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!

 

2019 Tundra TRD Off Road Crew max 4x4

I am not smart enough to digest all the charts and graphs, I too need an easy answer for daily driving/highway trips, and vary rarely towing my tractor and shredder (4000 lbs).

I just put on
Michelin Defender LTX M/S2 275/55/20

The door jamb says 30 front 33 rear, the guy at discount tire has said 40 all around, my friend who has the same tire on a midsize truck says 35 all around (he never tows).

MY brain says for daily driving have 2 psi less in the rear because there is no weight back there.

 

Door jamb tire pressures are recommended for optimum balance of ride quality and performance (traction, handling, braking, etc.) using an OE or OE equivalent tire and unmodified vehicle...

Adding air pressure will reduce your footprint (tread contact to surface), which increases MPG but decreases traction (particularly off road and under situations inducing significant weight transfer)... It will also give you a slightly harsher ride. This is significantly more noticable when you have LT rated C, D or E ply rated tires.

Underinflation will increase your footprint (which is why we air down off road, in the sand, etc. to increase the footprint and provide additional rolling friction (traction)... Underinflation is also the number one reason for blowouts as an underinflated tire has increased sidewall flex (to 'flatten out' the tread surface), and the additional sidewall flex and reduced carrying capacity of an underinflated tire creates excessive heat.

It's important to note that capacities and ratings on the door jam for payload, GVWR, etc. are all based on OE tires inflated to specs on the door. Increasing your air pressure will never increase your payload or your vehicle's capacities. However, when towing, running your tires at max PSI (50 in your case) will DECREASE heat build up caused by the excessive load and reduce the chances of a blowout. Your ride quality may decrease, but it will keep the heat down, increase MPG, and reduce sidewall flex (especially in corners).

It's also important to note that the MAX capacity on a tire's sidewall is based on the tire being run a max PSI. This is super important on trailer tires. You should never run p-rated/standard vehicle tires on a trailer. They are not engineered to do that job. Trailer tires are generally indicated by their 'ST' rating and most will have a MAX psi of 80, and should always been run at that psi to reduce chances of blowout. Yes, the trailer will probably have a bit of 'bounce' unloaded, so if you're traveling a significant distance unloaded you can drop PSI (just a bit) to reduce that bounce. But, don't do that at the expense of not filling back up prior to the trailer being loaded up, as that makes the trailer tire much less effective and more susceptible to overheating and blowouts.

So, the short of it...

When not towing and during non-inclement weather, you're probably good to run between what's on the door and about 35-36psi...

If you're running in snow / ice, I'd lean closer to what's on the door jam and have some extra weight in the bed of the truck...

When you are towing, you're probably be best off to be closer to max PSI to reduce heat (especially in the summer) or if you find that too harsh maybe down in the 40-45 psi range. If you're towing in the winter, don't drop below what's on the door jam, but you'll probably want to be in 36 psi range to open up the foot print a bit for increased traction.

 

Thank you for taking the time to write all that.

I get all of the preliminary information, I understand tires, weight transfer, contact patch etc.

When you say 50 psi (my case), clearly that is rear, what do I do in the front when towing? I have very little experience towing.

How do you feel about f/r staggered for daily driving? Example, lets say I choose 35 front and 33 rear

 

When towing I'd run all 4 corners the same as you're experiencing higher levels of weight transfer throughout the entire vehicle when cornering, braking and dealing with trailer sway. Again, goal when towing is to increase carrying capacity and reduce sidewall flex w/in reason to keep tire temps lower.

The light rear end is definitely one of the reasons Toyota suggests different PSI front/rear... there's nothing wrong w/doing it, but I've always had weight in my bed (be it a topper on my '08 or the Decked system w/a decent load and tonneau cover on my '21)... So, I've never had a 'need' to run staggered to reduce the bed hop a lot of folks experience w/our rigs on certain highways.

Also, you're going to 'feel' your tires a bit more because you already have reduced sidewall flex from the 20s you're running.

I'm guessing if you're sitting around 35-36psi (all 4 corners) when not towing, travel your daily routes and then bump the rears down 1-2 psi and see if that improves ride quality, and you may find that it's worth the trial and error. Also, note that if your PSI differs between the 4 tires by too much it will often trigger the TPMS warning light.

If it were me, I'd add (4) 50-lb playground sandbags (1) in front of and (1) behind each wheel in the bed of the truck (basically tucked against the bedside where the wheel wells are), and shoot for a psi somewhere in the 35-36 range on all 4 corners. Prior to adding the topper to my '08, this is how I ran the truck at all times and found the best 'balance' in ride quality, handling and performance...

 

The light rear end is definitely one of the reasons Toyota suggests different PSI front/rear...

The confusing thing there is that they say 30 front and 33 rear.

Thanks for the advice!

 

My bad... My brain processed your original post backwards, and I thought you said 33 front and 30 rear. Doesn't change what I'd do w/the truck, but that's just me.

I would guess that the reason for the increased pressure in the rears is to reduce potential oversteer conditions (makes it more difficult to pitch the rear end out) by having a lower PSI on the front corners. When we were intentionally trying to create an oversteer condition for the vehicle (making it easier to break the rear end loose in the corners) we'd put a higher PSI in the fronts vs the rears to achieve this. Again, this is only a guess from experience playing w/road cars, but the physics would still be similar in a truck...