JD_AMG

http://buildafastercar.com/tech/Drilled-Brake-Rotors

wht01ws6ta

iTrader: (45)

Ye Olde Fbody.org Gear Calculator says the outside diameter is

265/35/18 = 25.303 inches

and

295/30/19 = 25.969 inches

Not sure if that is a big enough difference to matter or not?

http://www.f-body.org/gears/

Ironhead

I've not done any driving events with the GM engineers. However, more than one Corvette club has. When they brought this up, that was the answer they received.

I don't have a link for you. Like I said, there was no official press release. Do you really think the engineers would sign an affidavit affirming their statement for someone to post?

I've not read the paper (although for $15, maybe I should) but from what I know of it, they state that drilled rotors can prevent pad glazing.

Well yeah, slots and holes will shave the pad. That's been stated here. So if you use the wrong pads for your intended activity or otherwise overheat them somehow, your braking performance may not diminish as much as it would otherwise. That's not quite the same as drilled brake rotors stop the car better than blanks, is it? Use the proper pads and/or cooling and we're back to blanks perform better.

I believe the paper also states that the holes can interfere with rotor cooling since the air escapes from the vanes. Makes sense to me.

I guess you told me. Where do you keep that chip when its not on your shoulder? I'll stick my superiority complex there.

davidadavila

bottom line is this has been discussed here and in other threads to death...no they will not improve if you just checnge rotors to drilled and slotted same circumfrence, second if you see race cars have now a days just slotted rotors or blanks with old suface compounds it was necesary before but now its not, if you are looking for an improvement in performance change to a hawk pad and just slotted rotors and brake lines if you want....drilled rotor are eye candy and if you get cheap ones they crack in hard braking... im personally going with the brakets for the larger rotor use my same calipers and in future upgrade to som c6 zo6 brake calipers buts thats just for the bling factor... search is your friend like mentioned before

Suaveat69

Actually GM did a test on drilled vs. non-drilled and the drilled had better cooling and less fade compared to the non drilled. Drilled brake rotors do slow a car down better and it is exponential as speed increases. Drilled rotors have less fade. So, yes they do provide a benefit BUT they will CRACK under extreme use.

http://www.sae.org/servlets/productD...D=2006-01-0691

Has anybody actually tested this theory-Do a braking test with blank rotors and then switch to drilled and re-do the test and publish the results? GM did.

FiredUpZ28

Pad technology has improved over the years, they don't make those gases anymore as far as I know.

Unless your driving on a road course or its a show car I just don't see the point in them at such a risk. Just my $0.02

GM cars and Porsches n what not have Brembo drilled rotors that have the holes cast into them so they don't crack.

Foxxtron

iTrader: (1)

Read carefully...they state similar experiences over like what Sam, Korry, and myself have. Whilst there was some evidence of improved performance, the conditions varied along with many other tradeoffs consistent with the information posted around this forum and many others that involve performance racing and/or engineering.

As opposed to the inconsistencies in that report, the research group I was in actually started with 5 different cars of stock brake systems each running their own respective sets of rotors, pads, and brake fluid. Each car was subjected to conditions which they're expected to perform. Each pad and each rotor set for each specific vehicle were not mixed, but each of the pad sets were identical, and the brake fluid was as well. Tyres were changed between intervals as well. The only difference was that each set had rotors with different rotor face patterns, otherwise the ferrous compound was identical.

Frankly, as an engineer I see many SAE reports from professional firms and major corporations to be quite well most of the time, however some are inadequate. From reading that one from 2006, I have witnessed occasions almost exactly like the data they've published, however for the most part, I find it to be flawed by the fact that their controls aren't very consistent. And to add to that, I find the information to be packed in a 28 page report with only 4 references leaves science and engineering readers starving for a bit more information. It would also help if they could actually have the different rotor styles manufactured under tighter controls then perform further testing (ours were manufactured in tightly controlled sets). It'd be nice if we could also see grain structure analyses and some possible microscopic dislocations as well.

Whilst this article is peer reviewed, it doesn't necessarily denote that it cannot be without flaws. Again, from my experience in both college and on the track, I agree mostly with the results, but my disagreement lies within their stated process.

wht01ws6ta

iTrader: (45)

Doesn't matter if they are cast or not, they still crack. These are Brembos with cast holes:






Now, what might keep them (GM cars and Porsches n what not) from cracking is that they have a larger pad/rotor surface area so the pressure is distributed over a greater area. Larger rotors will potentially stay cooler as well so that probably helps to keep them from cracking.

z28bryan

iTrader: (7)

The fronts are like .4 of an inch shorter than stock and rears are about .3 taller than stock. Not sure if that little makes a difference? That would make the difference ~.7 of an inch between front and back.

Is it the difference in tire diameter front to back that eff's up the ABS or is it more the difference from the stock diameter? Both?

