Drilled Rotors and Track Use

[VaSteve]

What you are seeing in the next post is a set of rotors I used for one event. Truthfully, these were my back up rotors, I got them in a package deal with some calipers and kept them around in case I needed a set. They had a little time on them and had some minor cracking around the holes, but nothing that wouldn't pass tech inspection.

I used these at VIR only with PF-97s.

[VaSteve]

:(

[HoodPin]

Looks like they may have had more than just "a little time on them". I noticed that my new set of front rotors on my 944S2 was showing some micro-cracks after the first track weekend. My experience has been the microcracks stay around for quite a while, before a debilitating crack suddenly appears.

[MatP]

What brand are they? Some drilled rotors <cough> Coleman <cough> are only good for two weekends. They are not all made equal.

[APKhaos]

Even the best drilled rotors fail this way in track use. The temp cycles kill them.
Solid vented rotors are best, and slotted rotors are a good option if you are convinced that it makes a difference [I'm not].

[VaSteve]

No idea what brand...used. LOL. I'm upgrading to PF-08s next season. I wonder if I should add more cooling as well.

[Dr K]

You need to use your brakes less, Steve. Don't you drive a 944? ;)

[VaSteve]

This over-annucianting man will tell you about my new brake upgrade

How Car Brakes Work: "What Stops Them" 1935 Chevrolet Division General Motors - YouTube

[N Fotouhi]

Given that you have choices for slotted rotors for S2, why would you guys even consider drilled? Heck, You can even have someone slot the rotors.

A set of cross drilled would last me a whole season on the S2 and I was running at 3K+ weight of E-class car.

I can only get cross drilled for the 993 and need at least two sets of front (two drivers) per season. I only buy OEM from the dealer.

[BlackTalon]

I got them in a package deal with some calipers and kept them around in case I needed a set.

Given that you have choices for slotted rotors for S2, why would you guys even consider drilled? :?

[TurboPooch]

Over the years I have tried almost every front rotor variant and manufacturer. Granted I have cooling ducts and use the brakes to their maximum but the best longest lasting are the Porsche solid vented rotors. But they are pricey. Lately I have been using Sebro solids and find that for a third of the price of OEM they last almost as long but not quite.

[CanAm]

I haven't found OEM drilled rotors to last long when used on the track. PFC floating rotors (solid with dimples) have lasted much longer. I'm now trying solid vented rotors, so far so good.

[ausgeflippt951]

But it's the cross drilling or slotting that makes the car look like a REAL RACE CAR. Without them you're just another poser.

[roundel]

A local supplier supplied my cross drilled Kaufman (IIRC) rotors. I complained that I did not order cross drilled. They said, "try em and if your not happy we will replace." I used them for one weekend and the cracks connected the holes. I returned them for a replacement set of non-cross drilled for free and suggested that they not provide cross drilled rotors to track junkies in the future.

[Vicegrip]

Solid vented OE or OEM for me. All rotors will wear out or crack at some point. Thermal delta is what cracks them. The wider the delta per cycle and the higher the ramp in and out the less number of cycles. Good materals and methods matter too. some brands seem to have less of a service life than others. Reduce the thermal deltas. We can't reduce the number of times we cycle the brakes or the energy absorbed per cycle* so we need to reduce the heat retained.

I wonder if drilling and slotting and dimpling matters at all with modern non gassing pads.

*good driving methods and or larger nads can reduce the over use of brakes.

[TurboPooch]

*good driving methods and or larger nads can reduce the over use of brakes.

Amen, brother. Getting the car slowed earlier at higher speeds but maintaining higher speeds thru the corners keeps the air flowing and the temps down.

[Chopper Dropper]

^^^^^ What they said, don't look as cool but work and last better. My understanding as well that newer pads don't gas off as much, nads are cooler as well
Dirk

[BMAN]

Not the norm I guess but I've had good luck with OEM cross drilled.

Ran the GT2 with drilled front and rear; 3500+lb car, w driver, with a lot of straight line speed. I got a full year out of the fronts. They did show cracking after the first use but the rotors never failed. Rears were fine after two years. Pagid yellows.

I've got almost 2 years on OEM cross drilled in the Cup and still okay but ready for a fresh set. Pagid blacks.

Cayman has had the same set of drilled rears for over 3 years but ready for replacement. We started with AP solid/slotted on the front which lasted over 2 seasons. Replaced GiroDisc but they only lasted 6 months. :shock: They were there first rotor I've had that failed; cracked through the outer edge. Big downside for slotted, IMO, is they don't give as clear an indication of wear as compared to drilled. Pagid yellows and PFC 08.

Cannot say whether OEM drilled are better than aftermarket because I've only run OEM. But in my experience there is longevity difference based on brands with solid/slotted rotors.

[ausgeflippt951]

Brian -- which of your cars use floating rotors?

I've never thought much about this but I would not be surprised if cracks propagate less readily on floating rotors, since the alignment is "perfect" all the time -- there's hypothetically no axial stress through the rotor.

[BMAN]

Brian -- which of your cars use floating rotors?

None but I am told they do wear better.

[CanAm]

I've never thought much about this but I would not be surprised if cracks propagate less readily on floating rotors, since the alignment is "perfect" all the time -- there's hypothetically no axial stress through the rotor.

Please elaborate on this, I'm not quite following, and the structural engineer in me wants to understand.

[Vicegrip]

^ Seems simple enough but I am a BE not an SE. I suspect other aspects of a floater such as higher operating temps would negate any positive aspects less axial stress might provide.