Tire PSI Question

[drewensley]

I recently go new tires put on my 2023 Sierra 1500 Elevation Crew Cab with the 5.3L.  They are rated for a max psi of 80 and that is what the dealer put in them.  The truck is now riding super firm and I can basically feel every crack I drive over.  I know the door placard calls for a psi of closer to 35.  Where should I be?  What it harm the tires to go down to 50 or 60? Thanks in advance!

[jwhjr]

Holy crap at 80 unloaded you must need a helmet to stop from hitting the roof!  I'd put them closer to what the recommendation is inside the door.  I usually put mine around 37 or so cold and adjust that as the temps change here in MN.  Good luck!

[TrueBlue]

What size are they?

 

Both the 275/60R20 and the 255/70R17 trucks list 35psi on their door stickers. I fill mine cold to 33 and they warm up to 35.

Here's a chart  you can use as a guide in case you load your truck down

 

Edited October 18, 2023 by TrueBlue

[drewensley]

I put a 4" lift on it so they are 295/60/20 Mickey Thompson Baja Boss A/T tires

[eppieguy]

Google the Chalk Tire Test, best way to find the proper PSI for your tires with the current load. Sounds like you have "E" rated tires, I ran mine at 38-40 PSI on my 19 High Country, I found that to be the sweet spot.

[Grumpy Bear]

1 hour ago, drewensley said:

I put a 4" lift on it so they are 295/60/20 Mickey Thompson Baja Boss A/T tires

 

For proper tire inflation on Mickey Thompson Tires, please contact M/T Tech Department at 800-222-9092 (Option 5) with original tire size and stock tire pressure. (The front and rear stock tire pressure can be found on the driver door placard/sticker)

[newdude]

@drewensley   Chalk test as mentioned is a good move but more importantly, inflating to equal the load rating of the factory tire is as well.  

 

E load tires give you much more pressure range to equal out to the factory P tires.  

 

Toyo tires has a great chart on this explaining the proper PSI to get the equivalent load ratings on an LT C, D or E load tire to the correct load index in lbs that can be matched to the tire it replaced.

 

So.  GM uses 275/60R20 for 20 inch wheels.  Both tires are a 115 load index, so the weight the tire can support at xx PSI.  115 index = 2679lbs at 35psi.  

 

LT295/60R20 in Mickey Thompson (and Toyo as well) are E load.  Load index is 126.  126 = 3750lbs at 80psi.  So using the Toyo chart and scaling down to 2679lbs load, that puts your target inflation pressure between 45-50psi to obtain the proper load index to match the original equipment tires.  

 

TLDR.  Try 45-50psi and see how it rides.  This PSI will give you the right load range to the original tires as well.  Don't go lower IMO unless you haul nothing but you in the truck.  Towing or extra passengers, air them up to 45-50psi minimum.    

 

Charts I used - Application of Load Inflation Tables Version 2020-7 (toyotires.com)

Edited October 18, 2023 by newdude

[redwngr]

 

Door sticker recommendation is for pressure when the tires are cold.

 

It is also the pressure for  if the vehicle is carrying it's max rated load. 

 

If the vehicle is driven unloaded, or lightly loaded then the 'best' pressure will be less than the door sticker pressure.

(I get that most don't bother to get scale weight and find a 'load vs inflation' table for the tire size and load rating to find how much pressure can be reduced)

 

Tire makers know pressures increase when they've been run.

It would be near impossible to establish pressure for after driving since the time driven, speeds driven and load carried will all impact how much the pressure rises from the cold pressure. 

 

 

[Vincej138]

35-40 PSI cold and your fine. 

[lennybg]

On 10/18/2023 at 3:53 PM, redwngr said:

 

Door sticker recommendation is for pressure when the tires are cold.

 

It is also the pressure for  if the vehicle is carrying it's max rated load. 

 

If the vehicle is driven unloaded, or lightly loaded then the 'best' pressure will be less than the door sticker pressure.

(I get that most don't bother to get scale weight and find a 'load vs inflation' table for the tire size and load rating to find how much pressure can be reduced)

 

Tire makers know pressures increase when they've been run.

It would be near impossible to establish pressure for after driving since the time driven, speeds driven and load carried will all impact how much the pressure rises from the cold pressure. 

 

 

Keep in mind that door sticker only applies to the factory brand and size of tires. 

[asilverblazer]

The door sticker indicates the "original equipment tires" and has a specified minimum PSI to carry the vehicles maximum load capacity. You'll note that the sticker does not indicate a brand or model of tire. Interestingly, the only deviation from the specified PSI addressed in the owners manual is for sustained high speed driving over 100 mph, where the PSI should be raised by 3 over cold.

 

The tire has a maximum PSI for the tire.

[redwngr]

4 hours ago, lennybg said:

Keep in mind that door sticker only applies to the factory brand and size of tires. 

Of course.

 

And the info on the tire is max pressure and load for the tire, not for the vehicle it is installed on.

[TrueBlue]

1 hour ago, redwngr said:

Of course.

 

And the info on the tire is max pressure and load for the tire, not for the vehicle it is installed on.

Important point, yes.