5.0 Mustang & Super FordsHow To Chassis Suspension
1996 Open Track Mustang GT- Driven To Traction
What To Do And Expect When You Head Out With A Fresh Open-Track Car
Horse Sense: Years of track experience prepared us for how good our Maximum Motorsports suspension was going to be-sort of. A couple of corners into our first lap and we were grinning like a couple 500-watt jack-o'-lanterns. This car is simply an awesome cornering and braking machine.
Faithful as a shadow, you've been following along as we've added the complete Maximum Motorsports suspension to our '96 GT project open-tracker, affectionately known around the office as The Stripe Car. You've absorbed our long tales about installing Panhard bars, K-members, tubular control arms, and coilover shocks. You followed along as we set up the suspension for the first time in the shop. And now, the really big day has come-we're taking our hugely revamped GT on-track for the first time.
Let's get one thing out of the way right away-the car is simply stupendous. It's a track-happy natural right out of the box, and we're simply aching to get more time in it. But before any more glowing reports, the business at hand is detailing what to expect during the initial track shakedown runs. What sensations should you expect as a driver? What conditions are adjustable with this sort of suspension, and how do you adjust them?
The answers fall into two general categories. The first is the most overlooked-the driver. Second, we'll examine the chassis and what you can do with it. Be assured our car hit the track with a minimum of trackside adjustments. In fact, we've hardly had to touch the machine, except to experiment for our own edification.
That Loose Nut Behind The Wheel
If you've experienced full-monty Mustangs with torque-arm suspensions before, you'll grin knowingly when we say the first time in such a Mustang is an eye-opener. Consider that the only Ford-built parts remaining in our suspension are the front sway bar, the spindles, and the rear axlehousing. Everything else is new, including the total driving experience. The improvement is so large, the first thing requiring calibration is the driver.
What you need to learn is the chassis is much calmer and easier to drive, yet a lot faster thanks to the better balanced grip. At playing-around speeds, the Mustang will go right where it's pointed. Pushed closer to the limit, it can be precisely slid with total confidence. Watch out! It's addictive.
How much time it takes to acclimate to the car varies tremendously depending on talent and experience. We'll note highly experienced road racers are well entertained with the Maximum suspension-it's what they use on their American Iron cars, after all. Old pros can spend years exploring this level of balance and grip. So if you're new, don't be surprised to look back a year later and realize just how far you've come-and just how much further you can go.
Count on the first weekend to be exploratory. If you can enlist the aid of an experienced driver to give you some feedback on both your car and driving, that's great. But by far, the most important thing early on is simply seat time. Assuming the car was halfway reasonably set up in the shop before coming to the track, you'll turn faster lap times sooner simply by turning laps rather than fiddling with sway bar end-links and spring rates. Get on the track and drive!
Once you have a basic feel for your new car, try different suspension adjustments to learn what those adjustments do and how they feel. This could start on the afternoon of the first day, or more likely the second day of a two-day shakedown. Make the largest possible adjustments at first. This gives the biggest change in feel, so you won't miss what might otherwise be a rather subtle change. On our car, that meant disconnecting the rear sway bar completely, then setting it to its stiffest position.
To completely dial in the car, it's necessary to push the chassis to near its limits. Only then can you get the car on the edge of traction where shock, spring, and rollbar stiffness really count. It may take awhile to reach this point, but this challenge is the joy of road racing. You may find suspension settings you liked at first feel cumbersome later. That's a great sign of driver growth, so don't be afraid to change.
And finally, while you'll naturally want to know your lap times, don't obsess over them. Limit your compari-sons, and then only to similar cars. Stick to the driving basics, and focus on your own driving improvement. It's the quickest way to fast lap times.
A torque arm and tubular K-membered Mustang feels different than a stocker. Expect strangely numb steering at first. This is because the front tires are flatter to the road. Thus, the steering remains lighter through a wider steering arc and range of speeds. This is in contrast with the stocker, which ramps up steering effort with increased speed or steering angle (the better to inform thick-headed teenagers that their Mustang GTs really will leave the off-ramp if pushed any harder). With a bit of experience you'll come to enjoy the increased steering sensitivity, and realize it really wasn't numb at all, just lower effort.
