FD for 46/36/24 triple crank?
 

I'm probably posting this in the wrong forum. I've got a Univega Alpina Pro steel mountain bike. I'm replacing the crank with a LX triple (46/36/24) from Ebay. I also picked up a bottom swing Deore FD-M591. The Deore FD doesn't seem like it will work with the crank. The inner cage plate won't clear the middle chainring when I've set the outer plate to be 1-2mm from the outer chainring.

The original crank and FD are LX FC-M560 (46/36/26) and LX FD-M561, respectively. The inner FD plate is smaller than the Deore one.

After doing some more research, I found a SLX FD-M660 that might work. I wanted to get some opinions on its suitability for this crank. I need a 28.6mm clamp, bottom swing, and clearance for 46T chainring and 22T capacity. It seems to fit the bill, but has anyone used this FD with a similar crank?


thanks

Close enough to the right forum. ;)

Yeah, checking the specs for that guy, it doesn't want a big ring larger than 42T: http://www.shimano.com/publish/conte..._mountain.html

My advice would be to "go back in time" and get an FD that's spec'd for a 46-48T big ring. What's wrong with the original FD-M561?

I have a period-correct, if not original, SunTour XC 7000 on my Schwinn, with a 48-40-28 or 48-40-24 ringset. With the latter configuration I have to be a little careful on upshifts out of low, but otherwise both work fine.

The crank arm is bent, and the derailleurs are broken. You linked to the 10 speed version, but I think the specs are similar to the 9 speed. Any thoughts on the SLX FD? Is it as simple as finding one that will handle the large chain ring?

+1 According to spec's the LX Stuff you have should work fine with this setup is there some reason you don't want to run use the LX stuff you have. The only potential issue I could see is if you have the wrong length BB for your new crank.

Ah. I Googled the SLX FD-M660, and the Shimano docs I found list a 42T max ring, although an Amazon listing showed 46T. Might have been a running change, or just a mistake in the listing. Does Shimano make a "MTB" FD with traditional mounts anymore?

If it needs to be a new part, you might be stuck with lower-end "road" FDs meant for wider chains, like the Tourney FD-A073 (max ring 50T), or the FD-2403 "Claris" (max ring 50T.)

(My "go back in time" reference meant to all the good used Deore FDs floating around that will handle a 46T big ring, 20+ capacity, and that were well-made...)

OK know things make a little more sense if you need to replace stuff nearly any M series FD from the 80's to mid 90's should work based on Shimano specs and experiance you can pic one up dirt cheap off ebay, a bike coop or a more freindly established LBS. I'm surprised the one you have doesn't work.

Here's my take/experience wit this.... even if you get a fairly modern (9speed era) Shimano mtb FD that will handle a 48t
big ring, you'll still run into problems b/c the cage is stepped and it wants a 12t gap between the big'n'middle, and
a 10t gap between middle'n'little. You can make it work, but it will be sloppy, b/c they essentially optimized the geo f or
their own Shimano-branded 48/36/26 cranks.

Best bet, as others stated, would be to get an 80s/early 90s mtb FD. Most will take a 48t top, and lack the radical steps
in the cage that demand specific tooth counts. I have an early 90s Suntour XC Expert that came on a microdrive bike, but handles
a 48t top, plus most of the various deerhead/mt60/exage FDs I've come across take a 48t top as well. These are easily sourced, and most often do not cost much....

IME, the 6- and 7-speed FD's handle wider chain better than the 9- and 10-speed ones do.... less rub and whatnot.

Good luck!

Ok. I noticed the min 12T gap as well. I'll look on ebay.

Thanks for the help.

Friction or index?

Friction - even though contemporary Shimano MTB triple FDs are specced for 42 or 44 tooth max chainrings they will shift 48. Deore, SLX, Deore LX (recently discontinued here in the States as far as I can tell) and XT should work fine.

Index - For best results seek out a similar vintage FD so the profile of the chainrings and inner/outer cage plates match up. The pull ratio of the shifter for your given crankset is also a limiting factor.

You could also try moving the FD up a bit more than the sticker recommends. Not optimal, but functional.

The front shifter is friction (SRAM X.0 gripshift). I haven't yet mounted the chain (still waiting on RD to arrive), but I can try the Deore FD. It just doesn't look like it will work. Kind of a hassle to send it back to Amazon.

I grabbed a LX FD on eBay. It should work. FD-M563.