Bicycle Mechanics - Puzzled over front derailer for triple chain rings.

Fellow BF'ers,

Here is what I have; Older Ultegra triple crank FC6503 (52-42-30) with a 45mm chainline per Shimano specs. I intended to use a new Ultegra double front derailer but it doesn't seem to have enough throw from low to high limit. I am using an older Sora Triple brifter and the front derailer will go from the 30 to 42 ring but it hits the high limit about half way between the 42 and 52 ring. I have adjusted the high limit to the maximum throw.

I ordered an Ultegra FD6603 triple and it seems to be doing the same. I know now the 6603 is for a 52-39-? crank set, but the derailer is hitting on the high limit, not the inner plate of the derailer against the middle chain ring.

What am I not seeing here?

Thanks and best regards,

Mike

The correct derailleur is FD-6503, though any other nine-speed road FD should work. As should the FD-6603, though not as well. Your problem apparently is something other than the part number.

Disconnect the cable and pull the FD to its furthest position with your fingers. Does it move far enough? Held all the way out, turn the high limit screw. Can you feel the FD moving in and out?

Report back.

Is the cable routed over the pinch bolt correctly? How much slack remains in the cable when you downshift multiple times to release all tension at the shifter?

The correct derailleur is FD-6503, though any other nine-speed road FD should work. As should the FD-6603, though not as well. Your problem apparently is something other than the part number.

The FD-6603 will not work with a 52/42/30 crankset. You'd need over 5mm of clearance between the outer cage and big chainring in order to get the inner plate to clear the middle chainring. If you want to use a 10 speed front derailler with a 52/42/30 crankset, the FD-5603 is the only option.

Sometimes new FDs come with little red plastic spacers that need to be removed. At any rate, it is not going to work with your 39 unless you modify the inner plate.

DMF,

I have enclosed some pics. I hope they are helpful.

I currently have a double Ultegra FD on the bike. There is very little if any slack in the cable when the FD is in the low setting.

The chain line appears to be about 45mm as far as I can tell. I presently have the high limit adjusted as far open as I can.

I double checked the way the cable is anchored to the FD. According to the installation instructions it appears to be correct.

FWIW the triple FD has about the same amount of travel as the double.

Mike

Could it be possible that you may need a BB a few mm shorter to set your crankset a little closer and tighten up the chainline a few mm. Looking at the photo the inner ring seems farther out then most tripples I have delt with.

I'm inclined to agree. I have a 118mm BB on it now. I've considered putting a 110+/-mm depending on frame clearance.

At this point I want to cover other possibilities before I order another BB.

Thanks for the response.

Mike

What kind of measurement do you have between the small ring and your chainstay at this point,you may not need to make such jump down (8mm) in size. I would make several measurements ,measure the distance between the small ring and the chainstay then max out the pull on your FD and see where the inner plate and the big ring come up and go from there. I would want to just be able to overshift the big ring and use the adjusting stop screw to set it up.

is the crank mated to the spindle splines properly? i have found that if you try to install octalink cranks with the self extracting cap and bolt on it is hard to align the splines.

If the chainline is at 45mm already, the bottom bracket length is fine and the crankset is seated properly on the bottom bracket splines.

In the full extension picture of the front derailler, those limit screws are far from all the way open. Both appear to be screwed all the way in actually. Remove the high limit screw completely and then you'll be able to see the full outward travel of the front derailler

joejack951,

Thanks, I'll try that.

Mike

The FD-6603 will not work with a 52/42/30 crankset. You'd need over 5mm of clearance between the outer cage and big chainring in order to get the inner plate to clear the middle chainring.

Thanks for the correction. I've never tried the combo. Note, however, that he said the inner plate was not hitting the middle ring (though that might be because it isn't traveling far enough).

If the chainline is at 45mm already, the bottom bracket length is fine and the crankset is seated properly on the bottom bracket splines.
I agree. Whatever slop there is in the measurement can't account for the nearly 1/2" shortage of travel.


In the full extension picture of the front derailler, those limit screws are far from all the way open. Both appear to be screwed all the way in actually. Remove the high limit screw completely and then you'll be able to see the full outward travel of the front derailler
Good catch!

To all who offered an opinion,

Thanks for the ideas. As I was verifying settings and checking the recommended adjustments I had one of those "hunches". I was relatively sure the chain ring crank was aligned properly with the splines. In the process of checking this out and reinstalling the crank I discovered I had not used the correct torque setting.

After torquing the crank to the proper value the large chain ring fell right under the FD. All the rings work great.

Thanks again for all your help.

Best regards,

Mike

To all who offered an opinion,

Thanks for the ideas. As I was verifying settings and checking the recommended adjustments I had one of those "hunches". I was relatively sure the chain ring crank was aligned properly with the splines. In the process of checking this out and reinstalling the crank I discovered I had not used the correct torque setting.

After torquing the crank to the proper value the large chain ring fell right under the FD. All the rings work great.

Thanks again for all your help.

Best regards,

Mike

Well I'm confused. I thought it looked quite a ways out in the pic. But if the spider wasn't seated, how did you get a good chainline measurement? What does it measure now? Are you sure you're measuring from the center of the tube to the center of the middle ring?