Photography Credit: Chris Clark
[Editor's Note: This article originally appeared in the December 2007 issue of Grassroots Motorsports.]
Everyone loves that new car smell, but when it comes to seasoned racers, a factory-fresh scent is a sign that there’s probably work to be done before the season kicks off. Generally, a little sorting is required before a new race car can be fully enjoyed. That’s where things like a notepad, pyrometer and some test days will come into play.
Fido might enjoy chasing his tail, but that’s not how races are won. Having a systematic testing and tuning plan can be the difference between driving a mutt or having a best-in-show winner.
GRM’s Tim Sharp has been driving—and thus sorting—race cars since The Beatles were still recording albums. He just spent the season helping to sort Capps Racing's two-car NASA American Iron Mustang effort. Their methods paid some nice dividends as they did well at the big show.
Here’s how it was done.
Before you can hit the track, you need to do some groundwork. The first and foremost step—before scheduling a single test day or even thinking about where you left the pyrometer after your last track outing—is to ask yourself a simple, yet critical, question: Are you spending your time with the right car? Until the answer to that question is a solid Yes, you might need to wait on scheduling track time.
If the race results clearly show that you’re trying to push a rope, then it might be time to buy or build something else. Check race results to get an idea of which cars are best for your chosen venue.
Talk to the local drivers before you buy or build. Once you begin racing with them, you become an adversary. Most race drivers are free with information until you start banging doors with them.
It’s also wise to review the national race results to see which cars are hot on a larger scale. Give extra value to cars that are winning at the venues used for the national championships, assuming a year-end title is your goal.
The NASA and SCCA club racing programs as well as the SCCA autocross championships all moved to new homes last year. If you have an eye on a NASA title, for example, having an extra bit of an edge at Mid-Ohio—the event’s host track—is going to be a good thing. Going after an autocross title? Don’t forget that the SCCA Solo championships just moved from bumpy concrete to smooth blacktop, changing the face of the event.
Next, consider which models have been developed the most as well as which ones have the most potential. Fox-bodied Mustangs, for example, might be the fastest cars in NASA American Iron competition today, but the new Mustangs are quickly closing in on them.
In addition to on-track performance, also consider sponsorship potential. Neither the factories nor their dealers have much interest in backing an extinct model.
For Dave Capps, experienced racer and team owner, picking the right car was easy. Multimatic had built 30 body-in-white new Mustangs—basically body shells with roll cages—for Grand-Am competition, and a few of them still remained. Since Capps had a major interest in a Ford dealership, this was the obvious choice for his new race cars. The Tyler Ford/Brandom Cabinets/Capps Van and Interstate Truck Rental Team (yeah, it is a mouthful) acquired three Multimatics early in the season and had them shipped to Tyler Ford in Texas.
For about $15 grand, Multimatic will deliver a new Mustang body-in-white on a pallet. The Multimatic cars are devoid of door trim, headliner and all of the superfluous junk a racer would remove anyway. They do come with a very nice roll cage, however.
Dave Irwin, Capps’s partner in Tyler Ford, directed the construction of the Mustangs. Irwin is an excellent race driver, organizer and mechanic.
Although the basic body-in-whites conveniently lack parts that aren’t needed, they are also missing some of the essentials. Irwin’s first order of business was to get the laundry list of parts needed to finish the cars, including suspension corners, steering racks, fuel cells, racing engines, Tremec transmissions, rear differentials, brakes, fuel lines, electrical harnesses, racing shocks, spring sets and so on. Luckily, Ford Racing will gladly sell everything needed to complete the race car package.
Once the parts for two of the three Mustangs had arrived, Irwin and two of his top Ford mechanics, Ed Warren and Tracy Alvey, started to assemble them. Within one month the cars were finished, dynoed and ready for testing at Oklahoma’s Hallett Motor Racing Circuit.
At this point, Dave Capps called and asked if I would come to Hallett to help sort out the cars and provide some driver coaching. I agreed.
Before testing began, we made notes on the existing spring rates and tire pressures, plus the settings for the alignment, shocks and anti-roll bars. Recording baseline settings and keeping a log of each change is essential. Without knowing your starting points and the sequence of your changes, it is impossible to determine whether you are making progress or moving backward. Remember, don’t end up like Fido.
While drivers are always eager to get on the track, the purpose of testing is to gather accurate data to help lower your lap times, not just to delay your gratification. Take time to prepare and get the most out of your testing.
First, we found a flat section of concrete in the pits and double-checked our chassis settings. In order to find the same exact spot again, we marked the pavement with duct tape.
We also measured the Mustang’s front and rear ride heights so we could return the car to its “scaled ride height” (previously done at the dealership) if we made any spring changes. Of course, having scales at the track would have been preferred, but we didn't have any with us. That wasn’t going to keep us from meeting our goals.
Photography Credit: Photosbyjuha.com
Fortunately, Capps’s guys did have all the equipment necessary to perform spring changes and make chassis adjustments. Besides a torque wrench, floor jack and jack stands, they also had alignment equipment, a tire pressure gauge, a pyrometer and preprinted sheets to record tire temp data.
