We’ve been busy on Project CrossTime lately and haven’t had a chance to show what we’ve been up to. We’re still waiting on some parts before we do some big projects on our little Miata. Luckily, we have been able to do our first two steps: tires and brakes. Talk about making a huge swing!
Just to recap, my friend Chris and I bought Project CrossTime off of Craigslist for $1,000 from a teacher who had moved to Malaysia to teach English. It is an original 187,000-mile car that we had to replace the clutch slave cylinder to get it moving, but otherwise, was good to go. We stuck a Hard Dog rollbar in it and started autocrossing and road coursing it with the cheap 400 treadwear tires. You’ve never heard tires scream for mercy as loud as these things.
It was obvious tires needed to be the first change. Instead of buying new for the second event, we were given a set of take-off Toyo RRs from a generous Spec Miata NASA Mid-South member. We got them mounted and went racing. To say they made a huge difference is an understatement. The extra grip showed us we were correct in thinking our next upgrade would need to be brakes.
The higher speeds through turns now meant higher speeds down the straights and into the corners, resulting in brake fade after about the fourth lap. It wasn’t horrible, but it was noticeable and it wasn’t allowing me to drive the car as hard as I wanted. It was time to upgrade the rotors and pads and I knew just who to call, two of the best in the business: DBA USA for the rotors and PFC Brakes for the pads. Though both companies offer rotors and pads, I heard really good things about both and thought I’d give them both a shot.
The Power Of The Kangaroo Paw
DBA USA is the U.S. division of Disc Brakes Australia. DBA has been in business more than 40 years and makes a variety of replacement and upgraded rotors for everything from passenger cars to off-road and road racing applications. I got in touch with DBA USA’s General Manager Mark Joseph before I blindly ordered the rotors to make sure I got what I really needed. It was a good thing, too!
Having a background in hot rodding, my plan was to go with cross-drilled and slotted rotors — those have been all the rage for quite some time now in the street/show car world. Heck, I have them on both of my street cars. But it turns out, that is not the best for all applications, especially for the type of HPDE and autocross driving I am doing now.
“Cross-drilled and slotted rotors can be used in a road race car, and can be used successfully if the driver has the luxury of warming up the rotors to operating temperatures before racing and then cool down after racing with a few slow laps,” Mark Joseph explains. “Not all drivers have this luxury, so that is why we don’t recommend using cross-drilled rotors. If you can imagine dropping an ice cube in a glass of water, the sudden thermal shock cracks the ice, same with cold rotors having sudden heat generated in the first few turns.”
On that great analogy, he recommended I go with the Club Spec Road and Race 4000 series T3 rotors. These rotors have tri-symmetrical curved slots (48 to be exact!) that result in a more responsive and smooth brake pedal feel. The slots also provide an increased number of out-gassing exit points for the brake pad friction gasses to escape, which gives a more consistent and effective stop (or in my case a slow down).
Obviously, heat is the number one enemy of rotors, so dissipating heat is critical to the life of the braking system. DBA uses a few different proprietary tricks to address heat dissipation: XG150, Thermal Stability Profiling (TSP), and Kangaroo Paw.
XG150 is a high-carbon alloyed iron that increases the thermal capacity, allowing the rotor to handle constant extremes of heat over extended periods of time. It is specially formulated to work with the TSP process to prolong the life of the rotor.
“Thermal Stability Profiling (TSP), is a heat treating/stress release process,” Mark says. “The rotors are placed in a heat-treating oven and heated up in a controlled environment. They are held at temperature for several hours then slowly cooled, again under controlled conditions. All stresses are released from the disc, then it is machined back parallel, and slotted or cross-drilled and slotted. This process helps in the bedding-in process, and virtually eliminates the disc running out. Since the stresses are released beforehand, and not in the bedding-in procedure, the discs remain parallel.”
The Kangaroo Paw design is catchy, but it serves a critical service. “All DBA rotors incorporate our patented Kangaroo Paw vent design,” Mark continues. “The reasoning behind this design, is to cause a ‘turbulence’ within the rotor center to increase cooling. Kangaroo Paw has 144 strategically placed ‘Pillar and Post’ teardrop shaped posts. This also eliminates the need of a left- or right-handed curved vaned disc. Its uni-directional, and can be installed on either side.”
