Ultegra 10 indexing bizarre
 

I've got bizzare rear shifting problems with my Ultegra 10 from 2006 (6600?) shifter/derailleur. After a lot of messing around trying to get the rear shifting dialed in properly I realized the following: the distance that the derailleur travels with each shift is a tiny bit farther than the distance between any two cogs. So, I can get the derailleur to shift properly over one end of the casette but by the time it gets to the other side it's skipping a gear. I can tune the derailleur to one end of the casette or the other but there's no way I can get it indexed properly across the whole casette. I set the limit screws first and I tried different approaches, including adjusting the indexing for one of the two middle cogs--no luck.

I finally gave up and just stuck the casette spacer between the 7th and 8th cog (which looks horrible). But now when I adjust the derailleur for, say, the 1st or 2nd (easiest or second easiest) cogs it shifts perfectly across the whole casette. Weird, no? I'm tempted to leave my hack job in place because it works great, but I'm still curious about what's going on.

I'm running a compact 50/36 in the front and a 11,12,13,15,17,19,21,23,25,27 in the back. I've got a short rear derailleur. I assume that my derailleur can handle a maximu sprocket size of 27. The needed derailleur capacity is (50-36) + (27-11) = 30. Maybe my derailleur can only handle a capacity of 29--???

Any ideas appreciated.

Thanks,
russ

Consider the derailleur hanger may be bent. ~7 bucks for the LBS to straighten it with the right alignment guage.

If you're getting all nine clicks from your shifter, and you've set the limits on the rear derailler, I can only think of three things:

1) Broken, bent, mis-routed or un-lubed gear cables. Check 'em.

2) Worn out rear derailler pivot bolt, wiggles. Not much to do except replace, unless you can obtain a replacement bolt.

3) Bent derailler hanger (the most likely, IMHO) as other poster suggested. Time for hanger alignment or replacement.

May seem stupid, but you're running a Campy cassette are you?

Just a note... the Park instructions set a much more liberal standard than what really works well IMO. I got their DAG tool, and found my hanger was within 3-4mm, but still bent. According to their instructions, 4mm is sufficient. After straightening the hanger on my bike to beyond my ability to detect (some fraction of a mm) the bike now indexes better than when it was new in 2005. So don't trust the 4mm they suggest, it's IMO way too sloppy for current 10sp Shimano derailers.

Have you changed your cable routing to the opposite side of the pinch bolt? That will result in a greater pull per shift.

Great suggestions. Thanks!

It's not the derailleur hanger, unless both hangers that I used (one on each of the 2 different bikes that the derailleur has been on) are coincidentally bent in a way so as to cause the exact same problem. And the bike has never gone down so there wasn't any opportunity to bend the hanger.

I don't have a campy cassette. It's Shimano 10 speed.

The derailleur pivot bolt is fine, to all appearances.

I followed basic installation and tuning directions (a la Park Tool and Zinn).

That leaves on the table the possibility of:

a) the cables, which were on both bikes along with the derailleur, so that may be the problem right there.
b) "cable routing to the opposite side of the pinch bolt" (vipiuva's suggestion). Uh, I'm not sure what this means, but I just routed the cable normally so I don't think I did this is the problem.

I'll replace the cables and see what happens. No one seems worried about the gearing on my cassette or the "derailleur capacity", eh?

Here's a link to Sheldon Brown showing the standard cable routing and routing it on the opposite/alternate side.

And the cable does not have to have that big of a bend to affect shifting - just run on the "high" side of the pinch bolt

. . . and the vpiuva-monster has it! Got home and noticed that I *did* have my cable running on the high side of the cable pinch bolt of the rear derailleur (based on the Sheldon Brown picture). Although my routing was a bit more subtle such that the cable didn't bend up like in the picture, but was just on the other side of the bolt and heading straight away from the housing.

It took me about 10 seconds to get the derailleur indexed properly! Nice! I never would've guessed that such a slight difference would affect shifting so much, but that just goes to prove that intuition is a poor guide to basic physics.

Thanks!

did it ever occur to anyone that these bicycles today are a bit over engineered? i mean really,do we really need a 20 speed gear ratio?2 gears in the front 10 in the back,looks like an awful lot of chain twist to me.you mean to tell me you can't find enough gear ratios with a ten speed?hell, you can only use one gear at a time,and now you have to pedal the weight of all those extra gears,have fun!

Not really. A 10-speed cassette is almost the exact the same overall width as 8 or 9-speed cassettes so the overall chain travel is the came.

Note to the OP: where did you get an 11x27 Shimano cassette with those cogs? Did you customize a 12x27 or is it really a 12x27? Also, Shimano's cassettes ending with 27T are all 21,24,27. Is this an aftermarket cassette?