tire pressure on tow vehicle

[Bobbyg2013]

should I increase the rear tire pressure by 10 psi, on my truck's tires or leave at the suggested 35 psi that is shown on the sticker on the door jam?

[campigloo]

I take a little different approach. My E rated tire max out at 80 psi. The light load pressure rating on the sticker is 45. I have 1200 - 1300 lbs tongue weight. The max load pressure recommendation is 70 psi. I measure the unloaded foot print, then hook up, fully loaded, and inflate tires to match that measurement. 65 lbs returns me to the unloaded foot print. Handles and rides good and does not overheat. On a warm day the tires gain about 7psi. The pressure listing for the front is 65 and that carries the heavy diesel just fine too. As someone else said, over inflating the tires is not really a good idea either

[markeheiden]

Pumping up the air in your tires to the maximum rated psi is correct if your tires are supporting the maximum weight rating of the tire. Otherwise they will be under or over inflated based on your actual load. It's not rocket surgery but I hear "advice" that is simply wrong consistently so I guess it needs to be made simpler to understand.

I took others' advice many years ago when I first started towing. I pumped up the 4 tires on my 7K pound trailer to the "max" 80 psi as suggested. The tires at this pressure can support over 12K pounds. The trailer (a 25ft toy hauler) was all over the road. I checked and adjusted tongue weight, sway controls, torsion bars etc. but none of this was completely effective at settling down the trailer. What solved it was dropping the air pressure to an appropriate for the load 60 psi.

This toyhauler as with most is not equipped with shock absorbers and that's fine usually. However what happens with over inflated tires is the sidewall which is designed to flex and absorb some of the energy from impacts does not. This energy is transmitted directly to the springs and that transmits to the chassis with no shock absorbers to dampen these oscillations, every bump in the road is exaggerated. It can in fact upset the chassis to the point of instability which is what I experienced .

These are LT rated radial tires and after lowering the pressure a bit they had a bit of sidewall bulge which is how a properly inflated radial looks. They do not get hot to the touch under any conditions which is the true test and the only real indication if your tires are under inflated. I also tow the same trailer fully loaded at 12K pounds and when I do I run them at the 80 psi maximum as recommended on the sidewall since oh yeah, they are then supporting the maximum weight as well.

You can get away with over inflating your tires to "the max" on your truck because the shocks are able to dampen the excessive oscillations from the road and inflexible sidewalls but sometimes it's just unsafe on a trailer to run the wrong air pressure be it too low OR too high..

[gmw_photos]

Briand wrote:
....snip....

Interestingly, they tell you to weigh your RV, which very people do.

Sadly, I think you are right about few people checking their weight. We see this over and over on this and other forums.

In my case, I admit to being a numbers freak, so I go thru the CAT scale regularly. I often tow, and it's four different trailers ( camper, equipment, and two different horse trailers ) so I simply like to know what all my numbers are.

[Briand]

Just checked mine and BFG says the same for truck tires. I guess as far as thee tire manufacturers BFG and Michelin go, you should use sticker on vehicle. So I was technically wrong in where to get your number.

Checking with the tire mfg is the right advice. Not sure that all my vehicles have this though.

Interestingly, they tell you to weigh your RV, which very people do.

I wonder what the mfg would tell you what pressure to use if you do not know your weight.

[RJCorazza]

For those interested in correct tire inflation go to the manufacturer's web site for the facts. Michelin's information as an example:

Michelin101

Michelin RV Tire Guide

[Briand]

I am stating fact. The other advice is ambiguous, that is unless you know precisely the load in your tow and trailer and know the calculation to get ideal ride vs tow tire pressure AND the weight of your tow vehicle and trailer.

All this is rather subjective, since you are not going to get the precise calculation.

The soundest advice to give is the one from the manufacturer. Air up to maximum pressure. There is a reason why maximum load is achieved at maximum pressure and a reason why it is on the sidewall. Same thing for lowest pressure.

Here is why I recommend highest pressure:
Is it exact science? Nope.
Will you get better wear if you use less than max pressure.
-- Nope, its worse.
Is it possible to not use max pressure?
-- Yep, if you are potentially ready for less than optimal wear.
-- Yep, if you are definitely ready for less than max load cap.
Will a tire explode if you have lower pressure than max.
-- *probably* not.

If you find the ride not tolerable you compromise wear and load to air down.

I tend not to do this.

A vehicle manufacturer's advice is pointless unless it is tire specific. I've had load range e of a tire of same size diff mfg behave drastically different. I'll stick with the tire manufacturer's advice.

Not exactly the same, but definitely related.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28249043/gotomsg/28249764.cfm#28249764

[dave54]

Briand wrote:
Lots of misinformation and confusing information here. If you want to get the most miles out of your tires, most even wear and carry the heaviest load, then inflate tires to the MAXIMUM that they specify on the side wall. I have never had a tire that did not state 2 pressures. Min and max.

When you unhook and drive with no weight it rides like a tank. It is always a trade off between max weight capacity and rideability. Not everyone needs maximum load carrying capacity, even while towing.

[APT]

Briand wrote:

The way to achieve the best wear and MAXIMUM load capacity of a tire to use the maximum pressure as stated on the side of the tire.

