Bicycle Mechanics - New cassette. Upshifting is very harsh.

I recently switched from a Shimano 105 12-27 cassette to a SRAM 1070 11-23. After removing chain links and making minor adjustments, I go for a test ride. Often when I upshift to a smaller cog on the rear there is a violent "CLUNK" as it drops on to the new ring. This causes my foot to jerk forward when this happens under load. But this clunk also happens when it's on the bike stand. Shifting to larger rings seems to be fine.

Is this just a difference in how Shimano and SRAM handle things or do I need some finer adjustment? This never happened with the previous cassette.

Thanks,

C

The most common reason for this is simply too little shift cable tension. Try a little more cable tension to favor shifts to the larger cogs.

I'll try that. Thanks!

The most common reason for this is simply too little shift cable tension. Try a little more cable tension to favor shifts to the larger cogs.

Wait.. I think you have it backwards. If it shifts to larger cogs fine, but jumps badly when going to a smaller cog, there is too much cable tension. Turn your adjusting barrel clockwise a turn or two and see if it helps.

I made adjustments to the tension and it didn't seem to help.

To be more specific: When I shift down the cassette (away from the hub) it's like the chain is dropped on the smaller cog as opposed to being lowered into it. So there is a skip/jump/hitch in the pedal stroke as if I missed a shift or something. But, the chain lands solidly into the next gear.

All of the equipment and bike are relatively new. Less than 200 miles.

You can try reducing your B-tension now that your largest cog is a 23 instead of 27. That will put your derailer pulley closer to the cassette and provide better shifting.

http://www.sheldonbrown.com/derailer-adjustment.html#btension

But I haven't found the B-tension adjustment to be too critical. Honestly I think you need to just reduce your cable tension until it shifts down smoothly. Try reducing it so much that it doesn't shift up smoothly, and see if the downshifting is improved.

Will do.

Wait.. I think you have it backwards. If it shifts to larger cogs fine, but jumps badly when going to a smaller cog, there is too much cable tension. Turn your adjusting barrel clockwise a turn or two and see if it helps.

Nope. If the shifts to smaller cogs is heavy and fast (clunking), it means the cable tension is too low. If you have too much cable tension, the shifts to smaller cogs will hesitate or not execute at all.

Always turn the adjusting barrel towards the problem. If the shift is heavy when shifting to the smaller cogs, then the barrel adjuster should be tweaked ever so slightly clockwise. If the other way, then counter-clockwise.

My guess is that you are sensitive to the way that the SRAM OG (Open Glide) design guides the chain onto the lower cog. Look at the SRAM cassette and you will see that most of the cogs have 1 missing tooth, this is the source of the clunk. I think SRAM would call the shifting precise or quick rather than harsh, but your opinion may differ. The previous advice on tweaking the cable tension should help a bit, but the nature of the OG design will always lead to a more sudden shift versus the Shimano IG/HG cassette design.

My guess is that you are sensitive to the way that the SRAM OG (Open Glide) design guides the chain onto the lower cog. Look at the SRAM cassette and you will see that most of the cogs have 1 missing tooth, this is the source of the clunk. I think SRAM would call the shifting precise or quick rather than harsh, but your opinion may differ. The previous advice on tweaking the cable tension should help a bit, but the nature of the OG design will always lead to a more sudden shift versus the Shimano IG/HG cassette design.

I think you are right.

I think this is correct. SRAM shifting tends to be a bit more "industrial" feeling/sounding, where Shimano tends to be smoother. Both work fine.


My guess is that you are sensitive to the way that the SRAM OG (Open Glide) design guides the chain onto the lower cog. Look at the SRAM cassette and you will see that most of the cogs have 1 missing tooth, this is the source of the clunk. I think SRAM would call the shifting precise or quick rather than harsh, but your opinion may differ. The previous advice on tweaking the cable tension should help a bit, but the nature of the OG design will always lead to a more sudden shift versus the Shimano IG/HG cassette design.