framebuilding question about u-brake pivot locations

[Chunkstyle2]

hi --

i'm working on my first framebuilding project -- a bmx freestyle frame -- & was wondering if any of you could point me toward information regarding the "official" locations for u brake mounts (dia compe 990 style).

specifically, i'm looking for:

1. the side-to-side distance between the centers of the studs next to each other.

2. for 20" bmx wheels, the distance bewtween the axle centerline & the centerline of the pair of studs.

i've measured a bunch of frames & forks & can come up with an average, but i'd like to use the "official" figure, if possible. i'd imagine either diacompe or shimano have published this info somewhere.

thanks!

dj

[velonomad]

Shimano had it published at one time, stud to stud on center IIRC is 80 mm for ~20-30mm width rims . I don't know what the reach range is on a 990, so I would install a wheel ,clamp the brakes against the rim and mark the stud centers on the stays. be sure to have the pads centered or a bit high in thier adjustment range when you make your mark.