Most people do not need the full load capacity of the tires. That is why vehicle manufacturers pay people to do exactly this:

In order to determine exactly how much you should inflate your tire based on a certain weight load is a calculation that not many people can do.

And publish the Tire and Loading sticker on each vehicle.

[RJCorazza]

gmw photos wrote:
you're right, there is no point in arguing it. Let's just say as gentlemen, we shall disagree.

X2

[gmw_photos]

you're right, there is no point in arguing it. Let's just say as gentlemen, we shall disagree.

[Briand]

gmw photos wrote:

Briand wrote:
Lots of misinformation and confusing information here. If you want to get the most miles out of your tires, most even wear and carry the heaviest load, then inflate tires to the MAXIMUM that they specify on the side wall. I have never had a tire that did not state 2 pressures. Min and max.

I will respectfully disagree with most of that post.

See my earlier post about the P tires on my Nissan truck. And to add to that, the tires ( 80 psi rated, load range E, BF Goodrich LT ) on our F350 diesel dually are maintained at door sticker stated pressure ( 60 rear, 75 front ). The truck is used almost exclusively for towing two different trailers loaded to 13 to 14K pounds. Original tires went 50K miles, and were wearing perfectly even, still had half their original tread. Replaced due to age and beginning to suffer weatherchecking.
Point is, max sidewall pressure is often not needed nor desirable, in my opinion. Y'all's mileage, tires, experiences and opinions will likely vary.

According to manufactures, the only way to acheive the maximum load capacity is to inflate to maximum pressure per side wall. This is true for all tires including P rated. Difference on P rated tires is that they should always be inflated to 36 or 42 PSI depending on XL or not. Then to calculate the reduced load capacity of the tire, you need to do a calculation or look at a table. Neither of these are great ideas. 99.9% of P rated tires are kept at their max pressure.

The way to achieve the best wear and MAXIMUM load capacity of a tire to use the maximum pressure as stated on the side of the tire.

Frankly there is no arguing this point. It is fact.

If you reduce tire pressure, the tire will not be rated to its maximum load capacity and it will wear differently.

In order to determine exactly how much you should inflate your tire based on a certain weight load is a calculation that not many people can do. It is much easier to inflate them up to max as stated on the tire sidewall or other official tire manufacturer's documentation.

[gmw_photos]

Briand wrote:
Lots of misinformation and confusing information here. If you want to get the most miles out of your tires, most even wear and carry the heaviest load, then inflate tires to the MAXIMUM that they specify on the side wall. I have never had a tire that did not state 2 pressures. Min and max.

I will respectfully disagree with most of that post.

See my earlier post about the P tires on my Nissan truck. And to add to that, the tires ( 80 psi rated, load range E, BF Goodrich LT ) on our F350 diesel dually are maintained at door sticker stated pressure ( 60 rear, 75 front ). The truck is used almost exclusively for towing two different trailers loaded to 13 to 14K pounds. Original tires went 50K miles, and were wearing perfectly even, still had half their original tread. Replaced due to age and beginning to suffer weatherchecking.
Point is, max sidewall pressure is often not needed nor desirable, in my opinion. Y'all's mileage, tires, experiences and opinions will likely vary.

[Atlee]

With P tires, which I suspect your's are, I would air the tow vehicle's tires up to the max on the sidewall.
My new truck, on the other hand, came with LT tires with E load range. On it I just keep the tires at the recommended inflation amount on the A-pillar yellow sticker, 50# front and 60# rear. I have a lot of excess capacity with my tires.

P tires don't have so much excess capacity, plus max air in P tires will help stiffen the sidewall as much as possible.

Bobbyg2013 wrote:
should I increase the rear tire pressure by 10 psi, on my truck's tires or leave at the suggested 35 psi that is shown on the sticker on the door jam?

[FastEagle]

“The National Highway Traffic Safety Administration has a legislative mandate under Title 49 of the United States Code, Chapter 301, Motor Vehicle Safety, to issue Federal Motor Vehicle Safety Standards (FMVSS) and Regulations to which manufacturers of motor vehicle and equipment items must conform and certify compliance.”

The FMVSS regulations are often misquoted or quoted out of context, leading readers of internet forum discussions about tires to come to conclusions about their tires that are unsafe, unapproved and unjustified.


“What Air Pressure Should Be Used?”
“The pressure your tires require is determined by the vehicle manufacturer in conjunction with the tire manufacturer and is based on the vehicle’s gross axle load. Every vehicle is required by federal regulations to include a tire information placard. This placard may also be referred to as the tire certification label or federal tire tag. Vehicle manufacturers are required by federal motor vehicle safety standards (FMVSS) to apply tires of a suitable size, load range and inflation pressure (as shown on the tire information placard) that are capable of supporting no less than the gross axle weight rating (GAWR). Consequently, the vehicle manufacturer’s specified tire inflation pressure is not arbitrary; it is established by federal safety regulations (ref: Code of Federal Regulations 49, 571.120, and Part 567).”

The quote above is from a major tire manufacturer. Because the vehicle manufacturer’s tire inflation pressure is established as a minimum standard for the tires fitted to your vehicle, the load capacity they provide is also a minimum standard.