Help troubleshooting chain skip?

[robc]

Hi all.
I recently built up a bike from a used frame (Giant NRS) and a new build kit. New chain and cassette in this build kit. For the first couple rides it seemed great, but now I am having problems getting the drivetrain dialed to handle hard pedaling. It has XT FD, x.9 RD, and x.0 twist shifters.
I am a total noob to building/adjusting bike drivetrains, other than the occasional fiddling with the barrel adjuster in the past. Can you give me some ideas on how to troubleshoot this problem? I did find out I had a tight link, and I thought that would be it, but after fixing that it still exhibits the problem.
Here's what I see happening: Things appear to work well when pedaling on the repair stand, but when I get the rubber on the road I have problems. It seems to be fine on my largest 2 or 3 cogs, but when I get closer to the center of the cassette, it won't hold a gear. Also, the slipping gets much worse when accelerating hard or standing. I have a hard time telling whether its 'phantom shifting' back and forth causing the skip, or whether it just skipping forward on the same cog.
If you have some advice on what to twiddle with to try and figure this out, I would be very grateful! Thanks in advance for any help and information!

Thx,
Rob

[Palmer]

I would a closer at the chain and see if you have a bent link. I would also suggest looking for another stiff link. You can do this by pedaling backwards and looking for the RD to jump...

[stoneage]

Chain length is OK? I try to keep mine as short as possible, to the point of not allowing a big ring/big cog engagement. Wrap? Adjust rear derailleur to allow more chain around the cogset.

[robc]

When I took out the tight link, I shortened the chain by a couple, and I should be close to the lower limit of my chain length. I will look for another tight link, but I couldn't see anything skipping when pedaling backwards after I fixed it.

[dejorn]

If you recently changed both the chain and the cassette should not be getting jumpint over the cassette. You should check your front chainrings especially the middle ring.

Earlier this year I had the same problem when I replaced the chain. The skipping was most prominant when I would "hammer" on the pedals during a race. The chain would "skip" sending my knees into the bars; same knee same spot each time. At first it seemed most prominant in the larger cogs in back leading me to believe it was the cassette. After trying different cassettes and even upgrading the drivetrain, I managed to determine that it was the middle chainring in front that was slipping. Although the teeth looked fairly good, there was just enough wear that under hard pedaling the chain would ride up on the tips of the teeth and "skip" until the crank came to a stop (usually because my knee hit the bar).

I hope this helps

[robc]

Well, the whole kit-and-kaboodle is brand new in the build kit I bought. Front is a RaceFace Evolve crank. I will inspect it closer though to make sure the chainrings look good. I have done most of my testing in the middle ring. I'll try the same thing on the small and large rings too to see if the problem is up front of in back. Thanks for the tip!

[manual63]

Chain length is OK? I try to keep mine as short as possible, to the point of not allowing a big ring/big cog engagement. Wrap? Adjust rear derailleur to allow more chain around the cogset.

You have a bike with gears?? I am ashamed of you now!!....:p

[manual63]

Make sure everything is lined up correctly. After you ride a few times on new stuff, you need to readjust the cables and all because they stretch. It sounds like your rear cable is slightly out of adjustment. Make sure it goes in all gears, mine, when it was new on my BigHit, got so out of adjustment it was actually one whole gear off. I adjusted it to line it up, but I didn't check to see if it when into the smallest and biggest ring....so it skipped in the middle. When I realized it was one whole gear off, I tightened to cable so it would not go into the largest ring. Then I went and readjusted it so it would shift nicely between all the gears. Hope this helps some.

Oh, and Bill, the BigHit doesn't count because it weighs 50 pounds......:p

[tedsti]

I am not sure how the cable routing goes on this bike, but you may have too short of a section going between the front triangle and the swingarm. The shifter housing may be pulling away from the mount locations during suspension flex. This is a common cause of ghost shifting.

[stoneage]

You have a bike with gears?? I am ashamed of you now!!....:p
errrr............. ahhhh............. I was speaking vicariously through....... no no no.......I was channeling through Paris Hilton. Yeah, that's it!!!!!

[stoneage]

I am not sure how the cable routing goes on this bike, but you may have too short of a section going between the front triangle and the swingarm. The shifter housing may be pulling away from the mount locations during suspension flex. This is a common cause of ghost shifting.
Duh!!!! That's probably it. I didn't realize it was a double sus. That happened to me on my Orbea dualie (Shad faints, wakes up, and faints again). Ghost shifted and frustrated me to no end. (Shad enters shock treatment clinic.)

[robc]

I hope that's the case. Sounds like a reasonable possibility. I think I made the cable run as short as possible now that I think about it. I would NEVER have thought of that without help!
(Insert deity here) bless the MORC forums. I'll let you know if it helps.

Thanks guys. :banana:

[manual63]

Duh!!!! That's probably it. I didn't realize it was a double sus. That happened to me on my Orbea dualie (Shad faints, wakes up, and faints again). Ghost shifted and frustrated me to no end. (Shad enters shock treatment clinic.)

Now that I am back from the clinic.....2000 volts hurt.......WHAT!!??....FS!!, you need to have your head examined.

Uhm....my BigHit is still excluded from this comment.....it's 50 pounds......:laugh::laugh::)

[bigwheel]

Two other possibilities:

1: Bent derailleur hanger. That can sometimes cause strange shifting. I have one of those Park Derailleur Hanger Gauges, in case you want to bring your bike to a Leb ride. The adjustment only takes a couple minutes. You can also get it pretty close by eyeball and a vice.

2: Another possibility (although not likely): Last week, my chain skip problem turned out to actually be the ratchet mechanism in my freewheel. I spent the whole night ride trying to adjust my derailleur. Then the ratchet gave out completely and I was stuck walking the bike out from the back corner of Leb.

[robc]

Hey guys,
Just wanted to let you know that I got er fixed finally! Bill & Ted (excellent), you were right on the money. My housing was too short going to the rear triangle. I finally got some more housing and a new cable and now its good to go. Solid! Man, that was frustrating, so thanks again for all the help fellas! Many bananas to the forums!
:banana::banana::banana::banana::banana:

See you on the trail,
Rob