Chalked my tires... and I'm perplexed

Yesterday I got some brandy new BFG KO2s LT265/75-16. Sweet tire.

Today I chalked them to set the ideal pressure based on this technique (Option #4 - "Let the chalk tell you"):
https://www.4wheelparts.com/tire-wheel-package-guide/tire-pressure-checker.aspx

Has anyone that has chalked their tires encountered some strange results? Specifically, imbalanced Left-to-Right pressures?

This is the first time I've tried chalking tires and I'm a little perplexed with the results.

First, I set the pressures to 46 psi based on the math in this load inflation table (pdf) and my factory door placard that states my tires need to be set to 46 psi for D-range BFG KOs. Found a flat piece of ground (driveway) and rolled the truck back and forth about 100'. Here's how it shook down:

• Driver side front - Lowered to 44 before it wore evenly across the tire face.
• Passenger side front - took it down to 38. Still had some chalk on the outside edges - about 1/4" left.
• Both rears - took down to 34, still had some chalk left - but about a 1/2"

I stopped lowering them because the driver side front was wearing evenly at 43 psi and I couldn't believe that the the passenger side front had a difference of 6 psi. Also, the rears at 34 seemed pretty low based on the load inflation tables (when compared to the factory specs).

I may try to repeat this next weekend when I have more time, but wanted to see if anyone else has had some strange results. Specifically, the 6 psi difference in the front L/R tires. I may go lower, but the truck felt a bit "vague" at 33 psi cold all around, as it left my tire installer.

 

The weight distribution of the vehicle is not the same on all corners.

Put a passenger in of your weight and I bet the RF needs more air. Plus the fuel load is on your side of the vehicle.

It's why race cars are corner weighted.

And don't forget, alignment matters too. Any camber of significance will negate pressure tweaking.

 

I just replaced a set of KO2'S after 40,000 miles, I typically ran 33f and 30r with no load. The KO2'S ride pretty rough so watch running high psi.
My tires had a near perfect wear pattern running this psi for 40,000 miles.

 

Yep, I'm with you. This is exactly why I was perplexed. I've corner weighted many racecars and haven't seen anything like this - where 1 corner was that much "lighter" (i.e. the right front in this case). Just didn't think it would show up in tire pressures that much if in fact what I'm seeing is accurate.

Wow - that's pretty incredible wear pattern - 33F and 30R. That's way lower than I would have thought. Is that in a 265/75 E-rated tire?

 

E load 265-75-16 . I replaced them with E load Cooper St Maxx , they are much more compliant than the KO2'S.

 

Ambient temp matters for the chalk test in the winter. You need to drive at highway speed for a bit before chalk test. As an example, when temps are close to freezing and mine has been parked, when I first start it the pressure light is on in my dash. After the tires warm up the light will go off.

 

Appreciate that. However, I set the pressure at the beginning of chalking, thus ambient temps have no affect. The point of chalking to check cold tire inflation and establish a baseline, not hot (after driving).

For every 10 degrees in ambient temp, you'll see a corresponding 1 psi change in the tire. Based on what you're saying for your truck, it probably means your pressures are so low that TPMS thinks you have an issue until the tire(s) warm up enough to increase psi and trip the dummy light off.

By the way, check this out:
http://www.nittotire.com/media/152964/techbulletin_ntsd-12-011.pdf
That's why I probably sound surprised by low psi's people are running. Under inflated tires at highway speeds can crush a tires longevity.

 

I read this from my phone the first time and missed this. Truck has a full tank of fuel plus me in it. So that could absolutely account for what I'm seeing. Appreciate that - I'll check it out next weekend when I get the time to do this again.