HELP front derailleur problems

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01-31-17 | 09:13 AM

#26

trailflow1

Senior Member

Joined: Jan 2015

Posts: 443

Likes: 23

Quote:

Originally Posted by L134

Could it be that the bottom bracket spindle is not the correct length for the crank and is placing the chainrings out too far?

Yep that's possible. If the frame uses Hollowtech II bb cups. There could be too many spacers behind the cup on the driveside. So the big chainring would be placed too far away from the frame.

If its a pressfit bb, its unlikely to be the problem.

Last edited by trailflow1; 01-31-17 at 11:24 AM.

01-31-17 | 09:44 AM

#27

cyccommute

Mad bike riding scientist

Joined: Nov 2004

Posts: 29,167

Likes: 6,235

From: Denver, CO

Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones

Quote:

Originally Posted by Bill Kapaun

To set the lower limit, have the chain on a larger ring and screw it in enough that the chain WON'T drop to the smallest ring.
Push the cage over a bit and back the screw out a bit.
Repeat until the shift to the smallest ring occurs reliably.

trailflow1 is correct about this. I've never set a limit screw in the manner that you are suggesting. Park Tools doesn't suggest your method. Nor does Shimano, for example. They suggest adjusting the inner limit screw with the cable with the least amount of tension on it. Adjustments to the limit screws should be done so seldom that worries about damaging the aluminum shouldn't a concern.

The limit screws should only need adjustment once...upon installation. If the derailer is moved from bike to bike, it may need another adjustment but the amount of adjustment required should never be enough to wear out the aluminum. Frankly, I'm not even sure that most derailers have the limit screws through threaded aluminum anymore anyway. Shimano's derailers look like they use some kind of insert.

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