The rear brakes still used a sold rotor but larger rear calipers with bigger pad area are being used.
Fast forward to 2018, the tires are getting stickier, just about all competitive cars have 1000 plus horsepower and a guy from Ireland named James Deene has stepped up the game even more. The cars are faster, the angle needed is even greater and the need for more driving precision to follow the lead car even closer became more important than ever. Left foot braking to gain angle and to control proximity became even more prevalent as a driving style and when brakes have to hold back 1000 plus horsepower driven by fat sticky tires, the demand on the system increases even more.
For our team, our brakes were adequate in performance but we were using a very aggressive high mu pad to get the results we wanted. Our brakes were impressively shooting sparks and glowing red-hot in many of the rounds and we had pretty rapid wear of the rotors and pads. However, the brake worked decently and we just put these things on a list of stuff to be swapped out in normal between rounds maintenance.
We did see a need to improve the brakes and we asked Stoptech to become a technical partner with our team to help develop a drift specific braking system to meet our needs better. As a first step, Stoptech’s engineers sat down with us to better understand the shortcomings of our current system and what we would need for better performance out of the brakes. They then developed the system we are gonna show you specifically for our car and team.
Our front brakes use the Stoptech STR-60 six-piston Trophy Sport caliper and a 328x 35mm aero rotor. This system has a significant increase in thermal capacity over our old brake system.
The Trophy Sport caliper is forged into a near net shape billet then CNC milled for light weight without sacrificing stiffness. The caliper also has a bridge assembly to make it ultra stiff which improves pedal feel. It has a hard anodized finish which is tough and corrosion resistant. Stoptech, with their large variation of caliper piston sizes, was able to build us a caliper that was compatible with the master cylinder piston sizing in our current pedal box. We wanted a little more gain in our front brakes so Stoptech made our front piston area slightly larger. Our STR-60 caliper also had more pad volume and more swept area which also helped our brakes have more bite with less stress.
Our calipers were loaded with Stoptech’s SR32 compound which has high initial bite and linear torque rise with increasing heat coupled with good wear characteristics for both the pad and the rotor. Stoptech felt that this compound should work well for drifting.
12 comments
What is the purpose of the cross drilled rotor with integrated slots from the drilled hole? Does it prevent cracking from thermal expansion?
I looked all over Wilwood’s website but couldn’t find those particular rotors.
Its mostly to vent the pad outgassing. It actually makes the rotor more prone to cracking and isn’t done much anymore.
Those are thermal expansion slots, which certainly would have been to extend the time before cracking started. When iron rings heat up to competition temperatures, the expansion must be planned for. If not, then iron will crack sooner (beyond the normal “crazing”). There are better ways to deal with this, yet the sprint car/dirt track market typically operate on tight budgets,, so this would be one way to get there.
On the one hand it seems funny that Stoptech keeps coming up… but they really are at kind of a sweet spot. I know from pricing stuff up what a quantum leap up it is to go to the next tier of brakes, and I’m not sure, say, an Alcon TA6 (same pad shape too, I think) is more than incremental gains for the 4x (or so) price jump. I like that some of the newer calipers they’re doing are using more common racing pad shapes than the Brembo shapes the 40 calipers use.
I really like StopTech because they have the tremendous range of piston sizes which enables them to match OEM proportioning. People don’t realize how critical this is and how it affects a car’s electronics nowadays and if the car is an older car, how it affects pedal feel and balance. That’s not the case in this car because it is a race car with a pedal box but for cars with a single master cylinder, it’s amazingly good.
For their street kits, Stoptech also has rigorous validation testing. to assure the vehicle dynamics are safe. When developing frictions and caliper systems, they have OEM level brake dynos and do extensive validation that way as well. They also have a PHD tribologist and develop their own frictions in-house.
Sure Brembo and AP have some more advanced calipers but those are not the ones people typically use for street and grassroots applications. Those are no better than StopTech. StopTech’s engineering office is right down the street from us and they are very generous with help and technical support.
Brembo or AP’s engineering department would probably roll their eyes at the thought of working with a drift Team or not even have any knowledge that drifting has advanced to a high-level motorsport.
Yeah; I have to respect the niche that Stoptech has carved out for themselves. It was a little funny because until I looked it up I didn’t realize the STR60 was using as big of a pad as it is; I like that and a lot of their recent design decisions, and that’s leaving aside the validation they do.
I look at it sort of like… yeah, you end up using Stoptech in a lot of builds. But I know walking pits and looking at prototypes and GT cars and stuff in the 90s to recently (there’s more good options now but you know what I mean) basically everything would have Penske shocks… well, sometimes there is just a “best” solution given constraints.
The pad surface area doesn’t change braking performance, just pad life.
It looks like that kit was a little over engineered for this setup – you could have gone lighter and replaced twice per season? It just depends how much different rotational weight/inertia makes to chassis and tyre dynamics. And team budget of course!
We didn’t just throw some stuff on the car, I worked with StopTech’s engineering department to come up with a system that would solve our problems and improve our brake performance. Pad area doesn’t change the amount of brake torque produced but it can greatly affect the fade characteristics of the brake besides just affecting wear! The system is not overbuilt, it is sized correctly to take the thermal loading that the car produces. With our previous system, we had to run a very high mu aggressive pad with a narrow effective temperature range. Brake temperatures were sky high, the rotors would glow red hot and wear was extreme. Consistency was also an issue due to the pads narrow temperature operating range. Overall performance was adequate. Our new system is only 1.5 lbs per corner heavier in the front and 1 lb per corner in the rear. We are running a 335mm low mass front rotor, not the internally thicker and heavier high thermal capacity rotor. To reduce the capacity would run the thinner rotor, you would only be saving weight with the vane thickness not by reducing material in the friction surface, not worth it in my book.
Great answer Mike – I love your articles. Keep it up!
@Mike Kojima – how important is lightweight brakes (unsprung weight) and small discs (low inertia) for drifting suspension and chassis setup?
Well, you have to have enough brake to do the job, and too much is just weight in a bad place. Having enough brake is the most important thing.
Great answer Mike – I love your articles. Keep it up!