Quick Tire Question- psi

[brett13]

Let's just hypothetically say I'm driving a Tundra with E-rated tires and might max out around 7500#. What psi in E-rated tires is appropriate for this sort of load? I'm running 40# empty. The tires are rated 3600# each or ~14k spread across all 4, so obviously a full 80psi is not needed.

 

[pvstoy]

Hi Brett,

No you would not put the max PSI in the tires. But some tire shops will put the max as to what the tire shows them…Wrong.

Hard to say because every combination will be some what different. Rim width and tire width and overall size. What you need to do when the tires won’t correspond to the door tag anymore is apply the chalk test.

Get your load set and set all your air pressures the same and higher than you think. Point your truck so you can drive straight for a couple 100 yards on a somewhat clean surface. On each tire draw a chalk line across the tire tread. Drive and stop and see where the chalk has worn. Off in the middle than let some air out and try it again until the chalk wears evenly across. Measure the pressure and write it down. Also it is good to do this in the morning when you have a cold PSI reading.

 

[brett13]

Thanks.

Won't that tell me how it is wearing rather than if the load is supported safely? Or is the answer the same for both?

 

[Alex]

Toyo has published a tire inflate guide on what psi you should inflate the tire when you witch from P to LT tire. The calculation is based on your stock load rating and new LT tire load rating. Based on that table, my stock 245/75R16 P tire with 29psi after switch to 265/75R16 LT range D tire. I need ~45psi in the LT tire. Let me know if you want the guide I can email you.

 

[EdoHart]

Yes, and yes.

Thanks.

Won't that tell me how it is wearing rather than if the load is supported safely? Or is the answer the same for both?

I think that if the tire is inflated such that the contact patch between the tire and road surface is maximized (i.e. follow Patrick's advice), that will carry the load in the safest way and maximize tread wear life.

 

[craig333]

Contact patch is a good starting point. Then see what feels right for you. My Jeep I run from 20-25 on the street. Some people who air down never reach that point. My truck I run at 80 psi. It feels better at max psi and with the heavy cummins up front I"m not so sure I don't need that much.