Brake dive is hugely reduced, and body roll while cornering is considerably flatter as well. Both are welcome changes, but they do slightly reduce the signals sent to the driver. Gradually working up to threshold braking and cornering is the answer to that. Do this by concentrating on braking at a couple of corners per lap, while staying comfortably within your limits elsewhere during the lap. Don't try to go fast everywhere at first, as this will only overload your thinking.
As you explore these new, higher limits, you may fall off the track from trying too hard. That's sort of OK, as long as you don't make a habit of it. At least you'll learn that when you lose it in one of these cars, they tend to simply skate wide rather than looping off in a dizzying, uncatchable pivot around the front axle. Control returns much more quickly too, so don't give up!
Overall grip is higher, so the lateral g-loading is increased. This isn't as evident in slow corners, but on high-speed sweepers, she'll really dig in if you have the guts to keep your right foot down. Getting used to these higher-speed cornering loads, and ultimately becoming comfortable with sliding the car at 110 mph as you tiptoe on the edge of tire adhesion, is what takes the longest for neophyte track drivers. It's also the key to low lap times. Because you can't drive this way on the street, and a stock Mustang can't do this-it doesn't have precise enough steering or steady enough lateral grip-this is often a totally new sensation, so it takes awhile to learn.
Most dramatic is the rear axle response. Here it's not so much what you feel-smooth, linear traction in response to steering or throttle inputs-but rather the surprising lack of wiggle-waggle the stock suspension makes you tolerate. Furthermore, the torque arm does a great job of planting the rear tires on corner exit, so you can use lots of throttle-and earlier than with the stocker. At first it requires conscious effort to remember to get on the gas early, but it works.
Torque arm Mustangs really like to be on the gas, and with the throttle floored, they'll hammer straight through rough sections and over curbs-often with some steering inputs. A stocker would go seven directions at once if you tried these antics with it, but a torque-arm car on the gas will squat a little in the rear and simply keep clawing forward, so be aggressive about getting on the straights.
Ultimately, torque arm/K-member Mustangs such as our Maximum Motorsports car are about calmness, predictability, and high limits. Stock Mustangs handle like a horror movie- you're sure something is going to suddenly jump out at you. That's gone with the torque-arm cars. They handle smoothly right up to the limit, and even beyond. No sudden scares, just predictable handling that invites exploration. The big surprise is how fun and easy it is when the chassis works with you. In the end, you realize you have to make a big mistake to have one of these cars bite you.
Maximum Motorsports' complete suspension package offers several adjustments, including Panhard bar height, pinion angle, sway bar stiffness, ride height, corner weights, and possibly shock stiffness if adjustable shocks are used (our Bilsteins with Maximum's race valving are not adjustable). Many of these adjustments are made only when initially setting up the chassis and are not part of normal track adjustments. These were covered previously in our shop set-up article ("It's a Setup," Nov. '02, p. 107).
Typical track adjustments are caster, camber, toe, rear sway bar stiffness, and possibly ride height or corner weights (front sway bar adjustment is another common track-tuning aid, but Maximum's adjustable front sway bar hasn't made it to market yet, so we're using the stock front bar). Because we have a street/track car, our corner weights are set as symmetrically as possible for all four corners. Even at Willow Springs, where there are six right- and three left-hand corners, we would leave the car evenly balanced. It isn't worth the time and energy to optimize the corner weights for the right-handers, then change them back to drive home. Leave that to race cars.
That said, the adjustable spring perches on coilover shocks are handy for open-track cars when running a high-speed open track one weekend and an autocross the next. Then the front ride height can be lowered to improve aerodynamics on the fast track, followed by slightly raising the front ride height for autocrossing.
Lowering the nose inhibits air from getting under the car and causing front-end lift. The nose-high autocross attitude adds caster for a better camber curve, gives more bump travel, raises the front roll center so it doesn't want to fall all over itself in sharp turns, helps reduce the load on the front tires due to the center of gravity shift while braking (a tiny help, but a help), and brings the roll axis closer to neutral (again, less "falling over itself"). The only downside is increased weight transfer side to side. In really slow corners, that might even help plant the front tires.
