531phile 

Shimano recommends a 113mm bottom bracket with the FC-M410 Alivio cranks to achieve a 50mm chainline. I installed this combo, but when I tried to adjust the front derailleur, I have to unscrew the high limit screw almost all the way. It is almost to the point that it will fall out!!! The chain now rubs on the front derailleur when I am on the high/high gear combo. The front derailleur is a shimano C50.

Now to complicate matters further, the barrel adjuster for the front derailleur attached to the shifter is stripped. When I adjust front derailleurs I like to turn this barrel adjuster almost all the way in. I turn it in all the way and then loosen it about three turns to give me some room for fine tuning. Since this barrel adjuster is stripped, I use a vise grip to turn it in, but I can't turn it in all the way.

So, I am at a lost as to why I can't get the front derailleur to be adjusted properly??? Now, does front derailleur throw differ from front derailleur to front derailleur or are they all the same??? Do I need a shorter length bottom bracket? or do I need to replace the shifter so I can get the shifter cable to be tighter so that the front derailleur can clear the chain in the high/high gear combo.

Thanks for any help.

FBinNY 

First of all, did you measure the actual chainline?

If you don't know how, measure from the center of the middle chainring to the downtube, then add 1/2 the diameter of the down tube. You want this to be 50mm or less.

Then to answer the other question, FD's do vary in throw model to model, but not by a whole lot since they're all designed around the theoretical 50mm chainline. OTOH the throw range does vary with the diameter of the seat tube. Makers use identical geometry on all the versions of each FD, so one mounted on a 1-1/8" steel frame, will sit inboard 1/8" more compared to one on a 1-1/8" frame. If you have a steel frame that could account for the limited outboard throw.

Lastly check all the detail of the FD installation, height, rotation, etc. since a slight misalignment can affect performance pretty significantly.

As far as the stripped adjuster. A shame but not a real crisis. Buy and install an inline cable adjuster, and park the lever's adjuster all the way in.

531phile 

I did not measure the actual chainline.

Bill Kapaun

Do you mean BIG:BIG?
That would be High/Low and considered cross chaining.

Sounds like you might have just a bit too much cable tension.

dsbrantjr

As FB suggests, measure your chain line. Using a caliper measure the tube diameter then the distance from the far side of the seat tube to the middle chain ring. Subtract half of the tube diameter.

Also check the torque on the crank bolts; if you have a square taper BB (I think you do) and the bolts are insufficiently torqued the crank may be too far out on the taper; they may also come off. Also check the clearance of your inner ring to the frame, there may be room for a shorter bottom bracket if all else fails.

Be certain that the high limit screw is truly what is limiting the outward travel; pull on the shift wire like a bowstring to see if that moves the derailleur out farther. If it does your cable pull is limiting the travel not the stop screw. Is the wire correctly attached to the derailleur? It needs to go a certain way around the attachment bolt.

If you leave too much clearance when the chain is on the inner ring you may run out of travel at the other extreme. Having the tail of the derailleur cage rotated too far inward may also cause chain rub, it doesn't take much.