I “glazed” my brake pads… couple questions

[Andy]

I went to the BMWCCA Driving School at Mid Ohio last weekend. I was on stock brake pads with 18,000 miles on them (my daily driver, a full season of auto-x and no track time). I didn’t check the pad thickness before going, but assumed with only 18,000 miles that there would be plenty of pad left (auto-x isn’t all that hard on brake pads).

On the second day, toward the end of my track session, it felt as if the brakes where coming to a grinding halt… no grinding sound, the pedal just felt as if they were grinding, plus the car was taking a little long to get slowed down. I was glad that it was the last day of the school and my last track session because I thought for sure I used up my set of brake pads, completely. I thought the grinding feeling, meant I was starting to get into the metal baking plate… I was not happy about that.

I checked the rotors, I could see (and feel) that the front rotors had lots of small (very, very small) grooves. The grooves weren’t deep, but the rotors were no longer smooth. The rear rotors were still smooth, but I could see lines starting to appear on the rotors like they were starting to groove. So I went out and bought a set of Hawk HPS pads.

When I changed the pads, to my surprise, there was lots of pad left, more then half!! However, the pad surface was smooth and shiney. I guess this is what is referred to as “glazing the pads”. I still went ahead, replaced the pads and bedded them in.

I have good stopping power with the new pads, however I can feel a difference in the pedal from the smooth rotor to the slightly grooved one. Should I have the rotors turned (smoothed)? Or will the new brake pads smooth the rotors out on their own? Should I bed in the brakes again? I’ve heard that it may take a couple iterations to get them bed in properly.

Another question… Once a set of pads have been “glazed” are they shot? Can they be brought back to life by trying to bed them in or even manually roughing them up? Just curious.

[FireFly]

I am by no means an expert on the subject, however, my wife recently did the same thing to her explorer. Took it into the shop and they said it needed new rotors because they could not turn them to fix the problem.

Seeing that I will be trading the vehicle next month, I opted to have them throw only new pads on it. The vehicle stops fine. They would not warranty the pads because they said I may get only 10k miles out of them due to the grooves in the rotors. But once again, the vehicle goes next month.

Good luck with the situation and lets us know the outcome.

[ff]

I'm no expert either, but the grooves in the your rotors are exactly what I would expect from the rotors on any car using metallic brake pads. Every rotor that I've ever seen has been in this condition. Turning the rotors will resolve the situation (until it happens again, which it will), but will also greatly increase the chances that they will warp under moderate to heavy use. You don't want that.

Two options:
1) Leave the rotors alone, and the brake pads will seat into the rotor's grooves in 500-1000 miles
2) Replace the rotors with new ones

[LeucX3]

I'm no expert, but I stayed at a Holiday Inn Express.


That's all. :p

[Nick325xiT 5spd]

I don't think I've ever had a rotor that stayed ungrooved for long.

And the shiny surface on the pad is also something I've seen on every pad I've ever taken off. Except for the Axxis Deluxes, which were crumbling. Grooved rotors just mean that you need to bed the pads in a bit more thoroughly.

[Nick325xiT 5spd]

Oh, and the crumbling sensation that you felt from the brakes is what happens when they overheat. The brakes stop working when you're on the backing plate.

[Cowboy Bebop]

if they are glazed too badly, just hit the surface with a file or med-coarse sandpaper enough to break the glazing, then re-bed them after you put them back.
propper Bedding is very important.

[Andy]

Thanks for the feedback guys.

I’ll go through a few more iterations of bedding them in and let you know how it goes.

[kurichan]

I glazed the CLUTCH on my last car: "official" solution: pop it at 6,000 RPMs a few times... It worked...

[elbert]

Do not use sandpaper--the particles will get embedded in the rotors and the pads. Instead, do a couple hard stops on the stock pads to clean up the surface.

If you decide to stick with the HPS, they will eventually adapt to the shape (grooves) of the rotor. As you said, you might need to bed them in again and the new pad transfers a film on the rotor.

[woody underwood]

I went to the BMWCCA Driving School at Mid Ohio last weekend. I was on stock brake pads with 18,000 miles on them (my daily driver, a full season of auto-x and no track time). I didn?t check the pad thickness before going, but assumed with only 18,000 miles that there would be plenty of pad left (auto-x isn?t all that hard on brake pads).

On the second day, toward the end of my track session, it felt as if the brakes where coming to a grinding halt? no grinding sound, the pedal just felt as if they were grinding, plus the car was taking a little long to get slowed down. I was glad that it was the last day of the school and my last track session because I thought for sure I used up my set of brake pads, completely. I thought the grinding feeling, meant I was starting to get into the metal baking plate? I was not happy about that.

I checked the rotors, I could see (and feel) that the front rotors had lots of small (very, very small) grooves. The grooves weren?t deep, but the rotors were no longer smooth. The rear rotors were still smooth, but I could see lines starting to appear on the rotors like they were starting to groove. So I went out and bought a set of Hawk HPS pads.

