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Is there 'really' a difference between (standard) E39 rotors of various brands?

21K views 41 replies 20 participants last post by  bluebee 
#1 · (Edited)
Serious question:

Is there 'really' a difference between E39 rotors of various brands?
ASSUMPTION: OEM size & fitment (i.e., nothing fancy ... apples to apples comparison).

Over in this thread today, the rotor-quality question came up:
- E39 (1997 - 2003) > Ever hear of Winhere brake rotors??

Personally, I'm leaning toward "a rotor is a rotor" ... as I have no anecdotal or personal experience otherwise ... but ... that's why I ask the question.

To be clear, I'm sure there 'can' be (perhaps huge) differences between rotors, mostly on the quality side ... but ... the question is whether ... in reality ... there is a meaningful difference between rotors of the most-recommended brands for our E39?

Given the following OEM-fitment replacement rotors:
- What rotors are recommended for street use on the E39

QUESTION: Is there really a 'meaningful' difference between these rotors?
Most often recommended replacement rotors:
- ATE solid (Premium One brand is OEM?)
- Balo (which model?)
- Brembo solid (which model?)
- Centric Premium ?model
- Zimmermann ?model


 
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#2 · (Edited)
When you say "meaningful difference", I am assuming that you are referring to braking distance since that is the primary metric to measure braking performance. Since the brake rotor simply acts as a surface for the brake pad to grip onto to slow down a moving vehicle, I would agree that there should be no performance difference (e.g. stopping distance) between rotors that are made of the same material, assuming the same brake pads, equal quality of construction and street use. While most rotors are constructed of steel, I do not think the coefficient of friction varies significantly between the various grades of steel used. Any performance differences in fade, cooling, etc. would be due to design, mass, etc. Things like brake warping, out of round, etc. are quality issues outside the scope of this discussion. Other issues like brake squeal are probably more dependent upon the brake pad used, vice the rotor.
 
#5 · (Edited)
A rotor, by any other name, will still stop the same!

When you say "meaningful difference", I am assuming that you are referring to braking distance
Good point!

I left 'meaningful' undefined because I wasn't sure what was meaningful.

I do agree, probably the 'most meaningful' metric is stopping feel & distance.

Fudman said:
Any performance differences in fade, cooling, etc. would be due to design, mass, etc.
Sounds reasonable that an OEM-shaped rotor would perform as OEM shaped-rotors do.

Fudman said:
Things like brake warping, out of round, etc. are quality issues outside the scope of this discussion.
I'm not so sure that's out of scope.

When I chose my first E39 replacement rotors, I simply researched the brands that you guys recommended - and simply selected the least expensive (taxed and shipped to my door) of those.

If it had been 'warped' (in quotes because what I think you meant was the faces were not parallel due to lousy manufacturing tolerances), or out of round (I'm not sure what that means), I would not have been happy.

So, I would disagree here and say that meeting the OEM specs would be as important a criteria as performance (i.e., stopping ability).

Fudman said:
Other issues like brake squeal are probably more dependent upon the brake pad used, vice the rotor
Agreed.

coated rotors don't corrode as quickly as non-coated
I'd lump that under cosmetics and not 'meaningful' in a performance sense.

the rotors balance well
Presumably you mean even distribution of weight.

Is weight imbalance (as opposed to size tolerance) a common problem?

How would we know if a rotor is not weight 'balanced'?

For example, following your recommendations, I noticed, in post 91 of the brake thread, that my new and old rotors had a weight-balancing slice taken out of the edge:
- What is this slice taken out of my rotor (1)

Note: Ignore the text on the picture - we found the answer (it was for weight distribution):

a rotor is probably a rotor
Intuition says the more the marketing guys try to tell us otherwise, the more the case is that, yes, a (recommended brand) rotor of the OEM fitment will perform like any other (recommended brand) rotor of OEM fitment.

A rotor by any other name will still stop your car.
Nice!

A rotor, by any other name, will stop just the same!

I wouldn't order a Chinese brand
Seems reasonable.

Are any of the recommended rotors Chinese brands?
 
