Like this?

These are Dallara IRL cars. My club ran them for a number of years without traction magnets on our wood tracks. It was intended to be a boxstock class with the only modification being a spec pair of slip-on silicone tires. We hoped that this would not be a tuner's class and that the racing would be close. As it turned out there were large differences in performance between the cars, a slower car could get lapped several times during a three minute heat. Finally we spent an evening testing all of the cars. One of our members had a Kelvin Light Bench, that was a sort of dyno stand and was connected to a computer so the data was collected to a spreadsheet. The RPMs for all of the cars were all determined first, next they were run around a skidpad in both directions and the minimum lap time was determined. Finally the cars were run around our most technical track. I still have the data saved from the testing. The motors varied in performance by a fairly significant amount. A particular car might be faster in one direction around the skid pad than the other direction. As you might expect the cars with the best combination of motor and skidpad performance were the fastest on the track.
So now what should we do to equalize the cars? First of all if your motor was a dud you would want to replace it. That left the handling issue. One of our club members is a world class tuner and he figured out a number of tweaks for these cars. If the cars still had their traction magnets the handling differences would probably have been minimized. As it was the front tires did not usually touch the track, having the front tires firmly planted on the track is important when you run without traction magnets. With these cars the guide flag holds up the front, so the braids have to be removed and the bottom of the body of the flag sanded to make it thinner. Normally the braids are looped around the body of the flag so the feelers attached to the chassis can make contact. That makes for a double layer of braid on the bottom of the flag. We glued the braid to the top of the flag to eliminate the doubling. Next it was determined that the front suspension could flex or might be crooked. The fix for that was to drill larger holes through the axle carriers so a piece of tubing could be installed to connect both carriers. With front wheels installed the whole front suspension assembly would be glued in place. That procedure would eliminate the differences in direction seen on the skidpad. The last tweak was to tighten up the rear axle bearings. All of these cars have plastic bearings and the axle is a loose fit. We used the Superglue trick to eliminate the slop. After all of that the cars were more evenly matched.
