Vehicle Manufacturers Tire Pressure Recommendation

[MRC01]

... And last, sometimes the inflation spec is for handling reasons. I don't think you can know if that is the case without going through the math.

Back when I used to autocross, the ideal PSI was a tradeoff between response and traction. For max traction we'd run the lowest pressure that would not allow the sidewalls to roll over (checking tire edges after each run). This was on DOT legal R tires and we were cornering at > 1 g lateral. But that low pressure can make the response a bit squishy so you might want a few PSI higher. Either way, we usually ended up running lower pressures than OEM recommended. Due to the tight courses, we weren't going much faster than 60-70 mph peak speeds, so we could get away with lower pressures than you'd run at higher speeds (like around a track).

Some people replace tires with something a bit bigger and wider than OEM, in which case you may want lower pressures.

 

[Tom NJ]

There is one variable in setting tire pressures that has always confused me. My owner's manual says to inflate the tires to the placard psi when "cold", which it defines as "After vehicle has been parked for 3 hours or more or driven less than 1 mile", but there is no mention of temperature. If I set my tire pressures in my heated garage when "cold" as they define, it will be much different than setting the pressures "cold" outside on a winter's morning. I understand that tire pressure can change as much as 1 psi for every 10°F, so a 40°F difference between my garage and the outside air in winter can mean a significant difference in my set tire pressure.

I tend to set my pressures in my garage so that they never drop below the placard specification when driving in the coldest weather I expect to encounter. That means they may have to start a bit higher than placard, but not much given that the friction of driving counters the effect of the cold air and road.

How should one account for temperature when setting tire pressures?

 

[The Critic]

There is one variable in setting tire pressures that has always confused me. My owner's manual says to inflate the tires to the placard psi when "cold", which it defines as "After vehicle has been parked for 3 hours or more or driven less than 1 mile", but there is no mention of temperature. If I set my tire pressures in my heated garage when "cold" as they define, it will be much different than setting the pressures "cold" outside on a winter's morning. I understand that tire pressure can change as much as 1 psi for every 10°F, so a 40°F difference between my garage and the outside air in winter can mean a significant difference in my set tire pressure.

I tend to set my pressures in my garage so that they never drop below the placard specification when driving in the coldest weather I expect to encounter. That means they may have to start a bit higher than placard, but not much given that the friction of driving counters the effect of the cold air and road.

How should one account for temperature when setting tire pressures?

Read this TSB from Toyota, it should answer your question:

https://attachments.priuschat.com/attachment-files/2015/10/96267_T-SB-0345-08.pdf

 

[Tom NJ]

Read this TSB from Toyota, it should answer your question:

https://attachments.priuschat.com/attachment-files/2015/10/96267_T-SB-0345-08.pdf

Thanks Critic, that is helpful. The chart seems to confirm that the tire pressure changes roughly 1 psi per 10°F temperature change, and that my method of never allowing the pressures to fall below the placard psi on the coldest days is correct. (Actually the chart indicates about 0.86 psi drop per 10°F but that may vary depending on the tire size).

I can monitor my tire pressures on my car's info screen while driving, and my car's readings match my gauge precisely. I adjust my pressures in my garage to a level such that they do not drop below the specifications on the coldest day while driving. For me that's about 3-4 psi over placard in the garage with the assumption that the maximum difference in temperature from my garage to outdoor temperature is about 40°F.

So far I see no drop in pressures when 30°F outside or about 25°F below the garage temperature. While the chart says this temperature difference should drop the tire pressures by about 2.3 psi, that doesn't happen since the heat of friction from driving counters the effect of the lower air and road temperatures and the pressures remain unchanged after leaving the garage. I am monitoring these changes to see how this changes when the outside temperature hits 15°F or less.

In any case my theme is to never let the pressures fall below placard specification on the coldest days, so my pressures will range between placard and placard plus 3-4 psi at all times.

 

[Jetronic]

So far I see no drop in pressures when 30°F outside or about 25°F below the garage temperature. While the chart says this temperature difference should drop the tire pressures by about 2.3 psi, that doesn't happen since the heat of friction from driving counters the effect of the lower air and road temperatures and the pressures remain unchanged after leaving the garage. I am monitoring these changes to see how this changes when the outside temperature hits 15°F or less.

And that's why they say to set the pressures after the car hasn't seen use. Using it increases the pressures over what they would be staticly if left in the cold

 

[circuitsmith]

I adjust my pressures in my garage to a level such that they do not drop below the specifications on the coldest day while driving.

That's my goal as well.
I park outside. Once a month, first thing in the morning, before the sunlight can hit the car, I check the pressure.
I compare that morning's temp to a 10 day weather forecast.
I set the pressure so it will be the recommended value on the coldest predicted morning.
Example if it's 50F that morning but a 40F morning is anticipated, I set to 1 PSI over.

 

[MaximaGuy]

Summers 35 cold and winters 38 cold has worked across all my vehicles.

 

[GoldDot40]

2002 Silverado 1500 4x4. I run "E" rated (10-ply) tires a couple sizes up from OE. Last time I bought tires, I got them online and had Tires Plus mount/balance them. 1st thing I noticed when I left was the truck was "wandering" all over the road. It would literally swap lanes unexpectedly.

Got it home and checked the pressures...all 4 were at 80psi. Well....that's what the max pressure on the sidewall says. Door placard says 35psi....which is where I've always run them. So I drop each one down to 35 and test drive it. Drives like a champ, exactly how I wanted it to. I was tempted to call up there to complain, but figured it wasn't worth my time.

Nearly 40K miles later and no cupping or abnormal wear AND they still ride great.