Rear ride height should stay the same at the autocross because lowering it consumes needed bump travel and raising it sacrifices rear grip for quicker roll oversteer. Some oversteer helps rotate the car around tight, gymkhana corners, but that's best done with a high-grip front end, not a low-grip rear.
As for the spring rates themselves, these should not need adjustment at the track. Assuming you followed Maximum Motorsports' spring-rate recommendation, you ought to be right on or really close to the correct spring rate. The only way to change this, of course, is by substituting different springs, so you'll need a supply of springs on hand if you wish to experiment. This is easily done with coilover springs, which are quick to change and considerably less expensive than stock-style springs.
For "let's see" experimentation, getting together with another Mustang owner with coilovers is ideal. Then you can easily enough swap springs during a test day.
Caster, camber, and toe are occasionally adjusted to change handling on dedicated racing Mustangs, but not so often with open-track cars. Some testing with a tire pyrometer will show if the tire is heating evenly across its tread, which tells all when it comes to dialing in inflation, caster, and especially camber. Once you have the alignment dialed in for your combination, it shouldn't require anything other than monitoring tire wear.
An exception would be if you wanted to run fairly flat camber on the street-say 31/44 of a degree negative-and more like 2 degrees at the track. This is a tire-wear issue, but we've been running 2 degrees of camber on the street and track with acceptable tire wear (and admittedly limited street mileage) and no tendency to tramline or nibble at uneven pavement. It's one less housekeeping chore too.
Changing the toe is easily done by scribing the tire's tread and measuring directly with a tape measure at 3 and 9 o'clock on the tread. Camber can be measured with a handheld camber gauge (as shown in our shop setup article); caster is inferred from measuring the camber with the tires turned.
That brings us to the rear sway bar. Stiffening or loosening the rear bar directly affects the rear roll stiffness, which makes a huge difference in chassis balance. With a well-engineered, tightly controlled suspension such as Maximum's, the rear sway bar plays a big role in dialing in under or oversteer. In fact, it is the primary tuning tool for balancing the car.
To show what the sway bar can do, we'll detail our recent bar-tuning experience at Las Vegas Speedway. We were running in a NASA High Performance Driving Experience open-track, which provided adequate track time on a superb road-racing circuit, and with just the right amount of cars on-track (never balked due to traffic, but other cars to play with). We're also big on NASA's HPDE policy of unrestricted passing in the faster run group. That allows us to keep up our speed while zooming past all those Vettes and Vipers.
Ehren Van Schmus, Maximum Motorsports engineer, started us out with the car on its usual Maximum adjustable rear sway bar set at its stiffest setting. It felt normal, except with light understeer (push) at midcorner.
At the end of the first session, Ehren disconnected the rear sway bar. The idea was to let me see what the sway bar did, and what effect it would have on the car. Then, as we progressed to larger bars, I could better differentiate what the larger sway bar was really doing and what other effects, or side effects, I might be sensing.
To my considerable surprise, the car was driveable with the rear bar disconnected. I thought it would be a total pig, with the rear body rolling all over the tires and the front pushing uncontrollably-but it wasn't. The main effect was increased understeer. There was a barely perceptible sensation of the rear of the car rolling over more than before, and the rear of the car would definitely sit down a bit more on corner exit, but that was it.
The car was slower with the bar disconnected, but that's not to say it was all bad. The looser rear meant more weight transfer both left to right and some front to rear. On slower corners this meant the outside rear tire would be planted harder, allowing a harder drive off the corner. The downside was the car was more difficult to turn in, so I had to brake harder, slow the car more, turn it in with a bit of muscle, go a hair slower in the early corner to bring the car to the apex, then enjoy a strong, grippy launch off the turn. The setup might be useful on a course with long straights and tight turns onto the straights. It would also help in the rain.
Also, if the car was driven a tenth more slowly, it actually felt fairly good. But as I tried harder, I started sliding past the apex on the corner entry. Then, as it launched off the turn, the front would still be pushing. The car would simply head wide and require backing off to stay on-track. But the feel was not all that bad unless you were really charging.