There are a couple of other cool features that aren’t critical to the effectiveness of the rotor, but show the attention to detail that DBA puts into them. They paint the non-friction parts of the rotor to keep rust to a minimum. Additionally, they have added three thermo-graphic heat paint markings on the outside edge that change color when specific heat thresholds are reached. These give you a quick visual indication if you are pushing the limits. Pretty trick!
The Gift Of Grab
PFC Brakes is a slightly younger company than DBA, but like DBA they are a global company, even though they were born and raised here in the U.S. Rob Krider wrote a great piece on the history of the company HERE, so there is no need to go into great detail, but I will say that PFC Brakes are spec on all forms of open-wheel racing including IndyCar, Indy Lights, Pro Mazda, USF 2000, and F4, so I knew who I wanted to turn to for brakes on my little hooptie Miata.
Now, I’ll be honest, I know very little about brakes, so I called Justin Cockerham, the sales manager at PFC Brakes to explain a few of the mysteries of how brake pads are made and how they generally work. I learned so much in the few minutes we had to talk.
“Obviously, each company has their ‘secret sauce’ when it comes to the compounds and things of that nature, but environmental concerns have really thrown a curveball to the brake industry during the past couple of decades,” Justin says. “Asbestos and other unsafe materials used to be the standard in the friction manufacturing process. Today, globally, there are still very harmful materials being used in areas of the world that are far more unregulated, but PFC patented its Carbon Metallic compounds without those harmful materials, which gave us a huge advantage for many years.”
Justin recommended we utilize PFC’s CarbonMetallic Compound 97 pads on Project CrossTime. According to PFC’s website, this compound has been a favorite of sports car endurance racing since its debut. It has less initial bite and average torque than PFC’s extremely popular 01 compound. It has great modulation, a very flat torque curve, and enhanced release characteristics. 97s are recommended as a general-purpose pad for club racing and track day events, or as a rear pad in heavy front engine rear-wheel drive applications such as Mustangs and Camaros.
When I asked why he chose this pad for my Miata, Justin says “the Miata is an easy car to over-brake, therefore killing momentum, which is the key to driving a Miata fast. The ability to modulate the brake to manage tire grip (i.e. threshold brake) is best done with the friction characteristic of the 97 compound. On a Miata that is built beyond the Spec-Miata format — with added aero, horsepower, etc. — then it could be beneficial to look at a more aggressive compound such as our 11.”
That spurred me to ask: what makes one compound different from another?
“All of our compounds are similar in that the foundational recipe and principals are the same, however, they are tweaked and tuned in certain ways to achieve different characteristics for certain disciplines of use,” Justin explains. “Really, the ‘science’ in differing brake pads is the blend between the abrasive and lubricating materials. People don’t really think about it, but there is as much (if not more) science in the lubrication properties as there is in the abrasives.
“Getting the pad to stop the rotor is easy, the hard part is getting the car to stop predictably and consistently over repeated cycles. That is where we tweak the recipes to suit the type of car or style of driving. Some street pads may even work better on some race cars than race pads. For example,TechSport Racing runs our street pads on their Subaru BRZs in the Pirelli World Challenge TCA class because that is what the ABS likes. We tried a less aggressive race pad, and it was still too much, so they stay with the street pads and are very happy.”
Justin likened brake pad compounds to the sole of a shoe. Just about any shoe will get the job done, but will it do it as efficiently as it should, and will it be as comfortable as it should be? “You wouldn’t want to wear dress shoes to go hiking, just like you wouldn’t want to wear hiking boots to go running. Brake pads are the same way, not one-size-fits-all.”
There are two additional qualities that excited me about PFC Brakes’ pads. The first is that the friction materials are pressed and fused along with a bonding agent onto the backing plate, so you could just about run the pad down to the plate. I wouldn’t recommend it, but you could. The second is that the pads go through a “race-ready” process, which essentially pre-beds the pad by putting it through a heat treatment skimming fixture. This bakes out the gasses from the bonding agent and cooks the outside of the pad, virtually eliminating the need to bed the brakes other than a few hits on your outlap to heat them up.
I will start this section by being honest and telling you I don’t have the tools to do scientific testing. I received a tire pyrometer and infrared gun from Summit Racing halfway through this project, so I can’t give you before/after brake temps, but I have before/after lap times on the road course at Memphis International Raceway and my “butt-meter” to tell you the results.
2/17/18 – First Track Day (ever!) — NASA Mid-South Summer in February event at Memphis International Raceway (MIR). 400 treadwear Douglas tires and stock brakes. Cool conditions, torrential rain, then semi-wet.
