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Turnin’ And Burnin’

Don’t overlook the importance of sticky tires and performance sway bars.

Ricardo Topete - March 01, 2012 10:00 AM

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When you pack up for a day at the track, don’t forget your torque wrench. Experienced track junkies know that it is vital to re-torque your wheels after every session. Robbie Grenda, vehicle owner, does the honors.

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The Toyo Proxes R888 and the Trade Union GT-500 replica wheels deliver a visual knock-out. The beefy 275/40/18 Toyos wrap themselves nicely around the 18 x 9 ½-inch chrome wheels. Notice the semi-slick shoulder area on the R888, which provides tremendous grip for razor-sharp steering.

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Robbie’s GT has the look and the goods to blitz the course. Trade Union’s GT-500 replica wheels lend an “all-business” demeanor that really complements the lines of the S197 Mustang.

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With the new wheels and tires, the GT maneuvered through the autocross course with grace. The gumball-like Toyos made it difficult to unglue the car around the tight course. The Mustang was able to dive deeper into the corners, carried more speed and took full throttle earlier exiting the corner.

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To limit body roll to promote better tire adhesion, GTR’s crew tag-teamed the removal of the stock sway bars and replaced them with a set of larger diameter bars from Progress Technology. Out front, the end link is disconnected from the strut.

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The stock front bar is a basic unbolt/bolt procedure. Once out, the stock end link is transferred over to the Progress bar. Notice that Progress has the autocrosser/road-racer in mind, as they provide three different mounting holes on their sway bar. This allows for tuning adjustments in handling. GTR suggested we start with the Progress bar on the softest setting.

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The beefier Progress bar is secured using the stock hardware and mounting bracket, but includes new polyurethane bushings to resist deflection when cornering. Generously smother the bushings with the supplied grease.

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With the front complete, team GTR begins on the rear sway bar, which proved to be just as simple to remove as the front bar. Removing the upper end link bolt allows the sway bar to drop away from the frame.

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The stock end link must be transferred over to the larger Progress sway bar. “Walking” the end link back and forth and lubricating it with grease is the only way to accomplish this without losing your sanity.

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Once assembled, the Progress rear bar is lifted into position. The factory hardware is re-used, however new polyurethane bushings are supplied. With everything complete, we went out for another round of cone crushing. We saw a net reduction of 3.19 seconds per lap at this point, a considerable improvement.

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Most auto enthusiasts tend to measure speed in a straight line, while a small percentage will also give equal importance to the turns. Successfully negotiating a tight, hairpin turn at full gallop provides a thrill that is hard to beat.

Having the steering wheel cranked with the rear tires in a controlled slide, feathering the throttle to maintain just enough grip, all the while flirting with the laws of physics. Yes, that is my definition of automotive euphoria. This month, we examine some simple and effective ways to make a car stick to the road.

There are multiple factors that will determine a car’s ability to hold the road during hard cornering: chassis rigidity, suspension, steering, tires, etc. Out of all those variables, tires have the most profound effect on a car’s ability to stick to the tarmac. It seems logical, as tires are the only communication that a car has with the road. Sharp handling can only be achieved if there is sufficient grip by the car’s tires, otherwise with a lack of traction, the car will simply slide.

Modern, high-performance street tires are full of compromises. They are designed to meet many criteria, such as traction, grip, life span, ability to channel water, resist heat, provide good ride quality and keep road noise to a minimum. Naturally, because all street tires must do all of the above reasonably well, they don’t excel in any one area.

Take for example, our test vehicle: a 2008 Mustang GT. The S197 platform (2005-2009) has been a huge success for Ford, as it offers good overall performance with strong acceleration and respectable handling in stock form. Ford outfits the GTs with Pirelli PZero Nero tires, which do a commendable job of putting the reins on the pony. The standard GT-issued Pirellis must work moderately well in all types of driving situations (wet and dry) and still cover the previously mentioned criteria that original manufacturers look for in a mass-produced tire. However, pick up the Mustang’s pace on some twisty roads and the Pirelli’s shortcomings quickly become apparent. Put simply, the Mustang GT is too much car for the narrow 235/55/17 Pirellis. The end result is a wild pony that drifts, slides and wanders around a corner.

Enthusiasts that appreciate a good handling car with lots of grip around corners will often ditch the stock wheels and tires in favor of wider (and nicer looking) wheels, which allow fitment of wider tires to increase road contact and grip. Moreover, just as critical to the footprint that a tire has is the design and compound of the tire. An ultra-high performance tire will, for the sake of maximum grip, forgo some characteristics that regular passenger tires (like the GT’s stock Pirellis) have to worry about. For instance, an ultra-high performance tire will have a shorter lifespan due to a softer rubber compound that wears at a faster rate. In addition, wet weather handling may suffer slightly as ultra-high performance tires tend to favor dry road conditions due to their inherent shallow tread depths.

