79pmooney

I need a front derailleur for a triple that mounts on a 31.8mm seatpost and travels as far inboard as possible. I have taken a triple crankset and mounted it on the shortest possible Plil Wood BB spindle (105 as I recall) in an effort to make the bike as knee friendly as possible. (My knees love track standard cranksets and chainlines and hate the standard 105 Hollowtech triple crankset I ran for years. Those knees are far more important to me than any sacred "law" I am violating.)

The crankset is an old Specialized 110/74 BCD (with the wonderful, very straight crank arms) set up with 50-38-24 chainrings. Cassette is 9-speed Campy and the chain 9-speed SRAM. Cranks are so far inboard the the left misses the (failry fat ti) chainstay by just over a mm and the 24 tooth ring by about the same. I has to grind down the heads of the inner chainring bolts to clear. Shifters are DT friction so that should allow any (downward pull) FD made without changes.

In the long run, I will get a Phil spindle 2 mm longer (this setup won't take very many ons and offs before contact) but that still leaves me with chairings that are very far inboard. The Shimano and SRAM deralleurs I have tried won't drop the chain off the middle ring onto the inner. I tried epoxying a steel strip to the outer cage of the SRAM FD. Shifted well but I had to trim for nearly all shifts in back and some combos rubbed a lot. And the plate dropped off second ride. Maybe if I grind off all the chrome I can make the epoxy work, but there has to be an easier way. No?

So this is a call for some FD wisdom. What FD (in 31.8) reaches in really far? Or has stops that can be ground down to allow it? Or functions well twisted clockwise to get the cage in further? If it is a 1 1/8" FD and has a band for the clamp. I could probably Dremel the body to fit 31.8.

And yes, this is a lot of work and brings up the question - why? I just Duck-Ducked "cost of knee replacement 2020". $20-34,000 per knee. I'd need two. I've been living with this condition (chrondomalacia patellae) since 1978. As I age, they are getting fussier about what works and what doesn't. The doc who diagnosed me told me that if I didn't play by their (my knees') rules, it would be replacement time. Every ortho I've spoken with since has told me that doc spoke the truth. I've now "q'ed" all my bikes (going from a large capital "Q" to a low small "q"). My knees love it. But this one is the hardest!

Ben

Cyclist0108

I don't know the answer to your question, but some pedal manufacturers make pedals with short spindles, and also there are cleats, such as Time, that have lateral float. HTH.

1X with a wide rear range might be another option.

79pmooney

Shoe/crank rub is the limit. (I actually try to stay far enough off that I can wear winter shoes and not rub with road grit. I have a box of dead Sugino cranks, all worn ~25% through from shoe wear. (Both traditional slotted cleats and Delta LOOKS allow setting the shoe quite far in.) And lateral float - absolute no-no for these knees. Traditional pedals and cleats work really well. So do black LOOK cleats.

Edit: I love having the gears 14-19 in one tooth steps (well, 17-19 is acceptable, just not ideal). To me, that is cycling at its best. This love is 45 years old since I rode my first 13-19 5-speed. And climbing on those cassettes or FWs on the right chainring is a joy I live for. Wide range cassettes are (for me) a huge step down. Now maybe I'll switch when the 17-speed cassette comes out. I now have a Shimano 13-28 on my 7-speed bike. It goes 21-24-28. I hate it. Phil Wood FW so fewer choices. I am not willing to take that almost 50 yo frame out to 130.)

Ben

AnkleWork

Many front derailleurs are limited by contact with the seat tube. Maybe switch to a double chain ring setup with a (narrower) FD for a double.

Re "sacred laws": consider standing whenever pedaling hard while continuously shifting your weight over the driven pedal. You can push a higher gear to maintain speed -- easy on the knees and a good workout. You can even get your upper body into play a little. As many have discovered, the TdF concept is nonsensical for anything other than racing.

bikemig 

TA cyclo tourist triples are the narrowest cranks I've seen. That doesn't answer your question but it does give you a different rabbit hole to chase.

https://velo-orange.blogspot.com/200...nks-redux.html

rccardr 

I would try a Shimano CX50 or CX70 front derailleur. Those are my go-to FD's for compact doubles or triples with a tight chainline.
Think they only come as braze-ons, but there are plenty of thin FD clamps out there.

Second choice would be a Shimano 5600,5700,6600,6700,7400,7402,7410 or 7700 FD. Some of those came in 34.9 but then you're limited to whatever the clamp/FD interface is with regard to clearance to the seat tube.

You also might want to try a Shimano 5800/6800 11 speed FD. Those sit so close to the seat tube that they have a setscrew adjustment.

79pmooney

I've been standing for half a century. Yes, I know both the benefits and drawbacks really well. (Maybe you noticed my great breakthrough, the 13-19 5-speed FW? WIth a 50something by 42 144 BCD crankset, riding New England as a racer, I did a lot of standing I also ride fix gears.)

I'm quite open to using double FDs. (Cage too small? Just means chain drag - quite rideable. I've been doing it for years. But not a double crankset. For this guy, compacts suck. I still love 52-42, well now 50-38 as I age and go slower, but the bigger shift of a compact? Throws off all the classic shifts us 144 BCD guys love so much. And still doesn't let me get a decent (knee saving) low unless I sacrifice the tight cassette.

