Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 10-18-10, 01:28 PM   #1
carleton
Elitist
Thread Starter
 
carleton's Avatar
 
Join Date: Jul 2005
Location: Atlanta, GA
Bikes:
Posts: 13,364
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
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
__________________
Quote:
Originally Posted by gtrob View Post
Roadies can run tempo all year as that's what humans were designed for. If you want to be a cheetah, lay around and lick your paws more.
carleton is offline   Reply With Quote
Old 10-18-10, 01:41 PM   #2
DaveSSS
Senior Member
 
Join Date: Sep 2008
Location: Loveland, CO
Bikes: Two LOOK 585s, one KG461
Posts: 4,987
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
DaveSSS is offline   Reply With Quote
Old 10-18-10, 01:44 PM   #3
carleton
Elitist
Thread Starter
 
carleton's Avatar
 
Join Date: Jul 2005
Location: Atlanta, GA
Bikes:
Posts: 13,364
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
I'll try that. Thanks!
__________________
Quote:
Originally Posted by gtrob View Post
Roadies can run tempo all year as that's what humans were designed for. If you want to be a cheetah, lay around and lick your paws more.
carleton is offline   Reply With Quote
Old 10-18-10, 06:18 PM   #4
FastJake
Constant tinkerer
 
FastJake's Avatar
 
Join Date: May 2010
Location: Madison, Wisconsin
Bikes:
Posts: 7,577
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by DaveSSS View Post
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.
FastJake is offline   Reply With Quote
Old 10-18-10, 08:48 PM   #5
carleton
Elitist
Thread Starter
 
carleton's Avatar
 
Join Date: Jul 2005
Location: Atlanta, GA
Bikes:
Posts: 13,364
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
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.
__________________
Quote:
Originally Posted by gtrob View Post
Roadies can run tempo all year as that's what humans were designed for. If you want to be a cheetah, lay around and lick your paws more.
carleton is offline   Reply With Quote
Old 10-18-10, 09:11 PM   #6
FastJake
Constant tinkerer
 
FastJake's Avatar
 
Join Date: May 2010
Location: Madison, Wisconsin
Bikes:
Posts: 7,577
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
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....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.
FastJake is offline   Reply With Quote
Old 10-18-10, 09:12 PM   #7
carleton
Elitist
Thread Starter
 
carleton's Avatar
 
Join Date: Jul 2005
Location: Atlanta, GA
Bikes:
Posts: 13,364
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
Will do.
__________________
Quote:
Originally Posted by gtrob View Post
Roadies can run tempo all year as that's what humans were designed for. If you want to be a cheetah, lay around and lick your paws more.
carleton is offline   Reply With Quote
Old 10-18-10, 09:29 PM   #8
DaveSSS
Senior Member
 
Join Date: Sep 2008
Location: Loveland, CO
Bikes: Two LOOK 585s, one KG461
Posts: 4,987
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by FastJake View Post
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.
DaveSSS is offline   Reply With Quote
Old 10-19-10, 12:50 PM   #9
Jed19 
Senior Member
 
Jed19's Avatar
 
Join Date: Oct 2004
Bikes:
Posts: 4,228
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
__________________
Regards,

Jed
Jed19 is offline   Reply With Quote
Old 10-25-10, 12:06 AM   #10
inthewoods
Junior Member
 
Join Date: May 2007
Bikes:
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.
inthewoods is offline   Reply With Quote
Old 10-25-10, 03:32 AM   #11
carleton
Elitist
Thread Starter
 
carleton's Avatar
 
Join Date: Jul 2005
Location: Atlanta, GA
Bikes:
Posts: 13,364
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
Quote:
Originally Posted by inthewoods View Post
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.
__________________
Quote:
Originally Posted by gtrob View Post
Roadies can run tempo all year as that's what humans were designed for. If you want to be a cheetah, lay around and lick your paws more.
carleton is offline   Reply With Quote
Old 10-25-10, 07:25 AM   #12
BobLoblaw
Dough Mestique
 
Join Date: Feb 2009
Bikes:
Posts: 349
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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.

Quote:
Originally Posted by inthewoods View Post
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.
BobLoblaw is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 08:45 AM.