Brembo's and Axxis pads from The Speed Factor

[mavisky]

Slotted rotors and 2 piston calipers filled with axxis pads will be my next brake setup for sure.

 

[prostreetdsmx1]

Drilled= weight loss (can crack) Slots= gases escape(run coolier) Dimples= ? looks cool Axxis= great street pad maybe light track use? (I'd burn up a set of Axxis in one weekend of road racing) Porterfield R4-E $175.00 for just the fronts. You get what you pay for.....

Greg

dude i can see you killing a set of pads in a day easily. Love the car by the way, congrats on the sponsorship deal.

 

[Doug99RS]

I don't buy in to the "cleaning water away" bit. Between centrifugal force and the sheer heat of the rotors, if there's enough water on there to affect the braking then you need to be wearing scuba gear anyways. The average car will boil off any bit of water that collects on it and if you keep the backing plate on the rotors you don't have to worry about water on the backside.

I beleive the dimples, slots and cross-drilling are all for gas evacuation. The amount of metal removed from drilling the holes in the rotors can easily be replaced with a lighter set of wheels. The slots help remove gases from between the pad surface and the rotor surface. Much like tires, as the pads get hot there is a build up of gas between the two surfaces. As this gas builds up the brakes begin to fade. Brake fade is also due to high temperatures in brake fluid. The friction between the brake pad and the rotor builds up a tremendous amount of heat. The heat transfers to the calipers and then on to the fluid causing it to heat up, boil and your brakes fade.

The vents in the rotors are there to help disperse heat and improve air flow. The slots, dimples and holes all disperse the gases from between the pad and the rotor surface.
Doug

 

[Greg Collier]

I don't buy in to the "cleaning water away" bit. Between centrifugal force and the sheer heat of the rotors, if there's enough water on there to affect the braking then you need to be wearing scuba gear anyways. The average car will boil off any bit of water that collects on it and if you keep the backing plate on the rotors you don't have to worry about water on the backside.

I beleive the dimples, slots and cross-drilling is all for gas evacuation. The amount of metal removed from drilling the holes in the wheel can easily be replaced with a lighter set of wheels. The slots help remove gases from between the pad surface and the rotor surface. Much like tires, as the pads get hot there is a build up of gas between the two surfaces. As this gas builds up the brakes begin to fade. Brake fade is also due to high temperatures in brake fluid. The friction between the brake pad and the rotor builds up a tremendous amount of heat. The heat transfers to the calipers and then on to the fluid causing it to heat up, boil and your brakes fade.

The vents in the rotors are there to help disperse heat and improve air flow. The slots, dimples and holes all disperse the gases from between the pad and the rotor surface.
Doug

Correct! The concept of the slots has nothing to do with water dispersment. The dimples may have a "small" effect on gas evacuation and brake fade is also due to high temperatures in brake fluid.
Greg

 

[definitiveno]

I don't buy in to the "cleaning water away" bit. Between centrifugal force and the sheer heat of the rotors, if there's enough water on there to affect the braking then you need to be wearing scuba gear anyways. The average car will boil off any bit of water that collects on it and if you keep the backing plate on the rotors you don't have to worry about water on the backside.

your right about the water. See bottom of article for the purpose of slots

I beleive the dimples, slots and cross-drilling is all for gas evacuation. The amount of metal removed from drilling the holes in the wheel can easily be replaced with a lighter set of wheels. The slots help remove gases from between the pad surface and the rotor surface. Much like tires, as the pads get hot there is a build up of gas between the two surfaces. As this gas builds up the brakes begin to fade. Brake fade is also due to high temperatures in brake fluid. The friction between the brake pad and the rotor builds up a tremendous amount of heat. The heat transfers to the calipers and then on to the fluid causing it to heat up, boil and your brakes fade.

