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Chain rubbing on big ring(13 posts)

Chain rubbing on big ringscottfree
Jun 24, 2002 6:03 AM
Dailing in new Ultegra 9-speed. Problem: When I'm on the small ring, I'm getting chain rub three cogs in, which is more than I'd expect from a normal crosschaining problem. Looking at it a little closer yesterday, I noticed that the chain isn't rubbing on the front der -- it's actually rubbing on the big ring itself.

This seems to be a chainline thing rather than a derailleur-adjustment thing. At least I can't see how a der adjustment would fix it. Suggestions?
Trim positionsjtolleson
Jun 24, 2002 8:28 AM
Other than derailleur adjustments, be sure you know how to use the Ultegra trim positions. A little click up or down (not a full shift) will settle the chain over.

That's not a great description. Anyone with better descriptive skills?
re: Chain rubbing on big ringMike Prince
Jun 24, 2002 8:52 AM
Look in the archives as a rather spirited thread surfaced there a few months back dealing with the same issue. Short story - either: 1) don't use the offending combos, 2) install a 1-2 mm spacer under the drive side cup to increase chainline and alleviate problem or 3) install an XTR bb with a 112.5mm spindle (vs. road doubles at 109.5 mm).

Option 2 is the easiest. QBP lists these spacers in their catalog so any shop should be able to order one for you.

Another question - is it a new group or a new frame as well too? If a new frame you may want to have the builder check the alignment of the rear triangle. This could cause the problem you describe also. But many Shimano users have the same problem independent of the frame.

Hope this helps.
Mike
Ah!scottfree
Jun 24, 2002 9:13 AM
I was just peering at the thing, thinking 'If I could just move the whole deal about 2mm to the right, everything should work ..." A spacer makes sense. Thanks!
Common problemNessism
Jun 24, 2002 10:37 AM
For some reason many people with Ultegra 9-speed are having this problem. The spacer should solve the problem but I wonder if Shimano messed up regarding how the bb centers in the frame?

Ed
I guess they figurescottfree
Jun 24, 2002 11:09 AM
people are just used to accepting the 'Oh, those are unusuable gears, designed that way, just ignore them,' excuse.

I figured out that, between these three gears and two others at the other end of the cogset that Shimano doesn't 'intend' for you to use with the big ring -- and not even counting duplications -- I have fewer distinct and usable gears on with 9-speed Ultegra than I have with my trusty old friction-shifted 7-speed, which never met a crosschained gear it didn't love just fine.

One of these days, people will realize that there's almost nothing superior about 9 and 10 speed cogsets, and a lot inferior. Whoops, maybe I should take that last graf to the Retro board!
Common problemzeke
Jun 25, 2002 10:19 PM
YOu mention many people with ultegra have the same problem. but if it were an ultegra problem, shouldnt all ultegra owners have the same problem, ie wouldnt it be a design flaw??

the spacing between all ultegra chainrings and cogs is set, so it seems to me that it must be a front or rear der. adjustment.

i have ultegra with no problems at all.
Problem is...Nessism
Jun 26, 2002 4:56 AM
...when the chain is on the small ring in the front and the smallest 2-3 cogs in the back, the chain is in a cross-over position. This causes the chain to run at an angle relative to the chainrings/cogs themselves. This angle causes the chain to rub against the large chainring causing noise. Adjustment is not an issue but the chainline is.
Also...Mike Prince
Jun 26, 2002 7:23 AM
Frame geometry and chainring/cog sizes will play a role in this. Short-chainstay bikes will have this problem more often because the design puts the chain at a higher angle. Also, a smaller small chainring has a similar effect. So, for a given frame and cogset, 53/39 will be more prone to the problem than 53/42 or 52/42. Same thing if your small cogs are smaller than someone else's from for the first 3-4 small cogs. In general, less distance between the front end of the chainring and the back end of the cog will force the chain to take on a more extreme angle towards the right rear side of the bicycle.

This in my mind expalins to a pretty high degree why some Shimano users have the problem and some don't. The best solution (and cheapest) is still the spacer at the BB. Either this or change gearing or frames (yeah right).

Mike
Mike, Shimano has a fix. See new post at top. nmscottfree
Jun 26, 2002 8:30 AM
Mike, Shimano has a fix. See new post at top. nmMike Prince
Jun 26, 2002 10:19 AM
It makes some sense to do this as spacing the BB can affect chainline the other way (poor performance on big cogs). I would be a little cautious with the chainring spacers as it won't take too much of a spacer to create a gap between chainrings that is exactly the right size for the chain to slip into.

This is not just an Ultegra problem either. The BB spacing and spline patterns are the same for all Shimano splined road doubles. I have Dura Ace on one of my bikes and have the exact same problem you did. Another bike has Ultegra and no problemo. I put in an XTR bb and my problem is pretty much solved.

I guess every problem has multiple ways to fix it. I personally would do the BB spacer if I encountered the problem again. The XTR solution works well but is expensive and the chainring spacer option makes me nervous.
Chain ring spacersNessism
Jun 26, 2002 6:18 PM
When Shimano changed from 8 speed to 9 speed they closed up the distance between the front chain rings. While this makes sense considering the chain is narrower, it also leads to the afore mentioned chain rub problem.

When I upgraded to 9 speed, I wanted to keep my old 8 speed Dura Ace cranks so I bought an Ultegra small chain ring to get the proper spacing. While this worked just fine, the Ultegra chain ring was ugly compared to the DA ring so I changed back. The result? No problems at all. This leads me to believe that adding the spacers to the 9 speed crank should work just fine. Just as long as the spacing doesn't go any further apart than the old 8 speed stuff, everything should work just fine.

Ed
re: Chain rubbing on big ringkcd
Jun 25, 2002 4:54 AM
Try flipping the small chainring--i.e., install it backward. On the one I have, the flange on the left side of small chain ring is thicker than the right side. Putting the thicker side next to the large chain ring would provide the additional space between the chain rings. I had this problem and this has worked.