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Discussion Starter #1
Hi all, could those of you in the know tell me if the brake discs in the pics below show signs of 'heat spots' or 'warping'? Currently, whenever the brake is applied at 60kmh or higher, on medium pressure, there is a loud 'drumming' sound and the care vibrates at what seems at high frequency.

If these 'heat spots' or 'warping' is causing the noise and vibration, what can be done to fix it, aside from replacing them? The disc was subject to high temp as it was used on a race track environment. However, during idle cool down the brakes or hand brake were not used, and the car was left in neutral.

I was told that brake discs can warp or form heat spots if the disc gets to very high temp. But surely the M5 discs were designed for this??

Are brake discs for the M5 big $$$ :eek:


Thanks in advance!
 

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hmm does it vibrate all the time above 60km/h or only if you pressed hard on the brake before?

When I drive on Germany Highway(Autobahn) and take a hard brake from 200-120, after that there is also a vibration, but not a for a long time...
 

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Discussion Starter #3
hmm does it vibrate all the time above 60km/h or only if you pressed hard on the brake before?

When I drive on Germany Highway(Autobahn) and take a hard brake from 200-120, after that there is also a vibration, but not a for a long time...
The drumming or "whooomm whooomm whooomm" type sound :3:, plus the vibration occurs at higher speed when the brakes has to be applied around medium pressure. At higher pressure and higher speed, the vibration becomes more 'refined' if you know what I mean?
 

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They are certainly damaged. You can see the outer half of the rotor is glazed and metal has even moved over the holes. It does not seem like you have a lot of wear so they MAY be able to be machined and new pads installed.

It would be best to replace those bad boys and learn to drive fast without destroying the brakes.

What kind of pads were you using?
 

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Discussion Starter #5
They are certainly damaged. You can see the outer half of the rotor is glazed and metal has even moved over the holes. It does not seem like you have a lot of wear so they MAY be able to be machined and new pads installed.

It would be best to replace those bad boys and learn to drive fast without destroying the brakes.

What kind of pads were you using?
Would you mind explaining further how a 'glazed' rotor indicates damage? And how you can tell that metal has 'moved over the holes' and the significance of this? I really would like to understand this better.

The pads that were on this particular car were Pagids RS19. First time use, and apparently still a lot of pad left. Surely the pads are not that abbrassive to 'eat' into the disc after such a short use :confused2
 

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Hope this helps. I would say those pads did not do you any favors but I am not an expert. zeckhausen racing (board sponsor) should be a good source for info here.

I inserted the wrong .jpg but you can see my comments on the glazing in the .pdf. The holes also do not appear round. There is extra metal on the left side of the surface. This is a result of the metal moving around on the rotor.
 

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No..

I don't believe they are damaged, in fact they looked the same as my discs after Silverstone. I was running the pagid RS19 pads which I think you were also running.

The photo is not great, but as my discs looked the same after Silverstone I know exactly how it looks. If you look at the pics, the two different colour are simply:
shiny part near the centre, the disc.
darker part around the edge, pad deposit (looks dark blue in certain light)

You will find that the darker part around the edge will get removed slowly as you drive, but it will take some time (if you have already swapped back to stock pads) as the pagid pads are a much harder compound.

My track day was on the 14th March and I still have some deposit left on the dics, but it has just about gone, also the vibration sound is greatly reduced.

As for the holes, that is simply brake dust. I haven't cleaned mine, but you should be able to poke it out, I used to use an unravelled wire coat hanger...
 

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The "rumbling" noise is typical of drilled rotors. I expect any braking action, especialy hard, will cause some vibration. As for the holes being blocked, that is probabaly brakepad material.
 

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Discussion Starter #9
No..

I don't believe they are damaged, in fact they looked the same as my discs after Silverstone. I was running the pagid RS19 pads which I think you were also running.

The photo is not great, but as my discs looked the same after Silverstone I know exactly how it looks. If you look at the pics, the two different colour are simply:
shiny part near the centre, the disc.
darker part around the edge, pad deposit (looks dark blue in certain light)
I was hoping this would be the case but I don't think so. Running my finger across it, it's all smooth. It's been suggested at another forum that the disc is warped and one of the reasons causing this could be:
a) improper brake pad bedding in (which I'm convinced was done properly) or b) caliper failure whereby causing uneven brake application which puts more heat to the outer edges

It has also been suggested that if they are warped, it should be 'grinded' and not 'machined'. What do you guys think about this?
 

