MC21 and NC30 calipers are different. NC30 calipers can be used on an MC21, however MC21 [without modification] cannot be used on an NC30.

I ran RS250 NF5 RWU forks on my MC21 for a year, which are also considerably shorter than the standard MC21 forks, and using the standard NSR alloy Enkie 3" rim and 110/70x17 tyre, never had the tyre touch the standard V-piece. Having said that, during extreme braking the fender would touch the bottom of the headlight fairing. Bear in mind though, as Hurdy mentioned, you could have an over-sized wheel/tyre combination if it's all NC30, which in conjunction with the shorter forks, could exaggerate symptoms referred to by Johnnymac.

You could try an NF5 top triple clamp, which has quite a deep "gull" shape, and would allow you some compensation by reseating the NC30 forks about 20mm lower. By going this route you will have to relocate the ignition switch, consequently losing the steering lock.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!