Tire pressure question

[Zooguy]

My 1999 Land Cruiser info;
DAILY DRIVER / Overlanding build
6,700 Lbs.
315/75/16 Kenda Klever M/T2 (35s stock wheels)
PSI tire pressure .... T.B.D.

OVERSIZED tires have a larger VOLUME of air inside them compared to the OEM installed tires that's a fact we can all agree on. Also, a LARGER air volume can support the same WEIGHT/MASS at a LOWER PSI when compared to the OEM installed tires. (Bigger tires need LESS PSI)

I know that Toyota has a recommended tire pressure for any vehicle they put out. However when you begin changing parameters on a car all bets are off as far as what is the best tire pressure for any particular bill when you change the vehicle's weight and tire sizes.

I'm not looking for somebody to tell me what tire pressure to run. I'm just curious as to what everybody else is running and with what changes to the factory weight and tire size.

There's a fairly basic method to determine tire pressure needed by rubbing chalk across the entirety of the tire in about a three or four inch wide strip. Flat level surface drive forward for about three rotations of the tire and pack up see where the chalk is rubbing off the tire and make appropriate pressure adjustments.

So if you've read this far please let me know your Land cruisers wait tire size and pressure you like to run. Thank you everybody.

 

[nissanh]

Bigger the tire lower the pressure as in giant farming tractor tires. But they don't make turns at 75 MPH so running low pressures with larger tires may pose a risk of overturning at high speed turns.

With E rated, you have to keep the pressures at or above 40 PSI to prevent damages to the plies in the sidewall. I have E rated and runs on 36-38. Factory specs says 29 PSI, which I will do if I have SL tires

 

[HokieCruiser]

man I love some beefy tires, nice!

 

[GerLC100]

Same here: going for 38 PSI in my 285/75-16.

I think Hoser posted this link before in a different thread: file you stock tire and load rating, file the new one and get the "right pressure" as starting point.

Tire Pressure Calculator

Easy to use tire pressure calculator. Use our tire pressure calculator to calculate the new tire pressure needed when changing tire sizes.

tiresize.com

 

[Jack90210]

Yep, I run 38psi when on LT-rated 33s (i.e. 285-70R17) for daily driving, and run higher pressures (~45psi) when traveling with multiple passengers, pulling a trailer etc. This is on a basically stock LX -- no bumpers, sliders, drawers etc.

The Tire Pressure Calculator linked above is a great tool.

 

[Jack90210]

<snip>

OVERSIZED tires have a larger VOLUME of air inside them compared to the OEM installed tires that's a fact we can all agree on. Also, a LARGER air volume can support the same WEIGHT/MASS at a LOWER PSI when compared to the OEM installed tires. (Bigger tires need LESS PSI)

I know that Toyota has a recommended tire pressure for any vehicle they put out. However when you begin changing parameters on a car all bets are off as far as what is the best tire pressure for any particular bill when you change the vehicle's weight and tire sizes.

<snip>

A couple of points, to hopefully make this easier to think about:

1) Air volume, by itself, has nothing to do with supporting weight; the air simply provides structure to the tire as a means of keeping it from becoming too hot via the energy imparted by the flexing of the tire carcass. When in use, speed, load, and ambient temperature all act to increase tire temperature. (Related: for any given size, an LT-rated tire will require more air than will a P-rated tire to match its load rating at a given pressure.)

2) When one changes parameters (weight, tire size) on a vehicle, one can still calculate the increase in load on each tire, and also the pressure required (from any tire's size/construction/load rating) to support it. No need to guess.