OP didn't mention the tire brand and model before and after either. Some tires are stickier than others.

wabmorgan

It's the difference fount to rear. The ABS would have no way to know if they are wheels are turning at a different speed vs stock... it just detects the difference in rotational speed. In other words.... if the diameter is the same fount to rear... the ABS would not know the difference between larger/smaller/stock diameters and speeding up/slowing down.

I'm not sure... but it sounds like it would be enough... and there is no way to "program" out the related difference either.

The ratio is 25.303/25.969=.974 or in other words... one is turning/reading 97.4% of the other.

That may not seem like a but when the sensors are detecting a difference in rotational speed... it is probably enough.

One way to find out.... would be to throw back on some tires that are all the same size. (If you don't have yours... see if your know someone with a z28 or T/A and swap wheels/tires out for a run)... I'd almost bet the problem goes away.

BMR Sales2

iTrader: (40)

I want to thank you for posting that, if we were in a perfect world this thread would end after reading this. But we're not so who knows how much longer it will go on.....

Gee where'd you get that info from

Well then genius, claim your $500 prize over at corner-carvers.com since you know so much.

http://corner-carvers.com/forums/showthread.php?t=21273

mitchntx

iTrader: (14)

https://ls1tech.com/forums/suspensio...at-washer.html

/thread

BMR Sales2

iTrader: (40)

Brakemotive

iTrader: (73)

I'm not sure about the CTS-V to be honest.

The paper has no mention of it interfering with cooling by disrupting the air flow.

Actually no company casts the holes into the rotor, they are all drilled in after the casting process. Another thing to mention is that many of the big brake manufacturers get their rotor blanks form the same foundries.

Firebirdfan

To the OP:

Your ABS is more than likely kicking in because of the difference of the diameter of the new tires from FRONT TO REAR. NOT FROM OLD TO NEW.

The ABS sensors "count" the revolutions of the front wheels to the revolutions of the rear wheels. If the revolutions are the same (i.e., no tires are slipping) then it stays inactive. As soon as the "counts" differ, ABS realizes the car is slipping in some way and activates the ABS and traction control (which is run by ABS by braking individual wheels) to bring the car under control.

With your old tires, they were ALL exactly the same size.

With the new tires, the rear diameters are larger than the fronts. They're close, but they're not exact enough. As the ABS is "counting" the revolutions, it sees that the rears are rotating slower (due to the larger diameter) than the front. It senses that the car is slipping in some way and activates in order to try to correct (even if nothing is wrong).

Got all that? Your problem lies in your tire sizes, not in your brakes themselves.

z28bryan

iTrader: (7)

Thank you for the explaination. This makes sense to me now. Basically car notices one set of wheels rotating faster than the other under braking power = ABS is triggered.

I typically use this link to choose tire sizes when I want to go with a wider tire and/or different size rim. http://www.miata.net/garage/tirecalc.html

You know what would have been ironic is if the OP put in drilled rotors, the car stopped worse and prevented going into ABS as quickly, and then thinking that the rotors fixed the problem

mitchntx

iTrader: (14)

One thing lost in all this posturing ...

Brakes on real race cars might very well be drilled and slotted. But the rotors and pads only have to last a few hundred miles.

For a street car application? holes and slots are driveway jewelry.
/thread

Major_Lee_Slow

iTrader: (1)

FWIW I have been actively pursuing a brake upgrade for my car since the SP rules now allow it and the most important thing that I learned was the the main reason most race cars use drilled rotors is to reduce rotating mass. However to compensate for the holes they run a larger diameter and as big of a pad that they can to offset lower heat capacity of the low weight rotor.

Sam Strano

iTrader: (41)

What Major_Lee_Slow says is accurate. In fact, the first cars to use drilled rotors were Porsche 908/2 hillclimb cars--but not the actually road-race cars. The reason the hillclimb cars did? They could afford to since a hillclimb is short duration and you are always slowing down uphill, both being easier on the brakes. It was done to reduce unsprung and rotational mass. Then again, they were also making frames from Magnesium as well to get weight down so they tried everything.

And today, you'll notice that most racing cars don't use drilled rotors at all. In fact I can't tell you the last time I saw one with drilled rotors. Slotted? Yes because that helps with glazing and evacuates any gasses from 1000+ degree racing pads. Consider that. Today when unsprung and rotational mass are still important, race cars do not run drilled rotors? Why do you suppose that is?

LilJayV10

iTrader: (39)

Didn't GM also have problems with Z06's burning up rotors on one side of the car because they used two left side rotors which had the vanes going the wrong direction?

I have had this same coversation with a friend of mine that drilled/slotted rotors are not as good as blanks. His response was that LeMans race cars and such have them, for which I had no come back to. So I said, "Cause Sam Strano said!". I think I will use that statement if I am ever in court. It should hold up.