“Chalking the Tires” and the Voodoo of PSI.

                                   By: Riggs   Aka: RiggsZ32   –  Setec Motorsports

Everyone knows that correct tire pressures can make or break you for an optimal contact patch (CP) aka traction (if you didn’t know this, you do now).  Ideally you want your expensive tires to do what they are supposed to, for them to do this you need to inflate/deflate them accordingly.  You might be thinking to yourself “How can I do this?” Your about to find out, but first we need to go over some basics:

Ø      Over inflating

Over inflating your tire/s will cause them to mushroom confining the contact patch to the center of the tire.  While this might be ok for drag racing (when on the front tires it “could” effectively reduce friction by keeping the CP small and in the center of the tire), it is not good for cornering, stopping, and control in general.

Ø      Under inflating

Under inflating your tire/s will cause them to make contact on the outside edges and not so much in the center.  Once again this isn’t optimal as the outside edges will wear faster, not to mention you aren’t using the center section of the tread (the center section being the flattest and best for friction/ performance).

Ø      Tire “rollover”

Tire “Rollover” (TR)  as I will call it for this article is the actions of the tire under hard cornering aka side wall flex.  While low profile high performance tires don’t have the tendency to do this as much as your basic radials, it can still be a problem.  Proper inflation can reduce the ill-effects of TR, you can’t always solve this problem entirely, but you can reduce it.

Now for the fun part, remember that sidewalk chalk you might have seen / used when you were little or maybe your kids use to mark up the driveway at home?  Well for this test your going to need to go buy some or steal it from your kids (hey you paid for it anyway right?).

ü      1: Take a warm up lap (or 2) to get the tires up to pressure

ü      2: Take your chalk stick, block, whatever and apply it to the tread and side wall of the tire on the outside edge about 1 inch down on the sidewall and 1 inch in on the tread.  Do this to all 4 tires.

ü      3: Take another hard lap driving as you would normally (for the track of course).

ü      4: Inspect your tires to see where the chalk has been rubbed off by contact with the asphalt.  Add air as needed (if chalk is rubbed off the sidewalls you need to add a few PSI as needed to keep the rollover to a minimum).  Next check the tread to see where the chalk has been rubbed off (if the chalk on the outside edge hasn’t been touched you need to let out some pressure).

Don’t get discouraged if you can’t get it correct the first few times, this is a subject with a learning curve, and it’s more like a black art such as voodoo.  If you are having problems with it or don’t really understand how to, ask an “old-timer” at your local solo2/autox or at the track.  These gentleman/ladies (girl racers = hot) should be more than willing to help you out and might even give you a few other tips, you can learn more about racing talking to the senior racers in staging a lot of the time especially if you are new to motor sports.  The knowledge is out there you just need to find it, or get hooked up with those who can teach you.  True racers just love racing, all aspects of it including helping those who are new to the sport.  Welcome to the family of racing, keep it safe and don’t be stupid, and most of all keep it sideways and those times down!

Thank you to Sean from Underground  Drifting and Racing of Canada!!