I've always been an advocate of smooth faced rotors for performance but, guess what, during the Martinsville stock car race I saw the demo on brakes and there they were! Slotted and dimpled rotors with six piston calipers. OH OH might have to adjust my thinking hat.

 

I commented before on a similar thread about disc brakes on dirt bikes. In the beginning, they had drum brakes. When the first disc brakes came out they were pretty crude. It was a thick solid rotor (no holes or slots, etc). Pretty low tech but much more powerful than the drum brakes that preceeded it.
Nowadays they are much thinner. Some have slots. Some are drilled with large &/or small holes. The outer edge is scalloped (they have "petals' or wave designs cut out). All done for (unsprung) weight savings. They look good but they also have a clear function: Reduce weight.
The only time the motocross factories use a solid rotor is in super muddy conditions.
That tells me that a street car should probably go with a solid rotor. The weight savings are probably minimal. My own inspections have shown that the slots, holes, etc get filled up with junk/dirt/etc.
Having said all that, I will most likely pick a slotted/drilled type rotor for the cool looks

 

I want HHR cut into my rotors....

 

Your first though on solid rotors for street use is still correct. Keep with it.

Martinsville and street cars are two different things. Even Martinsville and most other race brakes are a different issue all together.

I would say they slot them to clean debrie off of them as they are so stinking hot and there is so much rubber on the track there they need to clean them as much and as fast as possible. They offer no cooling. The brake air cooling hosed are the prime cooler.

Few race rotors will have holes and dimples anymore but most have a form af a slot or groove for cleaning. At 185 MPH you want to get full grip now not a half second later. It is something not required or noticed in street driving.

I am sure you have seen the brakes catch fire. that is often losse rubber on the rotors and they want to keep it off. If you have ever been to Martinsville you know how bad the marbles are. I have a chunk of Harvicks bumper and it still had rubber stuck all over it when I got it.

Six piston Brembo's are becoming more common on many street cars. But they are expensive to replace in cars like the new ZR-1 The pads and ceramic rotors are very expensive but will last an est 150,000 miles. Ceramic rotors are getting cheaper and in the next 5 years they will show up on cheaper cars like the Camaro and base Vette.

 

I find it funny how this thread started off with slotted rotors not making a difference to now they are an improvement for race only applications. I stand by my original posts that they do help. Sure the stock brakes are adequate, but some could also say why bother with a Stage 1 kit too. One can never have too much stopping power and when driving daily in DC where the interstate goes from 70 mph to a dead stop about 10 times on your way home, you start looking at ways to improve what you already have.

 

Here how it is best summed up. by Willwood brakes. They are one of the most popluar brake systems out and supply everything from OE to full race system. THis quote can be found here.

http://www.wilwood.com/TechFaqs.aspx#RT

Q: What's the difference between slotted and drilled/slotted rotors? Which rotor will be best for my application?
A: PSlots 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. Also, cross-drilling and/or slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads began to break down at extreme temperatures. This condition is often referred to as "outgassing.” When it does occur, the driver still has a good firm brake pedal, but a significant reduction in friction. Normally this only happens at temperatures witnessed in racing. However, with today’s race pad technology, “outgassing” is no longer a concern with pads designed for racing.

So in the final analysis, drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood provides rotors slotted, drilled or plain. For most performance applications, slotted is the preferred choice. With certain pad material, slotting can help wipe away debris from between the pad and rotor as well as increasing the coefficient of friction between the rotor and the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage; however, for street and occasional light duty track use, they will work fine. For more severe applications, we recommend slotted rotors.



While yes under track or extreme conditions slots do help. Under street there are still mostly for looks and provide little differance in performance. You street brakes do not see the rubber nor the brake dust conditions a race car will see on the track. For example in 250 miles at Martinsville a stock car will use more pad than your HHR will in 5 years of normal drive or more.

Many race cars will just use solid as they do not face a lot of dust or debris. They want the most metal for the heat sink conditions they are intended for.
The Howe chassie Monte Carlo stock I drove used wide five brakes like from a NASCAR Modified. They used solid rotors since there was little need to clean the pads in the type race the car was in. Short races use less brake and create less dust.

Now in road racing most cars have such large tires and longer races the dust never leaves the wheel. Just watch the dust fly when they remove the wheels.

Also slots will help in mud and off road condition on trails or in deep mud or water.

There is nothing wrong with buying these rotors it you like them. I have a set of EBC rotors on the wifes car. All I want to make clear is they do not in most street conditions as most HHR drivers see they will not improve performance in a measureable way nor will they solve anyones brake judder issues that some keep having.

I think the statment here on Willwood site is a good assesment of the perfromance and conditions. Note they are stated helping in race or performance applications. Also note how they state "with certain pad material, slotting can help" this means there are no absolutes and with slots increased performance is not the norm in daily driving.

So yes there are times and cases they may help but in most daily driving conditions as we see in HHRs they will no increased benefit other than making you look good. Solid or slotted my GTP stops just the same. Though it does make more noise in the brakes.

 

Once again, the improvement is from the PADS, not the rotors....if you were to put your stock rotors back on, ( cleaned up of course) you would feel no difference,,, if you want something that works, rotors that have a high vane count and are thicker AND larger diameter....
What we trying to do here is stop any misinformation that provides a false sense of security to say a person thats not so informed and tries to out perform themselves behind the wheel and gets into trouble.........................street cosmetics-yes......performance improvement-NOT....

 

I few years ago, I had a long conversation with a fellow with a brake company that makes really high end rotors. NASCAR type stuff that most regular drivers would never spring for. Aside from holding tight tolerances on machining, which is fairly obvious, the major cost of the rotors is how long they are allowed to cool in the molds before being released. In the foundry business time is money. Not only the time it takes to process the parts, but also the fact that the furnace is running around the clock, whether you're making parts or not. Top quality rotors are left in the molds for upwards of a day, allowing a very slow, controlled cool. The cheap Chinese stuff is kicked out of the molds while it's still glowing. This constitutes a huge difference in how the crystal structure of the iron forms.

I also asked him about slotting and drilling. He said that in this age of modern pad materials, it's a complete waste. Older organic pads would outgas, and those gasses needed to be ventilated. Anyone using organic pads in a high performance scenario in this day and age would be out of his mind, as the newer materials are far superior and don't outgas at all. All the slotting and drilling does is reduce available surface area for pad contact, reducing braking forces. The effect on cooling is minimal, which is more a function of the webbing in between the inner and outer surfaces, overall surface area, and air circulation.

Naturally, I asked him why they still produce slotted and drilled rotors. His answer was simple. Regardless of the merits, or lack thereof, people insist on buying them, including crew chiefs who ought to know better. If he didn't sell them, they would get them from someone else.

 

And..as far as Nascar and demo's .. you said it, demo, and they beautify the parts because it looks more high tech even though they do NOT use slotted/drilled rotors...don't believe the rules will allow it anyways....
If they used what they run they would be boring looking..same as whats on the grand parents buick....

 

As for the castings there are some who feel they need to be seasoned. No they don't need galic.

Some poeple and MFG claim that the rotors need to be heated up with proper temps to get the metal to set right to provide better service and strenght.

I have also seen this with engine blocks and heads. Rolls Royce use to make a big deal out of seasoned blocks.

I never really saw much differance in this but even the experts do not agree on this one. I think in the past with poor materials it may have made a difference but with todays better metals it may be less a factor. Metalology has come a long way since the old days.