#3 ·
Serious question:

Is there 'really' a difference between E39 rotors of various brands?

Personally, I'm leaning toward "a rotor is a rotor".
Probably correct...unless the rotors are manufactured with inferior raw materials or quality control isn't real a priority. The only difference I could discern was coated rotors don't corrode as quickly as non-coated. Other than that, as long the steel is of the highest quality obtainable and the rotors balance well, a rotor is probably a rotor.

A rotor by any other name will still stop your car. :D

a little poetic flourish there
 
#4 ·
The quality of steel and manufacturing process is why I wouldn't order a Chinese brand. I'd be worried about what happens the first time I go down a mountain and the brakes get hot. Ever see a Chery crash test video? They're probably out of round, unbalanced, and brittle.
 
#8 ·
I believe that there is a definite difference between brake rotors. If the foundry does not have good technology and quality control, all sorts of inconsistent grain structure and inter-metallic compounds (hard spots) are probable. Besides, consider that many aftermarket brake manufacturers sell 2 or more grades of rotors with the price ratio approaching 2 to 1. While I doubt the cost ratio is that high, I'm pretty sure that there is a difference between the bottom & premium grades. Unless their product spec sheets and descriptions are pure fairy tales.

I think that many common brake vibration problems are a result of the irregularities throughout the rotor. Further, the temperatures created during braking can be high enough to cause changes in the grain microstructure and growth of inter-metallic compounds that will affect the surface condition of the rotor. Especially if the foundry practices are deficient. A lot of reading and a little personal experience leads me to believe that at the very least, many "warped" rotor are not in fact distorted, but rather have hard spots of intermetallics &/or resultant uneven brake pad deposits on the rotor friction surfaces due to the irregularities. Both will cause braking effect variation as the wheel rotates.

Have you ever had brake shudder/vibration without any pulsing in the pedal? Many of my brake problems over the years have been that way. Friction variation is the most likely explanation. Especially since I could make a good case that a pure warp, i.e. run-out, in a rotor should not pulse the pedal (particularly with single piston floating calipers), would create only insignificant braking variation and would cause only mild steering wheel shake. (Thicknes variation is another matter & would cause both pulsing pedal and brake vibration.)

A prior car (GM), bought brand new, went 100k miles on the original Delco pads & rotors without any vibration ever. No complaints there. I bought brand name premium grade pads and PG grade rotors. "PG" being premium grade, so I was told. After about 10k miles I had a vicious brake vibration, but no pedal pulsing. I had the rotors turned. OK for 10k miles, then vibration back. I checked into the rotor brand & grade. It turned out "PG" was professional grade. In other words, bottom line, enough to pass a safety check - just don't keep the car. A learning experience for me.
I checked run-out and thickness - all in spec. I then tried hand sanding the rotors with good abrasive paper to scuff up and remove any micro irregularities from the surfaces. Good for about 10k miles & then vibration returned. Eventually I put Delco pads & rotors on & problem gone for for another 100k until the car died.

For the extra hundred or so bucks on a brake job, I'm not going to take the chance on no name, unknown quality or low grade rotors. BMW, ATE, Zimmermann, etc. for me.

But I am willing to buy for as much off list price as I can find :) The adage that "you get what you pay for" needs very careful interpretation in real life.

Regards
RDL
 
#9 ·
One thing to look for is the size of the cooling vein area. The larger the cooling area the greater chance of warping. Cheap rotors have a larger vein area so they can use less metal.

I found this picture that shows the difference from a Quality to cheap rotor.
 

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#11 ·
I put Balo's on the front couple month ago. I don't know what to say, they are made in Germany and so far their performance is just what BMW does... Stops you like no other.

Also the pads are important factor in braking and stopping distance (IMO).
But from my experience few days ago when I went and bought lower arms from NAPA which they were the best they can make with life time warranty and they were more expensive than Lomforders, they just didn't fit on the car! The bushing side where there are a lot of teeth, didn't go in the housing where it is supposed to be bolted.

Stick to a German brand because they made the car and they know the sizes and every little spec on the car whereas other companies who try to make parts for those, they are just pathetic.

