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      03-10-2013, 02:27 PM   #1
mike519
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OEM brake specs?

OK, just trying to figure out where my pads and rotors are at. Can someone tell me:

1) What's the minimum recommended pad thickness front and rear (Z4M)

2) Maximum "lip" on the rotors before I should be looking to replace them. Front rotors have a 0.019 lip at present.

Thx
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      03-10-2013, 02:45 PM   #2
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Quote:
Originally Posted by mike519 View Post
OK, just trying to figure out where my pads and rotors are at. Can someone tell me:

1) What's the minimum recommended pad thickness front and rear (Z4M)

2) Maximum "lip" on the rotors before I should be looking to replace them. Front rotors have a 0.019 lip at present.

Thx
Can't speak to the pads - wear sensors would let you know. The min rotor thickness is stamped on the rotor hats. Throw a digital caliper on them to check. At 42,000 km last year I was OK.
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      03-10-2013, 03:10 PM   #3
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It's not a 'lip' spec, but a overall rotor thickness specification.

As stated above, the minimum rotor thickness is stamped on the edge of the rotor. Normally, for the Z4M OEM rotors (ATE), the minimum front thickness is 26.4mm and the rear thickness is 18.4mm

OEM rotors start out at 27.2mm and 19.6, respectively.
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      03-10-2013, 03:11 PM   #4
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Quote:
Originally Posted by Caddyshk View Post
Can't speak to the pads - wear sensors would let you know. The min rotor thickness is stamped on the rotor hats. Throw a digital caliper on them to check. At 42,000 km last year I was OK.
Thanks Caddy.

I know the wear sensors would let you know when they are toast but I was wondering how close I am getting to that point. I have the wheels off now and just bled the brakes but wondering if now is a good time to do the brakes or if I am good for a while.

For the rotors, funny...I wasn't thinking of thickness, I was more concerned about the lip. I should have thought of that...brain fart. Thanks for the reminder.
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      03-10-2013, 04:11 PM   #5
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Quote:
Originally Posted by mike519 View Post
Thanks Caddy.

I know the wear sensors would let you know when they are toast but I was wondering how close I am getting to that point. I have the wheels off now and just bled the brakes but wondering if now is a good time to do the brakes or if I am good for a while.

For the rotors, funny...I wasn't thinking of thickness, I was more concerned about the lip. I should have thought of that...brain fart. Thanks for the reminder.
I went through the same thing; lip was quite pronounced so Ian and I measured the thickness and mine were well within spec.
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      03-10-2013, 05:55 PM   #6
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Quote:
Originally Posted by Shipkiller View Post
It's not a 'lip' spec, but a overall rotor thickness specification.

As stated above, the minimum rotor thickness is stamped on the edge of the rotor. Normally, for the Z4M OEM rotors (ATE), the minimum front thickness is 26.4mm and the rear thickness is 18.4mm

OEM rotors start out at 27.2mm and 19.6, respectively.
I think the new thickness for the front rotors should be 28mm on the front and 20mm on the rear, with 1.6mm total wear to min thickness, from what I measured on a new set?
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      03-10-2013, 05:58 PM   #7
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That is entirely possible. They might be making them a little thicker now??

The new Zimerman fronts I received have exactly the same dimensions of the ATE's
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      03-10-2013, 07:03 PM   #8
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Quote:
Originally Posted by aerobod View Post
I think the new thickness for the front rotors should be 28mm on the front and 20mm on the rear, with 1.6mm total wear to min thickness, from what I measured on a new set?
Yeah, did a little more searching and found the minimum is 26.4 front and 18.4 rear so you are bang on. My fronts are at 27.1 and rear is 19.4 so I am good for now but may need to replace at last the fronts after a track day or two this summer!

Funny though, the numbers that are stamped on the rotor hats do not match up to anything relevant to these numbers.
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      03-10-2013, 07:10 PM   #9
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Interesting.... I always went by the specs on the hats.
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      03-10-2013, 07:18 PM   #10
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Interesting.... I always went by the specs on the hats.
I have numbers on the hats that are something like 2174 and a separate 5 on the rears...forget the front number.
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      03-10-2013, 07:28 PM   #11
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Quote:
Originally Posted by mike519 View Post
I am good for now but may need to replace at last the fronts after a track day or two this summer!
I doubt that. Depending on the type/brand of brake pad you use will depend on your rotor wear characteristics.

"36K miles, 22 track days and my rotors are still at 26.9mm and 19.0mm."
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      03-10-2013, 07:32 PM   #12
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Quote:
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I doubt that. Depending on the type/brand of brake pad you use will depend on your rotor wear characteristics.

"36K miles, 22 track days and my rotors are still at 26.9mm and 19.0mm."
Me too - but I'm about 28K miles...
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      03-10-2013, 07:51 PM   #13
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Me too - but I'm about 28K miles...
Cool, I hope so. Would like these to last until I can afford a BBK!
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      03-10-2013, 08:19 PM   #14
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Quote:
Originally Posted by mike519 View Post
Cool, I hope so. Would like these to last until I can afford a BBK!
Brakes on these things are crazy good - BBK has bling for sure...
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      03-11-2013, 07:25 AM   #15
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Quote:
Originally Posted by mike519 View Post
Cool, I hope so. Would like these to last until I can afford a BBK!
You'd be surprised how many USED BBK's I show up on classifieds, you could easily snag one for half price. Check m3forum and bimmerforum (race parts and brake classifieds).
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      03-11-2013, 07:32 AM   #16
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Now I have a question.

If you buy a used BBK, how do you know they are good? Do you have to search for a rebuild kit? Do you have to rebuild it?

I am not adverse to using a 'second hand' brake system, but how do I KNOW it's good?
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      03-11-2013, 12:58 PM   #17
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Quote:
Originally Posted by Shipkiller View Post
Now I have a question.

If you buy a used BBK, how do you know they are good? Do you have to search for a rebuild kit? Do you have to rebuild it?

I am not adverse to using a 'second hand' brake system, but how do I KNOW it's good?
Rebuilding calipers is not something that needs to be done often IMO, but you could inspect the seals for leaks. Aside from that, unless the caliper gets stuck/siezed, I see no reason why you'd have to.

The only parts I'd get new when buying a bbk is stuff like new crush washers, new bolts for brackets, etc but all that stuff is relatively cheap.
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