Today’s Question comes from Pacheko @miataturbo.com
I run Sports Brakes all around on my turbo’d 1990. I decided to go with regular/jobber rotor with my HP+ since a lot of people told me that expensive rotor was money thrown out of the window… Knowing that the car don’t do more than 30min session, I’m daily driving it and I get no brake overheat.. Are these people right? Would it be beneficial to get proper rotor performance wise?
I’m on my second year with HP+ and I’m curious about trying something else, what pads/rotor combo would you suggest for my current setup?
Thank you for your time, this thread will be interesting.
What is it made from (Iron, Steel, Aluminum, Carbon ceramic, Carbon Carbon)
Where is it made
Is it 2 piece (hat made from aluminum, Rotor ring made from iron)
if it is 2 piece does it float?
Not wanting to spend all day I’ll try to keep the answer short. and focus on the standard parts store rotor.
Standard rotors that you find on Rockauto, Autozone, and so on come from china. They are covered and machined with oil, the material to make them is not as pure as it should be, and are never made engineered for racing. allow me to explain.
The machining process for Chinese rotors involves blasting the machining surface and tools with an oil to keep them cool, this lowers maintenance costs on the tooling machines. After machining factory workers will warp the rotors with an oil impregnated paper. This oil is in an attempt to prevent rust, the oil paper works well at rust prevention. The problem with using so much oil is that, it will impregnate itself into the iron. once that iron is impregnated the oils will come out under extreme braking. Most of the time when you see issues creating and keeping a transfer layer, Impurities like oil inside the iron is causing that issue. The impurities in the rotor are kicking the transfer layer off. Racing companies like PFC, Brembo, AP, will cut the rotors “dry”. Machining “Dry” means to machine the parts without any cooling oil. It is higher wear and tear on the machines, and that means its more expensive to do. Dry cutting will increase the rotors ability to obtain and keep a transfer layer and increase it’s performance. This will also extend a rotors and pads usable life. do try and avoid rotors with impurities. lately the trend has been to paint the rotors or cover them with powder coat. this is 10x worse than using oil. it is very hard and time consuming to remove the paint from a rotor and pad. The contamination is mind boggling.
Next is what it’s made from. Iron is easily one of the best materials used for rotors. Size for size an iron rotor will outperform a carbon ceramic rotor. If you have 14″ rotors, one in carbon ceramic, one in iron. The iron rotor will generate a more consistent and higher TQ output over the carbon ceramic rotor. Not to go too off track but that is why you see 15-16″ carbon ceramic rotors on oem vehicles. The oem manufacturers need the increased size to get the performance. Carbon ceramics will outlast an iron rotor and have a larger temperature range. …Sorry. Back on topic, right iron.. Iron is one of the densest materials in the universe. How pure the iron’s casting is makes a considerable margin in braking performance. Rotors that are casted in china are known to have quite a few impurities, and are sometimes labeled incorrectly. Anyone that has dealt with 304 *chinese* stainless will know what I’m talking about. These impurities will have a decreased effect on braking performance. Effects like decreased overall braking torque, decreased rotor life, and unstable tendencies at thermal capacity (AKA exploding rotors). I like to find Rotors manufactured and casted in the USA. The us has a higher standard of casting.
Finally the engineering in the rotors could take year to explain, so I’ll focus on balancing only. When a rotor gets hot it cones, it beds, and it looks like a wave. it’s never still. The material is constantly flexing. (FIGURE 1 A&B.) think about a top fuel dragster tire in slow motion.. It’s not 100% the same but it is close. That rotor is constantly trying to keep itself together and not explode. On the outer edge of a rotor will have high and low spots, these spots will cause an imbalance in normal 20+ mph operations. In order to stop a rotor from shaking suspension components all brake manufacturers need to balance them. Top Motorsports brake manufacturers will balance the rotor by cutting the entire outer perimeter of the rotor on a lathe(FIGURE 2) . This ensures that when a rotor is at thermal capacity, there will be no places of excess or minimal material. it makes the rotor stronger, and more resistant to cracking. Part store rotors balance the rotors by finding the heavy spot on the rotor and cutting that off. (FIGURE 3). In Motorsports this is a huge no-no. The hard edges give a place for cracks to start, the material has a thin spot on the rotor, and it means that the material that is spinning is not balanced through the assembly. it can lead to a cracked rotor, a long pedal, and unusual pad wear.
In conclusion. Are high quality rotors a waste? Like tools, good quality parts are never a waste. On average a motorsports rotor will outlast a parts store rotor long enough to justify the increased price. The increased performance is nice to have too. Parts store rotors have been known to work, they also let a lot of people down. If it was my money paying for my track day, I’m putting the parts on my car that will insure that I have a fun weekend. I’m not looking not fight the issues with a $30 rotor that costs me $800 of track time. Allot of people might say “they worked fine for me”. Truth of the matter is 80% of the Motorsports population knows how to build a motor, 10% know how to build a braking system. When the brakes that they said “worked fine” didn’t work “fine” and that person has no idea what the problem actually is.
Letters to a Brake Nerd: If you having an issue with your brakes, Ask the brake nerd (Johnny C). Or if you are looking to upgrade your brakes, ask. The majority of club racing related braking issues that come across, are from individuals who tried to upgrade their system without knowing the in and out of braking systems.
About the Brake nerd: ” Johnny C is the majority of my real name. I’m a “brake guy” by profession and by hobby. I have an obnoxious amount of brake tech swirling around my noodle. If I crammed that info into a Book, nobody would read it. It’s some of the driest information anyone could imagine. If and only if you have an issue with your brakes would you pay attention.
I’m a former PFC factory Rep. I’ve worked with top racing teams like Joe gibbs racing, Ganassi, Rum bum, Irish mikes, so on, and so on. I’ve been in the Motorsports world professionally starting in 2006. I’ve worked hand and had with teams and engineers to build braking systems and to fix issues with braking systems. ” – Johnny
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