Since our discussion focuses on how to improve a Mustang’s handling, we took our ’08 GT to an autocross event for some hot-lapping and cone-crushing action. What better way to test and evaluate some easy handling upgrades than on a closed course where you are encouraged to drive as fast as you dare? Vehicle owner Robbie Grenda (of Redlands, California) was very generous in allowing us to torture, er, test, his car in the name of research. Also on hand were the skilled personnel of GTR High Performance (Rancho Cucamonga, California), who served as our pit crew.

The first order of the day was to run the GT in stock form with the original wheels and tires. After several laps, we had established a baseline from which to compare. In stock form, our average lap time was 54.65 seconds. Not bad, but the GT swayed like a small fishing boat in rough waters and the Pirellis howled for mercy around every turn.

For the next session, we went for the gusto and slapped on a set of sticky Toyo R888 street-legal, competition tires. Toyo’s R888 tires are fully DOT-approved and are ideally suited for road racing, autocrossing, or the ultimate in high-performance driving. Since the R888 is bred for the track, it has unique design characteristics that promote maximum adhesion. For instance, the R888 has a stiff sidewall bead construction that yields increased cornering forces. Also, a 6/32-inch tread depth and large tread area increase dry traction, while the V-shaped grooves assist with wet traction.

Like the saying goes, “You gotta pay to play” and the Toyo R888s in our selected size will set you back around $300 per tire. Obviously, tire size will affect pricing. Not exactly chump change, but as our testing proved, it paid big dividends.

We selected beefy 275/40/18 Toyos for our tester. We also had to increase the size of the wheels to accommodate the larger tires. Wanting to preserve the “factory” look, we selected a set of 18 x 9½-inch Shelby GT-500 replica wheels from Trade Union. Chrome plating provides the extra “wow factor”. Trade Union reproduces many popular wheels specifically designed to fit Mustangs and prices them right for today’s economy. A full set of chrome 18-inch Shelby GT-500 replicas will set you back about $800, while the machined-finish version carries a lower price, if bling isn’t your thing.

For round two, we were rewarded immediately with additional grip. The 18-inch wheel/tire package bit down so hard around corners we had a tough time getting them to break loose! We found we were able to push much harder around the course before we got remotely close to the limits of traction. After only a few laps, our average lap time had been cut down to 52.64 seconds, a whopping 2.01 second reduction in lap time. That may not sound like much, but on a short, tight autocross course, that’s huge.

Next, we set our sights on tightening up the suspension a bit to complement our newfound monster grip. The crew of GTR swapped out the stock, dinky sway bars in favor of macho-sized Progress Technology sway bars to help control some of the Mustang’s body roll we were experiencing. In a couple of hours, team GTR had outfitted our test mule (no pun intended) with Progress’ 35mm adjustable front sway bar (part number 61-0807) and 24mm rear sway bar (part number 62-0807). Although each sway bar is sold individually for about $150 apiece, it is recommended that they only be installed as a matched set. Failure to do so will result in unbalanced handling.

A properly engineered sway bar kit is designed to reduce body roll created under hard cornering. When the body leans excessively, it prevents the suspension and tires from working effectively. As a result, the objective is to keep the car flat around corners, which is a task that the Progress bars excelled at. The larger sway bars provide more driver control and inspire more confidence. The moment the Mustang hit the first turn, the reduction in body lean was apparent. Now the sway bars and wheel/tire combination were working in harmony.

Not surprisingly, our average lap times dipped to 51.46 seconds, which represents an additional 1.18 second drop per lap. There is little doubt that given more track time, quicker lap times could have been achieved simply by tuning the sway bars and playing with tire pressures a bit. Overall, we saw a net reduction of 3.19 seconds per lap with two basic, but highly effective, upgrades.

So which handling upgrade is right for you? Well, it depends. If you are looking for maximum bang for the buck, start with Progress’ front and rear sway bar kit. For about $300 and a couple of hours of time, noticeable improvements to your Mustang’s handling dynamics can be made.

On the other hand, if you are due for a new set of tires or simply want to freshen up your Mustang’s appearance, nothing sets off a car like a set of racy wheels. That being said, if a new set of wheels are in store, why not step up to wider and stickier tires too? As we demonstrated, they can have a profound impact on grip. Consulting an experienced performance shop (like GTR) will help you choose the right tire/wheel that best suits your ’Stang’s needs. Class dismissed, now go hit some corners!

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