said7

Anyone notice that on this page....

http://www.mazdausa.com/rx8/news/default.asp?sniffer=1

they show slotted and drilled rotors. Wonder if this is going to be an option. The rims dont look the production model pic rims.

Any ideas?

ZoomZoom

I think that slotted and drilled rotors look great but they are not as safe as regular rotors.

Check out this thread. I should warn you that you might spend hours reading this tread like I did because I found it very interesting. You’ve been warned!!!

tallguylehigh

If I would venture a guess, I would wager that that picture was from the red Rx-8, the one before the yellow one that was on the car show circuit for so far.

SA22C

If you check the gallery, the new pics of the production model show no slotted/drilled rotors. That pic must be of an earlier model.

Matt
1979 SA22C
"No rotor, no motor."

wakeech

not to mention that the slots and holes in that brake rotor look fairly for show, and have nearly nothing to do with go... see how the slots are curved, and too long?? well, they reduce total area of the rotor that can be swept by the pad... not functional, but looks cool.
also, see how there're only 3 holes per ray, and (from the centre) taper to smaller holes?? again, not functional, and look kinda neat...

yes, cross drilled rotors suck longevity-wise, and give you no advantage in braking, at least on the street... if you were a track racer with a sky-high budget, you might consider cross-drilled rotors, which do give you a slight advantage over just slotted ones, but at the cost of longevity... (ahhh, yes, the mighty tradeoff that is performance...)

ZoomZoom

Sorry - Not True!!!

When you cross-drill and/or slot rotors the rotors run hotter. Therefore there is a decrease in stopping distance – not an improvement. Also, cross-drilled and/or slotted rotors are susceptible to hairline fractures therefore they are not as strong.

If there is any doubt please read the thread that I posted above.

P.S. They do look better though (maybe a little too rice).

Hercules

Hey if they can get good stopping distance with what they're using, why change?

Quick_lude

If crossdrilled rotors are so bad why are they on the Porsche 911?
http://www2.us.porsche.com/english/u...remsanlage.htm

Macabre

The Porsches technically do not have cross drilled rotors, they have rotors that are cast with the holes in them. Much more expensive to manufacture but it pretty much eliminates the reliability problem. Why bother? Looks is a part of it, I'm sure. Otherwise, The holes do offer cooling benefits when engineered properly.

Buger

Road and Track has the $179,000 911 gt2 60-0 braking distance as 116 ft.

The 350z supposedly does 60-0 in approx 113ft.

According to several calculations that were done, the rx-8 is expected to do the 60-0 in about 110 -111 ft.

It really shouldn't be too surprising since the rx-8 will also have 13" rotors and will be at least a couple hundred pounds lighter.

Brian

Macabre

Maybe you were looking at 70-0 for the GT2. Motor Trend tested the 350z at 115ft 60-0 and the GT2 at 107ft 60-0. Different days, of course, so not the best comparison, but there's little question that Porsches can stop. It's 2850lbs with 13" ceramic composite rotors that supposedly have a higher coefficient of friction, higher heat capacity, lower weight and much better longevity than iron rotors. $180k buys a lot of tech

m477

I don't think drilling any holes in the rotors would make any more horsepower....

Buger

Hi Macabre,

The April 2002 Road & Track with the Rx-8 on the cover had the info on the 60-0 braking distance. On page 129 (road test summary) they listed the 60-0 at 116 ft and 80-0 at 209 for the Porsche 911 GT2 (from Issue 8-01).

Of course there are many factors that may have been different to account for the different results between Motor Trend and Road & Track. The bottom of the page has a section on "interpreting the numbers".

60-0 mph braking has a 10 ft significant difference
80-0 mph braking has a 15 ft significant difference

The difference in the 60-0 distances for both the 350z and the GT2 are within the margin of error.

It would be great if the rx-8 could have ceramic rotors like the GT2 but alas it needs to be affordable. I did think that the GT2 was heavier than 2850 lbs though. I found a couple of links that mentioned a curb weight of 3175 lbs
(http://www.intellichoice.com/reports.../vhcl_nmb/9723) but perhaps different years had different weights?

Can you point us to a link that quotes the 2850 lb figure?

Thanks, Brian

RX7 Guy

The benefits of drilled and/or slotted rotors won’t manifest themselves in a single trial.

A few years ago, GRM magazine spent several thousand dollars upgrading the breaks on a Miata only to find that the stopping distance actually increased slightly. Everyone was so surprised by the outcome but they shouldn’t have been. The stock breaks were quit capable of locking up the tires so the limiting factor wasn’t the breaks but rather the adhesive properties of the tires. The upgraded breaks were heavier, had greater rotational mass & had break pads whose higher operational temperatures weren’t being achieved during a single trail.

The theory is that slotted rotors prevent the float caused by pad gassing but modern pads resist gassing until ungodly temperatures & holes aid cooling which is true but so does increasing the surface area which is much cheaper.

So if done correctly, drilled & slotted rotors do have benefits but only under race conditions…On the street, conventional breaks are just as good & possibly slightly better & always much, much cheaper.

Buger

:D The engine rotor would be lighter if it was slotted too. :p

Macabre

Of course I can't find it now! Must have been dreaming.

Sputnik

Dude, the reason why the braking performance decreased was NOT because of the weight and rotational mass, it was simply because they only upgraded the front brakes, causing a huge bias disparity.

---jps

Quick_lude

My bad, I should've clarified that the Porsche breaks are cast, not drilled. It sounds like the Rx-8 brakes will be very good.. combined with the low weight of the car and sticky tires.

fuz

Cross drilled rotors cool off so fast that they drop out of the optimal temperature range for braking, unless you have a ridiculously fast car. I really don't see any need for cross drilled rotors on anything but a pure track car.

cueball

Back to the original pic, i am pretty sure that those are the brakes off the first RX8 protype (the red one). Here is a pic.

Quick_lude

And your point is? :D Track baby! ( Need a thumb up smiley.. )

MikeW

All that those holes and slots and grooves do are keep the brake pad/rotor interface "clean"

Fresh pad + Fresh rotor = excellent friction.(huge wear though)

Do you know what kind of gas pressure it would require to lift the pad off the rotor under full braking pressure? A f**k of a lot, it is not going to happen, anyway isn't there recesses on the pad where the friction material is either bonded or riveted to the backing? and also a lateral slot (in the middle)