Front derailleur/shifter compatibility
 

My newest (2005 model) bike came stock with the typical useless massive racing crankset. :rolleyes: To gear this baby up properly for climbing hills with a load in the trunk, I installed a TruVativ Hussefelt 44/32/22 crankset. (and the smaller BB to fix the new chainline) The front shifter is a 105 brifter, and original front derailleur was a Tiagra. The Tiagra's shifting worked, but it was rougher than I was happy with.

To see if I could improve the shifting, I installed a new X-Gen front derailleur that I had sitting around. The Tiagra derailleur had enough range to shift from little ring to big ring, but it didn't shift smoothly with the new crankset. OTOH, the X-Gen FD doesn't seem to have enough range, but shifts more smoothly. For now I am compensating for this buy turning the shifter's barrel adjuster to higher cable tension for shifting to the large chainring, and lower cable tension for shifting to the small chainring. This works, but is obviously a great annoyance. (Both limit screws are backed all the way out to allow maximum range, BTW.)

My question for the wise ones is...is there any reason the 105 brifter shouldn't be expected to work well with the X-Gen front derailleur? I've been adjusting all day, but I can't come close to getting from little ring to big ring without adjusting the cable tension barrel adjuster to keep the chain from rubbing the cage at either end. The height and angle of the derailleur look perfect to me, and this is not the first oddball FD/crankset/shifter combo I have set up, but it is the first time I've set up a FD with brifters, and the first time I've had this problem.

In fact the damn thing is even taunting me! If I optimize the FD to work with the 22 ring, and then shift all the way up to the 44 ring where the chain is rubbing the outside of the derailleur cage, then apply pressure to the brifter as if I was shifting up one more index position, the FD cage goes to the perfect place, but that is beyond the last index position. So close...yet so far!

STI triples can be a trip to set up even when everything matches. You're mixing both road and mountain components as well as brands so I'm not surprised you're having difficulty.

Sometimes it's possible to attach the shift cable on the opposite side of the fixing bolt so that the cable is a bolt width closer to the pivot. That'll give you more derailleur travel with the same amount of cable pull.

Typically MTB front derailleurs will not work with road shifters (and vice-versa), which is why Shimano came out with their road-oriented "Flat-Bar" line.

Try a better-quality road FD like a triple Ultegra; don't worry about the chainring size issue; if you set it up right it will work.

There is indeed a reason to expect that it wouldn't work well - I'm guessing that the X-Gen (is this a SRAM derailer or what?) is intended to be used with MTB type shifters. Shimano, in its infinite wisdom, has declared that their road and MTB front derailers should require very different amounts of cable pull - specifically, mountain derailers require a lot more cable pull than road derailers. Why this is, I don't know. Shimano would probably give you a reason having to do with the different needs of road and mountain bikes. I suspect that this is 50% of the answer, with the other 50% being "Because people will need to buy more derailers from us." If it's a SRAM derailer, well, they pretty much have to play by Shimano's rules.

Anyway, Shimano sells (or sold) road derailers intended for use with MTB shifters, but not MTB derailers intended for use with brifters. I have just heard about RetroGrouch's idea, and it MAY be an option. Possibly. More details here: http://www.ctc.org.uk/DesktopDefault.aspx?TabID=%204068.

Another possibility would be to switch to bar end shifters, but that doesn't seem like much a solution at all, seeing as you would presumably like to stick with the brifters. I suppose, if you really want the smoother shifting of the X-Gen derailer, that you could install just the left-hand shifter from a pair of bar ends and use that to shift your chainrings. It wouldn't be as convenient as the brifter, and a bit funky to have a brifter for the rear and a bar end for the front, but it should work perfectly, if that's more important to you. Friction front shifting forever!

I disagree. No reason why SRAM's derailleurs should have the same cable pull ratio as Shimano. Their new road bike front derailleurs, for instance, are confirmed as not matching Shimano's ratio.

Are X-Gen derailleurs even designed to work with Shimano's mountain bike shifters?


+1
Or at least micro-indexing, ala Ergopower.

