[Camman]

So I will be looking at purchasing some new rotors for front and rear soon. I don't know what rotors I currently have but I'm running akebono pads in the rear and brembo pads in the front.

I have ordered akebono pads for the front and rear because I love how the akebono pads have virtually eliminated the dust on the rear and I hate the amount of dust the brembo's create on the front. The brembo's stop well but I don't mind losing bite and performance if it means eliminating dust.

Now, I want to know what rotors would work best for me. I don't track the car but I am a spirited driver. I love the look of drilled and/or slotted rotors but I don't want to run into problems later down the road. Slotted rotors sounds like the safest option if I want the cool look but keep the reliability. But will drilled rotors still be reliable if I only do street driving?

Or should I just stick with blank vented rotors?

Also what are some brands I should look at. Is ECS an okay option or should I stay away from them? I've seen mixed reviews on them

Thanks

[dhanni848]

I have read some posts like this a few times, and I am no expert at all but will let you know what I have read.

Blank rotors - actually give the most stopping power since you have full contact with pad and rotor. Track cars, from what I have read, use these.

Drilled - says it releases the heat from the pads easier through the holes, but less surface area touching. I have drilled just for looks, that is all. When I moved from blanks to drilled my braking became a bit smoother, not so touchy as factory.

Slotted - release heat through the slots again less rotor touching pad. Wears your pads out faster since the slots almost cut into them. Had some on my wife's car and hated them. They were loud too. I will never get slotted again.

Again any of these moves unless they are specific applications of what you want are for looks only! If you want full brake power get some factory blank rotors.

[mike-y]

for a street car, it doesn't matter much, just get what you like.

That said, I've seen drilled rotors crack during track use, so personally, I always run blanks. I just get the centric premium rotors - they are cheap, and the rotor hat is painted black, so it won't get that rusty film on it.

[jonluc88]

Originally Posted by mike-y

for a street car, it doesn't matter much, just get what you like.

That said, I've seen drilled rotors crack during track use, so personally, I always run blanks. I just get the centric premium rotors - they are cheap, and the rotor hat is painted black, so it won't get that rusty film on it.

+1 on that. I have Stoptech slotted and HAWK HPS 5.0 all around and I loved them. There is no noise when braking and it stops like a champ.

Honestly, slotted rotors are really for looks but the pads will make a huge difference.

Good luck man!

[Tom Droze]

I too am shopping for new pads and rotors, so I'm going to tag along if you don't mind.

[Cloud9blue]

Slotted rotors bite harder, but generate bit more noise during cruising and hard braking. For street use, the benefits are minimal though.

Akebono pads have fitment problem at the front, as they tend to get loose after awhile and clunk around in the caliper (doesn't harm performance, but annoying as hell for a supposedly quiet street pad). It has been reported by multiple people on this car, including me.

[avocet]

I find this info useful:
http://www.zeckhausen.com/How_to_sel...ake_rotors.htm

[CantCatchMe]

For street use, slotted all the way.

[Tom Droze]

Is there any benefit to Cryo treated brake rotors?

[avocet]

I cribbed this from a guy(username chris_seven) over at a pelicanparts porsche tech forum. Pretty sure his head is pointy:

Cryo Rotors
Deep cryogenic processing permanently refines the grain structure of metals at the atomic level. Carbon particles precipitate as carbides into a lattice structure and fill in the microscopic voids. This creates metallurgically improved and stabilized rotors that have a denser, smoother surface. As a result, you reduce heat and wear on brake rotors and pads.

I just don't like this explanation and unlike some of the other posts state I think the science is very dodgy.

Most rotors are manufactured from a Pearlitic Grey Cast Iron and this means that the normal benefits of deep cryopgenic treatment - which is the removal of residual austenite just aren't appropriate.

To say that lower temperatures fills in voids is a bit of a stretch.

One of the most significant dislocations present in the crystal lattice of most metals is a 'vacancy' dislocation and these are mobile and will diffuse in the structure depending on tempertaure. It is possible for the number of mobile vacancies to reduce but the vacancies would need to migrate to regions of high energy within the lattice such as a grain boundary and this action is very unlikely at low temperatures.

Diffusion of atoms in a lattice are usually governed by an Arrhenius Equation which is exponential with respect to temperature.

