Why do most high end MTB's run inners with Presta valves? They are more fiddly to use and I managed to bend the screw bit last night, when hastily inflating in the mud and the rain following a flat. Schraeder seem more sturdy, so why do you only tend to see them on cheaper bikes. Is it just an image thing?

presta valves hold air better, but are far easier to break

i use schrader because i mess around with the pressures in my tyres anyway, and it means i can easily use a footpump or petrol station pump

petrol station AIR pump

lol - I use both. Probably prefer presta as it's easier to use - especially to adjust pressures ( can let air out easier). Think I've only bent one core ever. Nothing really wrong with shraeder though, I just use what I end up with although 2 of my wheels only have a hole for presta.

Presta are great, never bent one either. I hate schraeder, I can never get the pump on to the valve properly.

It's pretty much down to personal preference, no real pro's or cons for either.

Most LBs sell little grommets to fill the gap between Presta valves and Schraeder drilled rims; worth getting to stop the irritating sloshing noise when water gets through the gap into the rim