It was my first official track day, so there were a few learning curves — learning the car, learning to race, learning to drive in a monsoon. But, by the end of the event, my instructor and I determined I was getting everything out of the car I could on the stock setup. In the last session (which was 45 minutes long), I was turning average and consistent laps of 1:39 around the 1.8-mile road course once it dried. My instructor Jonathan, noted that we were definitely on the limits of adhesion for the 400 treadwear tires as they screamed for mercy through the largely left-handed course.
The car was greasy to say the least, but it was predictable, which was comforting. For the most part, it would just push or four-wheel slide, but I could modulate on and off of the throttle to get the car pointed in the direction I wanted it to go.
6/26/18 – Second Track Day during SCCA’s Track Night in America (TNiA) at MIR. 40 treadwear Toyo Proxes RR tires and stock brakes. Warm, sunny conditions.
We did minimal work to the car as I was trying to source parts during this time, so the car was essentially the same except for the tires. We did gut the interior of carpet and door panels. I entered the Intermediate class which was a pretty packed class with about 25 to 30 cars. I didn’t get a ton of laps in that were clear of traffic, but I was clicking off some decent times of 1:34, with one or two forays into the 1:32 range.
The car was even more predictable with the stickies, but carrying more speed in the corners meant I had to be smoother with my throttle modulation in the corner to point the car. If I let off the throttle in the corner it would snap the rear end out as the front tires got more bite. It was noticeably faster through the corners.
One point to note here: 3,500 feet of the 1.8-mile course is the drag strip, so lap times are not going to decrease greatly without more horses under the hood. Just about any stock(ish) Miata will be turning anywhere from 105-108 mph at the end of the straight — no matter what you do leading up to it. I think a 5-second decrease in lap time is pretty significant with all else being equal.
7/24/18 – Third Track Day during SCCA’s TNiA (Advanced class) at MIR. 40 treadwear Toyo Proxes RR tires and DBA Rotors and PFC Brakes. Conditions were hot and sticky.
I had a few more autocrosses under my belt by my third event, including the SCCA Pro-Solo event in Blytheville, Arkansas, where I picked up a lot of pointers about Miatas in general, so I’d really gotten to know the car by then. This was the first outing (of any kind) with the new rotors and pads, as I just installed them two days prior.
It’s probably a bad habit, but I “check” the brakes before I get on them heading into a corner, just giving them a little pump before I really apply them. Well, heading into the carousel at the end of the front straight, I did my usual pump to check the brakes and actually ended up scrubbing speed before I was ready.
The first initial bite of the pad on the rotor surprised me with the difference in responsiveness. The pads grabbed the rotors with a lot more authority than I was prepared for — it took several turns before I knew where the locking-up point was. By the end of the first session, I was able to go much deeper into the turn before applying the brakes. I could get on them harder and scrub speed much quicker, which allowed me to set the car sooner before getting back on the throttle.
At the end of the event, I was totally comfortable with the new feel and was out-braking just about anyone into a turn. I could stay on the gas longer in the straights and brake later, significantly shortening the braking zone. My little Miata would get smoked down the long front-stretch at MIR, but I could make up the time on faster vehicles in the corners, often catching them by the time we got back around to the front-stretch.
So, it felt faster; but was it? After reviewing my lap times, the answer was a resounding yes! Changing to the new DBA rotors and PFC pads, was worth another three to four seconds. I went from being consistently in the 1:34 range, down to 1:28. As a matter of fact, I only had one lap in my final session that was above 1:30 (I got crossed up in the esses). Anytime you can gain a full four seconds with an underpowered car, that is saying something.
I’ve heard from many people that the stock Miata brakes are really good. I would agree with them to an extent; they don’t seem to fade much and they take a licking and keep on ticking, but there are better aftermarket options on the market that will improve your lap times without having to change the drivetrain. True, you might not be able to make that change in some classes, but for some of the more lenient classes, they allow brake changes without having to step up to the next class. Modify the drivetrain, the body, or change tires and you’ll be moved into a different category (likely Unlimited).
I think I made a great decision going with DBA rotors and PFC Brakes pads. The only problem now is that I am carrying so much speed into tighter corners that it is lifting the inside rear wheel. Without suspension or a limited-slip differential, I can’t get what little power I have to the ground. Hopefully that is coming soon. I will keep everyone updated in the build thread as I continue progress on the car and participate in more events. And now that I have some testing equipment from Summit Racing to show how the upgrades are doing, I will post that information as well. Stay tuned!