PSI recommendations

I just installed Michelin LTX AT/2, LT275/70/18R, 125/122R, tires on my 2019 Tundra and I'm wondering if anyone has a recommendation on what PSI I should use. I called the Michelin Customer Service number and the associate said they recommend 35psi on all four tires. Numerous tire sites recommend anywhere from 45-80psi for daily driving/towing. Discount Tire, who installed the tires, said they recommend 40psi unless I'm pulling our travel trailer. In that case they recommend 70-80psi (80 psi is the max). Does anyone know, based on their experience, what psi works best as a daily driver and while towing. I'm not confident the lady I spoke with at Michelin was very knowledgeable in terms of what PSI to use.

 

The easiest, most correct way to determine tire pressure is to compare inflation tables that you can find here:

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables

... or use a tire inflation calculator (that may or may not be 100% correct, but appear to be close enough..). I can't seem to find the online calculator for it at the moment... Either way, at 35 psi (closest to 33 psi on the door placard), a stock 275/65r18 tire is rated for 2601 lbs * .89 as p rated tires are de-rated when used on a pickup = 2315 lbs.

Now got to the line on the inflation table for an LT275/70R18 and find the cell closest to 2315 lbs without going under. Look up at the table header for the correct PSI. In this case, it would be between 40 and 45 psi. Do a little math and ~42 psi is the sweet spot to match the factory load rating.

Without a load, 40 psi is fine. I usually run around this pressure in the winter when not towing anything on the highway. With a heavy load or heavy trailer, I would recommend (and did, when I ran that size tire) inflating to 55 psi or so. 80 is WAY overkill. I've towed plenty heavy and have never put more than 65 psi in the tires. Normal sized loads in the bed and small to medium trailers, 45 psi is usually just fine (my typically summer pressure). I carry a small compressor and add a little air to the tires whenever I feel they are a little squishy or I need more stability. Once you get a feel for it, you can add or remove pressure before you load up or head out.

It's important to note the the load rating given above at around 42 psi is sufficient to keep the tires from exploding from excess heat under normal loading and towing conditions, while maintaining comfortable ride characteristics when unloaded. That doesn't mean it is the optimal inflation pressure for heavy loads or no loads, so feel free to add or remove pressure as you feel necessary so long as you don't under inflate the tires (less than 42 psi if towing or hauling).

 

Thank you, Blenton!

 

Send Michelin an email asking. Include your door jamb sticker and what tire and size you are now using.
They are going to know better than anyone.
What makes you think the lady does not know??

 

I've done both - sent emails and called the phone line - and got mixed results. One customer service agent was adamant that I follow the recommendation on the door placard, despite running a different tire size. Another was happy to consult 'the tables'. Another emailed a copy of both pages of the tables with my two different tires highlighted and the new recommended inflation pressure circled. So I can see how the OP might not have confidence the answer he received over the phone.

You can view the tires as a spring (that's what they are really) that behaves linearly in a certain range (through most of the inflation range) and non-linearly on the extreme ends of that range (really low or really high pressures). In the linear range, adding X amount of pressure adds Y amount of spring force, or load capacity.

 

I am running my ‘E’ tires at 40 psi and will add 5 lbs when towing. The truck is heavy enough to make that pressure smooth (relatively).

I can’t see running 80 psi too much fun!

I have ‘E’ tires on my trailer too and run them at 60 psi. The combo is stable and smooth.

 

The person I spoke with was very uncertain in terms of how to recommend a PSI outside of the door-jam recommendation. She put me on hold several times, leading me to believe she was asking someone else. When I would ask a follow up question, she would put me on hold again. I'm sure we've all spoken to someone on the phone, or in person, who was less than convincing when trying to get their points across. I'm not saying she was wrong, I'm just saying she wasn't confident in providing the information.

 

Thank you Blenton and PBNB for your responses!

 

Go to this link and scroll down to the drop down boxes.
Tire Pressure is one of the drop downs. Fill out the rest of the info they’ll email you back asking for the door jamb sticker then give you proper PSI once they have that. Or at least they did that for me.
https://www.michelinman.com/assistance

 

While not Michelin, when I jumped to a E-rated tires on my rig, I dealt directly with the manufacturer,. They asked the questions mentioned above and sent me back a lovely table of different pressures and a metric named Factor of Safety.

They took the Toyota pressures into account and gave me a scale to be below it (comfort), at it, or to exceed it (towing).

Part of the table was my front and rear axle weights, unloaded and loaded with my travel trailer.

I then also used the chalk test to confirm a good contact patch and the table was pretty darn accurate. I'd ask for that type of table from Michelin, but you'd need axle weights to get it.

 

Will do. Thank you Black and BFlooks!