Quick Question on Cross Drilled & Slotted Rotors - Third Generation F-Body Message Boards

rsrsrs · 10-07-2009, 05:04 PM

Right now Im in need a new driver side rotor. While looking at the prices on summitracing there's about a $5-10 difference between CD&S rotors and stock rotors.

My question is, is there a big difference stopping between Cross Drilled & Slotted and stock Rotors?

If there is a noticeable difference then I just might order 2 CR&S rotors. If not tho, then I'll just order the one stock rotor that I need.

for any info!

madmax · 10-07-2009, 05:59 PM

Last thing you need on a factory 10.5" rotor is less surface area.

Twin_Turbo · 10-07-2009, 06:04 PM

And less mass, although the difference is not too big. My buddy has cross drilled rotors stock size on his GTA and the holes are already cracked. Proper cross drilled holes are cast with holes and then drilled out, not simply drilled and chamfered.

Also, it's purely cosmetic, none of the modern street pads outgas anywhere near enough to warrant these holes.

The thing with rotor mass is, the rotor is your energy (heat - > kinetic energy converted to heat during braking) storage and the larger the storage unit the lower the mean running temp....now drill holes in an already small rotor....

rsrsrs · 10-08-2009, 01:27 AM

Quote:

Originally Posted by madmax

Last thing you need on a factory 10.5" rotor is less surface area.

so what your saying is dont bother getting cross drilled and slotted? Sorry but I dont get exactly what your saying.

I guess I'll just get the stock brakes then. Sucks having one new one and another looking all old and rusty tho lol

Twin_Turbo · 10-08-2009, 04:29 AM

Less surface has no real effect, same as pad size. It doesn't matter for brake force, friction also has no surface conditional. This doesn't mean it has no effect, it does severely affect fading because there's less localized heat buildup in a larger pad. Anyway, the potential cracking should be your prime reason not to go with cross drilled rotors. If you have to have fancy looking rotors, get some of those grooved ones....at least they don't crack.

madmax · 10-08-2009, 02:02 PM

From my own experimenting, on a factory 10.5" rotor you'll experience the following changes going crossdrilled:

The loss of surface area from holes and slots in your rotor will ABSOLUTELY increase your braking distance.

The temperature the rotor runs at will DEFINITELY decrease, a lot.

The chances of cracking, IMO, are negligible. My home crossdrilled, below minimum thickness rotor is still fine after 7 years. Does not have a whole lot of miles in that time but I'm not nice to them. I'd be more concerned with cheap materials from China myself, my rotors were cast in Canada. I've seen solid and vented (not drilled or slotted) rotors from China do all sorts of weird cracking and breaking. The metals they use are junk.

The mass argument is also kind of moot, if mass really was the only controlling factor then why not make the rotors solid? The fact is there is a lot more than just one single factor and quite honestly ignoring any one of them is just going to get you into trouble. The rotor must accept heat and reject heat, by pad surface area, pad pressure, vent surface area, and airflow.

All that said, I would advise not using 10.5" rotors with holes in them. Any benefits you will get are going to be useless to you, and the downside is the one thing you want improved, typical driving braking distance, will increase.