Vermilion

When I purchased my Burley Canto three years ago, it was in rideable condition but needed some work. A previous owner had installed MTB twist shifters, but the bike uses a road front derailleur, which of course has a different pull ratio. Front shifting could be made to work, sort of, but it was difficult to avoid chain rub in the middle ring without pulling the cable too tight when using the large ring or throwing the chain outboard.

My stopgap solution was to replace the front derailleur (going bad anyway) with a Sora road piece. Then, I changed the front shifter to a Microshift lever/trigger. I left the right twist shifter in place because it was compatible with the Alivio rear derailleur. Eventually I replaced the rear derailleur with a Sora and installed the matching right-hand trigger shifter. This works well and I'm not planning any changes, but I'm curious . . .

Twist shifters (my preference anyway) package better on a 'bent than trigger shifters; it's awkward to have shifters that hang below the bar. (In my case the shifters don't hit my knees.) Perusing photos of 'bents, I see quite a few if not most with twist shifters. I don't see how MTB shifters could be made to work with currently available parts because:

-- the front derailleur requires a high pinch bolt because the cable stop comes close to the derailleur, unlike routing on a DF bike where bare cable runs under the bottom bracket. Dual-pull derailleurs won't work because in some gear combinations, the cable will exit the housing/stop at a 90 degree angle, clearly a bad idea. An MTB front derailleur would have to be bottom pull only, high pinch bolt, and able to support a 52-tooth big ring. I don't see any currently available parts that would work.

-- the front twist shifter would have to be designed to use the road pull ratio and work with a triple, but I don't see any currently available twist shifters that do.

So I'm curious how the 'bent manufacturers got this work in the first place, and how current 'bent owners address these challenges when components need to be replaced.

Thanks for any info.

Moe Zhoost

Any thoughts about using a friction shifter?

Vermilion

A friction shifter should work OK since the rider, not the shifter, decides what the pull ratio is. If you don't mind using two different types of shifters, you could use an MTB rear derailleur (no cable routing complications) with an indexed twist shifter and a friction shifter for the front.

Another option might be to use a Tourney A073 (low end, I know) bottom pull/high bolt derailleur; it's rated for a 50T chainring but might work OK on a 52. One could also switch to a 28-38-48 cransket and compensate with a smaller cogset if needed. That would allow MTB shifters front and rear.

BlazingPedals

Not knowing better, I always used MTB shifters and road derailleurs. I adjusted the front to the middle ring and use the stops to set the inner/outer.

Leisesturm

My Performer Highracer came with MTB shifters and a Road Derailleur and Road Triple up front and a MTB Cassette and MTB Derailleur in back. As I always understood it, Road and MTB pull ratios are the same in front. The proof of that, I think, is that it works at all. There isn't any 'sort of'. If the pull ratio's differed by any amount you would not be able to use MTB shifters with Road front derailleurs. What is variable is the presence of a 'trim' function in the shifter to avoid chain rub. Some have it. Some don't. A trimmable shifter will have index positions that incrementally move the derailleur to accommodate the chain angle as it covers the span of the cassette. Chain rub is not usually acute on something like a Canto. Sometimes a sliding idler can help with chain angle.

Vermilion

Thanks, but road and MTB front pull ratios are not the same. After ditching the low-end Revo shifters on my 3x8 Canto (obviously not OEM equipment and incapable of trimming), I used GripShift MRX, the front shifter being "micro friction." Rear shifting worked perfectly with the Alivio derailleur, but in front, if cable tension was set so that the chain did not rub the cage when on the middle ring, shifting the three clicks to the normal position for the large ring pulled too much cable, which was obvious from the feel of the shifter. If the high limit screw on the front derailleur was relaxed even slightly, the chain would often be thrown outboard off the big ring when shifting.

Shifting two clicks instead of three between the middle and large rings sort of worked, but still wasn't quite right. If you really want this to be 100 percent (silly me, I do), then indexed MTB shifters can't be mixed with road derailleurs. The solution I ultimately adopted employs fully compatible components and a matching pair of shifters. If one were looking for the least expensive option, the pure friction front shifter at less than $15 would be satisfactory.

Jeff Wills

^^^ You are correct, “road” and “mountain” front derailleurs use different amounts of cable pull. Mountain front derailleurs use more cable movement to move the cage. Shimano used to make front derailleurs that shifted larger “road” chainrings with “mountain” shifters: FD-R443 and FD-R453. These are long out of production and weren’t common BITD.
When I built my RANS Phoenix a couple years ago, I used my preferred Shimano trigger shifters. To get around the difference in cable pull, Rose City Recumbents supplied a Microshift front derailleur. I forget which model it is but a call to Rose City will probably turn up that info.