Most chassis engineers have one cardinal rule when testing a new race car: Make only one change at a time. Why is this? Think back to junior high science; if you change multiple chassis settings before a test session and the car becomes much faster, which change actually helped? You don’t know, as one change might have made you much quicker while the other might have cost you time. You had a net gain on your lap times, but you might have still left something on the table.
During our first test session, Capps and Irwin ran the new Mustangs for 10 laps. During the first five laps, they were basically getting used to the cars and the circuit. During the second five laps, they began pushing the envelope.
When the cars came into pit lane, the crew immediately took four temperatures from each tire with their pyrometer. The temperature readings were called out by one mechanic while another one recorded the data. Each tire temperature was measured from the inside to the outside of the tire tread.
Next, while the tires were still hot, one mechanic made another pass around the car with a tire pressure gauge and called out the “pit-in” tire pressures.
Anyone watching this hurried process probably wondered why everyone was moving so fast, but the answer is simple: Tire temperatures and pressures are the best indicators of how a suspension is working, so measurements need to be recorded before the tires cool.
A properly working tire should have relatively close temperature readings from the inside of the tire to the outside. While it is possible to have slightly more heat at the inside of the front tires due to some negative camber bias, the readings should still be constant.
For example, readings from the inside to outside edge of 185, 180 and 175 degrees would be fine. However, again going from the inside out, temps of 200, 180 and 160 degrees would indicate too much negative camber. To work well, a tire must generate relatively equal heat (indicating equal friction) across its surface.
Furthermore, higher temperatures on the center of the tread—say 180 on the inside and outside edges combined with 200 in the center—indicates over-inflation. Lower the tire pressure, and you should be rewarded with better grip and faster lap times.
Photography Credit: Photosbyjuha.com
Despite the fact that a chassis computer program had yielded some excellent starting points, there were still some handling issues. The cars were prone to oversteer and were also unstable under braking. When reducing the compression of the rear shock absorbers failed to help, the rear anti-roll bars were removed. This helped considerably, because softening the rear suspension added grip to the rear tires and allowed the driver to keep the car’s tail from stepping out under trail braking.
Installing softer rear springs helped to stabilize the Mustangs during braking and turn-in even more. Ultimately, Capps and Irwin got the new Mustangs within a couple of tenths of the class record at Hallett. Not bad for a first outing, but we knew that the suspension setup was still not quite right.
Once back at the shop, Irwin found the problem: Someone forgot to bleed the excess gas pressure from the shocks. This was something so basic that we overlooked it at the track. The shocks had twice the pressure they were supposed to have. Before the next test, the problem was corrected and the cars handled far better.
Important lesson to take home: Before heading out to the track, check over everything, no matter how trivial it might seem. Checklists can go a long way toward making sure nothing is missed.
After the Hallett test session, we reviewed the NASA American Iron rules, went over our tire temperatures and downloaded computer data. (Blake Hinsley, son of Brian Hinsley, Capps’s partner in Interstate Truck Rentals, was invaluable as he pulled up whatever data we requested from the laptop in a flash. If you are not a computer wiz, invite one to your next session.) With our information compiled, we came up with a plan of attack.
Several items loomed large on our to-do list. First, there wasn’t enough time to install any aero devices on the cars before our first test day. In American Iron competition, the front splitter and rear wing are virtually open, and these devices can help stability under braking as well as handling in the corners. Our only solution was to wait to add some aero aids before the next sessions.
Photography Credit: Photosbyjuha.com
Next, I noticed that the Multimatic’s three-link rear suspension arms were very short, and used solid bushings. While these arms are required in the Grand-Am series, NASA’s American Iron class permits longer three-link suspension links fitted with rod ends.
Moving from solid bushings to rod ends would remove any binding in the rear suspension, reducing some of the cars’ handling quirks. Going to longer suspension arms mounted at a less severe angle allowed the cars to get optimal grip during acceleration without permitting wheel-hop under extreme braking. Once we got the cars back at the shop, the modifications on our to-do list were made.
More lessons: Write stuff down and review the rule book. You never know what edge you’ll find in there.
The team’s next track work took place at Texas’s MotorSport Ranch. For this one, Dave Capps pulled in another driver—my son, Spencer Sharp, former World Challenge Mustang shoe and the reigning West Coast Factory Five series champion—to help dial in the team’s new race cars.
Since the shock pressures were now set correctly and the cars had a new rear suspension setup, testing again began at square one. We knew that the cars were fast—remember, we were knocking on the door of the Hallett track record last time out—but we had to start with new baseline setups.
Some minor spring rate changes were made during the day, but the cars still handled better with the Ford Racing rear anti-roll bar removed. The off-the-shelf front spoilers and high-mounted adjustable rear wings also improved the Mustangs’ stability, rear grip and handling.
