Coming from disc brakes these days, i'm always on the quest to have the best bmx U brake possible.
My latest mod to get a bit more power and certainly a very nice smooth feel is this...
Click the pic to enlarge.
Basically I got a piece of spare brake cable. Stripped it down to the inner coating and ran a strip of that inside the silver thing which I can't remember the name of. You can see the end poking out a little.
Previously there was alot of friction from the silver thing due the the cable angle, as I don't have a Fly brake. Now it's smooth as, which means for a nicer feel and i can apply more power. Shouldn't need to run as much spring tension either.
I would recommend this mod to anyone running U's.