Scorpion tires - "Do not exceed 40 psi"?

[JeffC]

I was just checking my OEM scorpion tires and noticed in the fine print on the sidewall that they caution never to exceed 40 PSI or they might explode. This seems completely contradictory to everything I've read and how the trucks are set up upon delivery. Can anyone explain this anomaly? Does anybody know what is the true maximum PSI that we should run?

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[Zoidz]

If you read the entire message, it probably is referring to never exceeding 40 psi while seating the tire on the bead (installing and inflating the tire).

 

[Bcross]

If you are talking about the 20" AT tires my mobile service guy told me he always inflates them to 50psi.

 

[SwampNut]

What's the sidewall rating on them? 50? Rivian specs 48 right? Interesting.

 

[UnsungZero_OldTimeAdMan]

If you are talking about the 20" AT tires my mobile service guy told me he always inflates them to 50psi.

No harm in inflating to 50 psi and that is within margin of error for most commercial grade pressure gauges. But unless you are intentionally trying to eke out some small amount of efficiency, the factory recommendation is right on the federally mandated sticker in the driver door jamb: 48 psi, when cold. Tech may be recommending 50 because they almost never work on cars that are cold and parked out of the sun. And the 48 psi guidance is applicable for tires similar in spec to the factory AT, which is SL 275/65R20. So if you are running factory or similar spec'ed non-factory ATs, the "always" direction is somewhat inaccurate.

He'd be more correct if he was referring to non-factory LT tires of the same size. LT tires are designed for higher max load. Therefore the pressure to load scale is different and require you to stray from factory recommendation of 48 psi—in order to achieve equivalent/proper contact patch. Those who run LTs generally fill to 50~52 when cold.

 

[HaveBlue]

Newton's third law of motion effectively says the weight of the car has to be supported by the tires. Inflating the tires to say 40psi means you need enough square inches of foot print. If the designed tire footprint is 6"x10"=60sqin * 40psi = 2400lb of load capacity * 4 tires = 9600lb of effective GCVWR.

Lower the psi and the footprint has to increase to support the weight. If the footprint increases beyond the tire design, exceeding certain speeds will overheat the tire and it will blow out.

 

[Zoidz]

As I mentioned previously, it's a mounting warning, not an operating pressure warning:

 

[LivingInKaos]

As I mentioned previously, it's a mounting warning, not an operating pressure warning:

I've seen guys just blast the air in when seating and it blows the tire right past the bead with a bang. Scares the crap out of everyone around besides the one mounting.

 

[Zoidz]

I've seen guys just blast the air in when seating and it blows the tire right past the bead with a bang. Scares the crap out of everyone around besides the one mounting.

Or you could do the good ol' boy way. I had a flat on my 48" farm tractor tire (if you've never tried to seat one of those, you don't know what you're missing! lol) and I almost resorted to this, but I got it beaded using the ratchet strap method, which is safer.

 

[LivingInKaos]

Or you could do the good ol' boy way. I had a flat on my 48" farm tractor tire (if you've never tried to seat one of those, you don't know what you're missing! lol) and I almost resorted to this, but I got it beaded using the ratchet strap method, which is safer.

Yep, I have one in my off-road kit sized just for this.

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