Pickup tire pressure

[Hayseed]

My wife had a blowout on the highway the other day. I went to rescue her and could not figure out how to lower the spare from underneath the bed of the truck to change it (that's another story.) So I waited on the side of the road while she took the car to Firestone to buy a new tire. While she was there the sales associate told her we should be running 50 lbs. in the front tires and 70 lbs in the back tires and when pulling or hauling a load the back tires should be inflated to 80 lbs. My pickup is a F250 and the tires are rated for 80 lbs pressure. I have been running the tires at 50 lbs. front and rear and the ride seems fine to me.

My question is, if I have 70 lbs. in the rear tires and 50 lbs. in the front tires, won't the light rear end be bouncy? Most of the weight is on the front tires so it would seem to me that more air pressure would be used on the front and not the rear. I can understand adding air to the tires when hauling or towing but I gotta wonder about 70 lbs. when traveling empty. Thoughts?

[Autotech]

While I am generally hesitant to contradict another automotive professional, sometimes people say things that just make you just shake your head.

You are correct about empty loading, and which axle needs higher pressures. The best method is to start at factory specs, and carefully monitor tire wear, adjusting the pressures until the wear characteristics are the best. This will vary depending on your driving cycle, load use, and driving style.

I have a Ford Superduty Dually with the Powerstroke. I usually run empty, and with that heavy motor out front I use max pressure on the front axle, and between 60 and 70 in the rears. I could probably stand to go down to 50 or 55 in the rear because I'm wearing the centers out of the tires, but I also drive fairly fast, and carry moderate loads about once a week (I'm too lazy to air up and down every time).

Of course when loaded, you should adjust the tire pressures accordingly.

Higher pressures at the same load reduce sidewall flex, reduce contact patch, reduce rolling resistance, increase center treadwear, may increase fuel economy, and generally reduce tire temperatures.

Gregg

[Bird]

Chris, I'm not a tire expert and won't contradict someone else, but I'll tell you a little story and you can take it for what it's worth.

In 1991, I spent the summer working in my brothers' tire dealership/garage in Anchorage. It was a B. F. Goodrich dealership, but since there was no official Uniroyal dealership up there and the companies had merged, we also stocked a few Uniroyals, and the B. F. Goodrich warehouse manager was the only source in Anchorage at that time for Uniroyal warranties.

In the 4 months I was there, the only "warranty" issue we had with a tire was three or four Uniroyal Tiger Paws that came as original equipment on three-quarter ton Suburbans. Each of those cases was a tire that had developed a "bubble" from the outer layer of rubber separating from the cord (I think all but one was on the sidewall). Uniroyal did warranty them, but said the problem was a result of running too little air pressure. I can't remember the exact model of the tires, but the pressure rating on the sidewall was 70 psi. And the sticker on the door post (GM, in other words) recommended something like 35 to 50 psi and in every case, the tires were being run at the lower GM recommended pressure.

The Goodrich/Uniroyal "experts" said to never run a car/pickup tire at less than 80% of the number on the sidewall.

Like I said, you can take that for what it's worth. Otherwise, I agree with Autotech.

[Autotech]

Good point Bird. I had forgotten that some manufacturers underrate the tire pressures on the door stickers. In fact most informed folks believe that the whole Ford Explorer/Firestone debacle was due mostly to Fords reccomendation to run the tires at a pressure below that specified by Firestone. And since few people check their tires often enough, those tire pressures were even lower.....

These low pressure specs are used to give a "better" (mushier) ride. Personally, I like my vehicles to feel a bit better connected to the road.

Gregg

[Bird]

</font><blockquote><font class="small">In reply to:</font><hr />
In fact most informed folks believe that the whole Ford Explorer/Firestone debacle was due mostly to Fords reccomendation to run the tires at a pressure below that specified by Firestone.

[/ QUOTE ]

That's what I've been telling people ever since that debacle started; under inflated tires and poor drivers. [img]/forums/images/icons/laugh.gif[/img] And that's in spite of the fact that I've never been a fan of Firestone tires. [img]/forums/images/icons/grin.gif[/img]

[Gary_in_Indiana]

Add my voice to that chorus. I said from day one that the problem was NOT in the tires.

[Hayseed]

<font color="blue">And that's in spite of the fact that I've never been a fan of Firestone tires.</font color>

Me either, Bird. However, the origninal set of Firestone SteelTex radials that came on my F250 made it to 60,000 miles and had a little tread left on them when I took them off. I was impressed with the mileage and the performance so I bought them again when it was time for new tires. Maybe the reason I got so many miles out of them was due to the fact that I did not keep them pressured near capacity, thus not wearing out the center of the tires as Autotech mentioned.

Bird, if what you say is true about running tires at no less than 80% rated capacity that means I need to keep at least 64 lbs. of air in my tires all the time. I guess I will have to experiment with it... just seems that 64 lbs. would give me a bouncy ride. I don't mind the bouncy ride so much as my wife would... after all, she does seem to think the truck belongs to her! [img]/forums/images/icons/shocked.gif[/img] [img]/forums/images/icons/frown.gif[/img] [img]/forums/images/icons/crazy.gif[/img] [img]/forums/images/icons/smirk.gif[/img] I guess it comes down to making a compromise among comfort, safety and doing what I can to extend the life of my tires.

Autotech, I agree with you that the Firestone guy had his pressures backwards. Thanks for your input as well as your's too, Bird. I knew I would get some good responses here at CBN.

[rozett]

And never trust the dealer working on your vehicle. I put my 2000 Excursion (V10 4x4) into the Ford dealer for 50K service. Part of that service is to rotate the tires. Well, I normally run 45 front and 55 rear per the Ford specs, except that I air up to pull out horse trailer. Fortunately, I always check tire pressures before loading the horses.

Wouldn't you know it... the dealer rotated the tires and never checked tire pressurs. Now I was running 55/45. [img]/forums/images/icons/shocked.gif[/img] [img]/forums/images/icons/mad.gif[/img] I went back and told the service manager that I would have thought that the enitre Explorer/Firestone debackle would have resulted in a focus on tire pressure in the shop. He did not appreciate my comment.

The morale..... don't trust their work.... check it yourself!

[bgott]

I worked at a Firestone dealership before the problems hit the news and those Exploders used to give us fits. Not only were there problems due to underinflation but Ford's sloppy radius arm bushings would chop up the tires before 12,000 miles in many cases. After we'd sell the customer polyurethane bushings to deal with that problem we had to sell them two tires instead of one, the spare tire carrier would screw up the sidewall of the spare. Ford had bigger radius arm bushing problems with the earlier Exploders, the catalytic converter would melt the bushing on the right side. Rumor had it when I worked there that the tailpipe overheated the rear tire and caused failures but I didn't personally see any tires ruined because of it. Maybe that's where the problems with rear tire blowout came from?

[egon]

I've always run 60 psi in 3/4 ton trucks.

My other vehicles are usually about 5psi over the recommended.

Our current 3/4 ton with load range e tires has 80 psi in the tires. When empty I'll take that down to 60 psi.

Egon