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Brake rotor and brake pad compatibility

6K views 4 replies 4 participants last post by  sapiro 
#1 ·
Hello Folks:

I recently upgraded my 330Ci from Powerslot rotors using Ultimate pads to the new BMW Performance cross-drilled rotors using a new set of Ultimates.

Honestly, I was 100% satisfied with the Powerslot/Ultimate combination. The only reason I did the upgrade was to spend some money and put some new fangled accessory on the car.

The Powerslot/Ultimate combination had exactly 32,254 miles on it (I keep meticulous, FAA worthy records and receipts in a 3-ring binder).

I gave my old brake kit away to a fellow E46Fanatics member. When I took the old kit off, the pads seemed to have a surprising amount of thickness left compared to the new pads - about 70%...(I'd would have measured them today for an exact number but the new pads are already installed and the Textar website is not clear whether the backing plate is included in the thickness measurement).

Curiousity got the better of me and I went out and bought a micrometer so I could measure the thickness of the rotors. Here's what I found:

LF = 24.4mm
RF = 24.4mm
LR = 21.7mm
RR = 21.6mm

The minimum thickness for the fronts is 23mm (new they are 25mm), minimum thickness for the rears is 20.4mm (new they are 22mm).

My calculations tell me that the fronts still have 70% of their recommended life left, figured as follows; 2.0 millimeters is the maximum wear allowed, 0.6mm is tha actual wear measured, divide 0.6 by 2.0 = 0.3, or 30%. 30% is the actual wear as a percentage of the maximum allowed. Therefore, 100% minus 30% = 70%. 70% is the useful life that remains in the front rotors.

For the rears I figured they have 75% of the useful life left (I figured this from the more worn RR which was 21.6mm).

So, why am I telling you all this?

Everyone has their favorite pad, my own experience with the Ultimates being very favorable. However, there has been occassional mention about rotor and pad compatibilty with respect to wear. This has been in the context of a hard pad lasting longer than the rotor, and the wear sensor not indicating the brakes need replacing (because there is still pad left, though the rotors are gone).

My experience with the Powerslot/Ultimate combo tells me that the combination is highly compatible. Based on my calculations, the rotors and pads will wear out at roughly the same time.

This is a good thing; perhaps my experience will add a little "science" to the pad choices people make in the future.

In summary, the Ultimate pads seem to be a good match to OEM BMW rotors (which I am 99% sure that Powerslot used in my case).

FWIW,

Scott
 
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#2 ·
As usual Scott, great info on brakes at a very detailed level.

I'm still collecting user feedback on pads and am about to pull the trigger on some now. Brakes have been apart for a few weeks and need to get back on the car but I've waited to decide on the right pad. I can't remember whether I asked you or not, but since you've had OEM, Axxis Deluxe Pluses, and Ultimates. How do you compare all 3? I personally am looking for OEM bite and feel (or a bit better) and less dust. Deluxe +s fit the latter very well but not the former. I'm torn between the Ultis and the new R4S Porterfield. Whichever I choose, they will go on OEM rotors (for now). I can stand to wash the wheels more often if it means better braking, but hopefully not at a level the OEMs cause.
 
#4 · (Edited)
jpr, with you being a "hard grader" and all, I'm glad my methodogy and thinking met your standards!

shortyb, yes, I have used all three. My car came new with Textars. This was a really great pad with respect to bite when cold, noise free, and high temp operation (I never felt them fade on the public roads when I was driving in a "sporting fashion").

But, Textars were dusty. I'd get a hazing of dust after driving to the nearby gas station which was about 4 miles away.

So, I put Axxis Deluxe Plus pads on without replacing the rotors because the car only had 7,726 miles on it. Without question the Deluxe Plus pads were 99% dust free, which was their claim to fame. However, their initial bite when cold and semi-warm was consistantly inferior to the factory Textars. I wouldn't have wanted a dog to run in front of me with cold brakes!

I got the Deluxe Plus pads hot several times, driving in a "sporting fashion" on public roads, and never felt them begin to fade (but I'm sure they could be fried on the track).

At the time I ordered the Deluxe Plus pads they seemed to be a popular choice. But I simply didn't like them. But let me tell you this, I gave them the benefit of the doubt because the rotors had been used with the Textars previously and I wondered if I had compromised the Deluxe Plus performance because of this (this is a real issue and concern when you install a different type of pad in a rotor that's been previously used with another type of pad).

So, at 11,563 miles I ordered the Powerslot rotors and Axxis Ultimates pads. That has consistently been a very high performing combination that I have zero complaints. The Ultimates are more dusty than the Deluxe Plus pads, though the Ultimates are only about 1/3 as dusty as the Textar pads.

Where the Deluxe Plus pads were known for being dust free (true), the Ultimates were known to have exceptional cold bite (very true). Of all the pads I've had on my BMW I subjected the Ultimates to the most extreme sporting driving. I never felt them fade. The Ultimates have never claimed to be track pads so I can't speak for that usage, but they are most definitely one heck of a street pad.

Something else I've experienced in another car but never fully appreciated was the transition a pad has from having bite to fading. Dick Zeckhausen mentioned that the Ultimate pads behave very nicely when they begin to give up. They'll fade in a progressive fashion, thus giving you warning, instead of a situation where you have brakes in one corner and not the next. I had another high performance car that did that to me several times and that situation has a pretty serious "pucker factor". A couple of times, as David Hobbs would say, I was "sucking air" and wide-eyed because I had no brakes. As I said earlier, I never fully knew or appreciated that it's far better when pads give up in a progressive fashion.

One last thing, I have never had a problem with brake squeal, grinding, judder, etc., on any of my cars. IMHO, this is caused when pads, pad holders, and caliper pistons are gunked up with dirt, dust, and grease. Some people use that anti-squeal paste, etc., but I have never had to use that stuff. To me it introduces problems. The real solution is cleanliness!

shortyb, buy the Ultimates. You will like them. Especially since they seem to be compatible with OEM rotor wear.

Scott
 
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