Road v. MTB cranks

PJPenrouz

What is the difference between road and MTB cranksets in terms of compatibility? All I know is on my hybrid which is in fact an MTB with 700c wheels and road cranks I have to use road front derraileur and shifter for flat bars as well. Is this the only compatibility issue or is there anything else? E.g. can I use Ultegra cranks on an MTB frame and flat bars?
Cheers

PJPenrouz

Is the chainline the same?

John.T

There are several differences between road and MTB chainsets but they are not all on the chainsets. Shimano road and MTB front mechs have different cable pull so you have to use the correct shifter. There are work rounds by fitting the cables differently. MTB mechs come in different shapes to suit slacker seat angles and also to fit either 44 or 48 tooth rings. Road ones suit about a 73 deg seat angle and 53 tooth rings. MTB chainsets usually have a larger Q angle, that is the pedals and thus your feet are further apart.
If you were to fit an Ultegra chainset to an MTB with a road front mech the cage would not line up well with the chain rings. If you were to use an MTB mech then the curve on the cage would not follow the ring as it is designed for a smaller one.
You can make most things work Ok but not as well as the correctly matched ones.
The chainlines are different. 43.5 on road and 50mm on MTB.

synchronicity

John.T wrote:

There are several differences between road and MTB chainsets but they are not all on the chainsets. Shimano road and MTB front mechs have different cable pull so you have to use the correct shifter. There are work rounds by fitting the cables differently. MTB mechs come in different shapes to suit slacker seat angles and also to fit either 44 or 48 tooth rings. Road ones suit about a 73 deg seat angle and 53 tooth rings. MTB chainsets usually have a larger Q angle, that is the pedals and thus your feet are further apart.
If you were to fit an Ultegra chainset to an MTB with a road front mech the cage would not line up well with the chain rings. If you were to use an MTB mech then the curve on the cage would not follow the ring as it is designed for a smaller one.
You can make most things work Ok but not as well as the correctly matched ones.
The chainlines are different. 43.5 on road and 50mm on MTB.

Thanks for that. Very helpful info as I was thinking about putting together a few hybrids... I guess I'll have to at least match the shifters/mech/cranks.

geoff_ss

I have a Truvative 44/32/22 MTB chainset on the flat barred road bike I've just built I'm using a Shimano XT front deraileur and it works perfectly. The chain line in fine - all 27 gears are usable without any rubbing though I don't use the extremes.

I would really prefer a non indexed (ie friction) front gear lever but they don't seem to be available. I don't really need indexing even with a triple and they're totally superfluous with a double chainset.

Geoff

maddog 2

you can run a road c/set and front mech with mtb shifters as long as you stick to a double. Triples are more complicated.

other than that, just check the road c/set rings will clear the chainstays, which are wider on mtb frames.

PJPenrouz

Thanks for all the replies - very helful.
At the moment I have FSA Gossamer triple 53/39/30 with 105 mech and Shimano flatbar shifters - it works OK. My plan is to use a CX frame with flat bars, similar cranks/mech/shifters combination and XT at the back. I just like the large outer rings.
Cheers

acorn_user

I have a Shinano C101 front mech shifting a Sora triple (52-42-30). It was tough to set up. So tough, we took it to Steels Cycles to finish the job! The C101 is designed for 48t max. If I were you, I would not go above that with an Mtb mech designed for 44t. Your best bet is to find a mech for a 48t tooth and use that, with, say, a Stronglight Impact. I find the 52t ring to be over the top sadly, and don't often use it.

maddog 2

another reason to avoid triples........?