Rotors: Vented vs. Cross Drilled/Slotted

I need to get some new rotors for my '94 E34 and I am faced with a larger selection than I anticipated.

I'm curious what kinds of experiences people have had with the "performance" rotors (cross drilled or slotted). And are they really that much better then the OEM vented rotors that came on the car. I know they look really cool but looks can be decieving.

The mechanic I have recently started going too, who specializes in Bimmers, Audi's, Mercedes and VW's, says he doesn't think there is much point in me getting them and that they prefer to use the normal vented rotors in his shop.


Your thoughts?

There is not much difference in performance, unless you get the $3000 sports set. In my opinion it all comes down to brake pads. The other thing are prices, you can get some quality rotors off eBay which are as good as OEM. Drilled ones look really cool, and they are one of the reasons why I'm getting a set of new rims :) Also from what I've noticed drilled/slotted rotors seem to wear pads slightly quicker than regular ones. That is why I put ceramic pads on my ride, they last longer and there is way less dust.

i haven't had any experience with them, but two popular choice are the ATE powerdisc and the Zimmerman crossed drilled. I assume the heat from the slotted rotors escape quicker.

You have to be pushing your car hard for the brakes to fade. In racing applications I'd say they help sure, on normal street driving, I don't think so. I've also heard the crossdrilled rotors wear out the pads faster than normal rotors. You can add e34 540i brake ducts also to help cool the brakes.

I'm going with the zimmerman cross drilled. There not that much more expensive than stock.

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Originally Posted by BigKriss

i haven't had any experience with them, but two popular choice are the ATE powerdisc and the Zimmerman crossed drilled. I assume the heat from the slotted rotors escape quicker.

You have to be pushing your car hard for the brakes to fade. In racing applications I'd say they help sure, on normal street driving, I don't think so. I've also heard the crossdrilled rotors wear out the pads faster than normal rotors. You can add e34 540i brake ducts also to help cool the brakes.

I'm going with the zimmerman cross drilled. There not that much more expensive than stock.

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I second the zimmerman cross drilled choice of rotors,i installed them with jurid brake pads,my driving is very demanding type,its been over a year and just recently i noticed that the pads got bit worn out.Never had any problems with that combination,and will continue to have the same set.

jj

I have heard a lot about EBC rotors that are dimpled and slotted and their "green stuff" and "red stuff" brake pads (green for street driving and red for racing). Have any of you guys heard much about these?

http://www.ebcbrakes.com.au/

i'm under the impression the reds are still street pads. I'm getting a pair of reds for the front soon. The yellows and blues are for racing.

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Originally Posted by Clay 94 530i

I have heard a lot about EBC rotors that are dimpled and slotted and their "green stuff" and "red stuff" brake pads (green for street driving and red for racing). Have any of you guys heard much about these?

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These are very common in the UK. Anyone with a modified "hot hatch" seems to go for EBC discs and green stuff pads. They seem to work well on the smaller cars and I've heard nothing but good write ups about the green stuff pads. Not too sure about the rotors, they look a bit cheap to me and I don't know how they perform on the bigger cars as i've only seen them on smaller ones. They say that the red pads are more suited to track use as they are a hard compound. Brembo do good replacement drilled rotors or slotted ones. I'd be interested to hear how they perform on the E34's.

Drilled or slotted. Visually a great impact, killer in breaking performance when the right rotor is used. Don' t go cheap on these ones or you' ll be sorry very soon. Cheaper, inferior drilled rotors such as Zimmermann are known to be cracking on the edges 9 out of 10 times due to the inferior materials used. A original BMW rotor will out perform these discs with eyes closed. If you want optics and performance, for a reasonable price, do buy EBC as the guys suggested. These have the drilled/slotted optics but are not fully drilled through resulting in not cracking under any circumstances.The metal used is heat trated meaning the material is heated up to temperatures you will never reach whilst breaking thus no bent rotors will hunt you.
We use thes on the track and sprint days too and are very pleased with braking, non fading and duarbillity. One thing, do not buy redstuff from ebc if your car has ABS. It will not funtion propperly as this pad is just too hard.

Unless your running your e34 on the track consistenly or shell out for racing quality equipment - drilled, slotted, smothered, covered, etc... brake rotors are a waste of money. If you want to upgrade your brakes and still be able to afford fuel, go with a set of 850i brakes (you'll need 16" rims min.)

Most of the drilled rotors out there crack at the drill points and actually have less surface area contact with the pads. Which means they perform worst than their OEM counterparts. They are all show and no go.

OEM rotors are stupid cheap (even from a dealer) and balanced not by adding weights but by shaving material from the rotor. Like I said, financially, it doesn't make sense to "bling" your rotors. If you want performance from your brakes, change the pad compound to something more aggressive (you'll buy rotors more often though).

BUT if you have to do something, buy the slotted set. No issues with cracking and maybe even some benefit for evacuating exhaust gases.

my 2 cents
-ashley

I have 9 years experience in cross-drilled and slotted rotors under normal street or heavy street driving. There are tremendous difference between cross/slotted and stock rotors under any braking condition. It is very evident. I used same pads going from cross-drilled to stock (because I was selling the car and didn't want to spend money for other people). The grab is weaker with stock rotor... feels like slight fading... doesn't have intense grab as cross/slotted rotors did.

Now I use only slotted wherever I can. It is worth every penny especially in summertime where heat is intense. I always use MetalMaster with slotted or cross-drilled. Now I am experimenting with ceramic.

I like the grab of metalmaster better than ceramic... ceramic feels more like regular pad but alot quieter than metalmaster under intense braking but with no fade. I think it is waste of time to use regular pads with slotted/cross rotors as most of you mentioned you can't feel any difference.

As for between cross and slotted... you can't tell that much difference in performance... cross might be slightly better but it is difficult to tell. For the 7 years I had that cross-drilled... never did it ever cracked... It was Zimmerman made in Italy. Only caution is do not wash car when hot... cold water and super hot rotor is sure fire way to warp it... possibly crack it if you went from highway to car wash immediately... as in automated. Again... never in that 7 years did it ever cracked on me and I even had the rotor cut once... However, cutting a cross-drilled rotor is not advised... it warp as easily as any cut rotor.

with semi-metalic lining on my 540i/a. i put about 16,000mi. on them & they are showing very little wear. i get a slight noise under harder braking. it has limited my brake fade greatly, but does still happen. they are a definite upgrade from the stock disks they faded very easily for me. maybe i am just to aggressive.
tim s.

Thanks for all of the replies! This has been a huge help for me. From what I have gotten out of everyone's replies it seems that the crossed drilled and slotted don't seem to be what I need. It sounds like for a lot of money I am just buying apperances and possibly problems if I don't spend a small fortune.

Right now I am trying to figure out which brand is best? Most of what I see for OEM parts are Balo and ATE. I have heard a little about both and price wise they are about the same any major differences that I should know about? I was also considering possibly going with the slotted ATE power discs for the front (a little bit of show/flash would be nice) and normal flat discs for the rear... would this be a bad decision?

Thanks again for helping a newbie out with all of his questions!

I recommends ATE PowerDisc... you are on the right track. Rear slotted is never an option so no big loss there. About 70% of the braking force is in the front so that is where you need it.

Ditto too over here too... same car. Extremely low wear on brake pads. I had PBR MetalMaster with my crossdrilled for 6 years and about 60,000 miles on it with lots of meat to go. I am not easy on brake either... I always brake hard to "feel" my brake clamp down on the rotors... sounds like a mini airplane braking after landing.

Slotted rotors are quieter than crossdrilled.