|3iker

I'm trying to use my road FD on a 48/38/28t chainring. However the FD cage can't seem to travel far enough to the largest ring.
Does road FD move less than mtb FD?

gitarzan

Is it built for two rings?

fietsbob

There lies the question: triple road versus triple mountain a valid comparison.

Throw of the parallelogram can me measured, but not on a working bike,
as you have to back off both limit screws, and the chain is in the way.

Do a Berto, buy the parts and set up a measuring fixture.

wunderkind

see bicycletutor.com videos.

Al1943

Was the shifter in its lowest position when the cable was attached? It should have been, with all of the slack pulled out of the cable.
Is the chainline correct for the crankset?

|3iker

It's a triple FD.

Al1943, that was the first thing I checked about I dunno..... 1000x!
Apart from the road FD the crankset and chain are original.

surreal

The "throw" of road and mtb triple FDs are quite similar, but the little arm that the parallelogram sits on will be further out on the mtb FD, meaning that the parallelogram of the mtb FD will not swing as far inboard, and the parallelogram of the road FD will not swing as far outboard. If you have a mtn crank and a road FD, i wouldn't be surprised if the thing won't swing out far enough. Fixes? Get an appropriate mtb FD; one with the pull and swing you need, that'll handle a 48t large chainring. Or, if you have a square taper crank, you may be able to use a BB with a shorter spindle, depending on the requirements of your crank. Grabbing a dual-pull, high-clamp XT with the 48t large-ring capacity would probably solve your problem most easily, but it's hard to say with the available information.

-rob

Bezalel

They move the same amount but the road chainline is shorter that a MTB chainline so you might need a shorter bottom bracket. Also keep im mind that road amd MTB FDs have different cable pull ratios co you can't mix index shifters and FDs.

Cyclesafe

Not all road FD are the same. For example, "improvements" from the Ultegra 6503 to subsequent 10 speed Ultegra FD's made them no longer work well with a 48T big chainring. The IRD Alpina-d FD has been described as a clone of the 6503.

https://www.interlocracing.com/cdfrtder.html
https://sheldonbrown.com/harris/derailers-front.html

If friction shifting, an XT FD works fine.

surreal

holy crap, i'd forgotten about the likelihood that he's got an indexed front shifter. that'd complicate the mtb FD recommendation a bit. OP, let us know what cranks and shifts you're using. That info'd decide whether you want a different BB or a different FD.

-rob