When I use my front brake, it causes the bike to shudder, as though the pads need to be toed in. So I toed them in, and that caused a horrible shrill squeal. I've spent the last hour adjusting them, even swapped the rear brakes in, no dice. It's really quite annoying and frustrating. At the moment I'm choosing the lesser of two evils, the shuddering. At least I won't wake up the neighborhood. I've tried sand paper on the pads, steel wool on the rims, no luck. The pads themselves appear fine, they're not worn out. Anyone have any other ideas?

I should mention it's a suspension fork.

Wheels out of true?

Lose fork?

Lose headset?

Sometimes this can depend on pad material, sometimes it can depend on brake adjustment, sometimes it can depend of the brand and build of the brakes.

You were right to try to toe in the pads. However, if your fork blades (or suspension fork) twists enough, or if the cantilever posts deform enough, sometimes the hoped-for effect of toeing in will be nullified.

You didn't mention what brand of brakes and pads you are using, and I imagine that would help to diagnose the problem. Some brakes are more prone to this behavior than others. You also didn't mention if this problem has always been present, or whether it is a recent development.

The brakes and pads are both Shimano something or other, not sure, they came with the bike. It definitely hasn't always been present. I'm starting to think that the wheel is a bit out of true. I adjust the brakes again, and it's almost perfect, but it feels like once per revolution the brakes grab significantly harder. I believe that's the shudder I'm feeling. I'll take a look at the true tomorrow.

When I asked what brand of brake, I should have also asked if they were cantilever brakes, linear pull brakes, or caliper brakes...

And I should have realized that, they're V-brakes.