Chain skate on downshift

[ldamelio]

Before posting, I scoured the web and tried all posted solutions or this problem so as to not clog up the forum. 10 speed all Campagnolo drivetrain - all worked together well for years, no frame alignment issues. Recently installed new crankset (Centaur 10 UT compact) to replace Chorus 10 UT 39/53. Shortened chain accordingly - chain length correct visually and according to all formulas/fitting methods out there. On downshifts from big ring, the chain hangs up on top of the small ring and doesn't engage for a couple of pedal strokes - just 'skates' around on top of small ring before engaging. Happens only when rear derailleur is on the smaller cogs. Everything, including chain (except Wipperman quick link), is Campy 10 speed so no brand compatibility issues. I installed a new chain and no fix (old chain was mid-life). FD setup is spot on and I fiddled with limit screws, tightened crank bolts, pulled and reinstalled crank (everything correct including wavy washer and retainer spring), cleaned everything well, etc. All done with torque wrench to spec. Cable tension appropriate on FD. Specifics of parts are:

newish Centaur 10 FD
new Record 10 chain
new Centaur 10 Ut crank
older (50k miles, circa Y2K) Chorus RD

Any ideas ?

[druptight]

When you say FD is spot on, did you adjust its height? I usually find that when I've had this issue where it's up on top of the chainring and not engaged it's usually either limit screw related or FD height related.

[ldamelio]

Yep, FD height and limit screws perfect. These were my first guess. Fiddled with them anyway, even though they were near perfect. No improvement.

[rustychisel]

+ 1

need to lower FD approx 3mm for optimum with compact crankset (50T) from 53T 'standard'

[bart998]

If he "fiddled" with the height, he may now have the alignment of the cage and chainring off.

[druptight]

If he "fiddled" with the height, he may now have the alignment of the cage and chainring off.

Agreed. For my money this has to be FD related. I'd unhook everything, get it aligned in plane, height set, limits re-set, etc.

Do you downshift up front while cross shifted in the back often?

[ldamelio]

Guys - experienced mechanic here. Lowering the FD with the change from standard to compact is elementary and everything is aligned perfectly. I know how to install and tune a FD. It just isn't that simple a problem or I wouldn't have needed to post.

[rustychisel]

Guys - experienced mechanic here. Lowering the FD with the change from standard to compact is elementary and everything is aligned perfectly. I know how to install and tune a FD. It just isn't that simple a problem or I wouldn't have needed to post.

Fine, unwad your knickers... experienced internet posters are trying to help, not hinder you here. Some of us are also experienced mechanics.

[druptight]

Guys - experienced mechanic here. Lowering the FD with the change from standard to compact is elementary and everything is aligned perfectly. I know how to install and tune a FD. It just isn't that simple a problem or I wouldn't have needed to post.

Don't get upset - we can only know what you've told us, which wasn't this level of detail in the OP.

When you say "happens only on smaller cogs," which cogs are those? Smallest 2?

[jtakeda]

But did you try the FD height?;)

For real though. If you're confident about limits and FD height it's cable tension.

Try tightening the cable for the FD using a barrel adjuster.

[ldamelio]

Not upset (or wearing wadded knickers). Just trying to communicate that I've checked all the usual things and have experience/competence in doing so. The problem occurs when the chain is on the 12 and 13 on this 12-25 cassette. Thanks.

[druptight]

On my compact bikes I don't even have access to small front/small rear combo without the chain rubbing on the big ring, and on some bikes, you have the problem even with the next cog up (due to the 16 tooth difference). Is this the case, does the chain rub on the inside of the big ring in those cogs due to extreme chainline and the tooth difference? Could that be causing your issue possibly?

[dave thompson]

Didn't Campy make a early version of a 10-speed chain that was wider than the current version of their 10-speed chains? (I don't know, I'm not a Campy guy at all) Could that cause a problem?

[rustychisel]

It's more indicative of the angle of chain, most often associated with short chainstays accentuating the angle.

I know of people who vary the angle of the FD cage to address the issue, and others who have tweaked the front outer plate inward slightly (I wouldn't).

[ldamelio]

I'll try turning FD tail in and see what happens. There are also apparently different versions of Centaur 10 FDs so I may also have a subtle compatibility issue. I have another Campy 10 FD in the parts bin and can give this a go also.

[oldpotatoe]

Before posting, I scoured the web and tried all posted solutions or this problem so as to not clog up the forum. 10 speed all Campagnolo drivetrain - all worked together well for years, no frame alignment issues. Recently installed new crankset (Centaur 10 UT compact) to replace Chorus 10 UT 39/53. Shortened chain accordingly - chain length correct visually and according to all formulas/fitting methods out there. On downshifts from big ring, the chain hangs up on top of the small ring and doesn't engage for a couple of pedal strokes - just 'skates' around on top of small ring before engaging. Happens only when rear derailleur is on the smaller cogs. Everything, including chain (except Wipperman quick link), is Campy 10 speed so no brand compatibility issues. I installed a new chain and no fix (old chain was mid-life). FD setup is spot on and I fiddled with limit screws, tightened crank bolts, pulled and reinstalled crank (everything correct including wavy washer and retainer spring), cleaned everything well, etc. All done with torque wrench to spec. Cable tension appropriate on FD. Specifics of parts are:

newish Centaur 10 FD
new Record 10 chain
new Centaur 10 Ut crank
older (50k miles, circa Y2K) Chorus RD

Any ideas ?

Adjust FD limit screw inward and cant it a wee bit more tail out...since it happens on smaller cogs, with resulting chain angle meaning the chain is essentially closer to the FD, the chain needs to move farther. Make it real far..even it means putting a chainwather on there...smallish frame?

[ldamelio]

Peter - I will cant derailleur out as you suggested. Limit screw already maxed and I have Dogfangs on all my bikes - will do this when I get home this evening and post result. Frame is 59 cm C-T and chainstays 43.1 cm - nothing unusual, a 2001 Litespeed Tuscany so no short chainstays contributing to chainline problem.

[oldpotatoe]

Peter - I will cant derailleur out as you suggested. Limit screw already maxed and I have Dogfangs on all my bikes - will do this when I get home this evening and post result. Frame is 59 cm C-T and chainstays 43.1 cm - nothing unusual, a 2001 Litespeed Tuscany so no short chainstays contributing to chainline problem.

10-4, front ders can be vexing sometimes, maybe bend the tip of the fder in a wee bit. Gotta makes the fder more 'aggressive'.

[djdj]

I'm not an experienced mechanic, but given the mileage on your RD, perhaps it is not taking up the chain slack promptly when you move to the small ring, leading to sloppy front shifting?

[Rekalcitrant]

For what this is worth, I had the same problem a few years ago and some fiddling with the FD after similar advice from oldpotato solved it.