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BMW_M52_M20
05-22-2002, 07:55 PM
Well, I have seen the cross drilled rotors around and they are really the same price as what the stealer is charging. Does anyone find any advantages to using them or is it really just for apperance?
Thanks
Jay
:D

BigD
05-22-2002, 09:04 PM
Do you track your car? If no, it's just a stupid waste of money. I've been told drilled rotors warp. Now slotted rotors on the other hand...

BigD

BMW_M52_M20
05-22-2002, 09:29 PM
No, I don't track, thought of getting into it.
Regular rotors warp too. I thought that with holes in them, the heat could escape quicker and improves the warping problem?
Maybe I am wrong.
Jay

BigD
05-22-2002, 09:33 PM
Cooling probably helps but the biggest thing is the fact that you are drastically weakening the structural integrity. I'm sure the really expensive, high end drilled rotors don't have this problem because they are cast and heat treated after they are drilled and the are made with high quality metals. I'm sure you get what you pay for.

Note that F1 and the likes don't use drilled, they use slotted.

BigD

Gamite
05-22-2002, 09:44 PM
I wanted to get cross drilled too, but someone told me (empowerd) that they crack easily, especially in the rain.

When you drill into metal you naturally affect the structural integrity of the object. They might be fine in regular conditions, but say its raining, and you break real hard, the rotors heat up, lotsa stress, then you go through a big puddle and "CRACK" because of the instant hot to cold reaction.

They probably wont crack a lot, but enough to do some serious wear and tear on your pads.

SickFinga
05-22-2002, 11:16 PM
read this thread, a lot of interesting info on cross drilled rotos

http://www.maxbimmer.com/forums/showthread.php?s=&threadid=2620

bimmersport
05-22-2002, 11:19 PM
I have them on my car and no problem so far (knock on wood).*th-up*

Slowered318
05-23-2002, 01:31 AM
IMO slotted and drilled rotors are a load of &%^* i have brembo's on my car and they don't break any harder then the factory ones.. If you want superior breaking power you need to upgrade to a larger rotor/caliper, if you just want the look go for it.. just make SURE to ALWAYS torque your wheel nuts because the slotted rotors are can warp easyer then factory ones.

I Actually heard something about brembo coming out with a new kit that are heat treated and slotted and they come with pads that are mated to the rotors.. not sure about this but it's worth asking someone you can trust. A lot of speed shops are more then happy to say whatever it takes to sell you a break kit.

Daydream///M3
05-23-2002, 02:45 AM
Im going to order a set of 4 from gino at eliteauto
Brembo Crossdrilled Rotors Cadmium plated
Jay... e-mail me and Ill help you out AGAIN..............:P

djcontra
05-23-2002, 10:26 AM
I'm getting a pair of cross drilled brembo rotors from that guy Gino for $80 a piece or less. I need them, and oem rotors or aftermarket regular ones would cost me $70 each anyway, so i might as well get something better. The holes not only cool the rotor but also increase it's structural integrity. Airplanes use metal beams with holes drilled in them to make up the frame. The holes make the frame lighter AND stronger. I can back this process up with proof if you want as well =)

I'm going to take the chance anyway, my rotors are deadly thin, and i glazed and warped them from high speed stopping on the wasaga trip. My mechanic machined them for $30 to last me until i can get the replacements. Luckily while i was watching him, i learned how to replace the rotors myself, along with my pads now =)
(at least on the front end of the car heheheh)

M3Pilot
05-24-2002, 01:05 PM
Originally posted by 318iSwim
IMO slotted and drilled rotors are a load of &%^* i have brembo's on my car and they don't break any harder then the factory ones.. If you want superior breaking power you need to upgrade to a larger rotor/caliper,

Bigger brakes won't stop you any quicker, so if that's what your expecting then your going to be dissapointed.

It all to do with the mass of the car and remember you can't
out brake the tyres!!!!!!!

