Both the Yokohama AVS ES100 tires utilized on the Formula and the BFGoodrich G-Force KDW's fitted on the GTO were relatively new with well under 7,500 miles and only slight tread wear. Although both are top name brand performance tires, it didn't take long to find out where the limits of traction were when subjected to higher rpm launches.
A comparison between the stock...
A comparison between the stock 17x8-inch 5-spoke GTO rims shod with a P245/45ZR17 BFGoodrich G-Force TA KDW tire (on the right), versus the 17x9-inch WS6 rim with a 275/40/R17 M/T ET Street radial is telling. Although the stock tire diameter on the GTO rim is identical to the WS6/M/T combination (26.0-inches), the mounted tread width of the stock wheel/tire combination, as stated by the manufacturers (as measured from corner to corner), is 9.65 inches (BFG) versus 10.0 inches (M/T). The actual contact patch is measured at 8.5 and 10.5 respectively, giving the M/T tire a true two-inch advantage.
With a manual transmission and explosive power on tap, the Formula would spin the stock tires badly at 2,400 rpm or greater and then lose traction down the track, resulting in poor performance. With the M/T ET Street Radials mounted on the Formula, we never did find an elevated rpm that would spin the tires badly. In addition to averaging over 0.5 seconds better at 2,500 rpm or greater, the tire performance consistently increased in direct correlation to the engine rpm increase.
The GTO quickly found the breaking point of the stock rubber to be 1,500 rpm or greater. The Brake-Control Package wasn't used exclusively, because with the stock tires and the package enabled at elevated rpm, the stock torque converter would begin to rotate the rear tires on the starting line. Since the converter seemed to have stock stall speed just above 1,800 rpm, higher rpm launches that the M/T tires liked on the Formula were not possible with the GTO.
Although the M/T tires showed a 0.1 average gain when launched at 1,500 rpm or greater, it is quite possible the gain would have been more if the tire pressure hadn't have been reduced. Evidence of this is provided by Bob Cook who stated, "After bracket-racing the car in events following this test, the M/T tires responded better by elevating the tire pressure back to 18 psi. A whole string of low 2.0 60-foot times with a best 60-foot of 2.02 convinced me that the tires are very consistent performers."
As noted, the air pressure in the BMR drag bags was not changed after being set to 24 psi. Since the drag bags have the ability to modulate the rate of dampening, it would have been beneficial to have an additional test session to find the perfect combination of tire and drag bag pressure to optimize performance. However, it must be noted that all these tests take a great deal of time and they must be performed on the same day to ensure consistent weather and track surface.
When all of the testing concluded at the strip, two things were very clear. One, the M/T tires did indeed improve 60-foot times and two, the more power that you can throw at them, the greater the advantage they will provide in the way of increased performance and safety at the strip. According to Cook, "although the Mickey Thompson tires didn't produce huge gains in 60-foot times at my current power level, I am confident that the tires will produce bigger benefits as the engine power increases and a higher stall converter is employed."
For enthusiasts looking for a super-sticky drag radial that will dramatically decrease 60-foot times at elevated launch rpm and horsepower levels, the M/T tires are an excellent choice. If your late-model ride doesn't quite have 11-second potential, the M/T tires will benefit you by allowing more consistent launches and by preparing your Pontiac for the next level of mods. After all, with dozens of 9-second F-bodies choosing M/T ET Street Radials over traditional drag slicks, it's a clear indication that the tires perform.
SLP Brake-Control Package
In order to produce more consistent burnouts or to hold a manual transmission car from rolling though the staging lights, SLP's Brake-Control Package is a great addition for any high-performance Pontiac headed to the strip. The package employs an electric solenoid that, when switched while holding down the brake pedal, keeps the front brakes engaged after the pedal is released and until the switch is released.
For the tire testing on the '06 GTO, an SLP Brake-Control Package was installed, which allowed the owner to perform the recommended burnouts on the M/T tires and as an aid in elevating the launch rpm.
Although utilizing this package as a poor-man's transbrake isn't its intended purpose, it will allow an automatic-equipped car to load the converter up to the point that the rear tires begin to lose traction and start spinning at the starting line. R.A.
Drill and drill bits
Motive Power Bleeder (brake bleeder)
Metric socket set
Tire pressure gauge
Although designed for the...
Although designed for the '04 GTO, owners of '05-'06 GTOs can easily adapt the kit to work on their vehicles by removing the two 10mm nuts that retain the ABS module to the chassis and carefully bending the stock front brake line and pre-bent SLP brake line to mount the solenoid outboard of the brake controller.
Once mounted, the SLP Brake-Control...
Once mounted, the SLP Brake-Control Package looked factory-installed and right at home inside the engine bay of the GTO. In order to actuate it, the supplied wiring harness was routed through the firewall and a switch was mounted in the center console between the dual cup-holders. Before testing out the package, the front brakes had to be bled, which was accomplished in record time by utilizing a Motive Power Bleeder.
An SLP Brake-Control Package...
An SLP Brake-Control Package was secured from Afterthoughts Auto. Sold under Part No. SLP-24050 (Retail $155.50), it is specifically designed for '04 GTOs. The kit is compatible with the factory anti-lock and traction control systems and includes a waterproof electric solenoid, pre-bent brake lines and the necessary mounting and electrical hardware for installation.