Photography Credit: Chris Clark
We were making progress. Spencer drove the car to two wins after that test day, but the Mustangs developed a high-speed understeer which seemingly could not be corrected by anti-roll bar adjustments, alignment or spring changes. The decision was made to send one Mustang back with Spencer to Phoenix so Mustang chassis guru Bart Spivey could work his magic.
Spivey, owner of Barts Works and ex-engineer on the Baer Racing World Challenge Mustang effort, determined that the Ackermann angle was causing the Mustang’s understeer problem. Bart subsequently developed new front suspension pieces to make the car handle correctly.
Proof that Spivey had resolved the understeer problem came in the form of a 12-second victory at the fast Willow Springs circuit a few weeks later. However, the car’s heavy weight devoured a new set of shaved Toyos in just 35 minutes on the blisteringly fast Willow Springs track. More development work was still needed.
Another lesson: If a problem has you banging your head against a fixed, solid object, don’t be too proud to call in an expert. Sometimes fresh eyes—or just someone with a truckload of experience—will identify a problem.
Call Dave Irwin or Spencer Sharp newbies, and they will probably laugh in your face. But that is what they were at the NASA Championships at Mid-Ohio last fall. Neither Irwin, Sharp nor either of their Mustangs had ever turned a wheel on this track.
With so many measurements taken and adjustments made all at once, this is the kind of situation where that logbook comes in handy. It allows you to keep track of changes without having to remember numbers and details. It can also help get you up to speed at a new track, as it can act as a crib sheet.
You should have at least four basic chassis setups in your chassis logbook, one for each kind of track: short and clockwise; short and counterclockwise; long and clockwise; and long and counterclockwise. All road courses should fall into one of these four categories, so before you go to a new track, look at its layout and study the terrain. Set your baseline chassis setup using the track in your chassis logbook that is most similar to the new track.
Why not use the same baseline chassis setup for every race track? Because a driver with equal talent, an equal car, but a better chassis setup will beat you.
Consider this: A clockwise course has a bias of 360 degrees more to the right than to the left, or basically four more right-hand turns than lefts. Would it be wise to favor the right-hand turns when determining your chassis setup? Of course!
Photography Credit: Photosbyjuha.com
Let’s use Mid-Ohio as an example. Despite its 2.4-mile length, Mid-Ohio behaves more like a short course. How so? The track has a staggering 13 real turns, more than most tracks of its length. Also, the course’s off-camber, tight right-hand turns favor handling and braking over power and top speed, just as most short tracks do.
With the short clockwise setup on a car like our Mustang, you might want less negative camber in your right-front tire than your left-front. For example, you could have 1.5 degrees of negative camber in the right-front and 2.5 degrees negative camber in your left-front. Why do this? You have four more right-hand turns than lefts. You must exit these right-handers well to stay in contact with the leaders. Too much negative camber on both fronts can hurt braking.
Two of the most critical right-handers at Mid-Ohio also lead into the longest straights, making them the most important turns on the track. Your right-hand-turn-biased camber setting will take advantage of this and provide better exit speed off of these corners and down the straights. However, be careful not to go too far with your right-turn camber bias, since what you gain in handling in right-handers will be sacrificed in left-handers. In short, the driver must still be comfortable with the overall chassis setup.
Another important lesson here: Arrive at the track early. In addition to fine tuning your base chassis setup, you need time to learn the best racing line and observe the quick locals to learn the best passing lines.
Despite the fact that rain fell during the first two days we were at Mid-Ohio, the drivers were quick studies. Spencer Sharp finished fifth in the American Iron qualifying race on Friday and second on Saturday, earning him a second row grid position for Sunday’s championship race. Dave Irwin moved up in both the Friday and Saturday qualifying races and started on the outside of the fourth row for the final race.
Sunday’s race went okay for our two Mid-Ohio newbies. After a good start, Dave seriously flat-spotted his tires while trying to avoid an accident. He wisely parked his car, as the tires weren’t safe enough for any more hot laps.
Spencer did a little better, fighting among the top four drivers during the entire race. The race wore heavily on his tires, and he settled for a fourth-place finish. Not bad for a car and driver package that had never visited the track. Arriving with a good baseline definitely helped get everyone quickly up to speed.
Having finished second in the last two NASA Factory Five championships, Spencer came into the Mid-Ohio event hoping for a win. However, reality dictated that winning in a new car at a new track was going to be tough. That kind of stuff usually only happens in made-for-TV movies.
If hindsight is 20/20, we now clearly see where improvements could have been made. For one, the cars were too heavy. NASA uses a horsepower-to-weight formula for its American Iron cars. At wide-open circuits like Willow Springs, our Mustangs were tough to beat as that extra power let us run away from the competition. At a tighter, more technical track like Mid-Ohio, that extra weight became a liability as tires were overheated past their optimum temperatures.
While it’s impossible to rerun the 2006 championship races, plans are already in place for a better future. Less horsepower for each car means a lighter fighting weight, which should help with tire management at Mid-Ohio.
Rumor has it there’s even a sign in the shop reminding everyone to remember Mid-Ohio. Sometimes a little psych work helps, too.
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