Chalk test at 28psi cold?

I recently upsized my tires from the stock 265/70R16 GY Kevlars to 265/75R16 GY Duratracs. Tire shop set the pressure at 35psi. I did the chalk test after work when the tires were warm and resulted at 30psi. This made the cold tire pressure at 28psi in the morning. Is 28psi to low for my daily driver and nothing in the bed? Others here on TW have these tires up to 36-44psi?

I'm thinking to raise it to 30psi cold (just like the door jamb says) since both are C-rated tires and specs show max loading at 2470 lbs at 50 psi for both. Maybe the chalk test is correct and the extra 2psi will compensate for passengers and/or gear in the bed?

 

Interesting. I run 38 in my KO2's. 28 sounds a little low.

 

Yeah, I definitely don't want to be underinflated.

 

Shop put mine at 28..... rode like shit, it felt like the truck was supported by gummy bears.

 

My truck comes in at 4400lbs with me in it and i run 38 front, 36 rear.

But thats my preference and has served me well with even tire wear for the last 11yrs

 

What size and rating? I run 235/85R16 KO2 and 30 is about right for my truck daily but they are load range E. If I ran pressures like you do the tires wouldn't wear evenly.

 

255/75/17. I have a shell and a sleeping platform in the bed.

 

hmmm...chalk test as a baseline/starting point, and adjust up for personal preference. Sounds like a plan!

 

Your original Goodyears are 4 ply/P rated fwiw.

 

Those are on duratrac load range C as well

 

You're right. I didn't know what the SL on the Goodyear website meant until now, which appears to be a type of P rating?

 

I'm running 265/75 16 Toyo Open Country Mud terrain load range E tires on my truck and are set at 35 psi . The chalk test shows perfect wear and the ride quality is perfect

 

I wound up at 28 rear and 32 front when I chalked my 255/75/17 c range bfg km's. I don't really care what the number is, I care about contact patch and the driving feel. I get no tramlining, and the ride is pretty smooth!

 

When I had a set of LT265/75-16 C Duratracs I ran them at 30 psi all round for years and they wore evenly for 55k miles before I replaced them. The tire pressure sticker on the door assumes you are loaded to full GVWR because they don't want the liability of people running pressures too low with a full bed.

 

Seriously?
That door number leaves awefully squishy sidewalls and id NEVER run it empty let alone fully loaded lmao.

The front does not feel very secure at the 29psi mark

 

Sure nuff, thats how the sticker reads isnt it?
Wow

 

Ford got in trouble with under inflation, didn't they?

It also is based on the stock tires, which on my truck were 265/70R16 BF Goodrich Rugged Trails, which are rated by BFG for 2185 lbs @ 35 psi max inflation. The pressures Toyota recommends must be within that. The KO2 I run now are rated up to 80 psi and are load range 'E', so the 29/32psi numbers bare no meaning anymore. That roughly 30 psi works is happenstance but makes sense. The 235/85R16 is close in size and the truck's weight and distribution hasn't changed so why wouldn't the result be similar?

If anything I would expect the stiff sidewalls of the 'E' tires would mean a wide range of pressures would work without distorting the sidewalls or tread and in fact I can air down really far (my deflators are set to 18 psi) without excessive sidewall bulge. When I run them at high pressure my truck just doesn't weigh enough to really squat the tire, which is why I see the center wear faster at 40 psi. It also rides like it's on steel locomotive wheels.

 

3rd gen's need enough psi to support 1,954 lbs when equipped with LT tires.
At 37 psi you would have 1,986 lbs. At 28-30 psi, you are in the 1,600-1,700 lb range.

 

Can you explain where 1,954 lbs comes from? That would imply a GVWR of 7,816 lbs, right? AFAIK the 3rd gen GVWR are around 5,600 lbs. Or is that an axle rating?

My 2nd gen is rated 2,755 lbs front and 3,110 lbs rear GAWR or a total of 5,350 lbs GVWR. To do this with the stock tires you'd only need at most 1,555 lbs per tire, which would be required to meet the max rear axle weight. To meet GVWR 1,338 lbs per tires is all that's needed.

The Rugged Terrain is a standard load index of 111 (which is standardized to 2,403 lbs @ 36 psi, I don't know why BFG rates them at 2,185 lbs @ 35 instead) will easily meet that down to at least 24 psi, where it will still support 1,702 lbs.

But you're saying LT tire, which is typical of the BFG A/T KO2. In load range 'C' (for size 265/70R16, just an arbitrary size) they have a load index of 121 in a single wheel application. That's 2,535 lbs at 35 psi. The charts don't go lower than this so it's not really linear necessarily and that's the minimum rated load & inflation.

One thing that probably should be mentioned is the chalk test only works with brand new tires. You can't check contact patch with used tires because previous over or under inflation will have caused the tread to wear flat on the pavement. You could use chalk to test a new inflation to see the change, but it's not going to tell you anything about the ideal pressure.

 

When I had E load Duratracs on my patrol Tacoma, I ran them around 26 - 28 PSI. That was a personal choice, because 50% of my driving was off-road and I needed to have the extra give from the lower pressure, but not all the way down to 15 PSI for true off-road pressures since I still needed to be able to roll at 100MPH+ on the highway. Got 40,000 miles out of the tires with that setup.