Geolandar 35's chalk test: what are you running your pressure at?

[jsims006]

I've done the chalk test, im getting the same contact patch results at 55psi that I am at 45psi - am I doing something wrong? What are yall running your pressure at? The lower I go, the worse mpg I am getting.

[verdesardog]

I tried the chalk test with nonsense results so I just go by the tire load chart.
Unloaded front 45psi, rear 35psi with 315-70-17's on a Cummins 2500.

[Bill2014]

Chalk test
Everyone's use case is different. I still wear my front tire edges about 1mm faster than the middle at 65psi on the Power Wagon. (Stock rim width and tire size)

[DamageWagon]

Start high and work your way down. If you get the same patch at 45 and 55 it is because you’re already at full contact at 55 and need to go higher until you lose contact. At the point you get full contact, drop the pressure a few pounds to share the load across the tread, and run that and see how it wears over time.

[SimonandSimonBeast]

I just went through this with a new set of tires. Different trucks, different tire brands, different tire sizes, different tire types (AT, MT) will all yield different results. I do think it is the best way to validate if you are running correct tire pressure for your given set up. I actually started doing a video when my phone decided to stop the video halfway through and then it proceeded to rain. If they are new tires I suggest doing this again in a few weeks after they break in, and maybe run them around town a bit before you do it to warm them up a bit. As an example, I'm running Toyo MTs 37x13.5 R17. I started them at 35 psi all around when they were brand new and they all chalked out OK with more chalk reveal on the lighter rear end, and less in the front. After a few weeks I checked again with the same results in the rear, so I am leaving the rear at 35 lbs (~1.5" chalk reveal). At the front I had almost zero chalk reveal and could see some outside shoulder lug wear. I went up 5 psi which had no or little effect on the chalk reveal. I went up another 5 psi (10 total psi) and acheived about an inch chalk reveal. So, I am leaving there for now at 35 rear and 45 front. Again, this is what is working for my rig and tire combo. Do your own test. It is my opinion that some amount of chalk is left, around an inch to 1.5 inches depending on your tire and tire width, so that you not prematurely wearing your other lugs and not too much reveal that you are wearing your center lugs.

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[TommyDuncan]

I am leaving there for now at 35 rear and 45 front.

I've had these same tires for a couple of weeks in all different conditions and seat of the pants has me at the same pressures as you. I will do a chalk test eventually...

[SimonandSimonBeast]

I am leaving there for now at 35 rear and 45 front.

I've had these same tires for a couple of weeks in all different conditions and seat of the pants has me at the same pressures as you. I will do a chalk test eventually...

Good to hear. Sounds like I (we) got it right.

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[cb1987]

this was some months ago and cant remember air temp but did chalk test on 35x12.5 18 E with 40psi on all four. front was good pattern. rear was slightly overinflated by probly 5psi

[cholley12]

I run 48 and 40 on my G003's 35x12.5x17, but i also have a tool box full of junk probably 400 lbs total at all times.

[ScubaSteve]

17x8.5" wheels, I'm running 32lbs front and 25 rear with my 37x12.50 Toyo MT's...way less than a lot of other people, but that's what is getting me even tire wear and the best ride. A point that typically goes overlooked is that bigger tires require less pressure to support the same amount of weight, due to bigger footprint as well as stiffer sidewalls. Small highway radials an the stock Duratrash tires, are much squishier carcasses than most larger offroad tires. Combine that with the smaller diameter and width, and you need to run much higher pressures to achieve proper contact patch and wear. That said, the stock tires with 65 and 60 psi front and rear is really too high.

Also, everything Simon said.