The creation of a mobile vacancy is generally related to atoms not being correctly positioned within a lattice. The atomic vibrations caused by temperature will mean those unfavourably positioned will move out of the lattice and cause a vacancy.

A metal melts when approximately 7% of its structure is made up of mobile vacancies - this is true for virtually all metals and unless they are superheated they do exhibit significant crystal order just above their melting points.

This simply means that when a metal is cooled down to cryo tempertaures the number of vacancies reduces. When it warms back up again they reappear.

I do not believe that a cryo treatment can 'freeze' the number of vacancies present in a lattice and maintain them as temperature rises and no electron microscopy has ever been presented to prove this point.

"There is also a theory which states that the atom to atom spacing in a crystal structure has an ideal distance where the bond energy is at a minimum. Reducing the temperature allow this spacing to become more even and closer to ideal, creating a better crystal structure."


This is also a problem if we look at the basic physics:

G=H-TS So if the crystal structure is more ideal, there must be a reduction in G.

But there will be no change in H, since there are no reactions occuring at this low temperature, and no change in S (since its still pearlitic iron).

This means that there is no permanent change from lowering T to a small value, then after X time raising it to 293K again.

The statement is made that cryo treatment increases density so that means the rotor must shrink. So how much does the density increase and therefore how much does it shrink? The industry never seems to quantify these remarks or do they all think we won't understand?

Finally carbide precipitation is also bit of a leap of faith. It has been shown that in tool steels Eta carbides can be preciptated following cryo treatment.

The theory is that the solubility of certain solute atoms reduces at low temperatures. Carbides can't form at these temperatures as diffusion is too slow but they do form as temperature rises.

There is good X Ray diffraction evidence that Eta carbides are present it tool steels but these type of carbides are generally not present in cast iron other than as primary carbides which are entirely stable and form during cooling.

There is no X Ray diffraction evidence presented to show that this mechanism exists in grey pearltic cast irons.

To say that carbon particles precipitate as carbides is interesting. For carbon to become a carbide it must combine with another element - usually metallic.
There is never any statement of which carbide is formed. To form a carbide would also mean in general terms that the activation energy needed to form the carbide would have to be supplied and this is not readily available at -300 degF

There are carbides present in Cast irons but they are normally primary carbides and are are formed in the melt and during the early stages of solidification.

My conclusion is that there must be a benefit in cryo treatment of rotors as too many people say they have gained an improvement but the Science is flakey (no pun intended) and like most of these type of processes is a bit over sold.


It is aso a pity that there is little or no published data in terms of wear rate, heat transfer rates etc. The evidence offered is mostly apochryphal and consists of statements such as 'life is three times better etc.

[Fundguy1]

Blank is good street.

Drilled is mostly for looks. They Crack more easily.

Slotted allows built up gases to escape. Usually less fade and as good or better stopping power.

I have drilled and slotted stoptech because I like the look and I don't track it. If I did I'd have just slotted.

I don't notice any additional noise.

Probably more dust than blanks but I changed pads at the same time so I can't confirm.

[mojobmw_e90]

I have tried both on a daily drivin car and I realized that they all sucked compared to oem stuff. Tried hawk pads with stop tech slotted, stoptech drilled and I like the oem stuff the best. Best bite and most importantly no steering shake when braking

[Cloud9blue]

Originally Posted by Tom Droze

Is there any benefit to Cryo treated brake rotors?

Waste of money.

By the way, OEM is still the best feeling street pads from my experience.

[elh0102]

Given your use, the type of rotor will make no difference in performance. Smooth rotors require one less machining process, so one less chance for error. Assuming you buy good quality rotors, for street use, it's then all in the pad. You can get some very low dusting, quiet pads that give up very little in performance for street use. Stay away from high temp track pads, as they will never get hot enough to either perform well, or stay free of material deposits on the rotor.

[Camman]

Thanks for all the replies. Guess I have some thinking to do. Sounds like I can go any route but blanks will be the safest and most reliable route for street use.

[Tom Droze]

Originally Posted by Camman

Thanks for all the replies. Guess I have some thinking to do. Sounds like I can go any route but blanks will be the safest and most reliable route for street use.

