Rear derailer adjustment

Hi guys, I am having a really strange problem.

My gf's bike started to skip cogs yesterday. They were the 4 upper ones (lightest gears)

I checked the limit screw adjustments, to find they were, in fact, slightly out. Once adjusted, though, the bottom gears started skipping! I then adjusted the bottom limit screw, but then the original problem cam back!

To cut it short, I eventually managed to stop the chain skipping cogs at either end, but it still does it in the middle 3!!!

I don't know what to do!! I thought it was the cable tension, can anyone suggest a way to adjust this?

I don't particularly want to go to my LBS to find that a turn of a screw will do the job.....

Thanks!

Cable tension is set roughly with the screw that secures the cable to the rear derailleur, and fine-tuned with a splined fitting where the cable cover meets the derailleur. Sometimes a similar fitting can be found on the gear selector as well. Turning in reduces tension, turning out increases tension.

The limit screws can only influence the performance on the cogs on the ends, anything else is down to something else.
Since you're able to shift the problem around it seems most likely that either your cable tension is off, or the cable return isn't happening properly. Check cable and covers for damages, corrosion and dirt. Possibly remove cable, clean, lube or replace as indicated. Make sure that the rear derailleur moves freely.
Recalibrate the whole thing. You might want to set cable tension so there's a tiny element of slack when the derailleur rests on the lmit screw in its outermost position.

The repair section at www.parktool.com has the drill on derailer adjustment. It's also possible the derailer hanger is bent or there could be cable/casing issues.

Boudreaux makes a good (and sometimes overlooked) point about the derailleur hanger. Of the 4 bikes I've had built since October '03, ALL of them required adjustment of the hanger. All of the frames were new, right out of the shipping box. One was aligned with the Park alignment tool, and was still not shifting properly. The frame was checked again with a Campagnolo tool. It was off. Have the hanger alignment checked, just to be sure.

BTW, if you're building with Campagnolo, I suggest you have the hanger alignment checked with the Campy tool.

-Wm.

yeah, setting the limit screws won't help your problem with skipping. you need to adjust the cable tension, either at the shifting levers or back at your R der. barrel adjuster. that will most likely fix your problem. but maybe you have a more technical problem like you need to replace the cassette or maybe the chain, the der. hanger is bent. good luck.

~the turtle

Did you recently replace the chain? Sometimes a new chain on old/worn cogs will skip because the new chain links will not fit the stretched teeth. Adjusting the limit screws on the RD will do little to nothing.

__________________