Road Test: 2007 Ford Shelby GT500
Secrets Of The GT500
1. Engine
Shares bore, stroke, deck height, and bore spacing with the 5.4-liter Ford Triton truck engine. Cast-iron block; aluminum four-valve heads from Ford GT; camshafts from 2004 Cobra. Eaton R122 supercharger delivers max boost of 8.5 psi. 500 horses at 6000 rpm and 480 pound-feet at 4800 rpm only certified April 21--after first media drives. Target was 475 horses, but work with Eaton on supercharger geometry delivered more grunt. 92.6-horse/liter output beats 84.8 of 2003 Cobra. Engine weighs 175 pounds more than 4.6-liter.
2. Transmission
Tremec T6060 six-speed manual is latest version of T56 used in 2003 Cobra. Features triple synchros on first and second gears; lower 2.97:1 first-gear ratio; new remote shifter for shorter throws. Clutch is new 215mm-diameter Valeo twin-disc unit with cerametallic material to handle increased power and torque.
3. Suspension
On GT500 coupe front spring rates are 42 percent stiffer and rears 17 percent stiffer than regular GT's. Front anti-roll bar about seven percent stiffer, but rear bar is twice as stiff, with diameter increased by 4mm to 24mm. Revalved shocks give similar rate increases to springs at low shaft speeds, but at high shaft speeds (i.e., over sharp bumps) are closer to regular GT's. Front ride height has been lowered 10mm; rear ride height is same as GT's.
4. Rear Axle
Independent suspension originally planned but this was nixed because of cost and concern over durability with high-torque engine. Live axle upgraded over GT with stronger differential case material, new differential side gears, and increased ring gear bolt torque. Final drive is 3.31:1, same as GT with auto trans.
5. Brakes
At 14.0 and 11.8 inches, front and rear rotors are larger diameter than those on 2003 Cobra. New front calipers are four-piston Brembo. Master cylinder has been carried over from GT, but the brake booster and anti-lock brake system tuning are unique to GT500.
6. Wheels And Tires
Wheels are 18x9.5 inches all around, one-inch-larger diameter and half inch wider than wheels on 2003 Cobra, mainly to package the 14-inch front brakes. Bigger 19- or 20-inch wheels were rejected because of poorer ride quality and refinement and because increased unsprung and rotational mass would've hurt straight-line acceleration. Front tires are 255/45; rears are 285/40.
7. Exhaust
Dual 2.5-inch-diameter system with cross pipe is quarter inch larger throughout than 2003 Cobra to improve breathing. Exhaust tips are three-inch diameter.
8. Convertible
The GT500 convertible won't be available with the Le Mans stripes, as these weren't available on the original version back in the 1960s. The GT500 convertible's spring rates will be less aggressive than the GT500 coupe's, too: 8.8 percent softer up front, and 14.6 percent softer at the rear. GT500 convertible uses regular GT coupe roll bars front and rear.
9. Body
All 2007 Mustangs have reinforced bodies because of the GT500's extra power and torque. Selected panels are now thicker gauge steel, and extra welds have been placed on key seams and joints to improve rigidity.
10. Interior
Tach and speedo positions swapped so drivers can better watch shift points; seats have additional lateral support; chrome accents replaced with satin aluminum finish. Only two interior color schemes offered: black, or black with red inserts on seats and door panels.