GR8 Ride
05-24-2002, 02:00 PM
Originally posted by djcontra
I'm getting a pair of cross drilled brembo rotors from that guy Gino for $80 a piece or less. I need them, and oem rotors or aftermarket regular ones would cost me $70 each anyway, so i might as well get something better. The holes not only cool the rotor but also increase it's structural integrity. Airplanes use metal beams with holes drilled in them to make up the frame. The holes make the frame lighter AND stronger. I can back this process up with proof if you want as well =)



Holy cow, what an absolute piece of BS!

Cross drilled rotors do absolutely nothing for cooling; the ability to cool a metal surface depends on surface area, of which you're going to reduce by drilling holes in the rotor.

Secondly, how can you possibly increase structural integrity by removing metal that was cast in place? Nope, try again, it doesn't work that way. By drilling holes in rotors, you're actually creating the opportunity for spider cracks to develop, and potentially cause the rotor to fail. Been there, done that, had it happen to me.

Absolutely NO serious race team in the world uses cross-drilled rotors; slotted yes, x-drilled, never.

Cross-drilled rotors are for guys who spend their time at car shows, and not on the race track. If you're not planning on driving your car on the track, then go ahead and run cross-drilled rotors; it's not likely to cause any problems beyond accelerated brake pad wear.

If you're running them on the track, be prepared to replace rotors every year or sooner, as you're likely to see spider cracks running up and down your rotors. If one of those cracks reaches the edge, you're about to split a rotor, and potentially cause a MAJOR incident.

Also, cross-drilled rotors generally have LESS braking efficiency, due to the fact that they have less surface area for the brake pad to grip.

Guys, didn't we just discuss all of this a few weeks ago, and still nobody learned anything?


Pat

SickFinga
05-24-2002, 04:49 PM
Originally posted by M3Pilot


Bigger brakes won't stop you any quicker, so if that's what your expecting then your going to be dissapointed.

It all to do with the mass of the car and remember you can't
out brake the tyres!!!!!!!


hm then explain why m3 got bigger brakes than non-m3 cars?

got torque?
05-24-2002, 04:50 PM
Like Pat said, we've been over and over and over this one.

Cross drilled rotors do not run cooler.
Cross drilled rotors are prone to cracking.
Cross drilled rotors will NOT stop your car faster.
Cross drilled rotors wear pads out quicker.
Cross drilled rotors are not even endorsed by the engineers who make and sell them.
Cross drilled rotors are for looks only.

Tell me why they're a good idea again???????

If anyone can provide REAL PROOF and FACTS to negate what Pat and I have said above, speak up.

BTW, the aircraft construction one doesn't cut it. Not even close. Aircraft frames are not subject to friction or heat like brake rotors.

Kip
05-24-2002, 07:43 PM
Cross drilled is better for when the brakes are applied, as heat can escape more easily. Not cooling in general.
I wouldn't get cross drilled again... they warp easily (so be careful when you are getting your car washed.. try to avoid washing with brakes still hot hot hot)

Slotted is better.. and I do notice a difference between braking with normal and slotted/crossdrilled. Of course larger rotors would do the job even better.

And well.. it definitely looks pretty damn good. haha..

GR8 Ride
05-24-2002, 10:55 PM
Originally posted by Kip
Cross drilled is better for when the brakes are applied, as heat can escape more easily. Not cooling in general.
I wouldn't get cross drilled again... they warp easily (so be careful when you are getting your car washed.. try to avoid washing with brakes still hot hot hot)

Skipped high school physics again I see....


How is it that heat escapes from a cross-drilled rotor more efficiently, when you're APPLYING the brakes?

As you apply the brakes, the system is generating heat (friction between the pad and rotor). However, with the portion of the rotor which isn't in immediate, direct contact with the pad being the only portion which can shed heat, it does so based on surface area (from the metal to the surrounding atmosphere, or other surfaces in contact with it). The more surface area, the greater the ability to shed heat.

