

merlin55

I having the same issue, everthing else is the same except for a Dura-Ace chain. I'm starting to think it is related to the SRAM cassettes missing teeth on the smaller cogs.

thefsb

has this always been a problem for you or is it new? how old is the cassette and the chain?

i've noticed tat the catching is certainly worst on the tooth behind the missing tooth. but i find it also happens elsewhere on the cassette, just not so severe.

i just can't figure how come the chain can ride so far to the inside without ithe chain itself being too wide.

NRRider

Just a shot, but make sure if you are using Wipperman Connex link that it is installed properly. If the link is not installed correctly it will cause similar symptoms.

thefsb

it's a SRAM chain with a SRAM power-link connector. the power-link appears to be unrelated to the problem. it seems any chain link can catch a tooth of the next higher sprocket.

thefsb

The problem is the SRAM cassette.

1. When I put my racing wheels with Ultegra cassette on the racing bike, the problem is cured.

2. When I put the clincher wheels with the problem SRAM cassette on my long-distance bike (which has an Ultegra chain) the exact same symptoms appear.

How to cure a lumpy OG-1070 cassette?

HillRider

Since the problem seems to be characteristic of that SRAM cassette design, the only "cure" is probably replacement with a Shimano casette.

neil0502

Switch to an 11-speed chain??

thefsb

i think you're right, hillrider.

i rode two laps of the saratoga 24 hour race this month with a wheel that had this cassette on. after that i changed cassettes. i could only use the biggest 4 cogs, all others producing such klunks, lumps and skips that i was too scared to ride them.

guess i'll stick to shimano cassettes from now on.

MudPie

I have a similar setup: SRAM PG1070 cassette and PC 1090 chain with no problems. When researching SRAM cassettes, there is a difference between the OG (open glide) and PG (power glide) series. I read some anecdotal evidence of problems with the cut teeth on the OG series. You might want to do a search on OG vs PG cassettes and see if your problems are experienced by others. I forgot the exact problems, but they were enough to steer me towards the PG cassette.