Brake Tapping on Straight

[llll1l1ll]

I don't speak much on this board other than to hound you folk about various technical issues that I should be able to answer, but I can't.

Anyway, I'm procrastinating and watching car videos since I have nothing better to do at the moment. I noticed something, though, and that's the tapping of the brake while the car is on a high speed straight. They just lightly graze it--as if they are just feeling if the brake pedal is still there. I've provided a few examples:

throughout...

http://www.youtube.com/watch?v=x6UXHqngdxI&feature=related

and

around 0:34...

http://www.youtube.com/watch?v=qdWSyrqEnE4&feature=related

Anybody know why?

[ThePotsy]

They just lightly graze it--as if they are just feeling if the brake pedal is still there

I'd probably want to make sure my brakes were still there when I'm braking at the end of a straight.

Fade is not your friend.

[Wh33lhop]

It's to combat pad knockback. The pads get pushed back into the caliper due to wheel bearing/brake rotor axis deflection in the hard corners. They tap the brakes to re-snug the pads to the rotor before the braking zone in the next corner.

If you've got bad wheel bearings (lots of axial play) then sometimes you have to pump the pedal a few times after a corner before the pads are snug against the rotors again.

Here's an excellent StopTech article on pad knockback: http://www.stoptech.com/tech_info/wp_knockback.shtml

[llll1l1ll]

Wow, I would've never expected that for an answer.

[Slangbox]

Well done wh33lhop