As I said in my first post, I don't mind doing some work here. But I am not willing to sacrifice either my knees or my love of the sweet climbing gears.

Ben

79pmooney

Thanks rccardr. I'm going to scrounge up some seatpost diameter tubing, go to shops, mount some of those and measure them. (I also need to caliper my seattube again. I said 31.8 from the top of my head. (Standard ti seatpost.)

bikemig, thanks. I'm not sure I want to go down the TA erector set rabbit hole again. I spent several bikes and many miles on them. But I don't miss them. Versatile, yes. But stronger, stiffer, lighter, simpler, more durably finished and more reliable is kinda hard to give up. Still, thank you TA for being out there. (In 1978, the near perfect Mt Washington crankset. A cut down outer ring to serve as just a spider and a 28 tooth chainring. 13-21 n back. Shortened chain. Light! I rode a 5 hour Cat 1,2 road race the day before and was mental mush. But all I had to do was remove my cranks and racing chain, put on the TA and its shorter chain, swap rear wheels, remove WB cages and done. Not one job there that required any thought at all.)

Ben

rccardr 

Ah, 31.8. So you did say.
When we get back next week, I'll check the clearance and model number on my Cannondale ST, which is also 31.8. It's a Deore of some sort, and as I recall there was a lot of experimentation with inset when that was built five or six years ago.

ThermionicScott 

The CX70 FD *does* come in a 31.8mm clamp-on version: https://www.amazon.com/SHIMANO-Shima...W3I?th=1&psc=1

https://bike.shimano.com/en-EU/produ...-CX70-B-D.html

Eggman84

I would avoid the modern triple FD, they are optimized for very specific chainring combos. I have really good luck using older Shimano MTB FDs from the 3x7 and 3x8 days to shift my 3x9 touring bikes Specifically using XT FD-M735 nad XTR FD-M900; they come up occasionally on e-bay Can't say if they are the ones that move in the farthest, but they move in pretty darn far. If looking for something more modern, I would recommend the FD-CX70; heard good things about these shifting triples even though designed for doubles. Good luck.

79pmooney

Thanks Karl. I actually had very good shifting with my D-A 9-speed triple before I addressed the "Q" despite that it was for a very different combo than what I was running. But now it doesn't come close to working. Old school FDs tend to be narrow ans without contact issues with oldschool (low Q) cranks line my old Specialized. Now I don't know much about MTB FDs. But I'll look into them.

bikebikebike

A bit off topic , but parallel
does anyone have a reference for cable travel across a list of shifters / derailleurs?
I am looking for non indexing 3 speed fronts (FD) for use with 3 speed IGH.
Sheldon is helpful here , but incmplete

AeroGut

Can you provide an exact measurement of the distance you want from the outer wall of the seat tube to the inside edge of the DR cage? I've got a couple of bikes with 90's MTB derailleurs that I can measure for you, and I'll be at the co-op later today, so I can measure others if I know what I'm looking for. I think the MTB DRs are a good bet, since many were using larger seatposts and 22t inner chainrings that could get pretty close in, even accounting for wider BB shell and chainstays.

ThermionicScott 

BTW, I've heard a little speculation that Shimano may discontinue the CX70 FD now that they have a "series" part in the new GRX group. So it might be worth it to grab one soon if you're thinking of going that route...

AnkleWork

Yes, I meant that a double FD might allow more inboard swing before contacting the seat tube. Many in this forum would never consider tolerating some chain rub even when slight. It's amazing how many odd combinations can be made to work when we willing look past established norms and apply some first hand experience.

79pmooney

I could measure up where the 24t ring sits but extrapolating from my existing FDs is tougher. I didn't measure up the D-A FD when it was on and the SRAM was so different after I glued on the 1/8" sheet of steel that any measurement off that would be fairly irrelevant to another FD. I can measure where the FD sits with that plate missing and tell you what doesn't work. (FD shape and the twist in the FD relative to the Seat tube both make huge differences. We used to say FDs were like bumblebees. According to theory they shouldn't fly. Getting exact measurement off one FD is kinda like patterning an airplane design after a bumblebee. I wouldn't rust it fto get off the runway.

One thing that might be an issue with MTB FDs is my crankset; the oldschool, straight narrow arms that sit not far off the outer chainring, I have to take care setting up Shimano style road FDs so they don't hit the crank.

I just E-mailed a framebuilder to see if I can get a scrap of 31.8 seat tube. If I can, then mounting FDs and taking measurements will be radically easier. Still doesn't help me with what I need, but I will be able to do crude comparisons easily and share real numbers.

Edit: I'm being loaned a piece of ti!

Ben

droppedandlost 

Have you thought about shaving the low limit stop? I imagine some of these FDs will be really close to working and you could gain a smidge that way.

Retro Grouch 

In today's era of 11-speed 50t cassettes I'd think about changing the other end of the drive train.

79pmooney

Yes. I asked about it in the opening post.

79pmooney

Cassettes need a few more cogs to build a double as good as my triple 9-speed. Still waiting.