Thinking about replacing rotors with drilled and or slotted rotors. I've read differing opinions about effectiveness.
What type/brand are you running and what has been your experience?

 

 

Not on my Vette... I have a set of Drilled/slotted rotors from Power Stop on my Lincoln (140 mph top-end (yes, I've verified) and 4100 lbs, so the brakes get a workout). They work just as good as the factory slabs, but no better. HOWEVER, they do warp (not buildup), make a lot of noise, and dust my wheels horribly.

I can't find an upside other than looks... I would NOT do it again.

 

Drilling / slotting are for looks only. it reduces mass of the rotor which is bad unless you have too much rotor, which you don't.

None of the real performance brake mfgs recommend driling or slotting.

But if you only cruise around town and want to impress the ricers go for it.

 

Make sure that if you decide to buy "Drilled" rotors,that the holes are not drilled . They should already be cast with the "holes" the casting otherwise they`ll start to crack.
And i dont think the holes has much to do with weight but has its main purpose in helping the disc to cool,maybe

 

I've had a set crack. It sucks. Three of the four cracked on my FIRST drive! They were Chinese castings (my first mistake) with CNC drilled holes and slots (my second mistake). I bought them off eBay (my third mistake). I never got a refund or replacement rotors as the company (CCRotorworks) said I tried to crack them and that they've NEVER had this complaint before. I've got about 6 pages of email correspondence with them, if anybody wants some reading...

Anyway, "They" (whoever) claim it's for cooling and reduced rotating mass as well as pad scouring to combat glazing. In my experience, pad compound selection has more to do with braking performance than anything else. After that come fluid choice and maintenance. Get the right pads for your application. Racing pads AREN'T the best choice for street use, belive me. I've been through at least six pad iterations on the Lincoln and the best I've found for Hi-Po street use is a "club" or "autocross" compound that has good cold bite and moderate high heat (1000*) tolerance and still works when wet...Hawk, EBC, Performance Friction, and Porterfield all make good pads.

 

Back in the early 80's I drilled the rotors on my bike (look, everybody was doing it, it was fashionable & made me more appealing to girls ). First thing I noticed was that if they were soaking wet then the brakes would grab much quicker than they did before. This was a potential lifesaver on its own & was the main reason I did it. The downsides were that they'd eat brake pads (yes, I did chamfer the holes!), made a strange whirring noise when the brakes were on (the sound of my pads being eaten?), took more effort to slow down (less surface area?) & were severely weakened. I was riding down a resurfaced road that was covered with loose gravel. A car going fast in the opposite direction sprayed up a lot of gravel that peppered me. While it didn't hurt (fully dressed in the 70's safety gear of open face helmet, jeans, denim jacket & Zeppelin T-shirt!), or chip the paintwork, it cracked the rear rotor between 2 of the holes. The metal sprang slightly apart so that the next time I used the rear brake it was like dropping a boat anchor off the back. I stopped dead & it shredded the disc pad. Another downside was the rust that would form inside the holes & then spray all over me & the bike whenever it rained. If you've not got the problem of the rotors being exposed to rain (which you shouldn't with a car) then I'd say that it's not worth the trouble as the losses outweigh the gains. A friend got his rotors slotted and found that he had brakes immediately after getting on it in the rain (same as I did). He also found that brake pads were getting eaten & also found that he needed more effort to stop (something you may not notice with servo assisted brakes). Additionally, his rotors eventually warped badly. I'd spend my money on something more useful

 

This is one of the original rotors off my 75. It has been drilled for roughly 10 years, I lost 3 pounds per rotor in total with other modification, I use only organic pads and the rotor has no cracks. The picture doesn't do it justice. The rotor is mint.
The other 3 are the same.
I do not have a problem with eating pads.
There are lots of racing rotors full of through holes.

