2012 Jeep Grand Cherokee SRT8 Track Test
Testing the Hi-Po Jeep Without Run-Flat Tires
Edmunds tests hundreds of vehicles a year. Cars, trucks, SUVs, we run them all, and the numbers always tell a story. With that in mind we present "IL Track Tested," a quick rundown of all the data we collect at the track, along with comments direct from the test drivers. Enjoy.
Our long-term 2012 Jeep Grand Cherokee SRT8 is fast. Sixty mph comes up in 5.1 seconds (4.8 with 1 foot of rollout as on a drag strip) and the quarter-mile slips by in 13.4 seconds at 101.8 mph. Surprisingly enough, the Jeep doesn't even fall all over itself during handling tests, pulling 67.2 through the slalom and 0.87g on the skid pad. It put a beating on the 2013 Porsche Cayenne GTS and trounced the 2010 Land Rover Range Rover Sport SC — especially in handling.
That's fast for a sedan, let alone a 5,000-pound SUV.
Trouble is, though, our Jeep Grand Cherokee rides pretty poorly, a point we've attributed in part to the inflexibility of the 295/45ZR20 Pirelli P Zero tires. So, to save our spines some punishment, we ordered up a set of non-run-flat Sumitomo HTR Sport tires in the same size. They were $175 each; the Pirellis are $485 each.
We've already commented on how the new tires ride but as this is an SRT product after all, we're still interested in how it performs.
We scrubbed in the tires and took it to the track. Can the regular tires keep up with the run-flats? If not, are the savings — in both tire cost and abuse — worth it? Which would you pick?
Vehicle: 2012 Jeep Grand Cherokee SRT8
Driver: Mike Monticello
Drive Type: All-wheel drive
Transmission Type: Five-speed automatic
Engine Type: Longitudinal, naturally aspirated V8
Displacement (cc/cu-in): 6,399/392
Redline (rpm): 6,200
Horsepower (hp @ rpm): 470 @ 6,000
Torque (lb-ft @ rpm): 465 @ 4,300
Brake Type (front): 15-inch vented discs with six-piston Brembo calipers
Brake Type (rear): 13.7-inch discs with four-piston Brembo calipers
Suspension Type (front): Independent double wishbones, coil springs, stabilizer bar
Suspension Type (rear): Independent multilink, coil springs, stabilizer bar
Tire Size (front): 295/45 ZR20 (114H)
Tire Size (rear): 295/45 ZR20 (114H)
Tire Brand: Sumitomo
Tire Model: HTR Sport H/P
Wheel Size: 20-by-10 inches front and rear
Tire Type: Summer performance
As Tested Curb Weight (lb): 5,252
0-30 (sec): 1.7 (1.9 w/ TC on)
0-45 (sec): 3.1 (3.3 w/ TC on)
0-60 (sec): 5.0 (5.2 w/ TC on)
0-60 with 1-ft Rollout (sec): 4.7 (4.9 w/ TC on)
0-75 (sec): 7.4 (7.7 w/TC on)
1/4-Mile (sec @ mph): 13.4 @ 101.3 (13.5 @ 101.2)
30-0 (ft): 27 (previously 27)
60-0 (ft): 134 (previously 109)
Slalom (mph): 62.8 (previously 67.1), 59.9 w/TC on (previously 66.2)
Skid Pad Lateral Acceleration (g): 0.77 (previously 0.87), 0.78 with T/C on (previously 0.87)
Db @ Idle: 48.7
Db @ Full Throttle: 76.3
Db @ 70 mph Cruise: 62.9
Acceleration: With all-wheel drive, the less grippy tires don't seem to matter at all. Power braking gave just a hint of wheelspin, whereas with the summer tires I don't think we got any. Still launches super hard and sounds great all the way down the drag strip. Manual shifting is via steering wheel paddles or console lever (slap left for downshifts). Holds gears to rev limiter. Does not blip throttle on downshifts.
Braking: Nicely firm pedal, short travel. But...what does it matter? The GC SRT8 doesn't like to stop any more with these slippy new tires. First stop was shortest at 139 feet. Third stop (out of six) was longest at 145 feet. Final stop was 144 feet.
Skid pad: Pretty much all it does around the skid pad now is massively abuse the front tires, particularly the outside one. Nearly zero feel to the steering. Drastic reduction in grip level.
Slalom: The precision is gone. This test highlights how utterly critical tires are to a vehicle's performance. What was once a super-planted, intuitive-handling SUV is now riddled with understeer. But unlike before, it can now also get into slightly out-of-control oversteer moments during the slalom's quick transitions. Honestly, it's a bit of a handful. The pathetic ESC on number shows how much sooner the system intervenes now since the tires are providing so much less grip.
The manufacturer provided Edmunds this vehicle for the purposes of evaluation.