[perryinva]

No one here seems to put many miles on their G29s, not enough to need new rotors, anyway. I definitely like the look of drilled rotors (and yes, I know they do not perform as well as non drilled for normal and above normal use, etc, etc). Anyone ever seen a set? A mild Search uncovered none I could find. I would not even consider it until the OEM rotors were worn, if that ever happened. (Unlike the likelihood of changing out the massive dust generating BMW pads with Akebono, which I usually do after a year or 2)

[BEAR-AvHistory]

Originally Posted by perryinva

(and yes, I know they do not perform as well as non drilled for normal and above normal use, etc, etc).

Don't believe this to be true anymore as most high performance car come with drilled rotors from the factory. I have had Porsche Carrera 4S, BMW M stock drilled & my Cobra runs drilled rotors having had no issues with them.

If you have 19" wheels try matching rotor specs with an M4 stock rotor or if they come with them an M3. They are drilled stock.



If they match up an aftermarket replacement part should fit & be a lot cheaper.

[perryinva]

I have 18”, but that is still a good idea for down the road. So they only put drilled rotors on actual M cars then, it seems, which would make sense as the M pads have more surface area toncounter the loss of the holes. Interesting they didn’t offer it on M brakes on the G29 Z4. Inwonder if they were offered on the earlier MZ4s?.

[stlcdr]

I've investigated this and have found nothing. It looks like the M4 rotors are a different size (enough doubt to believe it's not going to work).

There are slotted rotors, though, not drilled - and not cheap. I believe ECSTuning has them, but for the money, I'm not sure it's worth it.

[vertigo corsa]

If it helps, GR Supra rotors are the same spec.

https://www.r1concepts.com/details/2...rotors/1088922

[BEAR-AvHistory]

FWIW I have bought brake parts including drilled rotors through both Jegs & Amazon with good service & no product issues.

[StanDiego]

Originally Posted by perryinva

No one here seems to put many miles on their G29s, not enough to need new rotors, anyway. I definitely like the look of drilled rotors (and yes, I know they do not perform as well as non drilled for normal and above normal use, etc, etc).

They absolutely do perform as well under normal use. They're just unnecessary for normal use and you'll go through pads faster. Besides helping to clear dust and hot gasses, drilled or slotted rotors help to keep pads from becoming glazed (from heat) by providing sharp edges that help to shave the glazing (and pad surface) away.

Though drilled rotors do have a tendency to micro-fracture, that's typically an issue only when used on the track where they get much more heat.

If you like the look and don't mind changing pads more frequently, go for it.

By the way, a very significant amount of brake dust comes from the rotor, not just the pads which is why we'll never be able to eliminate brake dust from current brake technology. Even Porsche’s new tungsten-carbide rotors generate some dust though much less than conventional iron rotors.

https://youtu.be/ZCj83_uF9dE

Turner Motorsport sells drilled and slotted rotors but I have no experience with their performance or longevity nor do I know how their weight compares to BMW's two-piece aluminum hub rotors.

https://www.turnermotorsport.com/BMW...rilled-slotted

They're cheaper direct from ECS Tuning (and more options) though.

https://www.ecstuning.com/BMW-G29-Z4...raking/Rotors/

.

[stlcdr]

Originally Posted by StanDiego

...

Turner Motorsport sells drilled and slotted rotors but I have no experience with their performance or longevity nor do I know how their weight compares to BMW's two-piece aluminum hub rotors.

https://www.turnermotorsport.com/BMW...rilled-slotted

They're cheaper direct from ECS Tuning (and more options) though.

https://www.ecstuning.com/BMW-G29-Z4...raking/Rotors/

.

Hmm, didn't see the one piece rotors...significantly cheaper than the two-piece.

[perryinva]

All true, but in BMWs the majority of dust is the pads, unless something has changed recently. I typically keep my cars a long time, and the pad changes always result in huge brake dust reduction.

I really like the BMW 2 piece rotors, so I doubt I would swap just for looks. I was just definitely interested in what the long time brain trust here had found.

[StanDiego]

Originally Posted by perryinva

All true, but in BMWs the majority of dust is the pads, unless something has changed recently. I typically keep my cars a long time, and the pad changes always result in huge brake dust reduction.

I really like the BMW 2 piece rotors, so I doubt I would swap just for looks. I was just definitely interested in what the long time brain trust here had found.

I used aftermarket in most previous cars but I really like BMW's two piece rotors and wouldn't use anything else unless there was a comparably priced (or less) aftermarket two piece with aluminum hub.

[Westside Guy]

Originally Posted by perryinva

All true, but in BMWs the majority of dust is the pads, unless something has changed recently. I typically keep my cars a long time, and the pad changes always result in huge brake dust reduction.

I really like the BMW 2 piece rotors, so I doubt I would swap just for looks. I was just definitely interested in what the long time brain trust here had found.

I recall that someone here in the Z4 forum had installed aftermarket ceramic pads and the brake dust was greatly reduced.

[StanDiego]

Originally Posted by Westside Guy

I recall that someone here in the Z4 forum had installed aftermarket ceramic pads and the brake dust was greatly reduced.

