carmudgeons.com - Pulsing f*cking brake rotors

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Quote:

Originally Posted by kognito (Post 532004)

Double blind . . .you'll have to remove the rotors too :mad2:

Removing the rotors and store them in a humidity controlled environment.

Double blind means someone else does it and I don't know whether they did or not. Can you be that person? :D

Quote:

Originally Posted by rumatt (Post 532012)

Removing the rotors and store them in a humidity controlled environment.

Double blind means someone else does it and I don't know whether they did or not. Can you be that person? :D

I think it would be easy to tell that I didn't :D

Quote:

Originally Posted by rumatt (Post 531992)

I also have Zimmerman rotors.

My theory on the commonality is that we don't drive our cars every day. My theory is that the rotors get slightly rusty from rain / humidity, but not in the spot where the pads are resting on the rotors. Driving scrapes the rust off off the rest, but the rotor is never the same from that point forward.

Should I do an experiment where I remove my brake pads every time I park the car? :ack:

The 535i pads were worn and the rotors needed replacing due to heavy rust; the OEM rotors were the most rusty brakes I've ever seen on any car at 50k miles. I'm not sure if it was Baltimore (where the car lived up to 42k miles) or the material that BMW has switched to. The Zimm's on the 528i never rusted or pulsated. They were installed at 50 or 60k and going strong at 130k. The 17-year old OEM rotors on the M3 never pulsated and that car wasn't driven frequently.

Quote:

Originally Posted by equ (Post 531991)

Could bad roads (braking on bumps e.g.) cause issues over time? I see a commonality among Rumatt, Terry and I and that's where we live and drive. :eeps:

I don't see how - in my case, it is definitely pad material build-up on the rotors, since I can get rid of it with aggressive re-bedding-in. Now, I do have to get my rims straightened at Wheel Collision every 2 years, but that's a different issue. :irate:

May have more to do with driving style - I'm probably the only person that ever reviewed soft-compound A048's on Tire Rack and listed my driving style as "relaxed". :D

Is it just that we drive like old men? Never get them hot enough?

I may not be perfect at stop signs but I'm so obsessive about it that I refuse to believe that's the problem. If it is then no non-enthusiast would ever be able to drive a BMW without the brakes shaking the car to pieces.

Matt, there's nothing wrong with your calipers. At least, when I had the car there was nothing wrong with them. I've seen the stock BMW calipers go wrong, but usually it's when someone tries to grease the slide pins. And then the symptom is the brakes get hot because they aren't releasing fully.

When I had my ZHP I had the same problem with the brakes (occasional pulsation). I believe what causes it is not enough hard braking events. I never found a better cure than an occasional full-panic-braking stop from freeway speeds.

The Mazdaspeed suffers from this occasionally as well. It is what it is. :dunno:

I swapped my old Hawk Performance pads on today and made a trip to Home Depot. I did a few hard stops but didn't bed them - theory being the goal is to scrap the hell out of the rotors, not create an optimal braking surface.

In gentle stops they seem fine but in hard stops they still pulse like a bitch. I'm going to leave them on for a few days while commuting to work and see what happens.

I'm still failing here. :mad:

Short version: Bedding with race pads took the rotors from awful (shaking the front end to pieces while braking) to very good. But it's not right, it's getting worse again, and I'm cranky. I'm now avoiding driving the car because the brakes are annoying.

Long version

Here's exactly what has taken place:

I put on Hawk race pads on for a week (no bedding), screeching everywhere I went, with Dave Z's theory that it scrapes a layer off your rotors.
Bed rotors with the Hawk pads, making sure to literally never touch the brakes afterward - even coming to a full stop in my driveway.
Next day, swapped on Textar pads and bed again. Same procedure. The brakes were f*cking hot.
Next day I evaluated them and I'd say it was 95% better. Braking under 60 MPH felt pulse free. Hard braking from 80 you could still feel a pulse. From 100 it was very noticible - a subtle, high speed pulse.
I repeated the bedding with the Textar pads. I saw no real improvement.
It's now been a couple weeks since the above, and as expected the pulsing is slowly getting worse. I can now hear and feel it at braking under 60MPH.

Unless someone has a better idea, I'm going to try the following things in this order

Try a series of 3 bedding sessions with the Textar pads, and see if that helps.
I guess I'll try another set of new rotors, maybe a different brand? Slotted like Terry Recommended?
Give up, push the car into the lake and buy something new.

start over with new rotors and new pads

Right. But I started from new pads and rotors once already. Doing it again only makes sense if I think I did something wrong, and plan to do it differently this time.. Right?

What am I doing differently?

Maybe I didn't bed them aggressively enough when they were new? I did bed them though. :(