Framebuilders - framebuilding question about u-brake pivot locations

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Chunkstyle2
02-01-06, 05:39 PM
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
02-01-06, 09:06 PM
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.