Derailleur guru

12 replies [Last post]

Wed, 03/07/2007 - 12:38pm

Anonymous

"Dear NYCCers
Could someone please direct me to a noted derailleur guru on Manhattan (I am on the west side but will travel).

A plastic bag fouled the rear derailleur and initiated a set of problems that necessitated a new rear derailleur for my Trek Madone 5.2 (put on at Trek).

Since then two LBSs have tried (each tried 3 times) to adjust the derailleurs, and there was some improvement but ...it still has a vague feel, often takes a double throw to get on the big ring, and under load there are surprise gear changes, and other exciting events. Nothing like the original-knife-thru-butter changes.

I think it needs the hand of experience rather than the enthusiastic but less helpful ""lets try this for awhile"" approach of some of the young ""mechanics"" at some LBSs. It is a great bike but this is spoiling my ride.

Thanks for your help.
Kind Regards
Thomas

Wed, 03/07/2007 - 1:16pm

Evan Marks (not verified)

Magical, mysterious.

Sometimes a new cable is what it neeeds, often for no apparent reason.

Maybe the derailer hanger got bent in the process?

Tried Conrad's?

Wed, 03/07/2007 - 1:35pm

Paul (not verified)

What he said

Remove your cable and ensure that the derailleur sits over your smallest cog. Fine tune as needed using H adjustment
Then move all the way up and ensure that it sits over your largest. Fine tune as needed using L adjustment

Now move the derailleur back and forth to ensure there is no binding. If all is good it's probably your cable. Release the cable in the front and move it front to rear with the intent of looking for any binding. Also check to see that your brifter is properly working

Wed, 03/07/2007 - 1:21pm

John M. (not verified)

Not a wrench here, but is it possible that the entangling of the bag might have bent your derailleur hanger? This is the metal tab that attaches the derailleur to the bike. When bent, the entire drivetrain will remain hopelessly out of alignment. If the incident was enough to wreck your original derailleur, there could have been unusual torquing forces on the frame too.

In my experience, a mechanic (not limited to bikes, either, BTW) might focus narrowly on the problem you describe instead of looking for a more holistic solution. Hangers are replaceable on most frames because it's a high-stress area of the bike often abused and damaged.

Wed, 03/07/2007 - 1:47pm

Robert Shay (not verified)

I have same bike, same problem...

I learned that on the sandy/dusty roads that my 10 speed is very sensitive to road dust/dirt(my 9 speed never had this problem).

When the cables, chain, and rear derailler are dirty, the rear derailler shifts from small to large cog fine but skips when shifting from large to small cog and will jump out of a cog under load. Solution - clean or new cables and housing, clean chain, clean rear derailler. On roads this time of year I have to clean my drive train and cables/housing every 50 to 75 miles - makes me want to go back to 9 speeds!.

I've also had a couple of missed shifts on the front derailler on Saturday (75 miles) and Monday (40 miles). I attribute this to the cable and housing operating at below freezing temperatures. It worked fine once the temps climbed above 40 degrees on Saturday.

Wed, 03/07/2007 - 4:57pm

Frank (not verified)

Ditto....

and ditto....

Wed, 03/07/2007 - 4:03pm

Tony (not verified)

imbert at master bike

see imbert at master bike on W 77th. he is the best.

Thu, 03/08/2007 - 12:38pm

rjb (not verified)

bent derailleur hanger

tom,
make sure whoever's doing the work checks by using the proper hanger alignment tool and not just 'by eye'. also, those hangers are usually alum, and quite weak - once straightened, they can go back out of alignment (get bent again) very easily, and the only way to really see how much is with that tool. good luck!
-rob

Thu, 03/08/2007 - 1:51pm

roadrash (not verified)

Switch to Campy.......

Thu, 03/08/2007 - 2:11pm

sspradhan (not verified)

Ask for Will at NYC Velo on 2nd Ave and 4th Street. Great shop, smart guy. Fixed my derailleur hanger issue when my local LBS clowns had no clue.

Fri, 03/09/2007 - 6:46pm

#10

pedalpusher (not verified)

just curious

Did you get a new chain with the new derailleur? Those surprise gear changes under load sound suspiciously like a new chain skipping off a worn cogset.

If that's not the issue, I concur with whoever said take the bike to NYC Velo. If Will can't fix it, Andy can.

Sat, 03/10/2007 - 11:35am

#11

rjb (not verified)

bent chain

pedalpusher just reminded me - when this happened to me, my chain got twisted and one of the links was bent. tom, to check for a bent link - sight with your eye along the chain from behind the cassette while pedaling backwards, the chain should run evenly/smoothly over the cogs and through the derailleur pulleys, for the entire rotation of the chain. if you see a bobble, it could be a bent (or stuck) link. a long shot, but worth checking.

Sat, 03/10/2007 - 2:29pm

#12

Robert Shay (not verified)

Cable update....

Instead of just cleaning my rear derailler cable this time, I decided to replace it. I noticed that the cable was kinked about an inch from the end that enters the shifter. Result of new cable (and cleaning)- great shifting. It probably got kinked with use - about 3,800 miles