bark_eater 

I picked up a Cannondale Coda 200m (I think), 94/58 bcd crankset with thoughts of using it as a compact double. When it got here I was surprised to find that the base of the square taper socket is actually just proud of the innermost grannie chain ring, while the base of the socket of a SR apex looks to be close to the same plane as the largest outer chain ring. Playing around on a flat surface it looks like the relative "Q" difference between the 2 cranks, from pedal threads and the outer chain rings is 5-8mm.
So my question is: Is it worth trying to use this crank set with a short 103mm(?) Bottom bracket as a compact double? or will the "Q" factor still be as wide as running a lower "Q" road triple?

Here's the crank:

bark_eater 

Would it help if I threatened to put it on a Super Course? Or a Trek 400?
I have a set of 46+30T 94 BCD chainrings, but am suspecting that a crank made for a 135mm hub and to clear fat aluminum chain stays might not be the right candidate for a 126mm spaced road bike. Any one else been down this rabbit hole?

nlerner

First I’ve ever seen of that crank. Is it intended for mtbs? Crank arms 175mm?

thook

i've never intentionally set up anything exactly like that, personally. i will say, however, i acquired a ratty later 70's raleigh record that had a shimano road bottom bracket with a deore lx crank installed. the crank is all i wanted from it. at any rate, i recall the crank arm not quite clearing the chainstay. really can't say why as i never bothered to find out. i suspect if the bottom bracket were adjusted outboard a bit, it would've cleared

otoh, my super le tour has a mid 80's sugino triple crank set up as a double with a road double bottom bracket and works fine. just no granny ring. came like that from factory. iow's, with the right bottom bracket, i don't see why that/yours wouldn't work

i know....not much help, right?...lol

bark_eater 

170mm. Coda was a Cannondale house brand, this is one of the lower series ones for mountain bikes, I have another slightly different Coda 94-58T "Touring triple" one that's on a Cannondale T700. It looks to have a shorter BB spindle and a similar high Q factor, but I wont have the opportunity to pull and compare any time soon. The little bit of research I've done points to using a road double leangth BB for micro drive triples, so my hope is that a short 103mm single ring bottom bracket will give a reasonable double chain line. And that some one else may have tried this before....

nlerner

It'll definitely be a challenge getting a good chain line given all of that material between the smallest cog and the frame! I admire your pluck, but if it were me, I'd go with a 110/74bcd crank set up as a compact double. Lots of those out there for relatively small money.

bark_eater 

Running 110/74 as a double 46-30t with a guard instead of an outer ring is the base line to improve on. I'll probably try and find one of the Shimano touring STX cranks next, to see if their any narrower.

Vaang

I had a similar problem with a different mtb crank. I wanted to run a Tune BigFoot 94mm BCD as a compact double with 46-29 teeth on my touring bike which is build around an Italian road frame. The manufacturer recommends a 113mm BB if used as triple on a mountain bike. I ended up using a 6mm narrower BB on the 130mm wide frame with no issues. On a 126 mm frame you could try to go narrower than that but considering how bulky that coda crank looks it might rub against the BB?

bark_eater 

Small update on this random project. Another cheap Micro drive crankset showed up after being MIA in the Xmas mail for 3 weeks. This one has a much lower Q off the bike, and is made by SR. Its rougher cosmetically than the Coda Crank, but disregarding the Cannondale misjudgment, I'm going to get to try the 46-30t coolaid with new chainrings for less than $75. I'll probably be selling the Cannondale Coda cranks when its "safe" to go to the post office, but if any one whos interested feel free to call dibs. Heres the SR:






P.S I'm not afraid to cut and file the 58 BCD granny mounting posts off this.

thook

what is the gearing on that coda? depending on that, i 'd sure be interested!!

bark_eater 

Dibs Noted! Their 44-34. The SR rings are 42-32-22T and will probably be available. I have an other Coda touring crank that on a bike that I may want to save or swap some of the rings for, Or sell that too. I'm in one of those semi rural areas where it was fine, until it wasn't, so it might be a while.

thook

fair enough. no hurry on my end. happy to wait

and, thanks for noting

Luc_D

Hey! How did the chainline worked out in the end? I am trying to get a decent chainline with a microdrive triple used as a double but I am unable to find a suitable candidate . I've tried a sugino impel and a shimano lx, with a 103 mm bottom bracket, both are way too far off.

bark_eater 

The SR crank had a bunch of cracked bolt holes, so I'm still looking. I think Shimano STX used 110 mm bottom brackets verses 107 on the LX, so that gives another 1.5 mm advantage on the chain line.

bark_eater 

Just a quick update. While I changed directions with the bike this was originally going to use a 94bcd double on, I did just end up with a Shimano STX FC-MC34, which when quickly compared to the Coda crank looks to have at least 10 mm less "Q". I haven't decided what to do with it yet. My drivetrain test bike has buggered and re-tapped bottom bracket threads so I'm a bit hesitant to swap in a shorter BB. I also haven't forgot about Mr. Thook's dibs, but I have not had a chance to see if the Coda will work on one of my other bikes as a triple.

ThermionicScott 

Just catching this thread for the first time. 94mm BCD makes a lot of sense, especially for today's "sub-compact" gearing. Shame that it's not more widely used.

103mm might be a bit tight, but I think 107mm has a good chance of success here. Try it!

tomtom50

I have an extra Deore XT Shimano FC-M737 94/58 crankset.

As mentioned the crank arms flare so for road use you need a short bottom bracket.

I fitted it as a 94/58 triple on a steel road frame using a sealed Tange 103mm bottom bracket, and chainline was fine for road use: 45mm to the middle chainring, the inner chainring clearing the frame by about 2mm.

95/58 cranksets all seem to have the flared cranks and need a short BB. I also have an STX RC and a Specialized, same flare. Using the short BB saves a few grams.

They seem to be a good road solution if you like small chainrings and you have a set of good condition chainrings. I don't think it is easy to buy a triple set that is pinned and ramped

tomtom50

BTW Q factor for the FC-M737 94/58 crankset on a 103mm BB is 159mm.