Seasonal Tire Pressure Adjustments Procedure.

[SpaceEVDriver]

Ford recently put out their winter driving tips and mentioned tire pressure, but what was said was pretty useless for making sure your tire pressures are actually correct.

I found a great procedure for adjusting tire pressure based on ambient temperature in a Toyota TSB. This is basically what I've been doing for years (on about a quarterly basis, but sometimes monthly), but has a more specific set of adjustments. You'll need a high-quality, accurate and precise tire pressure gauge. Consider the difference of the air temperature where you're checking the pressures and the lowest ambient temperature that may be expected in the next few weeks (especially in winter).

Use the above chart and these steps.

Example 1: Temperature Compensation – “Cold” Tires:

• The vehicle has been parked overnight outside shop (vehicle has “cold” tires) and "normal" tire pressures are 31.9 psi.
• Workshop temperature is 68 ºF, and expected lowest ambient temperature in the local area is to be 14 ºF.
• Subtract the expected lowest temperature (14 ºF) from the workshop temperature (68 ºF) = 54 ºF.
• Using the tire pressure chart (above), find the intersection of the cold tire line at the point corresponding to 54 ºF, and read off the value on the tire pressure change axis. In this case it would be about 4.9 psi.
• The tires should be filled to: 31.9 + 4.9 psi = 36.8 psi

Example 2: Temperature Compensation – “Warm” Tires:

• The vehicle has been driven on surface streets for about 30 minutes (vehicle has "warm" tires) and "normal" tires pressures are 31.9 PSI.
• Workshop temperature is 68 ºF, and expected lowest ambient temperature in the local area is to be 14 ºF.
• Subtract the expected lowest temperature (14 ºF) from the workshop temperature (68 ºF) = 54 ºF.
• Using the tire pressure chart (above), find the intersection of the warm tire line at the point corresponding to 54 ºF, and read off the value on the tire pressure change axis. In this case it would be about 6.7 psi.
• The tires should be filled to: 31.9 + 6.7 psi = 38.6 psi

Example 3: Temperature Compensation – “Hot” Tires:

• The vehicle has been driven on the highway for at least 60 minutes (vehicle has "hot" tires) and "normal" tires pressures are 31.9 PSI.
• Workshop temperature is 68 ºF, and expected lowest ambient temperature in the local area is to be 14 ºF.
• Subtract the expected lowest temperature (14 ºF) from the workshop temperature (68 ºF) = 54 ºF.
• Using the tire pressure chart (above), find the intersection of the hot tire line at the point corresponding to 54 ºF, and read off the value on the tire pressure change axis. In this case it would be about 9.0 psi.
• The tires should be filled to: 31.9 + 9.0 psi = 40.9 psi

To adjust back for summer driving, just put the tires at the recommended (or your preferred, but safe) tire pressure. Tire manufacturers usually assume ambient temperature of around 20 ºC (70 ºF) to 25 ºC (77 ºF). You usually do not need to reduce the tire pressure to below recommended when outside temperatures are warm, but if it's very hot, you may want to reduce pressure by 1 PSI per 10 ºF that ambient temperatures are above about 90 ºF.

https://static.nhtsa.gov/odi/tsbs/2014/MC-10133726-9999.pdf

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[GreaseMonkey]

Spoken like rocket scientist

 

[Mach-Lee]

I just use Gay-Lussac's law (what that chart is based on) with the current ambient garage temp and my target winter temperature (usually 266K in my case).

The other really simple method I use is to just look at the live tire pressure display, it should be about 2 PSI over the target pressure after driving for 20 minutes (check when driving in cold weather). Then you know how many PSI to add or subtract.

In the winter I run my tires about 3 PSI under spec for better snow traction (my snow tires are set to 36 psi). Full pressure isn't needed unless you're fully loaded or want max range.

 

[SpaceEVDriver]

I just use Gay-Lussac's law (what that chart is based on) with the current ambient garage temp and my target winter temperature (usually 266K in my case).

The other really simple method I use is to just look at the live tire pressure display, it should be about 2 PSI over the target pressure after driving for 20 minutes (check when driving in cold weather). Then you know how many PSI to add or subtract.

In the winter I run my tires about 3 PSI under spec for better snow traction (my snow tires are set to 36 psi). Full pressure isn't needed unless you're fully loaded or want max range.

We normally have around 100 inches of snow a year and the subsequent icy roads. But this year we have had increasingly not-unseasonal warmth (and are about 20 inches below normal for the season) and so I'm still running the ATs instead of snows and at 42 PSI.

I find the manufacturer recommendations to be weighed too much toward softness so usually run 5+% higher pressure in summer. I do typically run our snows a bit lower pressure than recommended when we do have snow and ice.

 

[ChasingCoral]

My Mach E lives in our carport & the Lightning in the driveway. I just go out on a cold morning and air up the tires to the proper pressure.

 

[CSmith]

We normally have around 100 inches of snow a year and the subsequent icy roads. But this year we have had increasingly not-unseasonal warmth (and are about 20 inches below normal for the season) and so I'm still running the ATs instead of snows and at 42 PSI.

I find the manufacturer recommendations to be weighed too much toward softness so usually run 5+% higher pressure in summer. I do typically run our snows a bit lower pressure than recommended when we do have snow and ice.

We normally have around 100 inches of snow a year and the subsequent icy roads. But this year we have had increasingly not-unseasonal warmth (and are about 20 inches below normal for the season) and so I'm still running the ATs instead of snows and at 42 PSI.

I find the manufacturer recommendations to be weighed too much toward softness so usually run 5+% higher pressure in summer. I do typically run our snows a bit lower pressure than recommended when we do have snow and ice.

Wait, EVs can function in the cold and snow? Who knew?

 

[WR221]

Good discussion. Note also that direct sunlight can bump up tire pressure by a couple PSI. Best to adjust tires when not in direct sunlight.

 

[MustangBarry]

Same gas law applies to footballs in cold weather. “Deflategate”?

 

[Womps]

We can go from 30 below one day to 40 above the next day when a chinook blows in. Trying to keep up to proper tire air pressures is challenging if one is religious about it!

 

[N1naz]

We can have EV Mustangs and self-driving cars (put a person on the Moon!) but we can’t have self-inflatable/deflatable tires???

 

[GreaseMonkey]

We can go from 30 below one day to 40 above the next day when a chinook blows in. Trying to keep up to proper tire air pressures is challenging if one is religious about it!

You mean like this?

 

[SpaceEVDriver]

We can have EV Mustangs and self-driving cars (put a person on the Moon!) but we can’t have self-inflatable/deflatable tires???

You can have that, but it's not cheap.

https://auto.howstuffworks.com/self-inflating-tire2.htm

 

[azerik]

Taking tire pressure to new mind blowing levels.
My painful case. 75 ambient at night 115 during the day.

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