The thing that puzzles me is that mountain bike vs. road should not matter. The two cranksets have the same chainring spacing, so why would they be so stupid as to design the shifters differently and introduce an unnecessary incompatibility? Don't they think people might want to change their gearing? Unfortunately "road" gearing really means racing gearing. Why do they assume normal people want a 52 chainring? I've never used the 52 ring in my entire life - it's dead weight.

I'll check if the cable attachment point can be moved somehow - that's a clever idea.

A front derailleur is a very simple mechanism - I'm not sure (other than weight) how Ultegra (or DuraAce) would be different or better than Tiagra? (My Sora bike has always shifted better, but I put that down to refined adjustment.) The reason I put the X-Gen derailleur on is that it's sized for 44/32/22 rings. It does already shift smoother than the original road derailleur, for whatever reason.

That's kind of what I'm thinking right now.

I have the EXACT same problem with a triple front (MTB) 28-38-48 ring and went to drop bars. Its an Altus derailuer, and I put Sora brifters on it. There just is not enough thrown between the small ring and the large. Its driving me NUTS. I may try a different derailuer tommorrow...another $20-$50 thrown into this disasterous project. I'd like to go back to Campy (Shimano can go take a left) but am not made of money. Fixed gear is sounding appealing.

That's kind of what I'm thinking right now.

The basic point here is that if you're using Shimano STI brifters with a triple crankset, you need to use Shimano road-triple front derailler. Shimano off-road grouppo front deraillers have a different amount of cable pull, and SRAM front deraillers are sometimes compatible with Shimano (in certain off-road grouppos) and either way don't have the same amount of cable pull as Shimano road front deraillers.

They do make other groups besides Record, you know. :rolleyes:

Thank y'all for the input. For its better shifting, I think I'll stay with the XGen and my fiddly trimming technique for now. Perhaps I'll get a friction shifter later.

Unfortunately the cable mount screw doesn't seem to be oriented in a way that will let me change the radius from the cable to the pivot without some custom machining...hmmmmm...machining...

Cruised a new bit of the Hamakua Coast today with the new gears. And new fenders. And a new flourescent yellow bike shirt. And new bike shorts. And new friends. Lots of firsts today. :D

I don't know th X-Gen derailleur you are talking about, but amongst Shimano front derailleurs, the amount of cable pulled is different between road and mountain derailleurs. Don't ask me why... On the other hand, mountain and road rear derailleurs are compatible.

Friction shifting is definitely an easy solution. Either install a downtube or bar-end left shifter (any chance you could buy the left shifter off someone who upgraded from 8 to 9 or 9 to 10 speeds?), or move to Campagnolo Ergo ($$).

Other solutions, depending on the exact nature of your problem.

– If you moved your chainline closer to the frame, are you sure your derailleur is able to go close enough to the frame? Check to make sure your derailleur isn't bumping onto the seattube or its internal mechanisms.

– Install a N-Gear Jump Stop. That way, you can set the inner limit screw a little bit further so the cable moves more inboard. The Jump Stop basically prevents you from overthrowing the chain.

– Grind your Tiagra derailleur. Many people seem to have good success by grinding the Tiagra derailleur cage so it's shaped more like your outer chainring.

If you look at the rear wheel spacing between the seat tube and the tire on a road bike you will usually find that there is no room for a downpull front derailleur to fit in between them. Road front derailleurs have a more upright cable lever to avoid tire contact, thus the different cable pull ratio. Mountain front derailleurs have a more "bent" cable pull arm that usually gets in between the tire and the seatpost. They can operate at a different pull ratio. A mountain derailleur will generally not work with STI levers. It is possible though to use mountain bike shifters on a road bike if front derailleur from one of the "Flatbar" groups is used.

The derailleur has plenty of range. The shifter just doesn't pull quite enough cable to make use of it. I'm getting used to trimming with the barrel adjuster at the right times. It shifts very crisply then. (Makes me want to get the FlightDeck now, to anticipate the gears better.) I just hope frequent use of the adjuster doesn't wear something out.

I also noticed the tight tire clearance with the FD pivot arm maddmaxx notes when I tried to install my fenders. Fortunately this is a "cyclocross" bike, so there is enough clearance, but I might have to make a small cut-out in the fender when I switch from 25 to 32 tires for unpaved adventures.

thanks again...learning new things every day.