When you cross drill rotors, you're losing effective surface area, except in the VERY rare case when using a SOLID rotor, instead of a vented one. I can't picture a single, performance car being built today with solid front rotors, especially not on a BMW.

As well, cross-drilling reduces the effectiveness of the vanes in a vented rotor to move air through the rotor, and help to cool both it and the caliper.

Pat

BigD
05-24-2002, 11:08 PM
Yeah, DJ my man, the structural integrity thing was a pretty serious fistfull of BS. :huh?: :P Airplanes' ribs, formers and beams have "lightening holes", and serve the purpose that the name implies. They are certainly not there for structural integrity.

Drilled rotors are not necessarily a structural failure risk if they are heat treated AFTER the bloody holes are drilled and high quality metals are used. If you're paying 80 bucks per rotor...well, you do the math on the odds that they are of such quality. You know, just because it's Brembo doesn't mean it's their best product.

And while tires have their limits, stock brakes certainly don't touch them, especially with 240+ series ZR tires. I don't know if you know him but Bruno with a black 535 put in 850 brakes and well, lets just say I want them! :eek:

BigD

M3Pilot
05-25-2002, 06:53 AM
Originally posted by SickFinga



hm then explain why m3 got bigger brakes than non-m3 cars?

I just can't believe how often this subject come up on all the forums I visit, someone should just sticky it!!!

As to why the M3 has bigger brakes it's so they are less likely to fade as there is a greater surface area to dissapate the heat generated.

Bigger brakes= less fade

Brake size is relitive to the mass of the car. With a bigger car you need bigger brakes becasue of HEAT, that is what stops the car. Friction between the rotor and pads, creats heat, you stop.

As soon as the brakes lock you are PAST the max stopping. You want to be close to locking them up this gives you the best performance.

Smaller brakes will also stop you the same, how ever they will not work as long. Of course too small and they will over heat real quick and fade.

Yes, tires make up most of the stopping power. If you want to stop in less distance, get sticky tires. You can NEVER out brake the tires no matter how big the brakes are.

Another reason for NOT going to bigger brakes..
1. A LOT more wight on the tires, slower 0-60
2. it puts a lot more stress on the spindle and tie rods, they don't last as long.
3. Depending on the kit there is not the varity of pads and rotors.
4. You can't run the stock wheels.
5. THEY COST SO DAM MUCH!

Hope this answers your questions,
Thank you and goodnight :D

Gamite
05-25-2002, 08:45 AM
Originally posted by Bad-Karma
Cross drilled rotors do absolutely nothing for cooling; the ability to cool a metal surface depends on surface area, of which you're going to reduce by drilling holes in the rotor.


This paragraph is contradicting itself. Since by drilling holes you are increasing the overall surface area of the disk. (I'm not talking about the surface that touches the pad but the overal surface of the object)

Consider you have a huge cube, and if you cut a huge hole out of the cube, then you increase the surface area of the cube because the sides of that hole are now contributing to the overall surface area of the cube. Same concept with the rotors.

But also the holes are so small on the rotor the surface area wouldnt be much larger.

Now, I dont know how much more this would be able to cool the rotor, but IMO the risk of the rotors cracking is too great, and you wont get any additional stopping power, you might get less cuz there is less metal being in contact with the brake pad.



I'm officially sick of saying "surface area"

GR8 Ride
05-25-2002, 03:29 PM
Gamite,

As I've said before, in the case of a solid rotor (ie, your solid cube), then you could potentially create more surface area.

This is one of the reasons I have less of a problem with cross-drilled discs in the rear of cars, as many rear discs are solid, and not vented.

However, in a vented rotor (which has a hollow center remember...), you have TWO sides to EACH HALF of the front rotor, both of which comprise a larger surface area than the relatively thin walls of the rotor.

Pat

Gamite
05-25-2002, 07:31 PM
I see what your saying, and it might compromise the venting. But depending on how thing the wall is and how large the diameter of each hole, you could still be increasing surface area, I'm not taking any sides as to which x-drilled is better or not, just wanted to state that fact.

