New drivetrain skipping

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t0pc4t
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New drivetrain skipping

Postby t0pc4t » Sun Oct 14, 2012 09:57 am

I've fitted a new drivetrain to my hard tail and I'm finding some odd behaviour when on 6, 7, and 8 on the cassette.

My bike had done about 9k mainly road miles and in that time I have changed the chain a couple of times but nothing else.

It was getting pretty creaky do I got a shop with a good mechanic to fit a new Deore triple chain set. I fitted a new cassette (shimano hg50) and chain. I also treated myself to some jagwire cables. The shifters are the original Deore and the mech is Deore at the front and Deore lx at the back.

A couple times I have had to re-tension the rear mech which I put down to not doing the pinch bolt tight enough.

My problem is that I get skips / slow changes on gears 6,7 and 8 on the rear cassette. This is more pronounced on the middle crank but I can hear something not right even on the top crank.

Yesterday I checked all the limits were correct, made sure the mechs were tensioned properly and shifting cleanly and cleaned the chain before re-lubing with finish line clean ride.

On the stand I can't see a problem it's only when I am riding that the issue manifests. Once in gear it's normally ok bust if I switch from top crank to middle it will skip.

On lower ratios on the cassette it doesn't seem to be an issue.

Chain is SRAM PC951 but I've had loads before and had no issues.

Be grateful if anyone can suggest what to check next, I'm not the best bike mechanic but I'm interested and I'd like to solve this problem rather than asking a shop to.
Whether you're a king or a little street sweeper, sooner or later you'll dance with the reaper.

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snapper52
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Re: New drivetrain skipping

Postby snapper52 » Sun Oct 14, 2012 12:56 pm

Had this problem recently myself after fitting new chain. Cured it by fitting new chainrings. No skipping at all after that.

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supersonic
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Re: New drivetrain skipping

Postby supersonic » Sun Oct 14, 2012 12:57 pm

He's just put a new chainset on ;-)

Check the cables are free flowing, it may not be allowing perfect changes. often new ones may be badly cut, too tight etc.

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t0pc4t
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Re: New drivetrain skipping

Postby t0pc4t » Sun Oct 14, 2012 13:08 pm

Thanks SS.

I'll check cable runs. It can actually happen without a shift on the rear just moving from 7th on top crank to 7th on middle.

I had to size the chain as the new cassette has different ratios to the old. Do you think it could be a badly sized chain? Jockeys needing replacement? I'm puzzled why it only happens in certain scenarios but that these appear to be fairly constant
Whether you're a king or a little street sweeper, sooner or later you'll dance with the reaper.



Cube Curve 2009

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supersonic
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Re: New drivetrain skipping

Postby supersonic » Sun Oct 14, 2012 13:16 pm

How did you size it? Shouldn't really make a difference.

Also check rear mech is straight.

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t0pc4t
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Re: New drivetrain skipping

Postby t0pc4t » Sun Oct 14, 2012 15:52 pm

I found a method on sheldon brown. Without threading through mech I went big - big on cassette and cranks then took an extra inch or so (one outer and inner link)

Will check straightness I had not thought to do that
Whether you're a king or a little street sweeper, sooner or later you'll dance with the reaper.



Cube Curve 2009

Giant Anthem X4



FCN=6

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The Rookie
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Re: New drivetrain skipping

Postby The Rookie » Sun Oct 14, 2012 19:28 pm

Then your chain is the right length.....

Also if your indexing isn't spot on changing ring at the front can make it hunt between 2 at the back, check visually that in all gears the guide (top) Jockey is in line with the sprocket.

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t0pc4t
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Re: New drivetrain skipping

Postby t0pc4t » Mon Oct 15, 2012 08:29 am

thanks Simon

Another thing I had not thought to check
Whether you're a king or a little street sweeper, sooner or later you'll dance with the reaper.



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