What tire pressure now with bigger tires?

kantho

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How do I know what pressure to run my new Toyo A/T III's? They are 285/75r17s. The door jamb shows 36 pounds but that's for the stock tires and rims. These are C rated with a maximum pressure of 50 pounds.
Is there some "tell" that my pressure is right? The TPMS shows up to 41 pounds when the tires are hot from running in the sun and that feels why too high but then I'm not really knowledgeable about what the "right" pressure would feel like.





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kantho

kantho

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I have mine at 34 and rides and handles very good
Thanks for your feedback. What size tire?

So many wonderful opinions on so many topics, I am honestly surprise I got only one. I'd love any ideas about how to tell whether my pressure is good, too high or too low. What are the clues? I am a newbie so I love to hear it all and yes, I did a search first.
 

PyrPatriot

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Per a chalk test, my Falken MT 35/12.5/17 on OEM wheels (7.5" wide, mfg recommends 8.5" wide min) 28-30psi gets me at full contact on pavement. But, my rig with family and everyday gear in it is about 5800lbs so take that into consideration as well.
 
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kantho

kantho

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Per a chalk test, my Falken MT 35/12.5/17 on OEM wheels (7.5" wide, mfg recommends 8.5" wide min) 28-30psi gets me at full contact on pavement. But, my rig with family and everyday gear in it is about 5800lbs so take that into consideration as well.
Definitely a noob here. What's a "chalk test?"
 

PyrPatriot

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Definitely a noob here. What's a "chalk test?"
aside from you being able to look it up, here or elsewhere, it is essentially taking a stick of chalk, covering a section of your tire treat completely across, and driving a car length to see how the chalk residue stuck to the tire. If there is more tire on the middle than the edges, the tire is underinflated because the center is not contacting the pavement as much. If there is less chalk in the center than the edges, the tire is over inflated as it is putting more pressure on the middle and pressing the chalk in more.

Alternatively you can also spray chalk (harder to find and more expensive) on the pavement in front of your tires and dive over the line, seeing how the width of the tire imprint looks. Harder to do, since a "12.5 inch wide" tire may actually only be 11" wide on the parts meeting the pavement. My 12.5” width only measured 8.5" when it was over inflated. As you can see, there is about an inch of thicker layer of chalk on the edges.
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Unkle Fester

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X2 on the chalk test. with so many variations of tire size, rim width, etcetera... a chalk test will tell you where you need to be.
 

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My guess would be 34 to 36, but the chalk test is the right way to do it
 

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