Cross-Drilled or Solid rotors: The Bottom Line Answers
 

Ok, there has been a lot of static in the forum regarding this topic. I want to know the final facts.

Particulars:

* Car MB: 300E
* Driving style: Aggressive - daily speeds over 90 mph (driving in Europe) Heavy usage of the brakes.
* Keeping the stock brake calipers, and thus, the stock size rotors
* Considering high quality (chamfered) Cross-drilled and/or slotted rotors
* Have heard that unless you increase the size of the rotor, cross-drilling merely reduces frictional surface area, canceling any braking benefits
* Have heard that slotted rotors eat pads and are non-functional gimick
* Have heard that stock solids function well enough, provided you couple it up with a high quality pad (e.g., Metal Master...)

Ok ... enough debate! What are the facts here? Let's go to the Bottem Line please.

Can anyone clear this up - in a straight forward manner?

Thanks,
David

I cannot, or shall I say, I will not attempt to get into this debate, but I can state my observations.

I have a 94 E500 with stock calipers and I bought some cross drilled rotors from KVR Performance (www.kvrperformance.com) for my car. I run PBR Metal Master Pads. I went with KVR becuase they were the only people that had cross drilled rotors that were OEM sized, they also have slotted or a combination of both. I did not want to change out my calipers and what not. KVR rotors are chamferred. I do know a few others that run these rotors with not problems.

For the record, I have an agressive driving style and I drive at least 85-90 mph everyday on the highway, though I have been slowing down to about 80mph lately as this is the time of the year I collect tickets. :D

I have been extremely pleased with KVR. I turned Carl from Bergwerks (www.bergwerks.com) onto these and he checked them out before I purchased mines and he said they were all good. They used quality materials. You may want to contact him for some more info.

Here is a pic of mines, though it is not a good pic as it doesn't show the rotors that much.

http://www.nemonis.net/shanta/wheels/1.jpg

I installed cross-drilled/chamfered Brembo rotors front and rear on a non-MB car I had a few years ago. I used the car for Monte Carlo style rallying in So. Calif. that involved a goodly amount of high-speed back road and mountain driving. I was experiencing serious brake fade and rotor warping with the stock brakes. The Brembo's, coupled with Porterfield R4S pads at both ends and Goodridge stainless brake lines were like a night and day difference. No more fade; consistent, solid braking performance, especially in the wet; and no more rotor warpage. I have to give a lot of credit to the Porterfield pads. They have excellent braking response at all speeds, even when cold, they hardly dust at all and they last a ridiculously long time for a performance brake pad. They're pricey, but a bargain in the long run. I would highly recommend them. I'll be putting them on my 300E in the near future.

Gary

Love your wheels Shanta !
 

One other consideration is Cryogenically treated rotors. I know of one member here that tracks his car and has used OEM, cryo treated rotors with good results.

I have purchased, but not yet installed some OEM, cryo treated and slotted rotors. Still need to get pads and refinish / rebuild the OE Porsche-Brembo calipers on my 500E.

Shanta -
Do you have the Porsche-Brembo aluminum calipers?
I can't tell from the picture.

I have the stock 94 E500 system which is the SL 600 brake system in the front. I may future wise upgrade my rears to the SL 600 system also.

Thanks for the compliment on my wheels. :D

That's right, forgot you had a 94.

Re: Cross-Drilled or Solid rotors: The Bottom Line Answers
 

1. better traction improves braking....get bigger tires.
2. drilling holes in your rotors reduces total swept area.
3. heat build-up is not a problem for anything but sustained track racing.
4. drilled rotors look cool :cool:

Re: Re: Cross-Drilled or Solid rotors: The Bottom Line Answers
 

yep...that about covers it. especially point #1

With cross drilled rotors, whether or not you track your car. Eventually, they will end up like this. Notice, this are chamferred

http://www.2phast.com/badrotor.jpg

I run slotted & cryo-treated rotors (320mm off of 600SL). The slots I do for looks-as I understand it, the brake compounds nowadays don't off gas like the old ones, so slots or holes are unnecessary from this standpoint. From a performance standpoint, solid rotors should be fine.

Cryo - plain & simple: it works! I ran cryo'd rotors for 20+ track days, and they never cracked...I'd still have them on the car if I didn't destroy them with a couple of sets of EBC Reds(VERY aggressive on rotors). Due to time constraints, I replaced them with slotted/non-cryo'd rotors, and they're toast after only 7 or 8 track days.

I've been on my rear slotted & cryo'd rotors for 3 years now, and they look as-new (my 600SL rear setup rtemains in the box, as the current rear brakes are completely adequate).