 

IVE NEVER SEEN SO MUCH NEGATIVETY ON THIS SUBJECT! NOT ONLY DO I LIKE THE DRILLED ROTORS, I DRILLED EM' MYSELF AND HAVE HAD NOTHING BUT GOOD RESULTS. THE PURPOSE OF THE HOLES AND SLOTS IS TO REMOVE BRAKE DUST FROM SURFACE AREA. SINCE THE DUST IS NOT IN THE WAY, YOU GET MORE PAD CONTACT, SO, MORE BRAKE WEAR. I SEE THESE ON MANY ROAD COURSE STYLE RACING CIRCUITS, AND THESE GUYS KNOW WHAT THEIR DOIN' ID GUESS. CANT REALLY SAY IF IT MADE A MEGA DIFFERENCE, CAUSE IT DIDNT. BUT I STILL LIKE EM'

 

Flynhi,

I must admit that slotted and cross drilled rotors look super. If you are just going to drive around and cruise they would work for you. If you are a very aggressive driver and are hard on your brakes I would not go this route. We have found that cross drilled rotors tend to develop heat pockets on them and warp or crack much easier than a rotor that has not been drilled on. So I guess it comes down to your driving style.

Tony
VBP

 

From what I have read and not from my experience, they only benefit is on cars that see a great deal of roadracing because the brakedust gets super hot and makes a gas that pushes the pads away from the rotor, reducing brake power.

 

I have Cross Drilled Rotors. They were forged and are Powerstop Rotors (cadnium "bling bling" plated). I don't reccomend the cad plating. It ruins your new brake pads and puts a nice glaze on them. Got them from a Brake Warehhouse in NY. I have had them on the car for a year and done about 1500 miles. I bought them because I wanted to get rid of heat. The holes are (according to there speel) to let air through the holes and help cooling, also supposed to help stop the gas thing happening between the pads and the rotor. I have stock brakes with exception of cross-drilled rotors and semi-metallic pads. I have more brakes then I need. I don't race, I don't autocross. I do go fast from time to time. I can slow down real fast without brake fade. They work for me.

If I push down hard the car will stop me fast. Hence I am getting better tires and seatbelts so I don't leave an impression in the windshield.

The biggest difference I found though was the pads. Semi-metallic really stop you. They do wear out the rotors but what do I care I drove 1000 miles last year :-)

 

Norval, did you drill out your rotors, looks like an easy enough pattern to follow, holes look like 1/4"?, and what were the other mods you did to the brakes to loose the weight....

 

So, I f I drill or replace rotors per Norval and then replace OE calipers with alum by wilwood or equal, I have reduced weight at each corner by 6-7 lbs.
Will I notice any significant performance change?

 

Read a really good article last night in Vette magazine where they put a killer set of 14 inch brakes on a C4. They were drilled and slotted. They were by Baer Claw. Guess someone forgot to tell them they wouldn't work.
Anyway I drilled my rotors, I think about 1/4 inch using a dividing head on the mill to get a uniform pattern.
I also turned the rotor on a lathe removing excess inner material, I hollowed out part of the hub. Each rotor lost 3 pounds, I weighed each one before and after.
I have never had a problem with cracking or permature pad wear.

 

I think part of the issue may be stress-relieve. Norval, your rotors were already used when you drilled them, correct? That would allow the rotors to relax through the heat cycling of normal use, right? Drilling holes in new rotors is probably where the major issues arrise... I honestly wonder, Norval, if your experiences would have been different had you drilled brand new rotors.

Let's not overlook cost. There is absolutely NO comparison between a $2000 set of drilled Baer rotors and a $500 set of drilled "Chinese" rotors....You always get what you pay for.

I'm not stating an opinion when I say that I've had SERIOUS quality issues with drilled rotors. I've had two full sets of drilled rotors, each from a different manufacturer, on the same car. My driving habits don't change. The first set cracked severely (2" long cracks) in multiple places on three of the four corners after ONE drive. The second set has been holding on pretty good, but have developed irregular "divets" the size of nickels on the surface from warpage. They have not cracked and continue to serve me well, but I believe they have an inherent flaw in either the casting or drilling process or the interaction between the two.

Certainly rotors can be produced that don't have these shortcomings, but they must be carefully engineered and would have to carry a respective pricetag. My warning is to stay away from cheap (<$1000/set) drilled rotors.

