vasko

I put a 26mm tire on my Trek 2120 and the rear tire rubs the bolt that attaches the cable to the front derailleur when the derailleur is on the large chain ring. It is an older Shimano 105 triple from 1997. I have rotated the derailleur as far as I can to eliminate interference without impacting shifting performance and it still rubs. The bike is my daily commuter and I'd really like to use a tire that was even a little larger, say 28-32mm.

Any ideas on how to eliminate the rubbing? Do any of the newer Shimano front derailleur’s have more clearance?

Dave

LtSPD2000

The derailleur is probably a braze on type attached to a downtube tube clamp. (I used to have that same bike) You should be able to loosen the downtube clamp and rotate the clamp counter clockwise as you look down on it just a little, (that should move the derailleur attachment oaway from the tire somewhat), then loosen the bolt that holds the derailleur itself in place and rotate the derailleur (back end of derailleur cage towards the wheel) Both adjustments should be in small increments. That bike was designed as a touring model and should handle much taller tires without rubbing.
Hope this helps.

AEO

650b conversion?

vasko

It is a clamp on derailleur. I've rotated it as far as I can without impacting the shifting and it still but it still rubs.

Dave

AEO

pics?

vasko

Here is a photo of the front deraileur on the largest chainring. Note there is nearly zero clearance between the cable bolt and the tire.

Dave

ericm979

Since all Shimano derailleurs have the same leverage ratio, I would suspect that they all have a cable arm that is the same length. But you might be able to find one where the arm was a bit farther forward. Try taking the derailleur into a good LBS that has a selection and compare it to their derailleurs.

Another thing you could try would be to thread the bolt into the other side of the arm and clamp the cable there. Check that there is no interference anywhere and that the cable does not rub on the frame. You might have to shorten the bolt slightly so it doesn't protrude.

Failing that, you can look for a make or model of tire that has a slightly lower profile. There is a suprisingly large variation between tires of the same nominal size. Unfortunately the actual size specs are hard to come by, so you'll again have to resort to comparing parts at the LBS.

Mhendricks

This may be a stupid question but is the spacing of the tires in relation to the chain stays equal on both sides? Do you have adjustable rear dropouts?

vasko

Not a stupid question, but the wheel is centered and the dropouts aren't adjustable.

George

Limit screw??

DannoXYZ 

That would hamper shifting into the big ring.

What's your chainline? Measure the distance from the centre of seat-tube to exactly in between the two chainrings. If your chainline is too far outwards, it makes you have to sweep the FD outwards more to getinto the big-ring. This pulls the lever-arm of the FD down and inward more than normal.

AEO

you say 25mm, but those look closer to 27mm.
are they marathon plus tires? they run a bit big.

vasko

Good eye. The are Marathon racers, should be 30mm, but they only measure 1.066" wide (27mm).

vasko

Went to the local bike shop. The new Shimano front derailleurs have plenty of clearance, but all the shop had were 10 speed derailleurs. They didn't recommend use a 10 speed triple on a 8 speed chain doto the narrow width. So I'm trying to find a newer 8 speed triple front derailleur.

LtSPD2000

A Sora Derailleur should work. You could also use a 9 speed triple. I have used them on 8 speed drivetrains in the past with no issues.

vasko

Thanks. It is really good to hear that someone has tried this and it works. I found three 9 speed triple front derailleurs, a FD-7703 (Dura Ace), a FD-6503 (Ultegra) and a FD-5504 (105). They are pretty close in cost, so I'm leaning toward the Dura Ace.

vasko

Thanks for everyone for all the help. I ended up replacing the old Shimano 105 front triple derailleur with a Dura Ace 7703 triple from a 9 speed group. I replaced the chain at the same time to be compatible with the narrower cage. The tire clearance problem is gone and the shifting has improved.

Thanks

Dave