Again, IMO only, the air pressure differences are with an unloaded vehicle with just the weight of the vehicle on the tires. Even then, I would want the tire pressures to be the same, front and rear. When I go in to a tight corner at speed, I want to believe in my mind that the tire grip is the same because all tires are the same. IMO, when loaded with enough weight, that becomes even more critical, again IMO.
My understanding is that the PSI differences apply both with and without a load, at least in my vehicle. The weight rating for each axle (GAWR) is listed on the Certification sticker on the door. Tire pressures are assigned accordingly.
As an aside, I was really surprised to discover that mine has
two door stickers; one located in the usual spot, and the other higher up on the door. Which is why I missed it at first. At least that’s my excuse!
Why they didn’t make just one combined sticker is a mystery to me.
Here’s the one I hadn’t noticed. It clearly states the assumed load and tire pressures for the front and rear:
You must be registered for see images attach
Here’s the Certification Sticker, in the place I would expect it to be. It too is specific about the GAWR and the load range of the tire to be used. In this case, E.
Again, the pressures are different front and rear.
You must be registered for see images attach
Tires are the only part of the vehicle in contact with the road. The contact area (contact patch) is very small. Changes in pressure, although not readily visible, except at the extremes, have a large effect on the shape of that contact patch. Again, I have to believe that GM, like all manufacturers, takes these things into account in determining tire pressures under different loads.
And it’s not just about tire wear. It’s about handling, which is uber important when operating a heavily loaded truck on the road.
Following the advice on the sticker, I went to the owner’s manual, and found this:
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It seems pretty clear what GM wants me to do with this vehicle, so I do that.
Finally, I’m really not trying to be difficult here. I’m persisting in this discussion because I believe tire pressure is something that most folks don’t fully consider or understand, but is arguably one of the
most important metrics on a vehicle. And there’s too much objective data underlying the recommended pressures to suggest that it’s just a matter of opinion.
