Why Vented Rear Rotors For DeDion Chassis?

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Because the solid ones don’t work well enough!

Well, you might not need vented rear rotors on your Milano or GTV6. Generally speaking, Alfa stock brakes are among the best in the world. However, if you use your car hard, especially on tracks that are very demanding on brake systems, you might find yourself running out of brakes. The culprit usually turns out to be the rear brakes. Unfortunately, one of the most sophisticated parts of the car’s design – the inboard mounted brake calipers and rotors – turns out to have some real performance limitations in cars that use (some might say "abuse") their brakes. The inboard mounting saves a lot of unsprung weight, which is a very good thing. However, it also moves the calipers and rotors into very close proximity with the transaxle, which gets very hot, and right next to the exhaust pipe, which, of course, is very hot as well. So right away, even without applying the brakes, they get heated up. Then to make a bad situation worse, these brakes sit in a very dead air zone under the car, and there is very little airflow to cool them. Consequently, since they get very little cooling from the surrounding air, every time the brakes are applied, they get hotter. In a track session, as the exhaust gets hotter, the transaxle gets hotter, and the brakes get hotter, it doesn’t take long before the rear brakes begin to get too hot and lose their effectiveness. In extreme cases, they fade and make no contribution to the braking effort.

Vented rear rotors solve this problem. They do not rely on the flow of ambient air to remove this heat. The design of the internal vents actually forces air through these rotors and force-cools them.

Performatek has two offerings for vented rear rotors:

This is a proven solution that works. Since the new rotors are thicker than the original solids, a spacer kit must be inserted between the caliper halves to fit them. This is the only modification required. The kit supplied by Performatek is precision machined and ground parallel and flat to the same specs as the ATE calipers. All new square-cut O-rings are supplied, longer bolts (the original long bolts become the new short bolts) are supplied, and new, longer, stainless steel pad retention pins are supplied. The new rotors bolt right up to the stub axles and half shafts. Stock pads (or aftermarket equivalents) fit the calipers.

The following is a testimonial from a GTV6 driver who complained about his brakes not being up to the task at VIR, where he gets most of his track time. After talking about his car, it became clear that he had made a lot of effort to cool his front brakes, so it was doubtful that this was the problem area. The rears, however, were completely stock. After installing the Tar•Ox rotors, he reported back his results:

"Andy -

I will have to tell you that I ran the piss out of the GTV-6 on Sunday at VIR. I really tried to abuse the brakes and put them into a punished position all day.  I had four 30-minute sessions. They never failed me all day. They felt consistent all day. I had absolutely no fade or overheating problem with my new setup.

My set up is as follows:

The car was a true pleasure today and worth the expense of the new brake setup.  

BTW, I would really like to find an air flow meter from a BMW730i

Please feel free to use me as a reference anytime."

Then again, 2 days later:

"Andy -

I could not have been more pleased with the performance of the brakes on Sunday.  I am going to begin on the 85 conversion Thursday.  

Sure would like to have the larger AFM by the 7th so I can go faster when trying to punish the brakes."

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