ifixbikes

Howdy folks. Today I was asked to convert a 3x Hybrid to a Road 3x and I thought it would be a no-brainer but I just couldn't get the Road 3x Front Derailleur to work perfectly.

Opus bike, original crank / chainrings were 42, 32, 22 - replacement cranks / chainrings are Ultegra 52, 39, 30 (I think?). The Alivio derailleur was not swapped as I thought it was capable of handling such a change.

I'm of an era which doesn't know a lot about the technical side of product differences but should a Triple FD not be capable of such a change? We also swapped from Trigger shifters to Brifter STI style...

Cable tension and routing... Check. F Derailleur alignment and height... check. DT Barrel adjustments done with slow and careful tweaking... Check. Still couldn't got all three to play well together.

I wish i had more info to offer. I'm sure your comments will stir my memory.

Thank you all in advance.

Jeff Wills

Older Shimano triple front derailleurs used different amounts of cable pull for "road"vs. "mountain" setups. The Ultegra requires less pull than the Alivio so try it.

Andrew R Stewart 

I'll also add that road and MtB frt ders (by Shimano) have rather different chain ring sizes they are optimized for. Also some MtB cranks space their rings apart more then some road ones. Andy

cpach

Not compatible. You need a road triple fd, ideally designed for a 52t big ring (some are designed for 50t, you can probably get one to work but it'll be worse. )

shelbyfv

Yes, be sure you get the FD that is designed for the 39t middle ring. Some are for 42t.

ShannonM

Distinction without a difference, IMHO.

I've never seen any Shimano road triple front derailleur not work on any non-weird triple crankset, including MTB cranks on 9 speed STI touring bikes, where 46/36/26 was pretty common stock gearing. Shimano didn't make a road triple FD that was "designed for" a 46T big ring, but lotsa Treks, Cannondales, and Surlys were built that way, and they shifted great.

Bicycle drivetrains are really forgiving, and specs are really conservative. Most combinations work so well that no rider in the world could tell the difference blindfolded. (Before they crashed.)

--Shannon

cpach

I disagree-- it usually works fine, but the ease of setup and shift speed are noticeably better when matching the FD to the chainring set.

shelbyfv

Yeah, when Shimano switched their road triples from 52-42-30 to 52-39-30, folks found the newer FD would not clear the 42t on the older cranks. And conversely the much shallower inner plate of the older FD did not do a good job pushing the chain off a 39t. Not a biggie if folks don't know this, was a long time ago. Maybe just a reminder that we can't know what we don't know.

andrewclaus

It may not work in this case, but try clamping the cable on the other side of the pinch bolt.

cyccommute 

I agree with ShannonM. The size of the chainring has little to do with how well a Shimano front derailer works. The cable pull is highly important but not the ring size. I just finished 1200 miles of touring with a Shimano Sora shifting a 44/32/20 XT external crank. It was shifting a 48/36/20 crank before I decided to reduce the gearing a bit. Set up was dead simple with no issues either with the 48 or 44 tooth ring.

One proviso: Set up and performance is generally easier and better, respectively, for Shimano’s cheaper front derailers. Tiagra and lower are easier to set up and have a wider useful range than the higher “better” Shimano derailers.

Ifixbikes: your issue is with the mountain bike vs road bike derailer. Swap to a road and everything should work.

Jeff Wills

Ah, but they did. The STX-RC front derailleur was designed for a 46/36/26 chainring set and a "road" front derailleur pull. I don't know if that was what was on the Treks and Cannondales you saw, but it's out there. Hard to find nowadays.

ShannonM

They very well might have been. The time frame would be about right, the front derailleur is the first part to get down-specced, and Shimano makes plenty of oddball parts for OEMs if the big ones ask for it. The scarcity of this particular front derailleur is evidence for it being an OEM-only part... every one ever made would have gone out attached to a bicycle, so there wouldn't be too many of them floating around.

Still, a good thing to have in the knowledge vault!

--Shannon