Avid BB7 setup and offset

Ramanujan

Hi,
I was reading from the Avid BB7 pdf that the rotor should be offset to the outboard side in the ratio 1/3 to 2/3.
I'm a little unclear what this means exactly.
Should there be a bigger gap (2/3) on the inside of the rotor or should the bigger gap be on the outside of the rotor?

thanks
R

thelonegroover

I used to have BB7's, can't recall it made very much difference on the gap.

jimothy78

not sure about the inside/outside on the BB7, but in my experience you want to have as little gap as possible (without rubbing) between the non-moving pad and the rotor, but you can be a bit more generous with the side that moves.

Before the brake can actually exert a stopping force, the moving pads needs to make contact with the rotor and deflect it into contact with the non-moving pad. Obviously, between first contact and second contact there's going to be a period of time when the rotor is rubbing on the single (moving) pad, but not enough to do anything more than wear (or possibly glaze) the pad, so you want this time (and therefore the deflection necessary to close the gap) to be as small as possible.

monkimark

jimothy78

Ah, that appears to be 1/3 and 2/3 of the gap relative to the calliper body itself, then, not the pads.

presumably, the thinking is that by having the bigger gap on the side of the non-moving pad allows for the rotor to be deflected in that direction without any risk of actually coming into contact with the calliper body.

Terrytibbs

Basically, as close as possible to the fixed pad. This just prevents the rotor from bending. Ignore the 1/3 2/3 thing, just as close as possible, preferably without it rubbing. That image appears to be the wrong way around.

The Rookie

Why ignore the 1/3 1/3's thing when the static pad is adjustable? Thus gap from calliper body to disc is wholly divorced from the gap from pad to disc.

I'd go with the drawing and leave the larger gap on the wheel side so that when the disc gets pushed across slightly by the moving into the static pad it is less likely to contact the calliper body, makes sense to me!