My surprise at how good the car was with no rear bar shows how oriented our thinking is by street-driven, stock suspended Mustangs. Their marshmallow spring rates, sloppy bushings, and totally wankered suspension geometry often calls upon the sway bar to hold everything together. With a proper suspension, the sway bar is a tuning tool only, so the handling doesn't fall to pieces without it. Ehren pointed this out by noting the difference in sway bar stiffness is only about a 10-percent gain in spring rate from no bar to our full stiff.
For the next session, we removed the original sway bar and installed a prototype bar Ehren brought for testing. The original bar on our car (PN MMRSB-5) is the stiffest of five rear bars Maximum currently offers, and the new prototype is two steps stiffer. I was wary of this bar, thinking it would turn the car into an oversteering handful.
Again, I was wrong. The car felt fantastic with the larger bar, especially after coming off the "no bar" option. Turn-in was crisp, with our heavy GT heading down to the apex like it wanted to. On corner exit, there was still enough traction to work with, and the front end didn't slide so wide. What was tougher was the car was more neutral, and thus required more precision from the driver, with less forgiveness for any sloppiness. I had to drive more carefully, but it was definitely faster and able to run in more than one line.
We learned several important points. First, the sway bar is a trimming device on a torque arm Mustang. It is not the primary roll control (springs do that), and it is not asked to do any other job. Therefore, it is a tunable, fine adjustment. Second, all other things being correct, the rear sway bar forces the front tires to do more work, which is where the increased turn-in came from. And, third, for hard driving in heavier cars, Maximum could add some stiffer bars to its lineup. It would be meaningless on the street because you can't drive at racetrack speeds there, but for the fastest, heaviest track cars, it would be useful (even all-out American Iron race cars don't need this much rear bar because at 2,900 pounds they are 650 pounds lighter than our dual-purpose car).
Finally, this sway bar is not for the squirrel hotdogging around in his daily driver street car. Our car is tightly sprung with 425/300-lb/in coilover springs front/rear. That's roughly equivalent to 800/280-lb/in springs in the stock suspension, and with this tight of a bar, it would be like a bar of soap on the shower floor. This has been a major concern of Maximum's in offering a larger bar. Most customers don't need it, yet the guys who insist on having the largest of everything will "just have to have it."
We're In Trouble
During the last session, I chased down a Viper and passed it, then went to work on a supercharged 32-valve Cobra. As you'd guess, compared to our 248-rear-wheel-horsepower GT, he was quite fast on the straights, and not too shabby in the corners for a bolt-on-suspension Cobra. I was able to reel him in, but while making the pass coming off the oval and into the tight infield chicane, I overcooked the entry and got a tank-slapper going. Sensing the car was unsaveable thanks to my eagerness, I let it run into the grass, and the white Cobra got back in front again.
Worst of all, we're hopelessly hooked on this track driving. No cops, tons of speed, and-best of all-a willing partner that cheers (nearly) every move you make.
Good Equipment Is Mandatory
A quick note on equipment is vital because you can't learn anything on junk tires and second-hand brake pads.
Nothing changes a car's handling more than good tires, so unless you don't want to learn anything, you must test on good tires. Old cast-off tires will only have you sliding around learning nothing but frustration. Trying to tune the chassis on old tires is a waste of time because tattered tires have no reserve grip available. You end up making all sorts of adjustments yet the handling doesn't change. In other words, old tires handle badly no matter what you do, and you'll never find chassis balance on them.
The same goes for the rest of the hardware-if you're going to learn at all, it's going to be on good tires, fresh shocks, new brake pads, and so on. Don't scrimp!
Bring Plenty of Brake
There are some tough truths to running a Mustang on a road-racing circuit. The balance is inevitably a little nose-heavy, tires wear quickly because of the total weight, speed, and mediocre weight distribution, and the brakes get absolutely pounded. It's a fact of fast-accelerating, heavy, V-8 cars-they use up brakes.
Our Baer Claw PBR-based Track brakes are rugged and haul down our wagon with impressive authority, but as with any brake, they required trackside maintenance to survive. If you're new to the road circuit, you'll be a bit surprised at the attention paid to the brakes, but they're a vital, heavily worked part of a road racing-type car.