Haselsmasher

I'm a bit hesitant to post this question - it must have been asked before. But some searching on my part didn't cause me to find something I felt I could leverage.

My adult son and I are learning together about derailleur adjustment. (I've been riding a long time but haven't ventured into doing my own work very much. He, on the other hand, started riding relatively recently. He's jumped in with both feet buying project bikes and moving stuff around on them, building Frankensteins, etc.)

The bike in question is a roughly 8 yr old Madone he bought used. Dura-Ace rear derailleur.

He gets to the starting point (chain on smallest cog, barrel adjuster all the way tight, high limit screw seemingly set correctly, cable seemingly pulled tight and derailleur cable screw cranked tight). When he attempts the first shift to the second smallest cog, the shift does not happen. If he adjusts the barrel adjuster multiple (2-3) revolutions counter-clockwise, the shift will then happen.

This whole scenario seems to tell me he still has cable slack when he's starting out - if the BA is needed to make the first shift. Yet he pulls the cable tight (and holds it tight) while he's cranking down the cable connection bolt on the derailleur. So it seems like slack is taken out by feel. But the attempted shift behavior I think is saying otherwise.

Any ideas on what we're missing? We're both scratching our heads.

Thanks!

Jim

markjenn

It varies by bike and RD, but typically you can't remove ALL the slack from the cable by pulling the wire tight and clamping. There's some residual looseness that has to be adjusted out with the barrel adjuster. The clamp is just to get cable tension in the general ballpark with the BA doing all the fine tuning.

The sequence..... 1) turn BA all the way in/slack; 2) pull wire somewhat taut and clamp; 3) adjust BA out/tight until you get a good/crisp shift off the smallest cog; 4) shift back to smallest cog and confirm that the stop screw is what is limiting the RD's movement outboard, not cable tension. This will typically put the BA right in a good range for future tuning.

With today's 10- and 11-speed drivetrains the amount of cable that's actually pulled between shifts is miniscule.

- Mark

dabac

If I think I’ve taken up too much of the BA’s travel before shifting is OK I might unclamp the cable, push the RD in by hand a little before clamping the cable down again.
Fast, but easy to overdo the pre-tension.

Or use the limit screw to push the RD inwards a bit before clamping down, then backing it out again.
Whatever works really. As long as I have some BA length left for on-the-road adjustment, anything goes.

andrewclaus

Another trick for cable tension is to manually shift the RD into the third smallest cog, stop pedaling, let go of the der, then install the cable. This "preloads" the cable, sometimes perfectly.

But if you're turning the BA 2-3 complete turns before you get a shift, there may be something wrong with the cable/housing(s), or more rarely, the shifter. It's hard to imagine leaving that much slack in the cable.

Andrew R Stewart 

Cable routing friction can cause the der to not track as the lever is commanding it to do so. While more common on an up shift (where the der return spring is the only force acting on the cable) it can be an issue on down shifts too, especially if there's internal cable routing. Also check the cable's last 1/2" by it's head, up in the lever. They are known to fray when old and the strands can also cause hang ups in cable movement. Andy

zacster

All of what has already been said, but look at the Park Tool guy's video on rear derailleur adjustment. He uses a method that takes the guesswork and the minor imperfections out.

And one other thing to check, make sure the derailleur hanger is straight! If not it will be difficult to adjust and get quiet.

Haselsmasher

Thanks so much all! Great ideas here - definitely things we weren't aware of that need to have attention paid to.

His Madone is at the top of his bike fleet. He has precious-little time to ride, so keeping the Madone road worthy all the time is top priority. He tried a couple of things in this thread today but no joy. One thing he described is that, as he gets the chain up to the middle of the cassette, then upshifts (back down the cassette) won't work. Something sure seems to be sticking or something.

Since keeping this on the road at "all times" he took it to his (very cool) LBS tonight. They did a quick "Let's see if we can get you going." while he stood there and they threw it in the stand. After a few minutes the tech said "This is gonna take some time to get right." They've said they'll explain what was going on once they figure it out. He's got a LiteFrankenSpeed exhibiting similar issues. So he'll use that as additional learning on getting things right.

Thanks for the suggestions! They help a lot as we learn the areas to check out as we get shifting set up well.

Jim

zacster

Are the cables the originals on the bike? Sometimes the easiest thing to do is just start there. If they are 8 years old on a bike that is used they could certainly need replacing, and the housing too. And while they are off check the derailleur by hand to see if it moves freely with the spring. Look for any deformities. And check that derailleur hanger. I have the gauge/bar and whenever I use it on someone's bike I'm always surprised at how bent they are even if they don't look it. And when I'm done the owner is always amazed at how much better it shifts and how much quieter it runs. I have to check my own main ride next time I put it on the stand.

masi61

Your description of something sticking makes me believe something is sticking! I don't know what generation of Dura Ace you are using (7800 series?, 7900 series? ) but I know that the inner wire is often starting to shred (up inside the shift lever) when symptoms such as yours are presenting themselves. The cable is acting as if it were about to snap off. It would be a good idea to pull out the inner wire (cable) and replace it, and then also replace the housing. If it came with the polymer coated inner wire, most mechanics I have spoken to recommend that you do not put the same polymer stuff back on. Instead, I have been told to run with Jagwire, burnished stainless cable for better durability and no shredding issues.