They absolutely do reduce brake dust but I believe braking performance may be reduced. I tried them on my Miata and personally didn't care for the performance or brake feel.

However, my experience is limited to one manufacturer and products are always improving so I'd consider trying ceramic again. What I won't do is compromise brake performance for lower dust.

[tracer bullet]

Generally speaking, pads that are good for cold stops (driving around town and having immediate braking performance) tend to dust a lot. Pads that are better for repeated stops (track) tend to dust less. The dust isn't really a fault of the pads, it's just indicative of the choice to have a pad that stops the car the best in daily driving. They're also less likely to squeal.

Again just generally speaking. Another possible solution to the dust is making it easy to clean your wheels. Sonax and a fuzzy brush got a long ways.

[Westside Guy]

Originally Posted by StanDiego

They absolutely do reduce brake dust but I believe braking performance may be reduced. I tried them on my Miata and personally didn't care for the performance or brake feel.

However, my experience is limited to one manufacturer and products are always improving so I'd consider trying ceramic again. What I won't do is compromise brake performance for lower dust.

I just did a search and here are some discussions about ceramic pads.

https://g29.bimmerpost.com/forums/sh...hlight=ceramic

https://g29.bimmerpost.com/forums/sh...hlight=ceramic

[Horseman]

Originally Posted by perryinva

I definitely like the look of drilled rotors (and yes, I know they do not perform as well as non drilled for normal and above normal use, etc, etc).

I am not mechanically inclined when it comes to cars. If I have an issue I take it somewhere, and not do it myself...

HOWEVER... considering how many fast cars come with drilled rotors, I'd say that they're doing this for a reason beyond simple aesthetics. Drilled rotors (from my understanding) stay cooler during heavy braking at high speeds while offering the benefit of reduced weight.

Now.. I'm not saying I'm right.. however, I'd like to know more about the validity of the statement that drilled rotors do not perform as well as non drilled.

[stlcdr]

Originally Posted by Horseman

...

Now.. I'm not saying I'm right.. however, I'd like to know more about the validity of the statement that drilled rotors do not perform as well as non drilled.

From what I understand - and I think it has already been mentioned - that the rotor can stress crack/break at these points. As such they need to be designed to take the additional stresses to take advantage of the 'cooling/gasses' factor.

It looks like Turner Motorsport has drilled and slotted single-piece rotors and just slotted two-piece rotors: the latter significantly more expensive than the former.

As much as I'd like the 'look' of drilled rotors, I'm not sure that a single piece replacement would provide equal 'performance' - or rather it's adding a weak point with no gain in performance, and maybe less, since it's a single piece design. Maybe that's not true, but I'm a fan of the phrase, you get what you pay for.

[perryinva]

I’ve been wrenching my cars for 40 years and am a retired mechanical engineer. Todays cars are way more complicated and more precise by design and function. There is far less that I can do nowadays on my cars than even 15 years ago. I can’t even easily check oil condition as there are no more dipsticks.

For the same diameter rotor and identical calipers & pads, drilled rotors have less surface contact at the pad, obviously due to the holes. That is why simply installing just drilled rotors to replace non-drilled has less performance. Slotted is better, but not bybtoo much and I never liked the look. Cars with drilled rotors by design (or rotor/caliper sets) always have either/and or larger calipers with more pads surface area that makes up for the holes reduced contact area and larger rotors, which do provide superior performance in basically all conditions. I will never track this car (or likely even get on a track again, with the BMW Performance Center being the only possibility and that’s not really a track) so extreme high speed performance or bragging rights is not the reason.

BMW brakes, in general, are excellent. I certainly am not 2nd guessing the engineers on this. The more I think about it, the more I realize I never should have brought this up, as these modern brake systems just have too much interrelationships with electronics and such, that it is best to leave them as is.

It was a gut post because one of the nicer features of my Carrera was the brakes, and one of the first things I noticed was this difference.

[tracer bullet]

Slotted and drilled can give better performance regarding the escaping gasses aspect, it is true, but most of us driving around town won't ever have normal rotors causing any issue in that regard. There's less contact to the pads but I'd bet most of us would never notice that either. Historically the drilled rotors could crack but the only people ever seeing that happen were tracking their cars and putting some serious use on their brakes, exposing weak spots.

I won't fault anyone for using slotted or drilled rotors, but would say they're pretty much just for looks on daily driving type cars.

The most noticeable performance increase would be from larger diameter discs and kits to move or replace the calipers accordingly. Or going from single piece to 2 piece and shedding some rotating weight. If weight's a thing, wheels and / or tires are usually a bigger bang for the buck but certainly both can be considered.

[Bimmerfun82]

Stopping power on the factory setup is very good. The M4 is so much heavier, and my M3 brakes were incredible to handle the 2 ton mass. If you are taking the car to the track ceramics would be best, I would imagine, with the M3/4. I wouldn't upgrade my wheels on the Z4, but if I were to spend the money I would probably go for an upgrade of the wheels for forged lightweight and possibly the exhaust.