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-   -   Question about strange brake rotor wear (https://www.bimmerfest.com/forums/showthread.php?t=1332753)

Walt White Coupe 06-01-2019 10:50 AM

Question about strange brake rotor wear
 
2013 650 ix with 30,000 miles.

Over the last 2000 miles I've noticed that the left front brake pad is not making full contact with the rotor at the outer edge. The brake pads still have a lot of life left based on current thickness and the wear on the rotors themselves is relatively minor with a very small lip at the outer circumference.

Tried some hard stops to see if that would make the pad fully contact the rotor but no change. Planning on trying some really hard stops next but wondered if anyone has seen something like this before. Thanks in advance.

Left Front Rotor:
https://www.mediafire.com/convkey/cc...2ncn8bho4g.jpg

Right Front Rotor:
https://www.mediafire.com/convkey/e1...u2w6s3bo4g.jpg

645/333 06-02-2019 04:26 AM

What you are seeing is actually quite normal, every car from different manufacturers I have owned all have the same break disc wear profile. It is how you see how the disc is wearing in terms of thickness. The deeper the lip the brake disc wear is higher. Looking at both pics again closer, there is a difference left to right, the lip is still correct but have noticed the wear to the outer edge being what seems half inch down the disc. Where the pads replaced 2k ago along with the discs? The left one could be the pad is not seated correctly or the guide pins where not cleaned correctly so the caliper is not floating correctly. Did they use BMW pads or after market? It could be pad face never bedded in correctly.

Don't worry.

Walt White Coupe 06-02-2019 04:37 AM

These are the original pads/rotors and they have never been replaced. They have 30,000 miles on them. And the band at the outer circumference of the rotor is about 1/4 inch wide.

645/333 06-02-2019 04:54 AM

Thanks for the update, given they are 30k plus you have done well if the pads disc's still have lots of material left. The lip test is a quick and dirty measure by the way, they should be measured with a micrometer with the wheel off as this will tell you exactly how much life is still in them.
Subject to breaking and driving profile it is normally two sets of pads to one disc and including the rears as they can wear just as fast as the front, but many do not follow this on modern cars with electronic stability control etc.
Going back to the issue, it may well be that they are now due a new set of pads, that the guide pins are now very dirty, which affects how the caliper floats, it could be dirt etc built onto the frame of the caliper, sometimes the anti squeal springs lose some tension, it amazes me that people seldom change then with the pads, they are cheap item. The answer in part is to leave it until the pads eventually go via the CBS on the Idrive, it will tell you how much life they have in them. Stripping down now will help to find the issue, but personally I would leave it till the pad change.

645/333 06-02-2019 05:01 AM

I did a quick check on my maintenance schedule and BMW show that pads and discs are a one to one in terms of change. Makes it a very expensive change given the price of Discs. Your car is very powerful and heavy and take their toll on the breaking system.

Walt White Coupe 06-03-2019 01:21 PM

I went through a typical brake "bedding" procedure that included around 8 hard slowdowns from 60 mph and I started to get some contact at that outer 1/4 inch edge with the brake pad. Hopefully with a little more miles and brake pad wear, I'll get full contact on the rotor again. Still wondering why this is happening.

Walt White Coupe 06-05-2019 05:08 PM

So I've only put around 100 miles and very light braking but I'm seeing contact on that outer 1/4 inch of rotor. Looks to me, like I said before, that with a few more miles it's going to correct itself. Still not sure what is going on.

https://www.mediafire.com/convkey/3a...y4hy620m4g.jpg

645/333 06-06-2019 05:14 AM

As mentioned in my previous posts is where the answer lies. All you are doing with the hard breaking is stressing the moving components, especially the guide pins if there are dirty or slightly corroded, you are using the antilock braking control to it's maximum possibly subject to how hard you are breaking.
Unless you decide to strip it down and look you will not find the cause.
Also I know this because the same was on my mini the left rear, I had uneven wear and grooves across the disc, all other wheels were perfect. I did the hard braking approach which cleared it up enough to satisfy myself until I come to a pad change, my brakes have done less than 9k miles. When I come to change my pads and discs I will monitor the components as I strip it down to change them.

645/333 06-06-2019 05:18 AM

You could contact HerbP on the E63 forum, he is a very knowledgeable guy and helpful.

Walt White Coupe 06-06-2019 10:19 AM

So the car has 30,000 miles and at my last state inspection the tech said my front pads are at 12/32 thickness and the rears are 8/32. Does anyone know what the new pad thicknesses are? I'm guessing around 14 & 10/32. I'll probably sell this car at around 50,000 miles so at this wear rate I may never have to replace the brakes. I like to anticipate braking and often will let the car coast to around 5 mph before I have to use the brakes. The way the car downshifts coming to a stop really slows it down without using the brakes.

645/333, thanks for your inputs.


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