Hubs
 

Can anyone tell me if there are any major differences between mtn hubs and road hubs? Dimensions would probably be most critical, I'm guessing.

TIA

Ellie

The mountain hubs I have seen tend to have longer axles, to reduce wheel dish. For example, a standard 8- or 9-speed road axle has a 130mm overlock dimension, whereas all of the 8- or 9-speed mountain axles I have seen are at least 135mm overlock.

Mountain bike hubs may also have heavier-duty bearings and thicker spoke flanges, but any high-quality hubset with the correct dimensions should be suitable for the typical non-racing cyclist.

Ellie,
I'll take a little stab. Mtb hubs are built a little sturdier and heavier because they have to stand up to more punishment than road hubs are expected to recieve. I don't think there is much difference in the width of the hubs themselves. Dropout spacing for mtb rear wheel is generally 135 mm, road 130 mm so they use different axle lengths. However, I am pretty sure that one could use an mtb hub on a road bike wheel and simply replace the axle with an axle of appropriate length and adjust the spacing with different spacers between the cone and locknut to match the dropouts. Although one could do the same in reverse, using a road hub to build an mtb wheel, I don't think it would be a good idea because I doubt a road hub would last long under real mtb use.
Hope this helps.
Regards,
Raymond

Added - It was not my intent to repeat John E's message. It wasn't there when I started. :D

There are some dimensions which change between hubs.
Overlocknut distance. 130 on racing bikes, 135 on touring and MTBs.
Flange-to-flange distance.
Axle diameter, mainly thicker in downhill-type hubs which use cartridge bearings.
MTB hubs also have better seals, although road hubs are pretty good these days.

You can mix road and MTB components, just look at any real touring or cyclo-cross bike.