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Discussion Starter #10
The "rumbling" noise is typical of drilled rotors. I expect any braking action, especialy hard, will cause some vibration. As for the holes being blocked, that is probabaly brakepad material.
Surely the rumbling and vibration should be present when braking on medium at 60kmh?? It wasn't there prior to the track day.
 

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hmm does it vibrate all the time above 60km/h or only if you pressed hard on the brake before?

When I drive on Germany Highway(Autobahn) and take a hard brake from 200-120, after that there is also a vibration, but not a for a long time...
i'm very jelous of your abilty to drive her on the autobahn....:M5rev:
 

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I was hoping this would be the case but I don't think so. Running my finger across it, it's all smooth. It's been suggested at another forum that the disc is warped and one of the reasons causing this could be:
a) improper brake pad bedding in (which I'm convinced was done properly) or b) caliper failure whereby causing uneven brake application which puts more heat to the outer edges

It has also been suggested that if they are warped, it should be 'grinded' and not 'machined'. What do you guys think about this?
What can I say, don't believe everything you read, but from my experience you will be fine. I thought you may need some convincing, so I took a pic of my front left and right discs, which show the same thing, although it is almost gone. I can tell you that mine were worse than yours after Silverstone. My rears also had it but to a lesser extent and they are perfectly fine now.

I also believe it is normal, MRichmond would be the person to confirm as I know he has used the pagids for longer.

Apologies for the quality of the images, I just took the snaps with my mobile in a car park.
 

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I can't tell you from a picture whether rotors are out of spec or not. I've used the Pagids as well and believe you should give it some time before deciding to do anything with the rotors. I 'believe' you simply have left over race compound brake pad material left on the rotors that is incompatible with the street compound. Leaving the Pagids on for a little (day or 2 depending on your driving) will scrub this off. Once the pads look consistently shiny across the whole surface, swap back to street and bed them in.

From what I know, BMW won't 'turn' or grind or whatever you want to call it (resurface) rotors even one time. They just replace them if they are out of spec. Since you are not in the U.S., I believe this is coming out of your pocket. So I'd suggest having a little patience before opening up your wallet to replace parts.

As someone else suggested here, call Dave Zeckhausen if you want the expert opinion.
 

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Leaving the Pagids on for a little (day or 2 depending on your driving) will scrub this off. Once the pads look consistently shiny across the whole surface, swap back to street and bed them in.
I actually left mine on for about 3 days, but I only drove round town during that time, so it did not have chance to get scrubbed off and the squeal was that bad I changed them back to stock.
 

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I actually left mine on for about 3 days, but I only drove round town during that time, so it did not have chance to get scrubbed off and the squeal was that bad I changed them back to stock.
I find it is more how you drive rather than how long you drive to clean them off. I will occassionally drag the brakes a little on the way back from an event to speed the process up. Lightly left foot brake down the highway. Not enough to heat them up, just enough to scrub the the brakes. (and of course checking my mirrors for unsuspecting people behind me who have no clue what I'm doing)

Around town, I'm somewhat of a conservative driver and it would probably take a while to get the race material off.
 

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Thanks guys. I've learnt so much about brakes from this thread. :cheers:
Just passing along knowledge, mostly picked up from all the great people you meet on here and at the track. Glad to help and hopefully save you time, money, and aggravation. Cheers :cheers:
 

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I can't tell you from a picture whether rotors are out of spec or not. I've used the Pagids as well and believe you should give it some time before deciding to do anything with the rotors. I 'believe' you simply have left over race compound brake pad material left on the rotors that is incompatible with the street compound. Leaving the Pagids on for a little (day or 2 depending on your driving) will scrub this off. Once the pads look consistently shiny across the whole surface, swap back to street and bed them in.

From what I know, BMW won't 'turn' or grind or whatever you want to call it (resurface) rotors even one time. They just replace them if they are out of spec. Since you are not in the U.S., I believe this is coming out of your pocket. So I'd suggest having a little patience before opening up your wallet to replace parts.

As someone else suggested here, call Dave Zeckhausen if you want the expert opinion.
+1, The only way to tell if a rotor is warped is with a dial indicator, not by appearance. Grinding is one way (the best way) to true a rotor...............BUT the heat it took to warp the rotor possibly could have done permanent damage to the metallurgical structure of the base metal, crystallization for example. If you remove metal in machining the surface the problem will reoccour with a vengance now that there is less metal mass on the rotor to dissipate heat. As someone said earlier, in a high performance brake replace the rotor. Safety first.

Your situation, as mentioned, is glaze...........easy fix. :applause:
 
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