rwiii

When I slam on the breaks hard I'm feeling a significant pulse through the pedal and it seems to be coming from the front breaks. No lights come on and it's dry pavement so I don't believe it's ABS. Also, the pulse is a little more aggressive and irregular for ABS. If my rotors were significantly warped I would feel some vibration under normal and aggressive breaking but I only feel it when I really lay on the breaks. It looks like there's plenty of meat left on the pads. I also don't see any leaks around the calipers. I don't know if this matters but it has been a few years since they've been bled and I know that should be done annually.
Any Ideas?

Sneaky Pete

How fast are you going when you apply the brakes? How far does the pedal depress?

extanker

have the rotors etc checked by a repair shop for true with a dial indicator and mike them for even thickness

rwiii

Sneaky, As slow as 25mph or less and hit the breaks hard.
extanker, No the rotors have not been checked. It just seems like something more dramatic than a wear issue but I have no skills--maybe it is.

996FLT6

Warped rotors is my bet. Mike

Imo000

I think its the ABS kicking in. You don't need wet pavement for it to come on, just have to hit the brakes hard enough to lock them up and the ABS pump will take over.

heligear

This can be caused by buildup of brake pad material on the rotors, the first thing to try is re bed the pads, it is not usually the rotors warping that causes the pulsing but an uneven build up of pad material, take it out to an area where you can do this safely, take the car up to 60ish and brake hard but not enough to set off the abs slow to about 30, try this 4 or 5 times if they smoke a bit that is ok, just don't come to a full stop that will cause pad material transfer to the hot rotors, then drive around a bit until the rotors cool off, try to keep it rolling without coming to a stop while they are cooling down.

rwiii

Should a light come on when the abs engages?

porsche-t

You will only get a light if there is ABS failure. On dry pavement my Volvo, Porsche and BMW R1200RT do the same thing during HARD braking. The Porsche is worse if I hit a bump. It will pulse quite a bit because the front is so light.

Sneaky Pete

rwiii.......Has this always happened when you drive or is this the first time your hitting the brakes hard?

rwiii

I used to track the car and just don't remember it happening on a 100MPH to 25MPH all-on braking deceleration. Maybe it is abs. I just ruled that out because of the dry pavement, slow speed and no light coming on.

Macster

It is the ABS. If there was a mechanical condition that was causing the brakes to pulse like you describe you'd feel this all the time, even under light braking.

I do not know where you are but probably it is cool (or cold) where you are the tires are not as grippy as they would be in warmer temperature. The tires are probably not new either and have become harder and more slippery from the heat cycling. My the front tires on both my Boxster and Turbo get like hard plastic towards the end of their useful life and under moderately hard braking even on dry pavement the ABS can activate.

Under normal -- street driving -- conditions brake fluid should be flushed/bled every 2 years. I have not noticed any issues with the brakes from letting the fluid go longer but the clutch in my Boxster was acting up until after I have the 2.5+ year old brake/clutch fluid flushed/bled.

Imo000

The ABS light doesn't come on when the system is activated. I can't beleive you don't know this.

Trj

I was getting a lot of that at the track last week. Usually trail breaking while under lateral load. Seemed to go away when I pushed down harder on them. I just thought it was abs interaction???

996_C4S

Breaks = brakes
Pulsing = ABS