[dowend]

Is it poosible to mount standard MTB cranks in a frame meant for BMX cranks?

 

[D_D]

You can use dmr wondercups.

http://www.dmrbikes.com/products/accesso/wondercup.html

Someone might sell a bb that uses big bmx bearings and a spindle that works but I have never seen one.

 

[Rik]

You can get cheapo tapered axle bottom brackets to suit BMX frames, but unless the bike is for light use, I'd avoid them.

A few companies are doing wondercups-style products, so hunt around if you're trying to get out of it on the cheap.

 

[RD]

the Crupi conversion cups are really nice. Mountainspeed doesn't make theirs anymore I don't think. check out www.danscomp.com for lots of products.