Rotor Cranks: MTB vs Road explanation (i.e. help)

[jambee]

Does anyone care to explain if there is any difference between what Rotor 3D+ is billing as a MTB crank vs road? Both seem to have 110 BCD

Road: http://www.rotorbikeusa.com/products/3D_plus_road_cranks.html

Mountain: http://www.rotorbikeusa.com/products/3D_plus_mtb_cranks.html

They seem entirely identical to me.

Ideas? Advise?

[crownjewelwl]

q factor

[rice rocket]

The inner ring is 74mm BCD on the mtn crank.

[Mikej]

May have different chain lines.

[Mark McM]

All 3 of the above - a wider spindle, which produces a wider q-factor, a wider chainline, and additional space for the chainring on the extra inner 74mm BCD.

[jambee]

Thanks Y'all.
This raises an interesting question: for a 135mm hub, would a MTB crank produce a straighter chain line? I'm obviously out of my depth here, but am happy to learn.

[Chance]

Thanks Y'all.
This raises an interesting question: for a 135mm hub, would a MTB crank produce a straighter chain line? I'm obviously out of my depth here, but am happy to learn.

If viewed on average, probably yes. But given the wide range of combinations the rider can select from that duplicates near-identical gearing then it may or may not.

One of my bikes has road cranks with 135 rear wheel spacing. The chainline is basically off center. Most of the time is doens't make any difference at all sense it's only a matter of crossing the chain at different points. Obviously my chain gets more angle when in the 11T sprocket whether in small ring or large ring versus if it had MTB cranks. On the othe hand the chainline is better when in the largest rear sprocket. And to me that's more important because it gets used more often plus also used when climbing which suggest more chain tension.

Unless it's under extreme conditions it's a non issue for me. Expect it would be an non-issue for most others too.

[Mikej]

Thanks Y'all.
This raises an interesting question: for a 135mm hub, would a MTB crank produce a straighter chain line? I'm obviously out of my depth here, but am happy to learn.

Chain line is a tricky measurement to compare. road vs mtb teeth offset will produce various measurements as well as mtn having 3 rings, and that mtb doubles are mounted mid/granny, so that chainline will also have a different measurement than the same crank w/ a triple.