The drilled rotor holes usually follow the vanes because the holes need to avoid drilling into the webbing and weakening the rotors.

 

Yup..what brutus and rob said.

Plating = bad on pads, they'll never be right again.

And direction only counts, on your second hard stop in a 5 minute period.

 

Also worth mentioning that brake rotors are made of cast iron which is quite soft.

 

true, but not always...



From here: http://www.zeckhausen.com/how_to_pro...all_rotors.htm

 

Ohhh...sneeaaky bastsards...

 

My first car with enough grunt to think about drilled rotors with vanes. In my uneducated mechanical mind I would have put them on so they were in rotation to force air into the vanes and not "spill" air.

I have new rotors and pads from Roger which will get fitted soon. When I changed the rims I checked which way the vanes ran and whoever did the last set didn't get a matched pair so I have one each way. Must check the part numbers to make sure I get it right this time.

Why "spill" and not forced? The rotors have a coating, do I need to run the old pads or is that just for the cad plated rotors?

 

Norm ... if you look at the backing plate and the brake ducting and deflectors you'll see that they all direct air to the centre of the rotor, so the vanes throwing air out works in harmony. Air blowers used on spas and industrial applications have similar closed vane impellers ... as do water pumps. Design of air pumps is very similar to design of water/fluid pumps using fluid dynamics principles.

Bed your new pads into the new rotors using a proven bed in procedure. Your new rotors won't be plated or painted unless you do it, so just clean the friction faces well with solvent prior to fitting caliper/pads. Recommendation of the use of old pads was only for scrubbing plating off rotors, so new pads aren't ruined.

 

these were marked and plated by brembo and installed on the proper side..

 

Well, they look great. Are these on your car? What's under the hood that needs such pie plates?

 

most 928's have PLENTY of brakes...IF they have proper pads and fluid for their application......

 

Brake envy is an ugly thing Brian is right about 928s they have plenty of brakes. For most the "upgrade" is simply for looks and bragging rights ! Not that there is anything wrong with that.

 

Ive raced both, and the holes seem to give less fade. braking force is near idential. the trapped gas function works better with slots, but holes work, but crack the rotor after only a few races.

the rotor is an air pump, clearly with aerodynamic forces generated while the rotor is spinning in its 1500rpm range at high speeds. however, i did test running the rotors backward for a race weekend, and didnt notice a bit of difference, it was a warm day, at a hard braking track too, but it was with new pads and rotos. maybe when they are taxed a little more,i would have had some ill effects. (also it was a very long club race of 40min)

flat rotors just seem to have more threashold fade, however, one pump during a threshold brake seems to solve it. with holes and or slots, i think that might not be nessesary.

mk

 

Mark: Your experiences that holes work..well, thats just working within the limits of the mass of the rotor remaining.

You cant argue against the fact that your temps will be higher, and cooling efficiency reduced in a drilled rotor.

But again, if the rotor you have..is still within the thermal budget of what youre asking of it..yes, it "works"..but its not a working positive.

 

i went through the surface area exersize and yes, its obviosly less. but, you are assuming a lot. cooling the surface and releasing gasses can have a net gain effect on braking capacity. it might even help with heat distribution, as you know, the outer rotor spins at a higher speed than the inner rotor area. all things being equal, yes, a flat rotor would have an advantage, but they are not. all factors considered, slotted rotors seem to work best . holes have near the same effect, but weaken the rotor and shorten its life due to cracking.

 

Over the years I've heard this argued both ways. On a hunch, I went to the Society of Automotive Engineers (SAE) website and found this article. Unfortunately, I cannot read it because I am not a member.

Maybe someone who is an SAE member (Doctor?) can read it and give us a summary.


The Effect of Rotor Crossdrilling on Brake Performance
Date Published: 2006-04-03
Paper Number: 2006-01-0691
DOI: 10.4271/2006-01-0691
Citation:
Antanaitis, D. and Rifici, A., "The Effect of Rotor Crossdrilling on Brake Performance," SAE Technical Paper 2006-01-0691, 2006, doi:10.4271/2006-01-0691.
Author(s):

David Antanaitis - General Motors Corp.
Anthony Rifici - General Motors Corp.
View All
Abstract:
A review of available information on the effect that brake rotor crossdrilling has on brake performance reveals a wide range of claims on the subject, ranging from ‘minimal effect, cosmetic only’ to substantially improving brake cooling and fade resistance. There are also several theories on why brake rotor crossdrilling could improve fade performance, including crossdrill holes providing a path for ‘de-gassing’ of the brake lining material and increasing the mechanical interaction, or ‘grip’ of the lining material on the rotor.

File Size: 1294K
Product Status: In Stock
Included in: SP-2017

See papers presented at SAE 2006 World Congress & Exhibition, April 2006, Detroit, MI, USA, Session: Brake Technology (Part 2 of 3)