Tire sizes

[itsaguything]

I think of myself as a “pay attention to the details” kind of guy. But all of this talk of tires had me wanting to confirm…

On the LR4 HSE Lux, with 2 speed transfer and locking diffs, I just assumed in the “new to me” category that I had the right (from the factory) wheels on him.
(Gender change alert: the LR4 is now a boy)
But I don’t. It came with 19s though the sticker in the door sill states 20s.
(But Topix states 19s for my vin).


Anyhow, by fluke I’ve been running the right pressures in my tires as I typically run 7% underinflated, purposely.

On this set of rims I’m running 255/55R19. The sticker states 255/50R20.
Had I followed the direction for recommended pressures, I’d be at 37 front, 43 rear.
By chance, I’m at the recommended pressure defined at https://tiresize.com/pressure-calculator/

I thought it felt too bouncy at recommended… Go figure.

 

[djkaosone]

I'm pretty sure the door card recommended psi ratings are optimized for fuel economy ratings/performance, traction, and air ride quality. It really doesn't matter what size tire you have, every tire shop will still utilize the suggested door card psi. It's safe to use close to those psi ratings, because tpms will let you know if you're really off. It's really up to you to dial it in to your preference.

 

[mm3846]

The door card is for load. NAS spec trucks only have the single PSI spec, ROW has two.. one for empty and one loaded. You can run the same front PSI spec F/R unloaded.

 

[itsaguything]

Yes it is for load.
My points were
1. that different sized tires require different inflation pressures in order to keep with the engineered handling and load characteristics.
2. The door card does not match the information at topix... you'd think they's be in sync.

It is simply described here: https://tiresize.com/pressure-calculator/

Cheers All!

 

[ftillier]

I believe the door card on my 2012 lists 19" wheels, but the same PSI as what you have listed above (37/43).

 

[itsaguything]

Interesting @ftillier . I wonder why the change between the model with the 5l and the scv6??

 

[itsaguything]

That was fun…. I had to look myself

So the calculator I’m still a pound off…

And as its a snowy day, what the h311…

Cheers All!