zimmerman x drilled & PBR ultimate ceramic

[gazellebeigem3]

anyone used this stuff? cheap prices, just wondering if its junk

[Dave]

PBR ultimates (or Axxis as they are also known) are great pads. Dusty as hell, but nice bite. Excellent aggressive street pads. Could use them for auto-x or light track stuff too.

The rotors, I can't say as I have no personal knowledge. I hear bad things.

[gazellebeigem3]

thanks dave, do you know what the issues are? quick to warp?

[Dave]

thanks dave, do you know what the issues are? quick to warp?

Rumor has it they crack. Again, I have no first hand knowledge.

[rwh11385]

SWEET. cross-drilled rotors! decreasing surface area = rockin' mod!!


my advice is buried in there somewhere...

[Dave]

FWIW - i use stock blanks. el cheapo to replace if they go bad. Charlie says the same thing. He knows better than me.

[Jand3rson]

I've heard a lot of good things about ATE Powerslots on the front, and I'd reccomend Brembo OE replacements for the rear. Cross-drilled rotors (on cars like these) are just a cosmetic thing, and are known to crack among other cons to them. Powerslots are cheap, as are the Brembos for the rear.

As for the PBR pads, like Dave said, dusty as hell but good bite. I've heard most of the good things about pads from EBC GreenStuff, low dust and good stopping power.

[rwh11385]

Cross-drilled rotors (on cars like these) are just a cosmetic thing,

make that PERIOD, are cosmetic...

[Jand3rson]

make that PERIOD, are cosmetic...

Even the ones that come on cars like much mor exepensive/faster cars like Porsches and Ferarris? I know they are a totally different makeup and are much larger, but are they still not as effective?

[gazellebeigem3]

i should clarify i am looking for a set up for m3 brakes. Powerslots are 133 each, or i can get the zimmerman set up (rotors, the pbr pads, and sensors for 350 bucks shipped. i think i may go this route and if i have problems go back to oem rotors

[rwh11385]

Even the ones that come on cars like much mor exepensive/faster cars like Porsches and Ferarris? I know they are a totally different makeup and are much larger, but are they still not as effective?

yes. i can't find the damn thread on bimmerforums about it, but you can read up here: http://forum.miata.net/vb/showthread...=cross+drilled

You never see cross drilled or slotted rotors on race cars, only on high end consumer cars for marketing purposes (people will believe that the slots and holes will cool the brakes down faster and increase stopping distance signifiicantly while not sacrifing long term logevity)

Why are they on Ferraris? Cosmestics. And people expect them... Do you know there is a street version of the a Ferrari with cross-drilled rotors, while the track version has blanks? (from the ghost Bf.c thread)

And Porsche gave reason for its drilled rotors as they help in wet braking while giving up some performance in the dry. That I will believe is true and you can find support it helps in weather braking. But it alludes to decreased performance in the dry.


Let's go to Brembo's site, http://www.buybrakes.com/brembo/faq.html#q22:

Why use drilled or slotted discs?
Drilling or slotting discs aids the disc in several ways:

The edges of the slots or holes continuously clean and refresh the pad surface as well as providing increased brake "bite". Additionally, they prevent gasses from collecting between the pad and disc interface.
The disc is lightened, thereby decreasing its rotational inertia.
Improved ventilation increases the disc's ability to shed heat, resulting in cooler operating temperatures

This "cleaning" effect can be had with ATE powerdiscs, if you wish to spend the $. I've never had an issue with initial bite, and will use my Powerdiscs and see if I notice any difference... cheap enough experiment for a $30 used pair...

The disc is a heatsink. Decreasing its weight decreases its effectiveness.

See 2nd line. It may have holes to aid ventilation, but the mass is reduced. Also, swept area decreases because now there are holes in it.

Regardless, backing plates and cooling ducts should solve almost any fading problem if you are tracking or racing, on stock disks, for most people.

And a point brought up is that modern brake pads won't really require or benefit from a drilled disc any longer...




so ultimately, they are for cosmetic purposes. and people have associated them with "performance", so they are assumed to be so and expected on performance automobiles. but for the most part they are only requiring replacement rather than being able to turn them... rockin'

[rwh11385]

http://corner-carvers.com/altimathread.php.html

quote:
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Crossdrilled rotors-by design, crossdrilled rotors were designed for track use. Why? Because, when you drill holes in your rotors, they are designed to dissipate heat (not to rid of brake dust as most people think).
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I found the root of your problem. It is right here. You don't know the definition of "dissipate". You also don't understand the interaction between a rotor and the pads. Here is how it works. The friction between the pad and rotor is what causes you to stop. This friction converts your forward energy into heat (remember Einstein: Energy is neither created nor destroyed, it is converted). Now that heat is a bad thing. Yes it is bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like shit. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Notice that DISSIPATE and DISPERSE are interchangeable? Once the heat is removed from the pad/surface area it is then removed. Notice where the removal falls on the list of duties? That's right - number 3. Here is the list again. Memorize it because I will be using it a lot in this post:

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle

#2 DISSIPATE the heat

#3 REMOVE the heat from the brake system

Let's look more in-depth at each step now shall we? No? Too bad assclown we are doing it anyway.

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle:
This one is pretty simple and self-explanatory. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you want) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. Does that make sense Ace? Good. Let's move on.

#2 DISSIPATE The Heat:
Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when I am coming down the back straight at VIR at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into. Make sense? This isn't rocket science here d00d.

#3 REMOVE the heat from the brake system:
Now comes your favorite part of the process. This is what you thought DISSIPATION was. It is ok. I will allow you to be wrong. This is the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the veins. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it. Got it? Good.

Now let's look at why cross-drilling is a bad idea.

First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause.

Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. Explain again just how drilling away material/structure from a CAST product DOES NOT weaken it? Since you are obviously a man of great knowledge and experience surely you have seen what can happen to a x-drilled rotor on track right? Yes it can happen to a non-drilled rotor as well but the odds are in your favor when pimpin' bling-bling drilled y0! Since you are also an expert on thermodynamics why not explain to the group what happens to a cast iron molecule when it is overheated. I will give you a little hint - the covalence bonds weaken. These bonds are what hold the molecules together boys and girls. You do the math - it adds up to fractures.

So why don't race teams use them if they are so much better? Consistency? Hmmmm . . . no. I am gonna go with the real reason her chodeboy. It is because of several factors actually. They are as follows but in no particular order:

- Less usable surface area for generating friction
- Less material to DISSIPATE the heat away from the pads
- Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material

[nando]

probably the best reason to use slotted rotors is for wet braking. seeing how I live in the PNW and it rains all the time here, they seem like a good thing to have. if you live somewhere dry I'd probably stick with the stock rotors, supposedly modern pads don't gas very much so there's really no benefit there. Of course I can still lock up my brakes (careful threshold braking) so I don't think I really lost much in the way of performance.

also I should mention that surface area has nothing to do with the coefficient of friction, but it will definetly affect cooling and heat transfer.