I guess we could get the exact diamters, thickness of the plates and diamters of the holes, we could figure out if in fact it was more surface area or not, but I believe we're on the same ground so its not really necessary.

Although, this would would be good to prove to anyone else.

got torque?
05-27-2002, 04:53 PM
While there is some truth to the fact that surface area CAN help to dissipate heat, 99.9% of people running cross-drilled rotors do not have the technology in place to benefit from the extra surface area.

Unless you have brake ducting that is SEALED via a purpose-built backing plate to the backside center of your rotor, so that you are forcing air into the centre of the rotor toward the outside (and therefore out some of the cross-drilled openings), you are not realizing ANY benefit from those holes.

Even then, it is difficult if not impossible to get air to travel into/through the holes, because of how the rotor is spinning, and the way that cooling vanes draw air through the rotor.

The brake rotor with the greatest mass , all other parts being the same, will run cooler, which means that the system runs cooler. A cool brake system is an effective one.

Cross drilled rotors are for looks ONLY. End of story.

WASABI
05-28-2002, 11:18 AM
I'm gonna be changing my front rotors soon (hoping this weekend),and was gonna go with the X-drilled (i was gonna buy charlie's after he does the big brake upgrade). my car is is strictly street driven, and didn't think would benefit from X-drilled rotors. so now,

my question is, does Brembo make regular style rotors, not X-drilled or slotted? I just called the dealer, they want $110 each for the OEM front rotors.

GR8 Ride
05-28-2002, 02:34 PM
Brembo makes front rotors, and they should be cheaper than the BMW stock ones.

Lakeside motors is where I've gotten a few sets of them, but they are probably not the only option.


Pat

WASABI
05-28-2002, 03:52 PM
Originally posted by Bad-Karma
Lakeside motors is where I've gotten a few sets of them, but they are probably not the only option.


Pat

please, i'd like to know what other options a have besides BMW and Brembo. thanks

GR8 Ride
05-28-2002, 04:16 PM
Brembo makes plain, ordinary rotors for BMWs. They're about the cheapest rotors you can get for E36s.

Zimmerman also makes rotors, and these are basically the premium, factory type rotors for BMWs (that, and the OE ones).

Zimmerman has both drilled and plain rotors.


Pat

SickFinga
05-28-2002, 05:19 PM
as far as I know BMW offered a cross-drilled rotors for E36 m3 as an option

SickFinga
05-28-2002, 05:28 PM
yeah not eveone uses Porsche brakes, but some bimmers do use em.
Randy has Porsche Boxter S calipers on hit e30
Porsche calipers fit e36 m3 and e46 bimmers. I dunno why they use it, but It looks really nice.

KIRASIR
05-28-2002, 05:37 PM
I am pretty positive that cross-drilled rotors were never an option by BMW directly. It could've been offered by a dealer as an after market addon. ETK contains no cross-drilled rotors p/n's for e36 M3.

Serge

Originally posted by SickFinga
as far as I know BMW offered a cross-drilled rotors for E36 m3 as an option

SickFinga
05-28-2002, 07:02 PM
Originally posted by KIRASIR
I am pretty positive that cross-drilled rotors were never an option by BMW directly. It could've been offered by a dealer as an after market addon. ETK contains no cross-drilled rotors p/n's for e36 M3.

Serge



I'm not sure, but on ebay someone was selling m3 and in the ad it was saying car was never abused blah blah blah, no mods, and cross-drilled is the option.

and then on dtmpower ppl discussed the car and agreed that it was original bmw rotors.

GR8 Ride
05-29-2002, 12:15 AM
On the E46 M3 from Europe, yes. In the US, the E46 M3 doesn't get cross-drilled rotors.

In Europe for the E36 M3, the rotors were two-piece, floating rotors, not offered as an option on the US Spec M3s.

There IS a part number for these, and it's quite common to install these rotors instead of the solid US rotors.

Otherwise, there was no factory, or BMW sanctioned option for E36 M3 cross-drilled rotors.