When I changed the pads, to my surprise, there was lots of pad left, more then half!! However, the pad surface was smooth and shiney. I guess this is what is referred to as ?glazing the pads?. I still went ahead, replaced the pads and bedded them in.

I have good stopping power with the new pads, however I can feel a difference in the pedal from the smooth rotor to the slightly grooved one. Should I have the rotors turned (smoothed)? Or will the new brake pads smooth the rotors out on their own? Should I bed in the brakes again? I?ve heard that it may take a couple iterations to get them bed in properly.

Another question? Once a set of pads have been ?glazed? are they shot? Can they be brought back to life by trying to bed them in or even manually roughing them up? Just curious.
#1 Autocross is harder on brakes than a weekend of driving school because you really don't ever get them hot. That probably where you screwed up the pads and scored the rotors.
#2 You probably glazed your pads because you came back into the pit area and used your brakes to stop...that's a no no and you're lucky you didn't warp your rotors. Was it wet any time during the weekend?
#3 Sounds to me like you weren't braking hard enough if you still had scored rotors after a weekend of school

[Nick325xiT 5spd]

#1 Autocross is harder on brakes than a weekend of driving school because you really don't ever get them hot. That probably where you screwed up the pads and scored the rotors.
#2 You probably glazed your pads because you came back into the pit area and used your brakes to stop...that's a no no and you're lucky you didn't warp your rotors. Was it wet any time during the weekend?
#3 Sounds to me like you weren't braking hard enough if you still had scored rotors after a weekend of school
So what if your rotors are scored after a weekend of 145 to 65MPH braking zones? And your instructor compliments you on your braking? (Note that said instructor also owns an E46 M3 and is a competitive SCCA club racer.)

Oh, and you're scaring other students because of your closing speeds in the braking zones. :p

[Andy]

#1 Autocross is harder on brakes than a weekend of driving school because you really don't ever get them hot. That probably where you screwed up the pads and scored the rotors.
#2 You probably glazed your pads because you came back into the pit area and used your brakes to stop...that's a no no and you're lucky you didn't warp your rotors. Was it wet any time during the weekend?
#3 Sounds to me like you weren't braking hard enough if you still had scored rotors after a weekend of school


#1. Nope, the rotors were perfectly smooth before the school. ...oh, and I disagree.

#2. I doubt it... a cool down lap without using the brakes, minimal brake usage on the way back to the pits and not using the e-brake when parked should have been just fine.

#3. Nope. Go ask Alan Beder how hard I was braking. :eek: ...and like I said before the rotors were perfectly smooth before the driving school.

[PhilH]

Andy, the same thing happened to me the one time I tracked my 330i for three days (strangely it never happened the few times I tracked my E34 525i :tsk: ). I remember it took a surprising amount of time for the the grinding noises to go away. I'm pretty sure they went away gradually...after about a week it would only happen under heavy braking (or was it only under light braking :dunno: ). Anyway, I didn't do anything special to address the problem with my glazed brakes, but eventually the grinding went away.

I don't understand woody's point #1 at all. How can not getting the brakes hot be bad for them? :loco:

[PhilH]

But you never really do any real braking in an autocross (at least I don't...that doesn't mean much I guess... :eeps: ). Sure you brake kind of hard from maybe 50 mph to 25 mph a couple times, but that's pretty much what you do on the street.

I don't get anywhere near lockup on the brakes in my autocrossing (again...my driving may not be the perfect example of how you should autocross), because I'm trying to stay smooth and maintain some momentum on the course. Also, you have maybe 7 runs of about 60 seconds each...TOTAL. That's a whopping 7 minutes of driving, most of which you're on the gas.

Track driving is different. Like Nick said, 145 mph to 65 mph repeatedly will test your brakes for sure. No matter what you do, one way or another, driver's schools eat up brakes.

[SergioK]

Stock pads aren't ideal for the track. They have a maximum operating temperature (MOT) rating (probably around 800-900f) and that level is definitely less than what they will get up to when used at the track. Once you get your brake pads past the MOT any number of things will happen. Some pads will actually being to break away from the backing plate (http://www.323ci.net/bimmerfest/pads.jpg)!

As far as having uneven rotor wear (small grooves), that's pretty normal. Most rotors won't wear completely 100% evenly because of the slight variances in the mix of the pad material itself. You should never turn BMW rotors. By the time you turn them, you'd need a new set.

[woody underwood]

My point, I guess, was that you're going to wear out cold pads faster than hot ones because of the added pressure required to stop. And I use my brakes a lot when autocrossing (Maybe that's why I never do any good!) but everybody has a different style. The post about the stock pads going over their "MOT" is probably why they glazed...good reply.

[edsmax]

Another question… Once a set of pads have been “glazed” are they shot? Can they be brought back to life by trying to bed them in or even manually roughing them up? Just curious.

Ok, I have a really stupid question: What does "bedding" the brakes mean?

I am going to attempt to change my own front pads with Axxis but am curious what proper break in or"bedding" of new pads means....

[SergioK]

http://www.bimmerfest.com/forums/showpost.php?p=442305&postcount=22