One of the novice passengers I took on one of my runs last weekend (I was a novice coach) remarked on how much grip the car had.

He said, “Wow, you’ve got good tires!”

I answered, “Yes, I have good tires.”

What I might have told him, if it had been a more appropriate time and place, is that the grip a car produces and that you feel from the passenger seat is the result of a host of factors, not just the tires themselves.

So, I started thinking about it and came up with the following ‘grip ingredients’ list. The first five are well-known. The last one is maybe not given enough attention.

1. Tire type. Yes, you have to have sticky autocross tires. There are only a handful of suspects, though the list changes from year to year and you must keep up-to-date. Right now I’m on Bridgestone RE71RS in the front and Yokohama A052 at the rear. The Falken RT660 seems to have fallen a small step behind. The new, 2023 version of the Nankang CR-S has tested well and is getting a try-out by some autocrossers. That’s the entire, current list, folks.
2. The tire width you choose has to be matched to the rim width. Not too wide, not too narrow. How do you figure that out? Your own testing plus the testing experience of others. Depending on how much money you have to throw at the sport, this may take one year or several. Or no time at all if you have a good example to follow. If you want to run an ND2 in C-Street you have lots of good, free data that will get you there with no effort at all if you can simply find one national-level competitor and get their advice. If you are running a Lotus in STU you’re on your own, buddy! I have 275mm on 8.5″ rims in the front and 295mm on 10″ rims in the rear. Some will say that a 275 is too wide for an 8.5″ rim. I did enough testing in years past to clearly show that 255mm was not sufficient in the front of either a C5 or C6 Corvette on an 18″ diameter rim. I can’t tell much difference between a 265 and a 275, but I think the 275 delivers slightly more lateral grip though it’s not as sharp-feeling. Even if it doesn’t give any more grip, it works well on my car, being slightly taller. I run the 295 Yok because it puts down power the best, even though it’s really too tall, being a 35 aspect ratio rather than a 30. I’ve run 305 and 315 Falken 660 tires on the rear. The 315 was not faster than the 305 and neither gives better lateral grip than the 295 on my 10″ wide rim so I suppose they are too wide for the rim. (And the Falkens, though having incredibly sharp responses, are not good at putting down big power.) You have to prove these things to yourself, given your specific car and setup.
3. Proper alignment. For most Street-class cars this means all the negative camber you can get, plus experimenting with toe, front and back, as part of the effort to get the car balanced so that both ends are contributing their maximum to the total grip in a sweeper. (Often this also includes anti-sway bar changes as well.) The car only sweeps as fast as the weakest end. If that means slight oversteer at the limit, so be it. If that means understeer at the limit, learn to drive with it. If you are not in a Street class then you can modify hardware to increase camber. This provides more options that have to be worked out via testing, or, once again, you may be able to find someone with relevant experience who will share and give you a starting point.
4. Proper inflation pressures. After significant testing I use 30psi front/28psi rear on my C6, given the tires mentioned above, on asphalt, but +/- 2 psi from these figures makes little difference. On concrete I increase by 1psi. In the wet I decrease by 1 psi. Do these small changes make a difference? I’m not sure, but I feel better about it! When I got the car I was advised that I needed about 5 psi more than I run now with the tires I was using. Testing showed that didn’t work for me and my car. This past weekend it was really hot (95F) and I got distracted and didn’t check pressures after the first run in the afternoon. Halfway through the second run I’m wondering what’s going on. Then I realized my oversight. When I got back to grid they were 6 to 7psi too high and that was plenty to degrade the grip to a perceptible extent.
5. Proper tire temperatures. Again, only testing can really tell you the story. The RE71RS tires on the front of my car can definitely be too cold at ambient or over-cooled with water. They seem to work best with 1 run of heat in them so that the surface is slightly warm to the touch, then I don’t let them get any warmer. The A052s in the rear you cannot ever allow heat to penetrate into the carcass. This requires spraying after every run except in extremely cool conditions. You only learn this stuff by letting them get too hot at a race or test session and watching your times get slower though you are driving better. Nothing is more frustrating or puzzling until you realize what’s happening.
6. Sensitivity to the tire contact patches. OK, this is the final thing I want to say and some of you may find it sort of nutty. But, here goes. When it comes to being able to maintain a car at maximum lateral grip in any kind of corner or sweeper it’s the driver’s sensitivity that’s key. Without sensitivity to the information primarily coming through the steering wheel into the palms and fingers and secondly through the car into the body through the seat, you cannot maintain the car close to the traction limit. To do this one must be controlling the turn rate very precisely to keep the tires from going too far over or too far under the maximum grip slip angle at the tire contact patches. Precise control begins with sensitivity. You must very quickly adjust if the tires deviate one way or the other which means you must feel it early. Too much under the peak is just slow. (Mario Andretti: “If everything seems in control then you’re just not driving fast enough.”) Too much over and you lose control (and lots of time) in a slide or push. But, you have to consistently go over the peak by a small margin. Otherwise you can’t know where it is! We must always be testing and challenging this limit, this peak. Now, to increase your sensitivity start with your driving posture. Nothing is worse for sensitive control than two hands in a death grip at the top of the steering wheel. Drop your hands to 9 and 3 (or below), relax and sink down in your shoulders and elbows and don’t grip the wheel any tighter than necessary. Relax until you can feel the weight of your arms hanging from the shoulders and stretching the neck muscles. This will feed blood into the hands instead of constricting flow. Sensitivity follows the blood. Practice this during all normal driving, then focus on it during some autocross runs. Never allow the shoulders to hunch up. Also, I love the partially wet skid pad drill we do in our local driving school each Spring. Nothing teaches sensitive control like hammering around a skid pad where the grip at each end of the car changes every second. After a few laps you’ll never be the same dull, clumsy driver again! Similarly, nothing trains sensitivity like autocrossing in the wet. Take every chance to run in the wet at local/regional events… don’t avoid them! Skin is waterproof!