Originally Posted by Tman1965

I don't think that there is any general rule about MTB pedals. It's perfectly fine to use them, neither UCI, USAC nor ATRA have anything against it.

I have always ridden Shimano SPD MTB on the Dick Lane Velodrome.

The only disadvantage is the relatively small contact area, thus the pressure on your sole is higher. Nobody is able to pull vertically out of an Shimano SPD. The problem with uncliping is always a twisting movement of the foot. But Shimano SPDs can be set pretty hard. Mine are not even set to the max and I have never had a problem. I'm not exactly a small light weight guy. Mounting straps is awkward unless you use something like the Shimano PD-M324.

Shimano first clipless pedal was the Dura Ace 7401, which was made by LOOK (My pair has written "made in France" on it). After that they came out with the SPD-MTB pedals and then the SPD-R pedals, which were highly appreciated by quite a number of track sprinters. The SPD-R mechanism is pretty similar to the SPD-MTB.

Thomas

P.S. Having said that, I wouldn't recommend them if you want to buy something new. This is mainly because the number of MTB shoes with really stiff soles is pretty limited. But if you have them already, go ahead. No safety issues. Maybe you get a nasty look from Carleton.