I've got shift problems! Help!

[brad c]

I have a 2000 k2 evo that flexes so much when I step on the gas that it starts to shift.  It doesn't actually shift, it just crunches.  Which direction is it trying to shift...larger or smaller ring?  Are there any possible causes I can check other than frame design?  If so what should I look for?  Also, if I can't solve the flexing problem, can I compensate ever so slightly with the deraileur adjustment to make the crunchity stuff stop?  By the way, if you haven't slapped a talas on your bike...do it straight away.  Rediculous improvement in stiffness and accelleration. There might still be some you can buy for a song.

[Thunderchild]

Have you shortened any cable housing; namely the section between the front triangle and the rear swingarm?  I did this once by accident.  The bike shifted whenever the rear shock compressed.  

Thunderchild

[brad c]

I did recently change all the cables and housings but if anything they're longer.  However, I'll put the bike up on the stand and test that tomorrow.  I appreciate the tip.  Oh, and can you really pedal hard enough to flex the rear triangle enough to cause shifting problems?  A friend of mine told me that was the likely culprit but I just don't see putting out that much torque.  

[kiwi]

has it always done this or just started?I thought lateral stability and flex were opposite.
The only thing i can think of is the tourque of the swingarm pivot and or a new pivot kit

[brad c]

Well, It's very likely that I'm using the wrong terms...as this is only my second season riding and I've got a lot to learn.  I've noticed shifting problems on the bike before but it wasn't untill recently that I noticed the problem happening consistantly, and specifically while accelerating hard.  Any tips on how to check or find the specs on those pivots?  I read the sticky about iron horse having parts, I may just order a new pivot from them just to buy stuff for my bike.  

[brad c]

I had another question but i just answered it myself.

[shovelon]

Just a few thoughts.

Check your deraileur hanger for broken or loose screws.

Check your drive side crankarm for any looseness. If you have a square taper BB, it could twist just enough to catch a tooth.

Check the slackness of your chain. A worn chain or weak derailuer spring could send your chain flopping around. I had this happen with an SRAM ESP deraillure that eventually got trashed. Went to XT and problems went away.

Good luck,

Terry

[Colin]

Is it the front or rear that's "crunching"?
If it's the front then the crank could be loose or misaligned. or the chainset teeth are worn.
Sounds more likely to be the rear, in which case.....
It could just be that the drive components are worn.
i.e. chain, cassette, jockey wheels.
I'd check these first.
If the chain is old and has stretched then it will cause gear "jitters".
If the cassette teeth have worn then the chain will jump about and skip teeth or try to climb or drop onto another gear.
If either of these then change the cassette and chain at the same time and ensure they are compatible.

[brad c]

I only have one season on the chain/rear cassett, and the front rings have less than 200 miles on them.  I didn't think about the jockey wheels.  My last ride didn't reproduce the same shifting problems but I wasn't pushing as hard so I don't know.  I'm definately going to check my whole drivetrain.

[Carbon_Angus]

yeah jockey wheels...

had an issue with a single speed that would eat up jockey wheels and then i'd jump the rear cog, or even front cog....depending on the mood of my bike.

good luck

[kiwi]

It sounds like you have new front rings?Maybe the chain alignment is slightly out and with a little bit of flex is just catching on the side of the next cog