I’m assuming these aren’t cross-compatible?

Have got some Mtn calipers would like to fit to a road bike (have got the correct levers)

it’s only the pull ratio that differs so if you have the correct levers you’ll be fine

There’s a different cable pull between them (i.e. the arm is shorter/longer). One way round you end up with no power, the other way the levers pull to the bar but I can’t remember which. So the road ones work with road levers or old cantilever brake levers, the mountain ones work with V-brake levers.

the mtn ones work with roadie levers -BUT need to adjust them often or they pull to the bar – got to be a pain in ass so i fitted road bb7s instead once i found a set on here !

The arms are actually the same length. The difference is that the ramps are steeper on the road version since the cable pull is less.

If you’re short of cash and need to get the bike setup soon, I’m just about to sell a pair of BB5 road calipers with new pads for £25….(sorry to hijack post !)