Tom Wilson
October 11, 2013

On the Autocross

Test day at the Speed Ventures autocross event at California Speedway in Fontana, California, dawned bright, clear, nippy, and windy. The Santa Ana breezes were howling through the nearby Cajon and Banning passes, whisking paper entry forms hopelessly into the distance and rolling steel trash cans across the paddock. It wasn't a gale, but a row of loaner open-face helmets were sent rolling drunkenly around the paddock and the event was delayed 45 minutes because the cones had to be doubled up to avoid blowing over. You could say it was breezy.

At least the wind was not a factor in our autocross driving. Both Ricardo Topete of GTR High Performance and I drove the test car so we'd have two impressions to work with. Both of us agreed the car was essentially hopeless on its stock suspension and tires. There was little grip anywhere, with the car swinging wide in the sweepers from excessive understeer. and rolling over on itself through the slalom sections. Luckily the course was simple—two sweepers at each end with slalom sections connecting the two—and thus easy to learn and remain somewhat consistent on.

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Our best stock times were in the low-43-second range for both Ricardo (a tenth faster) and I. We each could have gone just slightly quicker given more laps, but once it was clear we were stuck in the 43-second range, we moved on. No matter what we did to the chassis, the tires were at their limit and were not going to deliver significantly faster times even if the suspension was heavily augmented.

Bolting on the Nitto tires was a godsend. Like flipping on the light switch in a dark room, they made an immediate, dramatic difference. After three laps to re-adjust our lines to the increased grip, we lowered our times a flabbergasting 4.98 seconds (that's huge on such a short course). I'll admit to getting lucky and putting together one better-than-average lap to clock a 38.05 second tour. That would haunt us as we tried the Whiteline suspension parts because that one exceptional lap proved tough to beat!

But lucky or not, the Nittos were worth at least 4 seconds a lap. There is little wonder why. The Nittos are larger than the stockers, so all considered, they simply had more rubber on the road. But mainly the Nitto NT01 is a dedicated ultra high-performance, dry-weather race track tire with gum eraser soft compounding (100 tread wear versus the stockers 400 treadwear rating) and specialized construction.

Besides the greater grip, the Nittos were a big step forward in accurately placing the car and driving a tighter, shorter line. This was especially true at the east end sweeper where I found I could enter at the same speed as the stock tire, but tuck tightly around the cones to cover less distance, a tactic worth a half second by itself.

During the lunch break the GTR crew installed the Whiteline suspension parts. We opted to set the sway bars to full soft, which we figured was likely as soft as the stock suspension, or at the most, offering little increase in roll resistance.

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Back on course body roll might have been reduced, but not much. Trying to opt for the largest change possible (makes it easier to feel the difference when suspension testing) I asked to re-adust the sway bars to their stiffest positions. This got garbled in the wind and the bars were set to next to full hard front and rear.

Not to worry. The increased roll resistance helped, but we still couldn't beat that one 38:05 lap. So we tightened the front sway bar completely and left the rear bar at its next-to-stiffest position as we could all too easily dial in oversteer with the throttle any time we wanted. Again this helped, but still not enough to get past that low-38-second lap.

Analyzing our driving, I realized the combination of increased grip from the Nittos and more precise, faster turn-in from the Whiteline suspension would allow charging into the critical east sweeper a little faster, then holding a slightly wider but faster line through the turn, followed by a straighter, faster shot at the subsequent slalom section.

This was exactly opposite of what had gained us the half second in the morning, but the car's handling had improved such that a different, faster line was now possible to control. And with only the final run of the day to prove our theory we put down a technically correct, zippy 37.62 lap.

Critical to our success was the ability to balance the car front to rear with the adjustable sway bars, as well as the increased grip from the track tires, of course.

Even better, it was fun dialing in the combination, which is what it is all about, after all. I'll finish by noting our near-stock Mustang GT was one of maybe four cars below the 40-second range at the slalom, and that included many prepped Lotus Elites, Subaru WRX's and Corvette Z06s.

By the Numbers

Here are the Whiteline parts used in our autocross test. All are labeled for '11-'13 Mustangs but will fit '05-and-later cars.

KPR037 S197 Mustang adjustable Panhard rod $199.90
KSB729 Panhard-bar chassis brace $110.00
KSB653 Upper strut-tower brace (twin spar w/logo) $229.99
KTA140 Rear lower control arm $299.90
BFR65Z Rear adjustable sway bar, 27mm $249.90
BFF55Z Front adjustable sway bar, 33mm $249.90