Tire PSI Chalk Test

How To Check Proper Tire Inflation 

Now that I have bigger tires I am just not sure what PSI to run. Over inflation or under inflation will cause your tires to wear unevenly. How does one tell if their tires are properly inflated?

Chalk Test

All you need is some chalk and a tire gauge. 

Tools for chalk test: chalk and tire pressure guage

Step 1 

Check the tire pressure of all 4 tires. Three of mine read 31 PSI and the rear driver was 29 PSI. 

using the tire pressure guage to measure pressure

Step 2

Next, I chalked up a thick line across the width of my tires.

putting chalk on tire 

Step 3

After all four tires were chalked I drove back and forth on my driveway. It is very flat since we just got it repaved. There were no cracks, bumps or pot holes. 

Then I inspected the chalk on the ground and on the tire. Check out my before and after shots of all four tires.

chalk on tire before measuring

BEFORE

Before with chalk

AFTER

After when the Jeep has been driven

An over-inflated tire will bulge, and only the center of the line will touch the ground.  If you're tire is under-inflated, you'll see only the sides of the lines since the middle of the tire is not making contact with the ground.

Showing the edge of the tire

Knowing where the true edge of your tread is makes for easier calculations. I decided my tires were spot on. I have been running my PSI around 30 to 32 PSI on the asphalt. 

I understand there is some debate on whether this is an accurate way to gauge proper PSI. There are a lot of variables to consider and it depends on the width of your wheels. 
At that time my tires were 35" Duratracs LT 315/70R/121/1180.