How to get your optimum tire pressure
Saturday, 10 February 2001 08:00

Tech: How to get your optimum tire pressure

Tire pressure is one of the most basic, yet affects you car or bike on the strip more than anything else. If you don't have the short times (60 ft.) that you think your car or bike is capable of, it's probably because you are spinning (or bogging) at the line. This can almost always be traced to improper tire pressure.

Here are some tips-

1. Buy yourself a QUALITY tire pressure guage! Don't settle for the cheap pencil guages you see in the auto parts stores or gas stations. These are very inaccurate and more importantly, inconsistent. You want a guage that will at LEAST read pressures the same way each time. Meaning, if you guage reads 25 psi when the actual pressure is 24.7psi and 28 psi when the actual pressure is 27.3 psi, you want a guage that will read those actual pressure the same way the next time you check your tires. If the actual pressure is 24.7, then your guage should read 25 (like it did before) not 26 or 24 (1 psi CAN make a BIG difference!).

Get a guage with a dial face and flexible hose. This eases the use of the guage immensely. Also, get one that "locks" the reading so you can view it without having to put pressure on the valve everytime.

Another consideration is your guage should have a bleed valve. This helps bleed excess pressure from your tires more easily. It's not required, but it does make life easier since you'll be doing this quite often.

If you run slicks, your guage should have a range no greater than 20 to 30 psi. Anything higher, you will have a tougher time getting accurate readings, since you most likely don't run more than 15 psi anyway. If you run street radial tires, then a guage with a maximum reading of 50 to 60 is about right. You will more likely be using pressures between 25 and 40 psi.

2. Now that you have a guage that is accurate and consistent, how do you know what tire pressure to set your tires to?

The generic test (slicks or radials)-
Do a rolling burnout (spin you tires while moving forward). Check to see the tires marks left on the pavement. See if the width of the marks are the same shade across the tread width. If the center is lighter than the sides, this indicates you have too little tire pressure. If the center is darker or the mark is narrower than the actual tire, this indicates too much pressure. Adjust until you have a uniform shade across the mark.

Now look at your tires. Check to see the wear pattern on the tire. Does it go across the entire width of the tread? Check to see if the edges show more wear than the center (underinflated) or vice versa (overinflated). You want a wear pattern that is equal across the entire tread width. Adjust as neccessary.

If it's your first time running slicks, make at least three runs using about 15 psi (or whatever pressure you ended up with using the generic tip). This should establish a good base line. Check your time slips and look at your 60 ft. times. Generally, short times for slick shod cars should be in the sub 2 second range. If your times are slower than this, adjust your tire pressure (up or down) until your short times improve.

Same as slicks except your tire pressure should be around 25 psi (or what you ended up with using the generic tip).

Note: To improve 60 ft. times further, you'll have to experiment with launch rpms and clutch release techniques. The above tips are mainly for tire pressures.