If you look at a spinning drilled rotor from the side, you can see that the way the drill pattern works, every inch of the pads surface will at some point in the rotation or another slide over a drill hole. Any pressure that builds would be released into the drill and the gas would escape that way. I don't know if I need to address this or not but it's also pretty common knowledge that modern brakes pads of today (no longer aspestos) do not emit gasses when heated, so the whole point of drills is kind of moot any more, accept for weight savings

The vents in the rotors are there to help disperse heat and improve air flow. The slots, dimples and holes all disperse the gases from between the pad and the rotor surface.
Doug

Atleast you got the vents part right. Not to be rude in anyway, ive seen lots of shops that still advertise their products to do this or that, wich is all fugged up and nothing but blaintant false advertisement. Nothing more to say about it, it's just not accurate.

Those Poor Rotors

Let's look ot some common rotor "modification" and "performance" upgrades that you may have been exposed to. We'll try to separate the marketing from the engineering: Bigger rotors will make your friends think you are cool, bigger rotors look sexy, but bigger rotors do not stop the car. What a bigger rotor will do is lower the overall operating temperature of the brakes--which is a GREAT idea IF your temperatures are causing problems with other ports of the braking system.

Take, for exomple, a Formula 500 racer, a small 800-pound, single-seat formula car. While the brakes are certainly much smaller than those found on a 3000-pound GT1 Camaro, that does not necessarily mean that they need to be made larger. In fact, installing o GT1 brake package onto our formula car would probably do more harm than good. That's a lot of steel hanging on the wheel that needs to accelerate each time the gas pedal is pushed. So the motto of this story is bigger is better until your temperatures are under control. After that point, you are doing more harm than good, unless you really like the look. (And hey, some of us do.)

Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses somewhere to go. It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.

The one glaring exception here is in the rare situation where the rotors are so oversized that they need to be drilled like Swiss cheese. (Look at any performance motorcycle or lighter formula car, for an example.) While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember that nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life, at the expense of higher weight. It's all about tradeoffs.

Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

 

[nine5raptor]

My only issue with the whole slotting/drilling thing is that by cutting the slots/holes in the rotors, you are creating huge stress risers. If the rotors were done correctly, the slots/rotors would be cast into the rotor in the begining (or even better, forged into them). This way the grain flow would be around the imperfection instead of disrupting the boundaries.

edit: I was a bit late, the article above just said pretty much what I was adding to the conversation...

 

[1992AWDDSM]

Thanks definitiveno.

It's amazing, that some people continue to perpetuate myths for their own marketing advatage. And then those who blindly listen to the 'mob mentality' call out those who attempt to dispel the misinformation.

After all this time, you would think people would do a little free thinking of their own and do their own research before they attempt to question others.

Sure I could have gone with those pretty, cross-drilled rotors. But any slight benefit they would have been, would have been quickly out-weighed by the tremendous cost (at least to me) of replacing those rotors every time they stress-crack. Maybe some true, dedicated road race cars have them, but I would guess those guys have enough money to replace them every time they wear out.

EDIT: I read this and thought it was interesting.

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[1992AWDDSM]

Also, before I get misunderstood, I am in no way casting a bad light on The Speed Factor. I in fact, just dropped a cool grand on some D2 coilovers with them. So please, refrain from making accusations that I am bashing Speed Factor. These guys are cool.

 

[jtmcinder]

Thanks definitiveno.

It's amazing, that some people continue to perpetuate myths for their own marketing advatage. And then those who blindly listen to the 'mob mentality' call out those who attempt to dispel the misinformation.

Before you thank him too much, recall that he was the one who floated this idea:

Slots however have function. They are not intended to evacuate gasses but to clean the rotor of any water or other agents that can get between the rotor and the pad. They also keep your pads wearing evenly to distribute equal braking across the pad surface at all times.

In his defense, however, he did seem to retract the bit about water evacuation after being called on it, which is very cool. Don't see that often.

One thing that was missing in the passage taken (without giving credit, I might add) from scR Motorsports -- see: http://www.teamscr.com/rotors.html -- was a discussion of green fade vs regular pad fade. Yes, fancy modern racing pads don't give off much if any gas after they have been bedded, but they do have to burn off the excess binder -- see, also: http://www.baer.com/Support/FAQ.aspx#1. Furthermore, when you take a street pad over its limit (such as trying to LFB to 5 psi by mid-corner when autocrossing with Metal Masters and stock rotors), you will produce some gas. This is why reputable companies still make slotted and/or drilled rotors for the street.