 

[bbhero]

^^^^^^^^^^^^^^^^^^^

Great great point goldot.... Check those pressures... After any "service"...


I did a oil change for my wife's friend and I happened to check her tire pressures... 66 psi in 2 tires and one at 53 and another at 51... Supposed to be 35... I dropped them all to 35... Her Nissan rode much much better after fixing that nonsense.

 

[GoldDot40]

^^^^^^^^^^^^^^^^^^^

Great great point goldot.... Check those pressures... After any "service"...


I did a oil change for my wife's friend and I happened to check her tire pressures... 66 psi in 2 tires and one at 53 and another at 51... Supposed to be 35... I dropped them all to 35... Her Nissan rode much much better after fixing that nonsense.

Absolutely. I speak from years of experience. A lot of shops that use inflators with pressure gauges rarely check them for accuracy or replace them as needed. The employees will drop/throw them around and get them out of whack. As long as the gauge moved, they trusted the accuracy. I was constantly reprimanding my employees for just dropping ours without hanging them up.

You would think a "tire shop" would know what the tire needs based on the weight of the vehicle....or at least to NOT go by the max psi on the sidewall.

 

[bullwinkle]

Seems like the placard is just a starting point, and the best pressure is generally somewhere between max sidewall and placard-and higher loading and high speeds may mandate an increase to near sidewall settings. Going into winter, a little higher is better, because those cold winter mornings=the loss of a couple PSI.

 

[bullwinkle]

Adding-never let tire shops or quick lube places play with your tire pressures after a vehicle has been driven! The Transit 250 in my sig can raise the rear tire pressures from a cold 75 PSI to 95 or higher after a long highway run, and they'll try to drop them back down to 75! Which means they're too low the next morning when cold & I get to fill them back up again with my air compressor! I'm honestly trying to figure out when tire & other techs got so clueless, I don't remember them being this bad when I was younger.

 

[nwjones18]

The TPMS light on my Ram won't go off if I don't air them up to 39 like the door card says. It rides fine at that pressure though.

 

[Jetronic]

Does it ride well at 42 aswell? How long does it take the TPMS light to come back on if you fill to exactly 39 psi? I put a few psi extra in every customer car I service because if I don't they'll be back in a couple of weeks complaining I didn't check the tyre pressures at service. It's impossible to determine for every customer if they garage their cars every night, I would have to consider if the tyres are still warm from driving to the dealership, the temperature difference of the shop air vs the outside air etc...

Lastlyl, I don't consider that an overfill, rather the placard is a minimum.

 

[spasm3]

2002 Silverado 1500 4x4. I run "E" rated (10-ply) tires a couple sizes up from OE. Last time I bought tires, I got them online and had Tires Plus mount/balance them. 1st thing I noticed when I left was the truck was "wandering" all over the road. It would literally swap lanes unexpectedly.

Got it home and checked the pressures...all 4 were at 80psi. Well....that's what the max pressure on the sidewall says. Door placard says 35psi....which is where I've always run them. So I drop each one down to 35 and test drive it. Drives like a champ, exactly how I wanted it to. I was tempted to call up there to complain, but figured it wasn't worth my time.

Nearly 40K miles later and no cupping or abnormal wear AND they still ride great.

Did your 1500 come with e rated tires from the factory? Or P-metrics?
If P-metrics, your placard does not apply to the load range E tires and you are under inflated. According to member Capriracer, LT tires should be 15 psi above the p metric pressures.

I went from P-metrics to load range E tires on my avalanche, Im running 50 psi. 60 psi towing.

 

[GoldDot40]

Did your 1500 come with e rated tires from the factory? Or P-metrics?
If P-metrics, your placard does not apply to the load range E tires and you are under inflated. According to member Capriracer, LT tires should be 15 psi above the p metric pressures.

I went from P-metrics to load range E tires on my avalanche, Im running 50 psi. 60 psi towing.

Negative. I now have 40K miles on these tires and have run 35psi in them from the beginning. They wear as even as anybody could ever ask for, they don't have heat rings associated with too low pressures and they ride exceptionally well for 10 ply tires. I've rotated them once.

I just hauled 2000 lbs of #7 gravel in the bed of this truck and didn't bother increasing the psi and it did fine. 3rd time I've done this. The trip was about 6 miles.

 

[Tirerescue]

lowering the air pressure is not recommended! If you remember, this is why we have TPMS required since 2007. a certain vehicle company did a good job blaming the tire but they were lowering pressure trying to provide a better ride on a solid axle vehicle when everyone else was independent suspension. see where this leads... overheating the tire is grounds for disaster... run what the vehicle placard says.

 

[Silver]

As most of you know, there is a recommendation on the drivers side door pillar, and in the owners manual, stating the recommended tire pressure.
My 07 F150 regular cab truck recommends 38 psi. When the tires have had 38 psi in them the ride was so rough that if I were to run over a dime I could tell if it were heads or tails. So, I run 35 psi in them. There is no uneven tire wear so I must have found the correct psi (to please me anyway).
How many of you are in the same situation as me? Do you follow what's recommended, or something close to it?
I know there are quite a bit of variables. Like, the correct/recommended psi for loaded trucks, pulling trailers, campers, boats, etc.

My '05 Expedition is the same way, although it's probably got a lot to do with the Michelins that were on it when I bought it. Very stiff, bouncy tires. I run them around 30, even when towing a 5,000 lb boat (for about 10 miles) and they don't bulge much more than they do with no extra weight on them. I really don't like Michelins for this reason, from multiple vehicles I've seen with the same issue.