So, which rotors are better for racing applications, ported, or solid rotors with vents?

 

Hmmm...
What kind of racing ?

 

This may help you out.

Cross-drilled rotors DO NOTHING to improve braking performance. The holes are mainly for cosmetic reasons and to reduce weight.

If you're setting your car up for drag racing, then cross-drilled rotors would be good. For auto-x or hitting the local twisties, go with slotted or solid rotors. I'm not sure what you're referring to when you say "vents" but all 3 rotor types usually have the center vents for cooling purposes.

 

I do not agree. I put drilled and sloted rotors on my car and they do make a difference. For a street car they will not help much. When you do auto cross they help brake fade. I have read many posts on this subject and all I can say is look at the pros race cars,what do they have? I rest my case.

 

Well, I'm gonna have to contradict you here. I've done a bit of research on this. There is a book I have on brakes for street AND racing and it confirms what I stated. Also, check the Wilwood Brakes web site. They too back up my statement.

A drilled rotor cannot withstand the same amount of heat as a solid rotor and is therefore prone to cracking and early failure. Pro race cars do run drilled rotors in SOME cases. Usually where they don't use the brakes heavily and they're looking to save weight. Every little bit counts you know.

Take NASCAR for example – On a superspeedway, where the speeds are high and braking is minimal, they run thin, drilled rotors with small calipers. On a short track, where speed is low and braking is very heavy, they run thick solid rotors with large calipers. On a road course they'll even use six piston calipers.

IIRC even the CART cars no longer run drilled rotors.

 

I can only tell you my cars is better with them. I saw a thing on TV with a camera on a nascar front wheel during hard braking and the rotor would glow red. It was a drilled rotor. As far as them not doing alot of hard braking I believe everytime they use the brakes it is what we would call hard braking. I still believe it make a difference. I also agree the main reason people use them and I picked them at first is for looks. However in my case I believe they are better. I only drive my car in nice weather and maybe 5 thousand miles a year so who knows how long they will last.

 

In a way you are both right. Cross drilling a rotor will let it cool more quickly than non-cross drilled, allowing a higher temperature. However, when you use you brakes they they get hot (duh). This is where application comes into play when deciding on rotor type.

On a race car once they get hot the tend to stay hot for the duration of the race, thats why they can be seen glowing at every corner, they hold enough heat that the slightest push of the pedel makes them glow. One particualer super latemodel race comes to mind, where the lead car's brakes were glowing all the way around the track. After the race is done and they are inspected, the brakes are probably thrown away.

On a street car you use your brakes hard maybe once every minute or more (stopping for red lights), or longer if you are on the highway. This allows the rotor to cool back down to almost ambiant temperatures. When this happnes it is called heat cycling, something that cross drilled rotors don't like doing. The cycling leads to stress fractures propagating from the drilled holes, thus a damaged rotor which now needs to be replaced.

I'm not sure if the actual drilling of the rotors helps braking or not, but they were always a compromise design when they were introduced (for La Mans if I recall correctly). They traded life and comfort for reduced weight and (possibly) better braking.
Just my $0.02

 

I'm not trying to create some great debate here, but I thought you guys would be interested in reading this. It is from the FAQ section of the Wilwood Brakes web site:
http://www.wilwood.com/faq.asp#question7

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Q: Why are some rotors drilled or slotted?

A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity.

Slots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to "glazing" and the slots tended to help "scrape or de-glaze" them. Drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood has a large selection of drilled and slotted rotors for a wide range of applications.
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I do currently have AutoSpecialty cross-drilled rotors on my GTA. Whether or not they've improved my braking, I can't say for sure. I think the PFC brake pads are more of a factor. I do know that the drilled rotors seem to extend the life of the pads in daily street use.

The biggest factor in increasing braking is to increase the amount of braking surface. That's why we're all scrambling to upgrade our cars to the 1LE set up or buying Baer Big Brake kits. Bigger rotor = more braking surface = better braking.

For my 1LE upgrade I'll be installing a set of slotted rotors that I picked up.

 

it's all in the pads.
and for auto-x, regular pads work best no matter what anyone says. don't need no race pads or Z crap pads for auto-x. there is no brake fade on a 50 sec course.

on a road course race pads on regular rotors work fine.

 

Every single hole you drill in a rotor reduces it's "swept area". Less area= less brake force,

 

I have to agree.

Cross drilling and slotting is a waste of time and money, especially if you're trying to gain braking performance. Nice solid stock rotors and aggressive pads are the way to go.

 

I see I'm losing this one. Difference of ideas is what this country great. We do all agree on one thing third gens are great cars

 

I'm gonna go a step further and say that it's actually all in the rotor diameter, or perhaps more precisly distance of the caliper from the center of rotation.

I run cross-drilled rotors on my car, and have been running the same set for almost 3 years now, through 4 or 5 sets of pads without any cracking, gouging, or warping. So I believe that they're fine for street use (no heat-cycling issues).

However, I picked them only for cosmetic reasons, since my wheels have massive voids between the spokes. I didn't notice, nor did I expect any increase in braking ability caused by simply going from solid rotors to cross-drilled rotors.

If you want better braking, then the two things that are going to make a real difference, are bigger rotors, or bigger tires. Everything else is detail.

 

If I can make an analogy here, it's sort of like putting a K&N air filter in your stock airbox. There may or may not be an increase there, but it's mostly in your head because the stock setup is still holding you back. Getting bigger brakes/tires is like throwing the bigger engine in instead of going for the gimmick air filter.

 

You're correct when you surmise the distance of the caliper from the center of the rotor plays a part. Effectiveness of a disc brake system is determined by "swept area" which is (layman's definition) the total area the pad covers in one rotation of the rotor.

All things being equal, you can take the same caliper and 0.5" bigger diameter rotor, and you won't get any better braking unless you also move the caliper 0.5" farther out.

Keep in mind though, you can have better brakes than your tires will allow you to use, just like you can have a bigger engine than your tires will allow you to use. The stock brakes can easily lock up the 195/75R14 tires that are stock on my year sport coupe! Once you upgrade to REAL tires like 255/50R16, you've got enough tire to make it worth your while to upgrade the brakes.