RFC

I was tearing down a MTB over the weekend and realized that the Deore XT crank would make a great road double. By removing the small chainring and the washers/spacers, I now have a great 46/34 compact double for my Bianchi Volpe.

Capecodder

I was thinking of trying the same thing..... I have a 110 bcd triple with 48-38-28 rings and can remove the 28 and have a nice double crankset if it would work.

wrk101

I did something kind of similar. I took the largest two rings off a Sugino mtb crankset, a 47 and a 35 or so, and put them on my road Sugino crank. Came from a cheap donor, works well.

I then turned around and made a touring triple out of that MTB Sugino crankset. Love those 110 BCD chain rings.

nlerner

Yes, Sugino AT. Dropped the 74bcd ring.

Neal

tugrul

Did you use a shorter spindle to "fix" the chain line?

Looking at Sheldon's reference numbers, a road double centers at 43.5mm, but a Shimano MTB middle ring is out at 47.5mm.

ColonelJLloyd 

Lots of 110 BCD cranks out there and good 6061 and 7075 rings still being made (not the best looking, but . . ).

realestvin7

I was kicking this idea around as well.

sillygolem

It was my understanding* that a normal-sized mountain bike will have the center chainring line up approximately with the inner ring of a road double. Large seat tube bikes end up pushing the chainrings outward to accommodate the front derailleur.

*I happen to have a road and mountain bike OPCs sitting by me that do match up this way, but no three piece cranks to make comparisions, not to mention varying BB widths for Italian bikes.

bigbossman 

Just curious....... what are you pairing that 46t ring with, in the back? It seems to me you might spin out prematurely unless you had some real small gears in the freewheel/cassette.

ColonelJLloyd 

^ The wide range double with a 46-48t big chain ring works great with cassettes. I mean, 46/11 on a 700c is over 110 gear inches.

AltheCyclist

Won't you miss the 50 ring (i.e. spin it out if riding roadie, especially on even a minor downhill)?

ColonelJLloyd 

I'm a masher. I guess I'm outing my self as a weak rider, but the 48/33 wide range double and 13-28t 7sp freewheel (99-32 gear inches) I've been using is plenty for me. I'm not a good enough rider to be bombing down hills at 40 mph.

RobbieTunes 

No.

nlerner

I run a 46t max ring on lots of my bikes and for the sake of my knees went from primarily being a masher to primarily being a spinner. I find a 46/12 is plenty big gear for the kind of riding I do. I also find with that big ring up front, I rarely shift on to the small ring unless I have to do some serious climbing.

Neal

AltheCyclist

I thought mashers preferred having the bigger gears and more range?

ColonelJLloyd 

Like I said, I'm not a good cyclist. 99 gear inches is big enough for me. I thought 99-32 gear inches was a lot of range, but what do I know?

Puget Pounder

I find that using the older 110 Sugino road cranks work better. They're lighter, sleeker, and may not have the outset bolt holes that you see on some of Shimano MTB cranks.

Sugino RT doubles and Sugino VP (has holes for triples, but they're not outset) are great for this.

bobbycorno

I'm running a Shimano LX (black painted) mtb crank on my otherwise all-Campy Daytona Ergo road bike, but with a twist: it's a "sub-compact" double. I put the 46t "big" ring in the middle spot, and a 28t on the 74mm inner. With a 12-26 cassette I get a gear range of 28.5-101". Yes, it shifts just fine (tho' I'm used to "flat" rings from the days when that's what there was), and I'm a spinner (typically 90-110 rpms). My first ride on it was out Skyliners road, 44 mile rt w/ 2800' of vert. It sure was nice to be able to spin all the way out (even on the short 13% pitch). Convention be d**ned! I'm keeping this gearing.

(Oh, and I hit mid 30's on the way back in, even with a headwind on a not-particularly-fast descent. Who needs to pedal over 30 mph?)

SP
Bend, OR

ps - yes, I'm running a short bb: 107, IIRC

RFC

I have two of the Deore XT 46/34 cranks. One will go on my Bianchi Volpe with a 13-28 freewheel. It is my all purpose multi-surface bomber, so that will be just fine. I think I'll put the other on my RB-1 with a 12-23 9-speed cassette. When I ride compacts, 50 or 46 and 9-speed, I find that I do most of my riding in the big chainring with the 34 saved for real hills. And, yes, I do cross chain all of the time. I set them up to give me full 9-speed range when in the big ring.

As a rough measure, going from the 52 to the 46 generally moves the highest gear down about 1.5 "functional" gears, i.e., 12 becomes about 13.5.

Run Sheldon's gear calculator for 52-50-46 and a 12-23 and you will see the difference. It's not as great as you might think.

not_jason

Whatever I've got on my touring bike, by the looks of the original rings, started out as a mountain bike crank. I ditched the inner ring and replaced the two outer ones with a set from a compact double, works great. The FD is just about at it's maximum outward position to put it on the outer ring, but it does reach.

bennie222 

I basically did the same thing, but it's still on a "mtb". It's basically a monster cross / cyclocross bike I have a flat bar on it right now but plan to put a nitto bar and some sti shifters or bar end shifters on it eventually. I have some skinny cross tires on it now. Notice the Dura Ace front Derailleur.. I've set this up as a urban trail rider, to tear up the trails with my kids. It was cheaper than buying a cross bike...

txvintage

My Dawes Super Galaxy tourer has a complete Deore drive train.

ciocc_cat

I run 47-41 chainrings with a 13-23 6-speed freewheel. Here in mostly flat-to-rolling south Louisiana, I rarely need the 41-23 low and I've yet to spin out the 47-13 high on what passes for "downhill" (i.e., the descending side of an overpass).

RFC

Last night, I rebuilt the RB-1 drivetrain and added the Deore XT crank. Actually, the only stock parts left on this bike are the headset and the Suntour GPX FD. Now if we can just get a break in the weather so I can do some real riding.

Old Fat Guy

What BB did you use?