Could I use an mtb crankset on a road frame?

Specifically an XT crank (38,26 iirc) on a 68mm gravel frame with the rest of an ultegra hydraulic groupset.

Not asking if it’s a good idea! Just if it’s possible. BB spacers enough to fix things?

It’ll be built with a compact and a 11-30 cassette, but I wondered if the mtb crank could be subbed in to give super low gears should they be needed. Yes 38 x 11 would spin out easily, but the ride that needs low gears wouldn’t need high ones – above 25 mph I’d be happy to freewheel!

On my piçk and flick got a slx crank with 48/ 30 rings on. It’s also slx at the back but it should all work if you can tweek the chain line with spacers.

I also run mtb stuff at the back but thats mainly cause im crap at hills and have to grind up them.

It might be possible. My worry would be the smaller chanrings running close to the chainstays – you’ve only go a little bit of leeway with the spacers on the 73mm bottom bracket. Probably a frame specific issue. If it’s a 135mm spacing at the back that might help.

Oh, and the front mech could be a fun setup, esp if you keep the Ultegra one on.

I used an XT triple on my Vaya for a little while. Left the BB as it was (i.e. for road cranks) and stuck a spacer between the NDS BB cup and the crank arm. Worked ok for the short time it was on there. I probably still have the steel spacer which I made if you want to give it a try. No idea about chainline I’m afraid – I figured with a triple it probably didn’t matter that much.

Hmmm.

Some experimental spannering might be in the offing then.

not that that is a bad thing…!

Initially thought ring spacing might be the challenge, but on reflection rings size and frame design are all relevant. It’s a 142 bolt through rear, but I see that dropping the front mech low enough could be tricky too.

Ring clearance shouldn’t be a problem, but the front mech isn’t going to be happy with those ring sizes.

You’d be better with compact 50/34 or CX 46/36 rings and a hanger adaptor to allow you or run a wider spread at the back.

You can install the crank with some BB spacers but the front shifting is gonna be horrible if it will work at all. You won’t be able to use a mountain FD with brifters because the pull ratio is different.

Go with an 11-34 (at least) and try to find a 46-30 crankset.

It might be possible. My worry would be the smaller chanrings running close to the chainstays

That doesn’t make any sense at all, it’s the other way around. The bigger the ring the closer it gets to the chainstay. That’s why frames have a stated maximum chainring size.

I’ve used deore triple chainset (22/32/42) on a road frame before, deore mech too, with bar end shifters. Worked fine, but the gearing range was far too low, even with an 11-28 cassette.

if i needed low gears on a road or cx bike now, i would stick with 34/50 up front and use a larger cassette.

Iirc, i used the normal 1 spacer on the drive side, it all fitted together perfectly and was just as easy to adjust as anything else.

My Pick runs a SRAM MTB double. 28/42 rings. Uses normal road mechs, albeit a medium arm rear mech. You might have an issue with the front mech fouling something as its low but may well work. A friend uses a MTB XT double  on a road bike with an Ultegra front mech. Works nicely

If you can drop the front derailleur down the seat tube far enough you should be fine. Make sure the cage clears the chainstay.

I swapped the compact (50/34) rival crankset on my Raleigh Maverick comp for an X9 (38/22) with an additional spacer on the non drive side, and the set up works perfectly with the Rival22 shifters. No problems with the 10/11 speed compatibility or gear size.

I went that way as I didn’t want to add weight running a big cassette and long cage rear derailleur.

Not the best pics

I’ve got Ritchey Logic (sugino) triple on my Raleigh tourer if that helps? needed a narrower square taper than it did when was in the Bonty OR, front derailleur isn’t an issue cos I’ve just got a 42T single on the middle ring tabs.

None of that will be any help, apart from the fact that the 42×12 top gear very rarely gets spun out. I’m not going to be winning any races on it, but it commutes, audaxes and gravels perfectly well.

I’ve used an XT double chainset on my bike with a road transmission – front mech is the main issue, particularly if it will swing wide enough for the wider chainline – it’s really going to be down to experimentation

That doesn’t make any sense at all, it’s the other way around. The bigger the ring the closer it gets to the chainstay. That’s why frames have a stated maximum chainring size.

Does make sense if you’ve got a triple with the inner chainring mounts pushing the inner closer to frame. Spacers will probably issue though.

SJS sell an eccentric adapter to make a road mech work with MTB chainline but only works on skinny frame tube & 34.9mm clamp on mech.