Bicycle Mechanics - spreading FD cage for compact crank

Anyone have experience with spreading the front deraileur cage of Shimano Ultra-9 triple to get some additional width to work over the entire gear range without cage rubbing on a 50-34 FSA Energy compact crankset driving a wide 11-32 rear sprocket with Shimano XTR rear derailleur?

I have no problem shifting over the full range, but the front derailleur cage rubs the chain despite carreful adjustment. I purchased the Ultra-9 triple front derailleur hoping that it would better handle the compact crankset and the wide rear gear range. Spreading the front deraileur cage seems like the logical next step. Anyone Been there...Done that?

Doesn't sound to me like the right thing to do.

Where exactly does it rub? If your front derailleur is set up right you should have two shift positions for each chainring. That should take care of any rubbing on the sides of the deailleur cage. Check out the Park Tool website and follow their instructions beginning at the very beginning if you don't know how to get your derailleur adjusted that precisely.

My Energy crank with 109 octalink BB rubs on the big chainring when I'm in the little chainring and the two smallest cogs. I just use that feature as an audible indicator that it's time to change chainrings.

Doesn't sound to me like the right thing to do.

Where exactly does it rub? If your front derailleur is set up right you should have two shift positions for each chainring. That should take care of any rubbing on the sides of the deailleur cage. There is a trim position in the shifter for each chainring.

Spreading the front deraileur cage seems like the logical next step. Anyone Been there...Done that?That's not the answr, and I wouldn't.

I have done it and it worked fine, just don't go hog wild. Front dr's are cheap anyway so it's worth a try before you buy a new one that'd work without modification.

Are you sure that the chain rub is on the derailleur and not the inside of the big ring? With the chain on the 34 and the smaller cogs it's fairly common for the chain to rub the inside of the big ring due to the big difference in the 34 and 50.

Al

Progress report:

I took the screw out of the back of my Shimano Ultegra triple front deraileur and evenly spread just the rear portion of the inner and outer cage about 1/4 of an inch total. I inserted a 1/4 inch nylon spacer and a longer screw. In my first trial ride today, the chain rubbing is almost gone over the full 50/34 front to 11/32 rear. I'll test it over 100 miles this weekend to see if the chain jumps or jams.

I would avoid bending. It allways seems to take longer than it should to set up my fr d. Sheldon Brown's web site has some great tips on setting them up. His site is a huge resource for bike mechanics.

http://sheldonbrown.com/derailer-adjustment.html#front

If the derailer is designed to work with your cw range and has the correct curve and stuff. I would try to
1) put the adjusting screws in the middle position.
2) get the outer cage to come as close to the big ring as you can (1mm-1.5mm) w/o hitting.
3) remove slack from cable in low ring.
4) Adjust trim

I would avoid bending. It allways seems to take longer than it should to set up my fr d. Sheldon Brown's web site has some great tips on setting them up. His site is a huge resource for bike mechanics.

http://sheldonbrown.com/derailer-adjustment.html#front

If the derailer is designed to work with your cw range and has the correct curve and stuff. I would try to
1) put the adjusting screws in the middle position.
2) get the outer cage to come as close to the big ring as you can (1mm-1.5mm) w/o hitting.
3) remove slack from cable in low ring.
4) Adjust trim 1) WHAT??... 4) Trim is in the shifters and doesn't 'adjust'. Aome don't even have trim and if the front is friction, it's essentially infinitely variable. He didn't mention what the shifters are,but many that have shifters with trim to cure the problem,don't have a clue.... WWW.parktool.com repair section has good instructions too.

100 mile update:

I ended up making two modifications that allow me to shift all gears between 50/34 front and 32/11 rear. I have experience adjusting FD with 53/39 with 11/23, but the wide range compact gearing did require bending the rear of the FD cage for a slightly wider exit for silent running.

1) This was a new bike build with a nice and shiny braze-on deraileur. The new "D" metal block and lock washer that came with the front deraileur, even when tightened down, slipped after many shifts. The FD cage would end up skewed after many shifts and bumps. I did not want to bend the hanger to match the saddle point, so I roughed up the "D" block with sandpaper which stopped the slipping.


2) I kept the widened rear cage but removed the spacer and longer screw and just bent the screw bracket on the front cage. This kept a low, flat bottom rear cage.

100 mile update:

I ended up making two modifications that allow me to shift all gears between 50/34 front and 32/11 rear. I duno what the point is to that anyway,but whatever.... :rolleyes: