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Old 10-05-09, 05:48 AM   #1
TurbineBlade
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Does cable tension matter for friction shifting?

Hi, I am using a new RD and chain on my bike and set it up the normal way by setting stop limits, and removing "slack" from the shift cable and tightening the anchor bolt. In the stand, it shifts through all the gears great.

On the road, it shifts great and feels good in most gears...but a couple of gears give a "grindy/crunching" sensation when pedalling. No noise, just feeling through my feet that I haven't had before.

Does this have anything to do with excess tension on the shift cable? I always wondered if using the barrel adjuster really matters with friction shifting like it does for index...Can too much tension cause over-shifting of some cogs..well, maybe make it difficult for me to find the sweet spot?
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Old 10-05-09, 05:56 AM   #2
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A friction set-up can always be lever tuned perfectly if the mechanics are sound. Tension makes no difference.
Otherwise worn cogs or chain cause the grinding.
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Old 10-05-09, 06:01 AM   #3
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As long as the cable is tight enough for the working range of the lever to cover the working of the derailleur, cable tension doesn't matter in friction (non-index) shifting. You're adjusting the trim yourself after each shift so there's fixed relationship between the levers and RD position to adjust.

As far as the vibration you're feeling, if you can't resolve it by trimming the RD, it's probably related to sprocket wear. Since you don't ride on all your sprockets equally, some wear more than others. As the chain stretches it is better mated to the sprockets you ride the most, and will run less smoothly on the ones you ride the least.
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Old 10-05-09, 06:16 AM   #4
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Does the grinding feeling happen in gear combinations when the chainline is relatively straight? Or only in combinations where you are cross-chaining a bit?
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Old 10-05-09, 06:16 AM   #5
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I noticed a similar new sensation after I changed cogs and chain on my old and well used road bike a few years ago. It was chainring wear and it disappeared when I replaced the chainrings.
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Old 10-05-09, 06:54 AM   #6
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Your problem is caused by using a new chain on worn cogs.
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Old 10-05-09, 07:13 AM   #7
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Originally Posted by Dirtdrop View Post
Your problem is caused by using a new chain on worn cogs.
I've felt a similar sensation using a new chain on a new cassette. The feeling went away after a few rides. If the chain isn't slipping on the cassette, I'd keep riding it and and the feeling should disappear.
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Old 10-05-09, 08:33 AM   #8
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Did you check the B-tension screw?

If you're noticing the grinding in the largest rear sprockets, then it could be the B-tension adjustment. If this is set incorrectly, then the top pulley can run too close to the sprockets in back, causing issues.

Just a guess.
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Old 10-05-09, 12:38 PM   #9
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Great responses! Thank you.

The small chainring 42t is indeed old, and though it looks ok, it probably has some wear. The large chainring 52t is new.

It might just be the meshing of a new chain with this chainring. I will probably just ride it and hope the chain stretches a little to compensate.....By next spring I'll probably just replace the cassette, chain, and both chainrings all at once.
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Old 10-05-09, 12:46 PM   #10
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Derailleur alignment could be a culprit, if you are only having issues in a few cogs. Almost every bike I've ever seen had some sort of derailleur mis-alignment. Should be a cheap fix at the LBS, the tool DAG-2 is about 55 bucks.
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Old 10-05-09, 03:24 PM   #11
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Derailleur alignment could be a culprit, if you are only having issues in a few cogs.
That's what I was thinking, too. IME, this had a most noticeable effect when under load in the smaller cogs.
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Old 10-05-09, 06:31 PM   #12
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I'd also check my cable-tension. New cables tend to settle - called 'stretch' - and this will throw your derailleur(s) out of adjustment after about 5 miles on the road. 2 solutions exists:

1. Pull the cable until it's taut again and set the pinch-bolt to 48 - 60 inch-pounds.

2. Install a barrel-adjuster in your cable-line. These often have greater ability to adjust the cable than the one's that come as standard equipment at the shifters.

Not saying this is the case here. But am saying this is something to take into account.
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Old 10-05-09, 10:23 PM   #13
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While it's true that one should take the slack out of cables, that doesn't have anything to do with the noises he's trying to fix.

It's one or more of the "rear end" things others have suggested (worn cogs, derailleur alignment, b-tension adjustment, or simply not trimming the derailleur fully).

How much effort the OP wants to put into smoothing out this noise depends on how much it's driving him nuts, I guess.
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Old 10-06-09, 02:59 AM   #14
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On the way home yesterday, the sensation almost seemed to disappear for some reason. I'll try today and see how it goes. The feeling doesn't seem to be from trimming problems, as this produces a very audible cue.
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Old 10-06-09, 08:33 AM   #15
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Generally the sounds produced feeding the chain on the the bottom of the cassette, because of trim, RD alignment, or a "B" screw problem aren't felt as vibrations through the pedals. The "B" screw issue usually only becomes a problem on the larger sprockets.

Since he can feel the vibration I suspect that it's a chain, cassette, or chainring wear problem. That will affect how the chain comes of the top of the cassette or feeds onto the chainrings producing a telltale vibration which varies with the sprocket used and increases under load. If I'm right, better chain lube will reduce it significantly, but nothing will make it go away completely short of replacing the drive train components.
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Old 10-06-09, 08:36 AM   #16
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Quote:
Originally Posted by Panthers007 View Post
I'd also check my cable-tension. New cables tend to settle - called 'stretch' - and this will throw your derailleur(s) out of adjustment after about 5 miles on the road. 2 solutions exists:

1. Pull the cable until it's taut again and set the pinch-bolt to 48 - 60 inch-pounds.

2. Install a barrel-adjuster in your cable-line. These often have greater ability to adjust the cable than the one's that come as standard equipment at the shifters.
True for indexed shifting, but the OP is talking about friction shifting.
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Old 10-06-09, 09:01 AM   #17
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True for indexed shifting, but the OP is talking about friction shifting.
+100.

Cable tension/trim is the one thing we can definitely rule out with friction (non-index) shifting. Minor cable adjustments are meaningless since he has to trim by hand anyway. As long as he's able to shift the full range of the cassette the cable is fine.
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