The MGA With An Attitude
How to get started on tire pressure tuning for maximum grip.

Not for the faint of heart. This is for when you get really serious about wanting the maximum grip from your tires, and you don't give a damn about tire wear or ride quality, because both of those qualities will suffer. People say that everything is a compromise, and for a production car, that usually is true. Then one day you decide that ride quality can be compromised, and tire wear be hanged, you just want the maximum grip from your tires@ (That's a BIG period).

First, you need a good seat belt in the car. No compromise here; it will make the car go faster; trust me on this one. And of course you would not be able to get into an autocross event without it.

Get yourself a squeeze bottle of cheap white shoe polish with a foam pad applicator. Forget the acrylic stuff. Go for the $.59 bottle. You know, the stuff that washes off the first time it gets wet.

Also get a tire pressure gauge that you can depend on to be free operating and repeatable. It doesn't have to be expensive or especially accurate, it just needs to show the same reading every time you use it with a given pressure. Then you keep the same tire gauge in the car at all times and use the same gauge every time. We will be working with pressure changes of +/- 1 psi.

Then you need a big empty slab of cement or asphalt where you can do some serious tire squealing, and nobody will bother you. This may be the biggest problem.

You also need a ready source of a little pressurized air for adding to the tires occasionally. So, unless you have a service station with an air hose right across the street from your test pad, you better take along a pressurized air tank. If you start with fairly high tire pressures, 1/2 cubic foot air tank should suffice (at least 80 psi in the tank to start).

Since it's easier to let a little air out of the tires than to put more in, you start a little on the high side -- say maybe 40 psi in the front tires and 36 psi in the rear tires. Yeah, Yeah, I know it may say 32 psi maximum on the sidewalls. So ignore it.

Now, take out of the car anything that's loose or might rattle around. Get rid of everything in the boot. Spare tire is optional, but if you leave it in the car it has to be properly clamped down. Nothing under your feet, nothing behind the seats, nothing in the door pockets.

If you do this with anything more than 1/2 tank of fuel, you may expect to find a little fuel splashing out of the vented fuel filler cap and slopping down the paint. A light fuel load may be in order here.

Oh yeah. And check the engine oil. Be sure it's up to the high mark on the dipstick (famous last words). Also be sure the wheels are in good condition and screwed on tight -- no missing lug nuts allowed.

Look at a tire, any tire. Imagine that the tread is flat across, and the sidewall is straight, and that there is a sharp corner where they meet. It isn't, it isn't, and there isn't, but it's that imaginary corner where you start. Starting from that corner at the top of the tire, follow the surface down the sidewall. You will see at least one last tread block (row of tread blocks around the tire) on the sidewall before you get to plain smooth rubber sidewall. At the transition between the last tread block and the smooth sidewall there is usually a small raised ridge of rubber.

Now take the white shoe polish (this is what you were waiting for, isn't it?), and paint one little square tread block from the edge of the flat tread down to the raised ridge. Repeat this at 3 or 4 equally spaced places around the tire, outside wall only, the one you can see without crawling under the car. Repeat the markings on all four tires, and you will be ready to start driving.

Shoe Polish 102 covers the test drive and how to put the car through its paces to thoroughly exercise the tires.

Barney Gaylord

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