[jacksonpt]

My rear der is way out of adjustment... to the point where shifting is pretty much of a crap shoot - will it shift? if so, to what gear/how many cogs will it jump? How long will it stay in that gear? Will it push the chain into the spokes? Into the chainstay?

I've been trying to get it dialed in a bit better. I am making headway, but very slowly. I've read several posts and articles about tuning rear deraileurs, but basically I do the trial and error method. I adjust a limiting screw slightly, the re-evaluate. Needless to say, this is very inefficient, and only moderately effective.

So here are my questions. As I see it, there are 2 main ways to adjust the rear deraileur - the two limiting screws and the "nob thinging" under the rubber boot (like my technical terms? What's that thing called?). I think if I understood what exactly these things did, I could do a better job tuning the der. From what I can see, in my limited experience, the limiting screws adjust how far the chain is pushed every time you shift. The nob thing adjusts the alignment of the pulleys with regard to a specific cog. Is that right, or am I way off the mark? Additionally, when adjusting the limiting screws you can tighten them down or loosen them up. Does tightening them down increase or decrease the "throw" of the chain?

Am I even close? I guess if I understood how these things worked, tuning the rear der would be much easier.

Thanks.

 

[Orvan]

I'm a bit lost from your long post...

but generally..
there are four known adjustments on a typical r der.
1. "H" limit screw...how far you want the der to go towards the high gear (smallest)
2. "L" limit screw...how far you want the der to go towards the lowest gear (tall-big one)
3. barrel adjustment..the black knob thingie underneath the dust booth.. screws in clockwise and counterclockwise to adjust cable tension. This is how you finetune cable tension and rid of minute mis-shifts or jumps.
4. the "B Tension" screw.. a lil screw located in the back on a plate behind where the der is mounted on the hanger. This sets the distance between the upper pulley and the cogset. I always set my b tension all the way in (helpful if you're running FSR style dropout...ie: chainstay pivot is lower than the der hanger)

most overlooked problem on rear ders is the cable tension.

 

[Grimey]

I only skimmed your post but check out this article...
http://www.sheldonbrown.com/derailer-adjustment.html

The problem I fix the most is people playing with limit screws. Once they are set, they are usually set. Kinda like that infomercial that, set it and forget it. Everythign else is cable tension.

A problem that causes allot of shifting woes is deraileur hanger alignment. If the hanger is way off it will never shift correctly.

 

[jacksonpt]

Originally posted by Grimey
I only skimmed your post but check out this article...
http://www.sheldonbrown.com/derailer-adjustment.html

That is a great article, thanks.

 

[jacksonpt]

Originally posted by Orven
I'm a bit lost from your long post

Sorry... basically what I was saying is this:

To this point, when I try to tune my rear der, I just use the trial and error method. Turn a screw or barrel a bit and see what changed. Then see if it's better or worse. I don't know enough to be able to say, "OK, I'm pushing the chain into the spokes, that means I probably need to adjust X."

Making any sense yet?

So I was asking for someone to explain EXACTLY what each adjustment did. If I knew exactly how the limiting screws, barrel adjusters, etc. influenced shifting, then I might be able to trouble shoot my shifting problems and have an idea where to start tuning.

Does that clear it up at all?

 

[Loner]

I've always used the instructions from the shimano website. If you follow the step by step instructions you're usually pretty close to the optimal setting. After that I just use the barrel adjuster to fine tune it. If it doesn't shift properly to a lower gear I'll increase the cable tension and vice versa.

The instructions

 

[PsychO!1]

You have 2 stop screws. They stop the derailures movement at either end of its travel (hi gear low gear). I usually adjust these with no cable attached to the derailur, turn pedals and push derailur by hand. it should hit both hi and low gears easily without over shifting into the spokes or chainstay. Tightening the screws will limit the travel of the der (do this if it's overshifting), backing off the screws will increase the travel of der (do this if it's not hitting last or first cog.)

Attach your cable. make sure it is running smooth, lubed and clean. 99.9% of all shifting problems are cable related. Use your barrel adjuster to dial in the cable tension until shifting is smooth. Slow upshifts, turn barrell counterclockwise, slow downshifts turn barrel clockwise.

That's about it, good luck.

 

[jacksonpt]

Originally posted by PsychO!1
You have 2 stop screws. They stop the derailures movement at either end of its travel (hi gear low gear). I usually adjust these with no cable attached to the derailur, turn pedals and push derailur by hand. it should hit both hi and low gears easily without over shifting into the spokes or chainstay. Tightening the screws will limit the travel of the der (do this if it's overshifting), backing off the screws will increase the travel of der (do this if it's not hitting last or first cog.)

Attach your cable. make sure it is running smooth, lubed and clean. 99.9% of all shifting problems are cable related. Use your barrel adjuster to dial in the cable tension until shifting is smooth. Slow upshifts, turn barrell counterclockwise, slow downshifts turn barrel clockwise.

That's about it, good luck.

Excellent - that is exactly what I wanted to find out. Thanks.