Let's Talk Tire Air Pressure! (Raptor)

[jensht]

I wish the US would like the tire pressures like this.

It is pretty nice as the manufacturer can tailor both comfort and safety this way. My Volvo goes even further and lists tire pressure with the following options, maybe a bit overkill

Empty (1-3 passengers)
Comfort with speeds up to 100 mph
Eco with speeds up to 100 mph
Speeds over 100 mph

Full load
Comfort with speeds up to 100 mph
Eco with speeds up to 100 mph
Speeds over 100 mph

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[24'Ranger]

It is pretty nice as the manufacturer can tailor both comfort and safety this way. My Volvo goes even further and lists tire pressure with the following options, maybe a bit overkill

Empty (1-3 passengers)
Comfort with speeds up to 100 mph
Eco with speeds up to 100 mph
Speeds over 100 mph

Full load
Comfort with speeds up to 100 mph
Eco with speeds up to 100 mph
Speeds over 100 mph

You're inspiring me to lookup the German recommended tire pressures for other cars.

 

[galion]

During my chalk test, 33 all around was just right; the manual's pressure felt too firm. After many miles, tire wear is even, and the ride is much more comfortable.

 

[24'Ranger]

During my chalk test, 33 all around was just right; the manual's pressure felt too firm. After many miles, tire wear is even, and the ride is much more comfortable.

Can you elaborate on the chalk test?

 

[galion]

Can you elaborate on the chalk test?

Simple as that.

 

[jensht]

The one thing the chalk test neglects is tire temperature. Tires with sufficiently strong sidewalls will pass the chalk test but won't necessarily have enough inflation to keep temperatures down due to sidewall flex at higher speeds. Probably not too much of a concern with US speed limits, but something to keep in mind.

 

[24'Ranger]

Thanks for sharing. By looking at it, it's a good test for tire longevity but may not be the best for handling due to sidewall stiffness or other factors.

 

[Suiming.tay]

During my chalk test, 33 all around was just right; the manual's pressure felt too firm. After many miles, tire wear is even, and the ride is much more comfortable.

33psi is cold? In Malaysia, factory label at 36psi all round for 1-3 passengers. If I set to 36psi cold, it went up to 38psi after 10km run, which is too firm on windy road patchy road, the tail kind of skidding during cornering. It went down to 34psi cold if I pump the tire to 36psi warm. 34psi is not providing good ride or comfort ride on patchy road at 30kph~100kph. 36psi warm is the preferred pressure for me, except off road(ruts)

 

[Blue_Raptor]

“Cold” is a vague term. All manufacturer suggested pressures are at 68 deg F. This is a standard temp for all sorts of things like QC of metal parts etc.

 

[RANGER/HOBB]

The one thing the chalk test neglects is tire temperature. Tires with sufficiently strong sidewalls will pass the chalk test but won't necessarily have enough inflation to keep temperatures down due to sidewall flex at higher speeds. Probably not too much of a concern with US speed limits, but something to keep in mind.

It also varies with the weight of the truck; towing, truck load, and ambient temperatures as already spoken.

 

[Rguest3]

Proper Tire Pressure will depend on the weight of the vehicle whether it be empty or loaded. Then, based on the current tire specs you can calculate the proper pressure. (weights listed on the tire side wall) This will differ based on which tires you have installed.

A Ford tech, for example, will put your tires at 39 pounds as listed on the driver's door, no matter what tires you have installed. At 39 pounds the side of the tread, on an unloaded truck, will not be touching the ground. I lower the tire pressure, usually, so I can use the whole tire not just the center of the tread. 34/32 pounds seems to work very well and still have plenty of carrying capacity for the weight of the truck, then some.

I go by weight and tire specs, NOT what is listed on the door sticker from Ford.

 

[iamweasel]

For those who lowered the pressures from the OEM rating down to 35psi or lower, did you notice any reduction in MPG's at the lower pressures?

 

[famous47]

I put 36 psi front and 34 psi rear seems way better.

Same. I have 35 all around. Makes for a nice smooth ride.

 

[holdreset]

For those who lowered the pressures from the OEM rating down to 35psi or lower, did you notice any reduction in MPG's at the lower pressures?

I run mine at 36 psi. I always thought the door jam psi was for towing/max capacity ratings so you wouldn't have to adjust. My skinny ass, who never pulls a trailer, isn't adding much weight so that's why I lowered it. It rides fine, I'm at 8k miles, with no detectable abnormal tire wear, handling, etc.

 

[John E Davies]

I run 36 psi F and R with a 140 pound topper, two people at most, and minimal stuff, it is VERY fine with the KO3 tires (6 ply Load C) and rides and wears nicely. OTH my winter Nokian tires are much stiffer at the same pressure because they have stiffer sidewalls (8 ply Load D). They change the way the truck feels, even with the softer rubber compound the Nokians are more jarring over potholes. Acceptable to me, but I will stick with the KO3s for the rest of the year! Ford engineers did very well in specifying this tire for the RR!

Do NOT install Load E tires and expect any kind of comfort, they will completely destroy the ride quality. I think that many light truck and Wrangler owners never mention this, maybe they are too embarrassed by those poor tire buying decisions…

John Davies
Spokane WA USA

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