We'll note that Wilwood, which rose from NASCAR and stock car racing, still adheres to a system of measurements based on fractions and thousandths that we hate and can't comprehend, little less have tools for. This resulted in another wasted hour of driving around looking for a quarter-inch wrench to bleed the brakes with.
After a thorough bed-in and cool down, Project Miata was back out doing braking runs. Only on its second run was Project Miata able to eek out a 218-foot stop. None of the other runs were even close.
The problem comes from the change in front to rear brake balance. The front, which now uses Wilwood race pads, requires a lot more heat to properly operate than the Hawk Black pads in the rear. But the larger front rotors, which have more cooling and thermal mass, were consistently 200 degrees F cooler than the stock front rotors under the same test conditions. This combination of different pads and rotor temps causes the rear brakes to lock up before the fronts.
The problem of rear lockup is compounded by the huge amount of brake dive from the new front brakes. As more weight is shifted off the rear tires, less traction is available, which makes the rears even easier to lock up. So, a constant battle of getting more braking out of the front without locking up the rear brakes ensued. On average, the new brakes stopped the car in 230 feet, over 20 feet longer than the original setup. The important thing, though, is that we kept front rotor temperatures over 200 degrees cooler than before, which will mean a lot more at the track.
There's definitely room for improvement in the braking department. It's just a matter of proper pad selection for the front and rear. Since the rears were able to lock before the fronts, the simplest explanation (with all other parameters being equal) is that the fronts can benefit from additional braking torque. Ideally, we'd choose a front pad that provides more grip at lower temperatures. Stiffer spring rates to diminish dive might help too.
Previous InstallmentsDecember 1999Part I: Let the top-down fun begin
January 2000Part II: It's time to get serious
February 2000Part III: The family feud begins
July 2000Part IV: The great intake shootout
March 2001Part V: Standing alone: LINK engine management
July 2001Part VI: Finally, some real power
October 2003Part VII: Advanced engine management
October 2005Part VIII: Laugh all you want, the wing works
Project Miata now wears wider 16x7-inch Buddy Club P-1 Racing SF wheels for the street on 225/45R-16 Toyo T1R tires.
Project Miata's braking distances for 80-0, 70-0 and 60-0 mph were recorded for each of the ten runs on the stock and Wilwood systems. Data was lost for the 9th run on the Wilwood brake upgrade.
Brakezone's front brake upgrade uses Wilwood's four-piston Dynapro calipers and 11.75 x .810-inch, slotted two-piece rotors with directional vanes.
Front rotor temperatures were measured after each run to see how much cooler the larger rotors stayed. Based on these measurements, the Wilwood race brakes barely reached optimal operating temperatures.