New OEM Cross Drilled Rotors for the Base Boxster

[blinkwatt]

Originally Posted by J-RAD

Cross-drilled rotors do nothing in the way of cooling.

If that's true then why does every car in Le Mans use them?

[racer_d]

How many times have we hashed this over

One advantage to the cross drilled units is their ability to vent heat and gasses away from the surface area which has already been mentioned.

Will this make an impact in "street" driving? or a few highway stops? no, not really. But, in racing applications, managing HEAT of brakes is very important. When you are slowing the car down 10-20 times per lap for dozens to hundreds of laps, the amount of heat created can be extreme (1200-1500 degrees). Anything that helps lower this temp and allows the brakes to "last longer" at a higher efficency is worth doing. Hence their use on race cars. On street cars, it is more "marketing" to show a link between what is learned/used in racing and what can be used on the street.

In a pure "street" application, changing compounds of brake pads and tires (since this is what the brakes are "connected to") will have a greater impact in stopping distances than changing to slotted or drilled rotors, especially if they are the same size as the stock units.

[J-RAD]

Originally Posted by racer_d

One advantage to the cross drilled units is their ability to vent heat and gasses away from the surface area which has already been mentioned.

Venting boundry layer gases (as well as water and dust) away, yes. Venting heat, no. Cooling is what the vents are for (between the discs). The drill holes and/or slots help keep the brake pads clean. Drilled rotors may also possibly reduce rotating weight.

To quote the raceshopper site I listed above: "What handles more heat- A cast-iron kettle or a pizza pan with holes in it?"

Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."

Grassroots Motorsports (Feb 2001): "Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the ’40s and ’50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as “gassing out.” These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses somewhere to go. It was an effective solution, but today’s friction materials do not exhibit the same gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief, they don’t lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads—sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.

The one glaring exception here is in the rare situation where the rotors are so oversized that they need to be drilled like Swiss cheese. (Look at any performance motorcycle or lighter formula car, for an example.) While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember that nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life, at the expense of higher weight. It’s all about tradeoffs."

[J-RAD]

Originally Posted by blinkwatt

If that's true then why does every car in Le Mans use them?

They don't.

Most pro race teams don't use cross-drilled rotors anymore. They use solid carbon, slotted, or other advanced technologies. As an example:

These are from the RS Spyder:


And here is a photo from the 997 GT3RSR:




The Audi R10's rotors:

[blinkwatt]

Originally Posted by J-RAD

They don't.

Most pro race teams don't use cross-drilled rotors anymore. They use solid carbon, slotted, or other advanced technologies.

I stand corrected. It has been 2 years since I went to a ALMS event,lol I'm old and outdated at 19 years old.

[porsche986spyder]

Well, if you look at what I said earlier, the best of both worlds, Cross-drilled & Slotted would be the best as long as the surfaace area is larger than the stock application rottors. In which most cases, just about any aftermarket performance rottor that you buy to replace the stock ones are usually bigger. Never seen an aftermarket rottor that was the exact same size as the stock one, like someone said earier that would defete the purpose of having them cross-drilled or slotted. :ah:

[insite]

Originally Posted by porsche986spyder

Well, if you look at what I said earlier, the best of both worlds, Cross-drilled & Slotted would be the best as long as the surfaace area is larger than the stock application rottors. In which most cases, just about any aftermarket performance rottor that you buy to replace the stock ones are usually bigger. Never seen an aftermarket rottor that was the exact same size as the stock one, like someone said earier that would defete the purpose of having them cross-drilled or slotted. :ah:

the best scenario is a solid or slotted rotor with cooling ducts. better airflow will do more than just slots or holes.

most racing teams avoid drilled rotors anyhow. drilled rotors tend to not handle heat quite as well as solid or slotted rotors. they are more prone to hot spots; this causes the ferrous material to change to austenite, which is harder than the surrounding material. this in turn causes high / low spots on the rotor, ultimately leading to poor surface mating between the pads / rotors. this problem is exacerbated by the ferrous pad material used in most race linings.

[Franco]

Hi, I have all 4 Drilled Zimmermann rotors sitting in the garage waiting for me to install them, I'll take a photo when i get back from work and post it.

Paid $332.00 US for all 4.

[porsche986spyder]

Originally Posted by Franco

Hi, I have all 4 Drilled Zimmermann rotors sitting in the garage waiting for me to install them, I'll take a photo when i get back from work and post it.

Paid $332.00 US for all 4.

Do me a favor and measure the over all diameter of the Zimmermann Rotors and then measure them to the size of the stock ones and tell me what size they are. They should be slightly larger.

[J-RAD]

Originally Posted by porsche986spyder

Well, if you look at what I said earlier, the best of both worlds, Cross-drilled & Slotted would be the best as long as the surfaace area is larger than the stock application rottors. In which most cases, just about any aftermarket performance rottor that you buy to replace the stock ones are usually bigger. Never seen an aftermarket rottor that was the exact same size as the stock one, like someone said earier that would defete the purpose of having them cross-drilled or slotted. :ah:

But then you're looking at a complete brake system upgrade. You'd also need to get larger calipers, a new master cylinder, new pads, and so on....you understand.

Actually, most of the aftermarket rotor applications I've seen are indeed the same size. Essentially, they've just simply taken a rotor blank and drilled it.

Nonetheless, I'll say this about cross-drilled rotors...they look cool!

[porsche986spyder]

Originally Posted by J-RAD

But then you're looking at a complete brake system upgrade. You'd also need to get larger calipers, a new master cylinder, new pads, and so on....you understand.

Actually, most of the aftermarket rotor applications I've seen are indeed the same size. Essentially, they've just simply taken a rotor blank and drilled it.

Nonetheless, I'll say this about cross-drilled rotors...they look cool!

Nope. They are 1-2 inches larger and don't require any other upgrades. I have some on my car and the only other mod I did was to add better/newer pads. Everything fits.

Now there are some rotors out there that are massive and do require complete stystem upgrades like Bear and Brembro performance packages, but those rotors are somewhere in the neighborhood of 17-18 inches in diameter. My aftermarket ones are 1.25inches larger than the stock ones.

[J-RAD]

Originally Posted by porsche986spyder

Do me a favor and measure the oreall diameter of the Zimmermann Rotors and then measure them to the size of the stock ones and tell me what size they are. They should be slightly larger.

Originally Posted by porsche986spyder

Nope. They are 1-2 inches larger and don't require any other upgrades. I have some on my car and the only other mod I did was to add better/newer pads. Everything fits.

Now there are some rotors out there that are massive and do require complete stystem upgrades like Bear and Brembro performance packages, but those rotors are somewhere in the neighborhood of 17-18 inches in diameter. My aftermarket ones are 1.25inches larger than the stock ones.

I'm going to let you think about that some more for a bit.

[chaudanova]

Originally Posted by porsche986spyder

Nope. They are 1-2 inches larger and don't require any other upgrades. I have some on my car and the only other mod I did was to add better/newer pads. Everything fits.

Now there are some rotors out there that are massive and do require complete stystem upgrades like Bear and Brembro performance packages, but those rotors are somewhere in the neighborhood of 17-18 inches in diameter. My aftermarket ones are 1.25inches larger than the stock ones.

I think this is where there is some question in this thread... haha... 17-18" diameter... when the OP mentioned for you to think about this... i think he was referring to this part of what you said. Picture this... 18" diameter Rotors would be equivalent to my 18" diameter WHEELS.