As to Porsche calipers fitting BMW, they are by no means a direct fit. Porsche calipers are generally leading edge, while BMW calipers run on the trailing edge of the rotor. Completely new brackets need to be fabricated, along with some custom work to get the Porsche brakes fitted to E30s and E36s. Movit' has a kit for both the front and rears on the E36, using various Porsche calipers / rotors.

It's BIG dollars, and not something that I would consider a worthwhile upgrade.


Pat

SickFinga
07-04-2002, 11:16 PM
Originally posted by KIRASIR
I am pretty positive that cross-drilled rotors were never an option by BMW directly. It could've been offered by a dealer as an after market addon. ETK contains no cross-drilled rotors p/n's for e36 M3.

Serge




Finally I found. Yes corss0drilled rotrs were optional
here
http://home.att.net/~stl_don/euro_rotors.htm

Gamite
07-05-2002, 08:16 AM
Damn, I didnt quite understand what Pat meant about the "floating" rotors, but after seeing the pictures I understand, I've never see anything like it, either because its rare or I just never noticed it before. Thats gotta increase airflow by far. Facinating!


The rear's arent solid, is it like that on all M3's?

got torque?
07-05-2002, 09:59 AM
Floating rotors do not run cooler via improved airflow.

"Floating" rotors mean that the rotor is attached to a central "hat" that is typically made of a different material such as aluminum. This is obviously different that a one-piece cast iron rotor that bolts up to the hub.

They run cooler because the aluminum hat dissipates heat and prevents heat transfer into the piston/caliper assembly. As a result the entire system runs cooler.

GT

Gamite
07-05-2002, 02:40 PM
Originally posted by got torque?
Floating rotors do not run cooler via improved airflow.

"Floating" rotors mean that the rotor is attached to a central "hat" that is typically made of a different material such as aluminum. This is obviously different that a one-piece cast iron rotor that bolts up to the hub.

They run cooler because the aluminum hat dissipates heat and prevents heat transfer into the piston/caliper assembly. As a result the entire system runs cooler.

GT

I KNEW someone was gonna say that, but heat transfers faster through solid contact.. So it makes sense.

djcontra
07-16-2002, 12:12 PM
Well regardless of the downsides i got brembo cross drilled rotors installed today. I bought them at Elite Auto which is just north of my usual mechanic. They have a break-in period of about 800km so i have to be light on the pedal for that time until the new brake pads set in.
All in all, i think they look superb, and feel wonderful when braking and were about the same price i would have paid for regular oem rotors. I was in desperate need as my front rotors were wearing very thin and my braking was absolutely horrible! i'm glad i did this upgrade/replacement because i can now truly feel safe behind the wheel.
I'm going to have elite auto attempt to lower the back end of my car tomorrow to get the drop i want. Nobody i've ever brought my car to can figure out my Sachs coilover suspension in the rear, but after seeing so many racing porsches in the workshop of elite auto, i just had to ask if they knew how, and Gino said that he should be able to lower it for me. yay! :P

i'll take some pics if anyone wants to see them

djcontra
07-16-2002, 12:19 PM
ah what the heck
here's some pics
:)

djcontra
07-16-2002, 12:21 PM
one more
:eek:

GR8 Ride
07-16-2002, 12:46 PM
Originally posted by SickFinga



Finally I found. Yes corss0drilled rotrs were optional
here
http://home.att.net/~stl_don/euro_rotors.htm

Those are the European E46 (not E36) M3 floating rotors.

The E36 absolutely did not have cross-drilled rotors as an option.

And I STILL stand by my point; just because Ferrari, Porsche, Lambo etc have factory cross-drilled rotors, does mean that they provide ANY improvement in braking torque whatsoever.

If you talk to the engineers at Porsche and the Marketing guys at Porsche, you'd get two very different answers as to the benefits of cross-drilled rotors.

The Marketing guys win that battle; cross-drilled rotors look better, and better looks help sell more cars.


Pat