As you saw from my previous post, we are in the same boat with regard to brake rotors. I can tell you this, I've done two tracks days and the stock brake pads and rotors performed very well. My only mods to the brakes thus far are brass brake caliper guide pins, Ate Type 200 brake fluid, and stainless steel brake lines (which did very little). With the research I've done over the last several days I'm leaning towards either the Zimmerman cross drilled rotors or the slotted rotors from Turner Motorsports. It is my understanding that Zimmerman is the brake rotor supplier for BMW--hence OEM quality. I'm a bit less decided on the brake pads but I'm liking what I have been reading about the Hawk Street 5.0 brake pads. I haven't ruled out OEM brake pads either. I have new APEX ARC-8 wheels so I want a brake rotor that is a bit more pleasing to the eye but functions well also. For me, I am less concerned about price and I am more concerned about quality.

[Cloud9blue]

Originally Posted by Tom Droze

As you saw from my previous post, we are in the same boat with regard to brake rotors. I can tell you this, I've done two tracks days and the stock brake pads and rotors performed very well. My only mods to the brakes thus far are brass brake caliper guide pins, Ate Type 200 brake fluid, and stainless steel brake lines (which did very little). With the research I've done over the last several days I'm leaning towards either the Zimmerman cross drilled rotors or the slotted rotors from Turner Motorsports. It is my understanding that Zimmerman is the brake rotor supplier for BMW--hence OEM quality. I'm a bit less decided on the brake pads but I'm liking what I have been reading about the Hawk Street 5.0 brake pads. I haven't ruled out OEM brake pads either. I have new APEX ARC-8 wheels so I want a brake rotor that is a bit more pleasing to the eye but functions well also. For me, I am less concerned about price and I am more concerned about quality.

You guys must be real easy on brakes to make stock pads last multiple track days. Mine was toast after 3 sessions the first time I took the car to track.

[Tom Droze]

Originally Posted by Cloud9blue

You guys must be real easy on brakes to make stock pads last multiple track days. Mine was toast after 3 sessions the first time I took the car to track.

It might be because I like to keep my foot on the gas and not the brake!

Settle down I am just kidding. But seriously, both tracks I was on for the track days were described as being "brake friendly" by the instructors.

[mike-y]

Just another perspective on rotors. I've never seen a blank rotor fail. Not to say it's never happened, but I've only seen a few rotors fail, and they were all cross drilled rotors on cars running at the track.

I used to run the cheapest blank rotors on my honda which was tracked 6-10 times a year. They were about $16 each from autozone (LOL). I used to run carbotech track pads with them, and they'd get so hot, the rotor hubs would turn purple after the first few run sessions.

Never had one fail. I'd just replace them every year because they were so cheap, but I never had the need to buy a brand name rotor because the $16 ones held up just fine under lots of abuse. So for a daily driven street car that will see little or no track time, I would just get cheap rotors.

pad compound makes way more difference than any rotor would anyway.

[Cloud9blue]

Originally Posted by mike-y

Just another perspective on rotors. I've never seen a blank rotor fail. Not to say it's never happened, but I've only seen a few rotors fail, and they were all cross drilled rotors on cars running at the track.

I used to run the cheapest blank rotors on my honda which was tracked 6-10 times a year. They were about $16 each from autozone (LOL). I used to run carbotech track pads with them, and they'd get so hot, the rotor hubs would turn purple after the first few run sessions.

Never had one fail. I'd just replace them every year because they were so cheap, but I never had the need to buy a brand name rotor because the $16 ones held up just fine under lots of abuse. So for a daily driven street car that will see little or no track time, I would just get cheap rotors.

pad compound makes way more difference than any rotor would anyway.

I have seen brand new OEM blank cracked all the way through. It all depends on the car (weight vs hp) and the track layout.

Cheap rotors on a car as heavy as ours and making +400hp with FBO is just asking for trouble.

For street, I would just go get some rotor with good rust proof coating though.

[WreckerX5d]

Is there any type of rotor that's best against warping? My car seems to warp rotors. It might just be the way I bed them though. I was thinking of going with the drilled ones for that reason.

[Cloud9blue]

Originally Posted by Wrecker335d

Is there any type of rotor that's best against warping? My car seems to warp rotors. It might just be the way I bed them though. I was thinking of going with the drilled ones for that reason.

Check your wheel bearings and brake caliper guide pins and bushings. It is not right if you have "wrapped" rotors one after another with just street driving.