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      12-01-2016, 01:16 PM   #1
Franzino
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Replace brake discs everytime you change brake pads?

This was an interview with one of the engineers about the steel brakes of the M2/M3/M4... I find it very strange what he says about changing the discs each time when your track pads are worn out. With my AP racing discs on my Z4M is do around 6x brake pad changes until the discs arrive at their minimum thickness and need a change

There is a minimum thickness that a discs needs to have...I can not imagine that after one set of track brake pads you need to change your OEM M2 discs because they are to thin?

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      12-01-2016, 05:20 PM   #2
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I wouldn't think they need changing that frequently either. Certainly unlikely to be down to minimum thickness. So unless they are warped and have the shakes just change pads and carry on
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      12-01-2016, 06:00 PM   #3
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Quote:
Originally Posted by M+M
I wouldn't think they need changing that frequently either. Certainly unlikely to be down to minimum thickness. So unless they are warped and have the shakes just change pads and carry on
Maybe he recommends this because he doesn't have to pay for them on his car?
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      12-02-2016, 04:10 PM   #4
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Maybe he's got shares in the company who makes them!
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      12-09-2016, 02:41 PM   #5
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FYI: I ran through a set of BMW Performance Brake pads and after one set of front pads the rotors were down to minimum thickness.
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      12-09-2016, 04:22 PM   #6
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Germans love to have you replace the pads and rotors together. That's fine when they are matched to wear together, but soon as you change that the logic goes out the window (and dubious even stock). As long as you meet minimum thickness and there are no fatal cracks or high spots you are good... People often think rotors "warp", but that is really uneven wear caused by inconsistent metalurgy in the casting where the softer bits wear more than the harder bits leaving a lumpy surface. I once had a brand new rotor hop like the wheel was falling off due to a hard spot that looked normal to the eye. Get some ST43 brake pads and never worry about track pads again.... I usually get 30hrs of racing out of a set of fronts and I race it like I stole it (this is not on a BMW though, so YMMV)

Last edited by Spinnetti; 01-04-2017 at 04:11 PM..
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      12-09-2016, 05:08 PM   #7
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Quote:
Originally Posted by Spinnetti View Post
As long as you meet minimum thickness and there are no fatal cracks or high spots you are good... People often think rotors "warp", but that is really uneven wear caused by inconsistent metalurgy in the casting where the softer bits wear more than the harder bits leaving a lumpy surface. I once had a brand new rotor hop like the wheel was falling off due to a hard spot that looked normal to the eye. Get some ST43 brake pads and never worry about track pads again.... I usually get 30hrs of racing out of a set of fronts and I race it like I stole it (this is not on a BMW though, so YMMV)
If your at minimum thickness they are done for track use. Street use maybe.
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      12-09-2016, 11:15 PM   #8
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Quote:
Originally Posted by Spinnetti View Post
As long as you meet minimum thickness and there are no fatal cracks or high spots you are good... People often think rotors "warp", but that is really uneven wear caused by inconsistent metalurgy in the casting where the softer bits wear more than the harder bits leaving a lumpy surface. I once had a brand new rotor hop like the wheel was falling off due to a hard spot that looked normal to the eye. Get some ST43 brake pads and never worry about track pads again.... I usually get 30hrs of racing out of a set of fronts and I race it like I stole it (this is not on a BMW though, so YMMV)
30 hours racing is very impressive durability for pads. What rotors are you using now?
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      12-10-2016, 06:08 AM   #9
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Quote:
Originally Posted by Ulmi View Post
FYI: I ran through a set of BMW Performance Brake pads and after one set of front pads the rotors were down to minimum thickness.
Wow damn....then it's getting expensive... My rotors from my AP racing kit last around 5-6 sets of front Pagid pads. What is the price of a front set of BMW rotors?
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      01-04-2017, 11:54 AM   #10
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BMW has always replaced rotors with pads but I think it's completely unnecessary. No way a set of OEM street pads will chew through a set of rotors.
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      01-04-2017, 12:26 PM   #11
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Quote:
Originally Posted by CosmosMpower View Post
BMW has always replaced rotors with pads but I think it's completely unnecessary. No way a set of OEM street pads will chew through a set of rotors.
Never did that with my BMW who still had OEM rotors and OEM pads... Are they crazy!
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      01-04-2017, 01:43 PM   #12
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I always replace my street rotors with pads. Last time I changed them I measured them and they were past minimum thickness.

http://f30.bimmerpost.com/forums/sho...4&postcount=24

Last edited by omasou; 01-04-2017 at 02:06 PM..
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      01-04-2017, 02:50 PM   #13
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Quote:
Originally Posted by M+M View Post
30 hours racing is very impressive durability for pads. What rotors are you using now?
Especially considing this is on a Big Assed Lexus LS400 with stock brakes running up at the front of the field. So many forum "gurus" seem to like to spend a lot of money with little benefit. I use the cheapest ebay/Amazon rotors I can find and change them as frequently as they need it, which tends to be the same frequency as expensive rotors.. Then, just for fun (no real value or need) I CNC cut them to make them look fancy. Favorite is to wave cut the outer perimeter like on the RS Audis which reduces weight a bit and exposes more surface area at the hottest part of the rotor (which does add cooling value). I've never run pads a full 30hrs, but have lots of sets of pads at about 40% left - kind of false economy to have to pit in a 24hr enduro to save on pads so I swap them out... I end up using them for 15 - 24hrs (depending on race length), and the rotors last a long time (I've got ducts to the center of the rotors too).

New
https://www.amazon.com/photos/share/...Vyu2wRyAbKpUFC

...After 15hrs of hard use and some rain thrown in.
https://www.amazon.com/photos/share/...cyXsj3PnPahlfT

Last edited by Spinnetti; 01-04-2017 at 04:14 PM..
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      01-04-2017, 04:14 PM   #14
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Quote:
Originally Posted by Spinnetti View Post
Especially considing this is on a Big Assed Lexus LS400 with stock brakes running up at the front of the field. I use the cheapest ebay rotors I can find, then just for fun (no real value or need) I CNC cut them to make them look fancy. Favorite is to wave cut the outer perimeter like on the RS Audis which reduces weight a bit and exposes more surface area at the hottest part of the rotor (which does add cooling value). I've never run them a full 30hrs, but have lots of sets of pads at about 40% left - kind of false economy to have to pit in a 24hr enduro to save on pads... So I use them for 15 - 24hrs (depending on race length), and the rotors last a long time (I've got ducts to the center of the rotors too).

New
https://www.amazon.com/photos/share/...Vyu2wRyAbKpUFC

...After 15hrs of hard use and some rain thrown in.
https://www.amazon.com/photos/share/...cyXsj3PnPahlfT
I also run cooling ducts to the center of the rotors on my rally car. Still wouldn't get near that longevity. Must be too much left foot braking overlap while on throttle !!
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