Various Tire testing to find out the Hellcat's True Potential

[HellcatMike]

Mopar?s reputation at the drag strip has been secure for more than 50 years, ever since Chrysler CEO Lynn Townsend told his engineers to get busy building a modern Hemi to rule them all. If not a lineal descendant, the 707-hp powder keg in the Challenger SRT Hellcat is a spiritual scion of the 426 Hemi, and it?s in a car that will turn mid-11-second quarter-miles right off the showroom floor.

Hmm, mid-11s? That?s quick, but not nearly as impressive as the blown eight?s output. Power is nothing without traction, and the stock $60,990 Hellcat is somewhat lacking in the latter. There are a few reasons, starting with the same slab-sided sheetmetal as lesser Challengers, which limits what tires can be fitted, plus a prudent corporate policy to spec street rubber that provides reasonable wet-weather traction plus 20,000-mile durability. That and a tire-pressure recommendation that is safe for everything from a Minnesota winter to a high-speed run through Death Valley in July all add up to a compromise.

Like every drag rat in America, we wondered how the Hellcat would run with more-focused tires, so we rounded up two sets of alternatives, fit them to the driven wheels of a Hellcat automatic, and went to Auto Club Speedway in Fontana, California. We also decided to install a pro driver. Andy Durham and his dad, Ron, are veteran SoCal racers who run a roaring 2011 Challenger Drag Pak with a Viper V-10 in regional NHRA events [see Snakes on a Lane below]. Ron ran the pit for us while Andy did the driving. Also in attendance was Challenger SRT development manager Jim Wilder, a drag racer in his spare time. Unfortunately, Mother Nature showed up, too, with Santa Ana winds that blustered at up to 15 mph right into our Hellcat?s face, slowing it down. But it was a handicap that applied to all of our tires, and when the time slips were spit out, the results were surprising.

Pirelli P Zero 275/40ZR-20 (106Y)
Price: $517 each
Time Slip: 11.5 sec @ 119 mph

Choosing tires for the Hellcat was no easy task, says factory man Wilder. ?Because of the torque level, grip was a huge priority.? In the spotlight were the Pirelli P Zeros *fitted to the Chevy Camaro SS. But that tire?s Y speed rating (186 mph) was deemed too low for the Hellcat, which has no limiter and can run close to 200 mph. Pirelli *massaged the compound and cut the tread-block height for the Hellcat to create a (Y)-rated version, the parentheses denoting ?tested at speeds greater than 186 mph.? The 275/40 rear tire is not wide, but width only helps lateral grip, not longitudinal traction. To enhance the latter, you need to lengthen the longitudinal contact patch without dropping the pressure so low that the tire folds over on itself. Inflated to 32 psi, the Pirellis put the Hellcat through the quarter-mile in 11.7 seconds. We dropped the pressure to 24 psi to flatten the Pirellis out and roasted them a bit in the burnout box to warm them to the desired 150?200 degrees F. That knocked a couple tenths off the elapsed time, but Andy still had to feather the throttle on launch. As Wilder watched him struggle off the line, he noted: ?You have to be gentle. If you slip the tire, you have to get completely off it, then feed it back on.? Not an ideal way to drag-race.


Nitto NT555R 275/40R-20 102V
Price: $325 each
Time Slip: 11.2 sec @ 122 mph

These grooved street-legal tires are made in Japan?it says so right on the sidewall?and what do the Japanese know about burnout boxes and Christmas trees? Apparently, quite a bit. So far, Nitto is the only company that makes a soft-compound drag radial that fits the stock 20-inch Hellcat rim, but it?s V-rated, so don?t exceed 149 mph with these fitted. That wheel sounds like silly equipment for drag racing until you learn that this giant aluminum forging weighs a mere 28 pounds. We set the Nittos at 20 psi, Andy did a burnout similar to the one he performed on the stock P Zeros, and the Christmas tree lit its lights. Right away, it was obvious that the car had better footing as the Hellcat moved out with a bawl not normally heard from cars with 100,000-mile powertrain warranties. Two-tenths of a second fell off the 60-foot time and three-tenths dropped off the quarter-mile. ?I can definitely be more aggressive on the throttle,? said our professional wheelman upon his return. The time slips agreed, even if a head wind cut the expected trap speed by at least 5 mph. The Nittos are expensive (though mid-pack here), but the


Hoosier Drag Racing 28.0/10.0-17
Price: $244 each
Time Slip: 11.4 sec @ 119 mph

These bias-ply meats are standard equipment at any serious drag meeting, and with raised white lettering and treads as smooth as rolling pins, they convey a distinct professional intent. The problem: Hoosier doesn?t make the tire for a 20-inch wheel, so we had to go with a steel racing rim large enough to fit over the Hellcat?s massive brakes. The Black Rock 942 17-inch all-black rim, at $90 each, is an affordable and mean-looking item but not terribly lightweight at 40 pounds. The bias-ply Hoosiers on steel wheels out-weighed the Nittos on aluminum rims, the reason we think the quarter-mile times slowed by a couple of tenths. Andy reported a squirmy rear end on his first run, but once he got accustomed to the, uh, vintage nature of the bias-plies, his confidence improved and his right foot got heavier. The 60-foot time, at 1.685 seconds, nearly matched the Nitto?s 1.676 seconds, but the gap grew after that even though the wind was finally tapering off. We were only able to pull an 11.398-second ET out of the Hoosiers. The Durhams thought we might break into the 10s with the Hellcat, as has been done elsewhere, but not on this day with the Santa Ana winds, and not with these tires.

Bankruptcy shmankruptcy. In the dark days of 2011, Dodge demonstrated that the show must go on by offering 50 Challenger Drag Pak cars to the public. Gutted of such amenities as rear seats and windshield wipers, and fitted with a two-speed slam-bang automatic parked behind an 8.4-liter Viper V-10, the Challenger Drag Pak could launch a team into NHRA Stock or Super Stock contention for a price starting at $85,512. Roush Industries assembled the units for Dodge, and Arcadia, California?based racers Ron and Andy Durham took delivery of the first one off the line. Ron figures it makes 850 horsepower and 740 pound-feet of torque, and his car has run a 9.10-at-145-mph quarter while winning three Super Stock class victories at NHRA national events. Dodge has already shown a 2015 Drag Pak running an aluminum- block 426 Hemi Mopar crate engine. The show goes on.

Article Source: Car and Driver

 

[LonestarHellcat]

Awesome stuff.