My point is that there will be small differences and you might not be able to detect them and small details/differences can be hard to detect on rotors but in my case (the control arms) it happened to be easy. They just didn't fit lol. The materials could be better don't get me wrong but if those engineers couldn't make it fit perfectly as it is supposed to, then personally I don't think they are capable of making something they claim to meet or EXCEED OE specs.... Maybe I shouldn't judge on a single experience but it was a very frustrating experience.
 
#12 ·
Good thread. Just to contribute, how about the Euro floating rotor vs. NA rotors? Any big difference?

My M5 has these, but I haven't pulled the wheels yet for a close look. Will do so when I'm ready to adjust the Bilsteins.

BTW, I'm still trying to connect with someone who has first hand knowledge of adjusting a Bilstein PSS9 coilover kit. If you know anyone, please ping me. I'd appreciate it.
 
#16 ·
Thanks guys, will reach out. Appreciate it.

Might want to contact 540i M-Sport as he has PSS14s, which I think might be the same adjustments.
I think those are the ones you can adjust with a button inside the car.
 
#30 ·
I used Centric Premium rotors
Just for the record, I had a long conversation with the head of marketing for the company that makes Axxis/PBR brake pads ... who said the Centric/Stoptech equipment is always rebranded.

That is, they don't make their own stuff ...

He was specifically referring to the pads ... but we should find out if that is the case with the rotors. If so, then there is no such thing as Centric rotors, per se, if it is true that all they make is the box.

REFERENCE:
Louis Luera, Marketing Manager of FMP North America, (makers of Axxis & PBR friction materials) 3529 Cannon Road Suite 2B #515, Oceanside, CA. 92065, 760-295-6034, 619-204-7146, bmna@msn.com)
 
#25 ·
I'm the one who posted the Winhere thread. I bought those rotors because that's all I could get my hands on that day. If I'd had more time I might have waited for different rotors- Balo or maybe Zimmerman. But the Winhere rotors are working fine. I bedded in my Hawk pads on them pretty aggressively and not a trace of vibration or noise after 500 or so miles.

That being said, you never know what you're getting these days. I'd always bought nothing but Zimmerman rotors for my track 911. But after breaking two of them in a year, and hearing others tell me the same thing, I changed. I'd had good luck with Zimmermans on my track 911s for years but all of a sudden they've become less reliable. I also used nothing but SKF front wheel bearings for decades on the 911's but this past winter I couldn't get one to slip on the spindle. I pulled out my digital caliper and measured them and they were out of round. I had 6 sets in my parts bin and measured them all. 2 were bad- the first one that was out of round and a second one that had an ID that was smaller than all the others. The 4 good ones were made in Germany, the two crappy ones were from Indonesia. What I'd thought was a good German company was sourcing some of their parts from the far east and the quality control was junk.
 
#33 ·
#34 ·
I'm not sure about the vein/thickness of metal question.

Wide vein/less metal = better heat dissipation but less wearability
Small vein/more mteal = better wear but less heat dissipation

No idea which would be best :) (unless you've got a sticking caliper piston!)
 
#35 · (Edited)
I'm not sure about the vein/thickness of metal question
On the topic of vanes, cn90 posted today a reference in this thread:
- ATE Rotor Power Slot "Grabbing" ?

The reference said to count the number of vanes in the old and new rotor.

They said it should have equal numbers of vanes, and they specifically said fewer vanes would be detrimental to cooling.
 
#36 ·
Brembo has put a single, small "dimple" in some of their oem style rotors that is a wear indicator. When the dimple is no longer visible, the disc has reached the maximum wear point.
I have them on my car presently....got them a few years ago.

I am about to swap out the fronts with Zimmerman Z coat. Fronts still have quite a bit of "meat" on them....but rotors are not all that expensive, and rather go with new on the front for this brake job. I will reuse the rears...they look almost new after 70k miles.
 
#37 ·
Some information that came out of this thread today:
Many years ago, I used to care about ATE, Zimmerman, BALO etc.

Now that I am getting older, the only thing I care ...

