Brake pad rotation
 

When I brake, my the front of the pad rotates up towards the tire. It only happens under moderate to heavy braking. At the moment, I have them angled down so they can't reach the tire unless I slam them on hard enough to flip over, in which case I have bigger problems.

Any ideas on how to fix this? I've tightened them as much as I can.

They're nutted Tektro 556

Something is seriously wrong if the pads are truly rotating when you brake. Are you sure the brake itself isn't loose causing the movement you are seeing? If the brake is tight, I'd take things apart and make sure there isn't severe wear on the brake arms or something wrong with the studs on the pads that prevents you from fully tightening the pads.

oban_kobi: Those are long-reach calipers. What kind of setup have you got which requires them?

+100. Brake pads should never rotate radially. Either the brake caliper itself isn't bolted securely or something is missing or broken. Get it fixed pronto as it's a safety hazard.

I suspect that the pads aren't rotating, but the brake arms are flexing forward raising the front end of the shoes (pads).

Step one is to either grab the arms and wiggle them to see if there's any play. There shouldn't be any except a trace so they don't bind at the pivots. Once you do that you'll still have some flex (not free play) When you apply the brakes the motion of the rim pushers the arm forward, and that will cause the shoes to rise somewhat. Mount the shoes a bit lower to compensate for the flex, and check your work by applying the brake and pushing the bike forward causing maximum arm flex.

Thanks everyone, I'll take it apart when I get out of lab.

I have such a long reach because I got a frame without wheels and just threw on 700c's I had, but it had apparently used 27 inch before.

EDIT: I checked, and RBinNY is corret, it's flexing. Even with the shoes all the way down, it flexes enough to just hit the tire.

Double pivot brakes move around a pivot above the rim,
U brakes and Center-pull also.
cantilever and V brakes move around a pivot below the rim.
where the pivot is , effects the arc of motion of the brake pad.

I know, and that's not what the problem is.

It seems as though the bolt that holds the outer arm on isn't screwed in all the way. I tried screwing it in, and of course, stripped the bolt. I contacted the company about getting a replacement, maybe they'll be nice and do so.