My suggestion is that you think about the pads and the rotors and how you will be driving as a package. OTS kits with funny-looking rotors are fine for everyday driving. Heck, I'm quite happy with Powerslots and EBC greens for what I do. But you're going to want something that is much better planned if you do back-to-backs from 100 to 30 (or worse).

And when your life depends on it, the internet might not be the best place to get your information.

- Jtoby

 

[97TSIAWD]

Jtoby has a point. My friend races a Z06 around tracks in Ohio, they take corners very fast, some 120 and faster to about 20-40 corners. He has tried several setups, tires, rims and brakes. He tried, slotted, drilled a combination, and found that any rotor that had a surface that was not solid would get too hot and crack no matter what brand it was. So he merely upgraded to a six piston caliper and a larger solid rotor, vented (not sure what pads he runs). Now his is an extreme case and I would say that a normal daily driver, even an autocross person is not going to drive the car as hard as he does, so these type of rotors would probably be fine. Everyone's setup for brakes is going to be different, test it out and find what works for you.

 

[crankbender]

seems to be all figured out.

If you are really worried about brake cooling you should look at adding additional venting to the general area. Unfortunately our bodies do little to fan the area around the brakes, and what little air gets there is heated by ICs and underhood movement.

Anybody designed a brake cooling duct kit for the DSM yet?

 

[97TSIAWD]

seems to be all figured out.

If you are really worried about brake cooling you should look at adding additional venting to the general area. Unfortunately our bodies do little to fan the area around the brakes, and what little air gets there is heated by ICs and underhood movement.

Anybody designed a brake cooling duct kit for the DSM yet?

Well there are serveral hard autocrossing and track racing DSM's around, the two on the front page come to mind. I would think maybe that yellow card would have some sort of venting, however I have never seen a product from a company for venting. I imagine doing it yourself would be a real sort of hacking job, but if a company would R&D something I imagine it would be really beneficial to a lot of DSM'ers. Interesting thing to look into. Thinking about it, if the stock sidemount were gone you could remove the inside wheel cover to get some airflow, but I don't know how well this would work.

 

[jtmcinder]

I have never seen anything OTS. It seems that everyone who does it, builds their own.

Removing the inner liner won't do much. The wheel well is a high-pressure area already and so this won't increase the airflow through or across the rotor. It might even make matters worse. You need to send the air in through the center (near the hub) and have it flow out through the vanes.

- Jtoby

 

[GTM]

I have never seen anything OTS. It seems that everyone who does it, builds their own.

Removing the inner liner won't do much. The wheel well is a high-pressure area already and so this won't increase the airflow through or across the rotor. It might even make matters worse. You need to send the air in through the center (near the hub) and have it flow out through the vanes.

- Jtoby

I do think that there is something to be learned from our 2 wheel cousins who have been using vented multi piston brakes for years. I don't understand why so many posts seemed to address gas rather than air, did that make it sound better...

Many years ago we had "V" belts and I concluded the more V's the better, so following that logic and physics why don't we have grooved brakes? My guess is they don't want to tool up for the tighter standards which would require pads to match. We know the Bernoulli effect exists or our hard drives would have made it about as long as an old 78rpm phono disk. Were it not for new glues and better pads they would be in a constant state of fading for they are always hot from the air friction. But when you do encounter that large puddle of water and then have to slam on the brakes you find out the pads are hydroplaning on the rotor unless you provide grooves/slots/holes just like tire tread. Drive down the highway without touching the brakes for some distance, use the hand brake to stop the car and check the front rotors ... carefully. The unvented disk will be a couple hundred degrees hotter.

As for the other portions of the discussion and wheel well pressures you will note the louvers on top of the wheel arch which are being included in the serious high performance cars appearing on our streets.

Lots of things have been tried including wheels made to act like fan blades to draw more air through the brake area. When people are ready to give up some opening in these "air dams" where they mount all kinds of trick colored lights and substitute cold air ducts we might see some changes.

Cheers,
GTM