The disc: it is just a hunk of metal (I know some people will "attack" me for this), as long as you get a decent hunk of metal, you are OK.
FYI, I used Duralast Rotor in my 2007 Honda Odyssey, 4 years later, still good.

For 2003 530i, the Duralast front rotor (PN 34202@ Autozone) is $50 for your car.
I think these are all good points raised regarding rotor selection. To simplify things for the next person interested in rotors, here is a recap of the bidding and some other time-honored truisms regarding rotors:

1. Stopping distances are not affected by the brand of rotor.
2. Rotors do not have a major affect on subjective braking attributes like modulation, feel, bite, etc. These are primarily affected by brake pad brand and material.
3. All rotors will rust (on the braking surface). Coated rotors (edges, hats, etc.) rust less than uncoated rotors.
4. Some rotors might result in fade earlier than others due to design or material but most rotors should have similar fade qualities.
5. OE rotors are no worse but are not necessarily better than aftermarket rotors.
6. Stick with a recognizable brand of rotor and the quality should be adequate.
7. Holes and grooves on rotors are cosmetic bling and serve no functional purpose on a street car. However, they do look cool!
8. Poorly drilled holes can result in premature rotor life due to stress cracking.
9. Rotors rarely, if ever, warp. Most pedal pulsations are due to pad deposits left on the surface of the rotor.
10. Bedding a rotor can usually remove these deposits and eliminate braking squeaking.

Bottom line, you will not achieve noticeable braking performance improvements by changing rotors. You can achieve appearance improvements and you might achieve limited durability improvements. The size of your wallet should determine the optimal rotor solution for your needs.
I disagree...

There is a DIFFERENCE between the cheap Chinese metal rotors and a good quality rotor IMO.

I would stick with Brembo and Balo, preferably Balo.... :D

Try looking here:

Genuine BMW front rotor for $79.60 each:
http://www.bmaparts.com/item.wws?sku=405 06026 001&itempk=71217&mfr=GENUINE&weight=23.45

Brembo Front rotor for $70.68 each:
http://www.bmaparts.com/item.wws?sku=405 06026 253&itempk=71214&mfr=BREMBO&weight=23.50
 
#38 · (Edited)
I put new Zimmerman rotors on my the rear of my 530i a few weeks ago... with Pagid pads. The store I went to (CARQUEST) recommended these for the car. On my old Toyota, I didn't care as much as the Chinese made rotors seemed as good as any other,, I was impressed with the pads they sold me a few years ago... I think they are still on the car all these year later. I have no clue what brand is on the front of my BMW. As I bought the car used and the fronts look good. They are all slotted and drilled. I Have never had a hard brake situation while driving in t he BMW. So I have no clue how it will react.

I have yet to take it up into any mountains either.

and the Z coating sure looks strange on rotors. Not sure if there is any color change yet, as it hasn't been driven far yet.
 
#39 ·
For the record, while there may be little difference between solid rotor brands, the year of your 540 apparently matters greatly for fit as evidenced by this scary thread today:

You were sold rotors for an 04/00 540i. You need rotors for a 9/99 build 540i.
 
#40 ·
#42 ·
I found this looking up rotors for someone today...

The rather dated information in this article implies that we should WEIGH our rotors (and record the new weight) as one comparison of new rotor quality.
- Danger Ahead: Motorists at Risk from Substandard Brake Parts, Suit Alleges July 10, 2009
This spring, Affinia contracted with an independent lab to compare Dura's rotors to the ones they typically replace, the original rotors that ship from the manufacturer.

According to the test results included in the suit, Dura's rotors were in some cases up to 18% lighter, Affinia alleges. In addition, the rotors allegedly had significantly larger air gaps within them-in some cases up to 68% bigger-than called for by the original manufacturer specifications.

According to the complaint, Dura and CRW made "false or misleading representations that some of Dura's brake rotors meet or exceed Original Equipment specifications and performance when they do not."

Because Dura lightweight rotors are less expensive than Affinia's rotors, Affinia claims it will suffer "irreparable harm, lost sales and damages." Affinia does not allege that all brake rotors supplied by Dura are substandard.
Unfortunately the article doesn't say what the resolution was.
 

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