LMAO, "hit" the apex is the right word, even if backwards!! :D

That is why if you want holes in your rotors, get holes that are cast into the rotor, and not drilled, that way when the rotors are cast, the metal aligns itself around the hole which is much stronger, another cause for that is getting water on your rotors.

Drilled rotors do look cool I have them on my 300CD with 560SEL front brakes. I am trying out ate power slots on 500E front brakes right now, I will see if they really do cut up pads.

If drilled and slotted stuff was a bad idea brembo wouldnt do it. Look at their GT kit you can choose what you want.

Take it easy,

omegabenz

I agree with you on the cast part of " cross-drilled " rotors.

I remember talking to a Brembo rep. one time & he stated to me, nothing pisses Brembo off more, than some " tuners " buying Brembo rotors, cross-drilling them and then selling the rotors for twice the original cost.
Of course when the rotor develops cracks, Brembo gets blamed for it. :eek:

Zimmerman rotors (cast) and textar (yellow box) pads. Best combo i've ever used.

Ditto for the rotors, but Mintex Red Box for pads.
Love it. ;)

on my 560SEL brake upgrade I have Zimmermann (xdrilled) cast? (possibly) rotors, and OE mercedesbenz brake pads.

Does anyone know if my rotors are cast or drilled? I bought them because they looked cool!

I could understand how brembo would be pissed if someone drilled their rotors, etc.

From my understanding,all Zimmerman rotors are (Cast) with holes which leads to a much longer life of the rotor.

Yes, Zimmerman's are cast.
When you get them brand new, have a look at the holes.
No drill marks there. ;)

You are right, I looked at mine tonight, the chamfers are even cast.

Do rotors have to be cryogenically treated before they are used? My rotors have less than 1000 miles on them.

Unless you are racing, or plan to abuse your brakes, I would not bother with it.;)

I cryo'd/frozen a pair of ATE PowerDiscs for the pre-1994 500E and a pair of Zimmerman rotors for the 1994 E500 (aka, 600SL rotors), and both are wearing very well with aggressive city driving with both Textar and Poterfield RS4 pads.

Cross-drilled is only needed for lighter-weight in the rotor. Again, you only want "cast" cross-drilled rotors.

BTW: Porterfield verified that "outgassing" doesn't happen anymore. Go with a solid-disc, esp. cryo'd.

Cross-drilled sure looks cool though. . .

:-) neil

Brembo's and Porsche rotors are cast with the holes already in place. Brembo does not make any components for Porsche, Porsche manufactures all of their components in-house.

You would think that these would be a solid reliable choice, well maybe they are for street use but on the track, all of the Porsche teams have stopped using OE Porsche cast holed rotors and are now using solid rotors.

Even the cast holed rotors are cracking in track use.

aka "perforated" :)

It seems like there is a gap in the English language for cast cross drilled rotors...Ill see what it is in German.

So the best thing is to CRYO Solid rotors, good to know.

But can rotors be cryoed after they have been driven used for 1000 miles.

Rotors with casted holes look cool!

Thanks again,

According to the Fountainhead's website no, because stress-cracks could have already developed, and cryo would only make them come out more.

:-) neil

If that was the case...then why would they cryo engine blocks and transmission parts. I would think that it would be the same problem.

Puzzled...

All parts can benifit from cryotreating. The earlier the part is treated, the better.

As stated before, cryotreating cannot fix micro stress cracks that have already begun, but it can slow down the rate of further cracking.

Ideally, the part should be cryotreated before any machining is done on it.

So to answer this question, you can cryogenically treat used parts, but you will not see the same amount of benifit as you would, if the rotors had been treated when they were new.

Cryogenic, Ion Beam, Shot peening, and anealling are all very helpful metal treatment processes but any time there are edges and diffrences in density (holes in metal) accross a surface it will be more suseptable to damage from stress risers. These are both thermally and mechanically induced shear stress accross the face of the rotor. Chamfering the holes attempts to disperse the heat loading during the transition in the rotor face rather than have a 90 degree transition. Also chamfering reduces surface area under the brake pad in addition to the loss in hole surface.

Not every vehicle or application is the same. A braking system that is well engineered as a system will lend itself to better performance for the target application. Replacing unmatched components will place you in the engineering seat and you will have to take the same risks when you change a component of an engineered set whether OEM or aftermarket.

In summary, do what works for you, whether you application demand is over all reliability, asthetics, performance, or racing.

etc, etc, etc.....

BTW, Hi George, haven't heard from you in a while on the 190REV forum.

Yes Even with The Factory Crossdrilld rotors I cracked them!

Then I had porterfield cyro treat them..NO more Cracks!

they're called "perforated" rotors in english.