Cyclologist

Upon swapping a 10 spd 105 front derailleur onto a bike that originally had a 10 spd ultgera front derailleur, I noticed while adjusting the front derailleur limit screws that the return spring hits the frame unless the limit screw is used to keep it from hitting. This wouldn't be a problem except that the chain rubs the front derailleur when in the small ring/big cog combo, meaning that the front derailleur needs to go in further, except it can't. There is already a tiny chip in the seat tube the return spring has produced from hitting the frame at high force upon return. I've already installed the ultegra on another bike and don't want to swap it back in order to determine whether it didn't have this problem, but based upon the finding that the derailleurs are indistinguishable, except for the finish on the cage, I don't think it was any better, and I actually think the chip was already there from the ultegra. The bike in question is a Felt F65. Any recommendations?

froze

Ok, that's an odd one.

It would seem on first thought that the rotational alignment of the cage may be off a tad, probably toed in. The outer plate of the derailleur should be in a position so that the cage remains parallel to the chain when the chain is on the outermost ring and outer most rear cog. Check to be sure it's parallel to the chain first. If you have to make an adjustment here then you will have to readjust the H and L screws.

If the above doesn't work you may want to try a rubber liner like a piece from an old thick rubber tube to place inside the bracket/clamp that goes around the frame. The thought process here is that by adding a bit of space like what a washer would do, would be enough to prevent the spring from hitting the frame.

Retro Grouch 

That's what I was thinking. A real high percentage of front derailleur shifting problems can be traced to improper alignment of the derailleur on the frame.

Cyclologist

Thank you for your suggestion, however I can assure you that the derailleur cage and derailleur outer cage plate is aligned perfectly with the outer ring.

Indeed, placing a spacer between the band clamp and the seat tube would bring the derailleur out just far enough to alleviate this problem, however I'm left wondering whether the band clamp would have difficulty closing properly. I'll see about perhaps making a shim out of aluminum soda can, since I'm worried that a rubber shim would lead to too much movement and thus sloppier shifting

froze

I'm not saying you don't know what your doing because it sounds like you do. But I assume you checked the alignment with the rear outer most cog along with the outer ring at the same time?

froze

Also check the height of the derailleur placement on the frame, because if it's tad too high this would require the derailleur to move a tad further in either direction to get the chain to move. Again once this is done you will need to readjust the H and L screws.

If all this is ok then try the rubber washer thing I described earlier.

Cyclologist

Hmmm. Can't say that I did.

I just checked that right now though and that looks good.

Thanks. When I swapped the shifters, I outlined the placement of the band clamp of the previous derailleur and used that as a starting point for the replacement. I did a quick check at the time and it checked out okay. I just double checked right now with a penny and it could move down a mm. I'll try moving it down then and let you know if that helps.

Cyclologist

So, if a little is good a lot must be better... I moved the front derailleur down to within 1-2 mm of the outer ring teeth, much closer than a penny's width and unfortunately it made no improvement to the problem from before.

froze

Interesting; did you have time to check alignment of the cage to the outer ring to the outer rear cog as noted previously?

Cyclologist

Yes, see post 7.

froze

Sorry; well I'm out of ideas. The only idea I have left is to remove the derailleur, cut a small piece of rubber from an old tube so that it fits about 1/2 way around the seat tube but facing the derailleur, and reclamp the derailleur clamp around that to see if the thickness of the tube is enough to make the spring clear the frame.

Maybe someone else has a more intellegent answer then me.

Cyclologist

I'll try that. Thanks for your help.

due ruote 

I guess the good news is that in Urbana you probably don't have a lot of use for the gear ratio in question. You don't mention anything about the bottom bracket - can we assume you changed nothing in that regard?

Cyclologist

Yes, that hasn't changed. It is the stock FSA carbon crank standard on '06 F65 model.

2manybikes

If you rotate the derailleur slightly on the seat tube you may change the contact point on the chain, allowing better adjustment.
If there is any small taper on the seat tube that you can't see it may help to raise or lower the derailleur a small amount. You may be able to bend the derailleur cage so that it is in a slightly different location when it hits the frame. Then adjust it out a little. A longer BB spindle may help, by moving the crank away from the seat tube slightly.

Also the 9 speed deraileur can move a little where it is bolted to the tube clamp, can the 10 speed ?

Cyclologist

The bike's just been sitting in the basement since it ain't going anywhere any time soon with this weather, but I've been wondering after reading a few things, is it likely that BB axle length is too short? Is the BB on this crank adjustable, and with the turn of a dial or something bring the chainrings further out? The crank is the following:
FSA OMEGA, 2-PC Carbon with CNC 7075/T6 Alloy Chainrings, 50/34T

If not, considering the dilemma, would it seem readily apparent that Felt spec'd a crank with a BB too short? If so, does anyone know if this crank comes with the option of using a longer BB?


Again, if it only had a good 1-2 mm, I think it would be fine, but as it is, the granny and big cog combo rubs the cage and the cage can't go in towards the frame any further. TIA

yes

I had this problem when putting a new crank on. I used the recommended bb length, but my seat tube was a tad too large for that length bb. A slightly wider bb should fix it, or if a 1 mm spacer on the right side will fix it, you could do that to move the whole bb 1 mm to the right. You probably wouldn't notice that your feet were shifted over by that ammount.
I just bent the cage on my derailleur slightly, but my problem was small. You can use the limit screw to prevent the der. from hitting your seat tube.

urbanknight

If it's aligned properly but still rubbing, the derailleur might be bent. That happened to me when I was having a hell of a time adjusting mine. Then I noticed it was tweaked, which can easily happen bumping into anything because they're so thin.

Cyclologist

That's a possibility, but I doubt it since it worked flawlessly on the bike it was on before, and it didn't get bent in the processes of swapping.