Ghost shifting question??

[bevaaler]

I will make this short and simple.. I just put together my new 29er (Kona Kula) and took her out for maiden voyage yesterday. The bike was riding and shifting fine until I started up some steep inclines. I noticed mostly during climbing in the middle chainring & sometimes the granny that the bike would start skipping and trying to change gears when under moderate to heavy pedal power. On some of my final climbs out of Emeral Canyon, the disk brakes started rubbing.. I thought maybe the rear triangle was flexing or maybe the adjustable drop outs were moving, but everything seemed pretty tight and couldn't see that they had moved.. I am a shiaty at best mechanic, so I figured someone out there could give me some advice.. So far my 29er experience has not been that great, but it could be something very simple.. I am not sold on the darkside yet.. Any help, advice, whatever would be very much appreciated.. Thanks, Erik

Its a brand new drive train, 08' XT rear dr with Deore shifters, FSA cranks and chainrings.. Will check alignments again, it seemed OK but maybe with some cable stretching it has changed.. Thanks

[el_d00der1n0]

shouldn't have anything to do with the fact that your wheels are too big.

try messing with the indexing via the barrel adjusters. tighter to make it get up better, and looser to make it drop down better. don't crank them a bunch. just about a click at a time.

[jeffj]

If you have made sure the RD is adjusted properly (follow the installation instructions and it's usually pretty good). Put the shifter in second gear and see if the pulley on top of the RD is lined up directly in line with the #2 cog on the cassette. Look to see if it looks like the chain is being pulled slightly one way or another. You can usually see if the RD needs adjusting by looking at these things.

Shimano RD or SRAM?

If it's shimano, the first thing I would check is to make sure the housing from the swingarm to the RD is a fairly decent sized (length) loop and regardless of RD brand, if the housing runs under the BB shell to the swingarm, that is has enough room to not pull tight as the swingarm moves.

I have seen these two things cause ghost shifting many times. Doesn't look like it should, but it does.

Once those two issues are ruled out, make sure not cogs are bent or loose.

[BeantownRider]

After checking the RD alignment and the cogs, you should take a look at the chain as well.

On two occasions I've had brand new chains seize due to burs. Basically, one link was fused and didn't rotate. The affect was so similar to ghost shifting that it took me several rides and lots of frustration before I figured out the problem.

[SDstumpy]

I'd definitely check the chain out. I had the same problem last week. I had just replaced the chain but somehow one link got a little tight and caused the chain to skip. I won't buy a SRAM chain again. The power-link is nice but you can't replace tight links.

[lukewiens]

yeah...usually after a cable swap or rotor swap i get the same deal for the first couple of rides. i would just continue to adjust the boogers and my bet is they will even themselves out.

probably a little cable stretch and caliper mis-alignment....it is pretty easy to over diagnose things too quickly.

[92se-r]

Shimano = ghost shifting.

[el_d00der1n0]

Originally Posted by 92se-r

Shimano = ghost shifting.

not on mine.

[thephat]

In summary, eliminate each of these possible causes.

1. Tight or bent link in the chain. Contrary to what another poster said, tight links can be fixed, or replaced on a Sram chain. First try to work it our with some light side loading. Make sure the plates are not pressed together so tight that they make the link bind. You can also remove bad links, and install another power link.

2. Check cable tension.

3. Look for bent or deformed teeth on gears.

4. It sounds like all the parts are new, so it can't be a worn item?

5. You can have an issue with housing or cables that causes skipping.

6. Check the der hanger.

7. Is the rear der damaged somehow? Is it strait?

Originally Posted by 92se-r

Shimano = ghost shifting.

Only by a factor of two to one compared to Sram.

It used to be worse, but Shimano redesigned the cable routing for the rear der, making for less friction.

Not trying to bash Shimano. They make the best cranks on the market at every price point, and all Shimano is pretty good.

[thephat]

You can find stiff links in the chain by putting your bike in the smallest gear in the back, and back pedaling. Watch for jumping as the chain runs through the rear der pulleys. If it jumps, that will be your tight spot.

[DeeZee]

Originally Posted by el_d00der1n0

shouldn't have anything to do with the fact that your wheels are too big.

try messing with the indexing via the barrel adjusters. tighter to make it get up better, and looser to make it drop down better. don't crank them a bunch. just about a click at a time.

"shouldn't have anything to do with the fact that your wheels are too big."

[Cableguy]

Is the cassette new too? If you are mixing/matching new chain with old cassette, you will get ghost shifting. The only solution is to put back the old chain or replace the cassette.

[92se-r]

I agree Tani. I personally run a Shimano front der. and crankset. Didn't like the way the Truvativs and Race Faces mounted their crankarms together. Shimano by far has the easiest to install and best mounting system IMO of the 3. I also didn't like the SRAM front der. The cage seemed to rub more no matter how I adjusted it. The Shimano front der seemed to have more range without rubbing. I just hate the Shimano shifters and rear der. I was constantly maintaining them and cleaning. Can't speak about the new Shimano stuff though. Supposedly pretty good I hear.

[Upsidedown1]

Chain.

[Solo]

Originally Posted by lukewiens

yeah...usually after a cable swap or rotor swap i get the same deal for the first couple of rides. i would just continue to adjust the boogers and my bet is they will even themselves out.

probably a little cable stretch and caliper mis-alignment....it is pretty easy to over diagnose things too quickly.

+1, I don't think your troubles are as serious as you may think. Try adjusting the barrel nut on your rear shifter counterclockwise to "tighten" the cable until it no longer ghost shifts under load.

There are lot's of simple causes for a rotor to rub during break in, unless they're bent or really dragging you down, I wouldn't worry. Just break them in and readjust as necessary.