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Old 10-18-11, 06:37 AM   #1
plantrob
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Front derailleur - not getting the adjustment right

I've been riding my Raleigh, equipped with Ultegra 9-speed components, compact crankset, for a year now. When new, I think I had cross-gearing noises on the biggest cog (25), and maybe very slightly on the second-biggest cog (let's call it 1.5 cogs). Then I crashed, and found I had to adjust the derailleur a bit. Since then, cross-gearing noises occurred on 2.5 cogs; my attempts to correct that failed. Over time, the tuning got a little further out of whack, to where on occasion I'd drop the chain when shifting up to my big ring. So this past weekend I fiddled with it again, turning the high limit screw just about as far as it would go (adjusting the derailleur position inwards), which was only slightly farther than it had been already set. I was delighted when, on a quick test ride, not only did the chain drop problem go away, but I had only slight cross-gearing noises on the biggest cog. Problem solved, I thought. Only the next day, on a real ride, when I got into the little-cog/big-ring combination, did I learn that I had merely shifted the problem to the other end. What am I missing? The noises only occur during part of the pedal stroke, so chain ring flex or lateral movement is certainly at play.

When looking into other cranksets this morning, I noticed the following blurb in the promotional description of a 105 FC-5750 crankset:
It features a larger gap between the top and low gear, for less chain rub in small gear combinations.
I would have thought that spacing the gears further apart would worsen, rather than improve cross-gearing issues. Am I misunderstanding the mechanics?
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Old 10-18-11, 07:24 AM   #2
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When in the bigger ring, cross chainning noise is due to the chain rubbing on the inside of the front derailleur cage. In the smaller ring, cross chaiining noise can be from the chain rubbing on the outer fd cage plate OR from the chain rubbing on the inside of the bigger ring.
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Old 10-18-11, 08:27 AM   #3
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You might try losing the frame clamp on the derailer and repositioning it slightly up or down or slightly side to side in a couple of different positions to see if that helps.
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Old 10-18-11, 08:38 AM   #4
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IMHO Ultegra 9 speed front deraileurs do not work well with 35/50 cranksets. I fussed around for a year with mine and it never shifted well. I think the shape of the cage is wrong for the smaller diameter of compact rings, and I've worked on bikes for many, many years.

Go buy a 10 speed 105 or Ultegra front deraileur.
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Old 10-18-11, 09:03 AM   #5
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Go buy a 10 speed 105 or Ultegra front deraileur.
Even though my cassette and chain are 9-speed?
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Old 10-18-11, 02:54 PM   #6
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Then I crashed
Check your RD hanger alignment before you drive yourself crazy. It's probably bent.
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Old 10-18-11, 03:31 PM   #7
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Check your RD hanger alignment before you drive yourself crazy. It's probably bent.
I agree. I think the crash is the key to the problem. Either the hanger is bent or one of the derailleurs is bent (or any combination there of).
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Old 10-26-11, 11:51 AM   #8
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Thanks for the responses. I took a closer look at the derailleurs, but did not see any obvious damage. Would a bend be obvious to the uninitiated? When I find some time, I'll try to play with the hanger attachment and see if I can nudge things in the right direction.
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Old 10-26-11, 01:42 PM   #9
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plantrob, Make sure the FD cage is parallel with the centerline of the frame. If the RD is shifting up and down normally then it maybe alright, or at least not badly damaged. If you look at the RD from above, the two wheels when on the big-big combination should be very close to parallel with the frame's centerline... not a proof positive test, but good enough.

Bicycles crashing are like a piece of bread with peanut butter spread on it falling to the floor , they always land on the side you don't want them to. For bikes, it's the drive side. Also make sure the wheels are in their drop outs correctly.

Brad
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Old 10-26-11, 05:16 PM   #10
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Would a bend be obvious to the uninitiated?
It wouldn't even be obvious to the experienced. You'll need to borrow a tool or take it to a mechanic to have it checked.
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Old 10-26-11, 05:31 PM   #11
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When adjusting the high limit screw the chain must be on the largest chainring and smallest rear cog.
When adjusting the low limit screw the chain must be on the smallest chainring and largest rear cog.
There needs to be only 1 or 2 mm clearance from the derailleur's side rails to the chainrings on the limit screw side.
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