 

IMO - Raybestos makes good stuff.
They say the "Brutestop" rotor is for those who like to show.
They are reasonably priced at $52 rockauto dot com.

http://www.raybestos.com/usa/features/rotors.htm

 

I bought a pair of 14 inch rotors for the front and they were $500 plus hats. I will not be drilling these. Not because of bad experience but because no one seems to know.

 

IMO, more meat on the rotor far outways the benefits of the weight savings...especially on a street car....

 

And mine was to approach drilling your existing rotors with extreme caution. Norval, that pattern looks exactly the pattern I drilled. Maybe I should explain it a bit better? As I said, drilling or slotting of brake rotors was a "must do" mod in the early 80's if you had a disc brake equiped bike. Most people would drill the stock rotors as the "racing" ones were expensive to buy. People who were cruisers noticed better initial brake grip in the wet & some noticed higher pad wear (pads weren't particularly expensive so it wasn't a problem & it may have also been related to pad material). Those of us who rode so that heavy braking was frequently used noticed other problems with them. I've listed most of mine but friends often reverted back to stock as their rotors could warp after heavy use. My rotors were cast iron with chrome plating (they worked excellent with sintered pads but were terrifying in the wet, hence my drilling them) while other people had stainless steel rotors, etc. Maybe material has a bearing on this? Something ALL people who used their brakes heavilly noticed was that more braking effort was required, not much, but enough to notice. If you're pulling on a hand lever, or pressing on a brake pedal, then you'll notice slight differences in the amount of force required. With vacuum assisted brakes you probably wouldn't notice. Our guess was that drilling/slotting had reduced the swept area of the disc and, thus, friction. Those people who'd bought expensive drilled/slotted rotors often fitted dual rotors on the front (if not dual as stock) or would change the master cylinder to give extra pressure, & ended up with excellent brakes.
After cracking my rear rotor I fitted a new one & left it stock, with the drilled one still on the front. I then went to Spain & rode through the Pyrenees with a passenger & luggage in the heat of the mid-day sun. The brakes were used a lot in the mountains and at the end of the day putting the front brake on lightly gave a pulsing feel. On investigation I found that the front rotor had warped badly, probably due to the heat. The rear rotor, which I use far more than the front (which is not how you're supposed to do it) was fine. Years later I went to the French Riviera with some mates & we rode through the mountains in the south of France. The roads were like those you see in James Bond films, or Ferrari adverts, so we camped up & spent the next day just riding up & down those switchbacks & crazy gradients as fast as we dared (no pillions). At the end of the day both my rotors had turned bright blue, but were still true. None of us had brake problems, yet some of the people were the ones that had also drilled their rotors 20 or so years ago (obviously they'd been replaced in that time!).
I'm not saying don't do it, I'm saying that if you do then pay attention to them for a long time after you've done it. C3 brakes, even when working correctly, aren't the best brakes on the planet, so do any modifications with care. If I was going to fit drilled rotors I'd also seriously consider some performance callipers as well. It'll cost, but how much do you value your life? Your life depends on how well the brakes work & while you can say "Oh, I never go fast enough to worry" it only takes one time for you to need excellent brakes when you haven't actually got them. I know this from experience, even at 47.36mph excellent brakes could mean the difference between life & death, if not of you, then of somebody else.
And, while Norval & a lot of other people here know what they're doing, there's going to be somebody reading who might think "Unsprung weight? Drilled rotors? Eureka!" & then goes & drills a sequence of 1/2" holes through their rotors. As for negativity, this is supposed to be a forum where people state their opinions & experiences. Mine weren't that good with drilled rotors. Maybe the Vette rotors are of a design/material/heat treatment where the same problems won't occur, but I'd wait for somebody else to try it & report back after a decent mileage has been done in all conditions eg. not just dry day driving at speeds of up to 55mph, but wet weather driving & high speed driving where the brakes are frequently used to bring the car down to low speed ie they might be fine at "normal" speeds, but will they be OK if one of us crazy Europeans, or some Texans, find that they need to stop quickly at 140mph (my wifes relative was killed in a high speed Vette wreck in Canada, apparently the brakes couldn't cope with the speed he was going at).