Tire Pressure Question

Hey guys! So ive got a little bit of a mechanical question for yall...


Ive been working on an f250 whose door stickers say to inflate the rear tires to 80psi and the fronts to 50, which I do. It always seemed a little odd, but whatever...


Anyway, one of the front tires has a slight leak. Its not too bad, but I have to remember to add air like every week...


Well, I forgot. I was out running errands (shop truck) and I noticed that tire was aweful low... And so, I stopped at the first gas station I came to and added some air.


Turns out I overfilled it (there wasnt a gauge on the tire chuck I used) but I must say, that side of the truck has never ridden, or steered better.


So, I was wondering why the pressure differences? My newer F150 says to inflate all 4 tires the same. I rarely tow with this truck...


Why shouldn"t I inflate them all to 80psi? Thanks in advance...

The 50/80 split is for maximum load. When you hook up a gooseneck or put a bunch of weight in the box, most of that weight is carried by the rear tires. The 50 PSI in the fronts is deemed by Ford to be enough to carry the weight that you will put on the front axle when loading properly (that is, not overloading the axle).

If you let the rear tires down to about 50 PSI when you aren't hauling, you'll find the ride improves, but you'll likely lose some fuel mileage.

I wouldn't overinflate the fronts too much. 5PSI you could probably get away with. My uncle's insurance jacked him around when he hit a motorcycle (which was driven by a guy who had a history of getting hit) because his tires had 45 PSI instead of 35 due to a faulty gauge.

You can, but 50psi for a truck with no load will ride better. You have 10ply tires(load range E) Rule of thumb 4 ply=35psi,6 ply 50psi,8 ply 75psi,10ply 80psi. These are at max load and max PSI. Good to see you on here Lance.

I'll go somewhere the other replies haven't and say this. The tire pressures on the door are only going to be good for the tires the maker put on the truck when it left the factory. That said, look on the sidewall of the tire for the correct pressures, and inflate them accordingly. Along the lines of what others have said, the pressures listed will typically be the max pressure to inflate. As you'd expect, a tire with a higher pressure is going to be harder, and make the ride a little harder, where a tire with a little less air is going to be softer and make the ride a little smoother.

Personally, I look at the whole thing like this. One, a tire with more air is going to be slightly larger in diameter and should give you a slight increase in fuel mileage due to more movement per revolution (at least on the rear). Two, a real truck isn't designed to ride like a passenger car, it's designed to be a truck and have the ability to haul a load. So, why worry about the ride as long as it does the job. Third, and final, if you find yourself with the need to haul a heavy load, and your tires aren't aired up to their max, then you've got to find a pump to get them up there or take a chance on damaging something due to the lower than necessary pressure. On the other hand, if you keep them aired to the max (ie-properly in my opinion), then you will always be ready to haul whatever you need to without any problems. But that's just my .02 for what it's worth.

The recommended tire pressures are a compromise between ride, handling and tire life. Sure, you can run 80 psi in the front, but you'll find the tires quickly wearing out in the middle of the tread. Likewise, if you take a look at your rear tires, you'll probably notice they aren't wearing evenly, assuming you normally run with a light load.

Do a search on Google for the make and type of your tires, and it will tell you the air pressure to use for the load you are putting on them.

Dusty

One reason it might have steered better is that one front tire had less rolling resistance than the other so the steering would have been pulling slightly toward the tire with less pressure. Any play in the steering would not have been noticed because all the play was at one side and the low tire was keeping it there.

Did you have to put a fuel pump in that Chevy?

Lanse, The door sticker is a max load-ON The Original Tires! Check and see what the tire says!
Since I left 2x4 1/2tons pickups as my main truck I have never run Max pressure unless I was towing or carrying a heavy load.
Back in the Old 16.5 tires days of late 70s and the 80s I would back off the tire pressure 25 to 30 lbs, when all I was doing was the normal day to day running and checking livestock, farming and such. On a Regular cab (2door), 3/4ton, Long box, 4x4 I typically ran 35 fronts and 45 backs. All the time! never had any problems. Even pulling 2 full,1000 gal Anhydrous Ammonia Fertilizer trailers. The only time I really needed to air up was when I had our Gooseneck cattle trailer on and had it full!
My current Truck an 01, F-350 Dsl, 4x4, Long box. on single wheels. I do not run max air more like 60 in the fronts (because of the Dsl) and 60 in the rears. Unless I am in a really heavy load situation.
Go back and Look at the Ford Explore, BFG Debacle! Fords Explorer Suv was what it was. Ford wanted to Soften the ride of this SUV and did so by Adjusting Air pressure down to about 25lbs, the average person being what they are Average......Don't stay on top of tire air pressure,they loose a few lbs to seepage, time, nail hole.....Decide to go on a short weekend trip to the big city 200 miles away, 4 big heavy people, luggage, and 4 tires severly under-inflated maybe one, down into the teens (lbs) and 100* weather ===== one roll over wreck in the medium or ROW and a Death or 2 has transpired.
Everybody blamed BFG for the problem But Ford was equally to Blame for droping recommended tire pressure too low.!!!!!!
A few lbs of adjustment and improve ride, on a really stiff sprung truck or improve the carrying capacity off your Norm! It is Your Call!!
I have adjusted my air pressures on tires to get max tire life, ride or carrying capacity all my life,,, Do Your Due Diligence The Tire company will always say Max pressure but 45- 50 lbs will improve ride and tire life....if max loads are a little to seldom occurrence. that IMHO!
Later,
John A.

You can inflate all to max load but it will ride like a buckboard... you will fill every pothole, every piece of gravel in the road. As others said,,, you can lower them when not hauling and get a smoother ride.. You can raise them for better gas miles.

You can put rough riding tires on there like wranglers or get quiet smooth, easy riding tires on there like michelins... mud grips for noise or street tires for quiet ride. If your an oil field or pipeline welder, you tend to go for mudgrips on the rears and can forget using a radio while going down the road. Bigger tires will ride and handle worse in all cases but let you get a bit further into a field before you bury it.

Now..

lets talk about the stiff clutch on some of the early ones that will eventually give you back problems.

Quite possibly... But I havent gotten back to that truck yet :/ So many projects...

Okay a few things 1- On the Explorers it was FIRESTONE tires that caused the problems. By the way Firestone is a division of Bridgestone Tire & Rubber. Maybe Ford set the inflation rate to low to try to make it ride smoother, maybe Firestone made some tires that weren't up to snuff, after all they had a big strike and were building tires with managers and replacements. Most of it was caused because most Americans aren't into car care like we should be (and yes I'll plead guilty to it too!) It was such a big deal because one of Henry Ford's grandsons married one of Harvey Firestone's granddaughters, a lot of the Fords running around today (and running Ford Motor Company) are descendants of Harvey Firestone. Most of the issue is Firestone didn't want own any possible mistakes and tried to push it all off on Ford. This caused Ford to decide against using Firestone tires as OEM ending a relationship where Firestone had been the preferred supplier. It also caused a dip in the value of Used Explorers hurting a lot of folks that owned them.Remember it was not the first time Firestone had major quality/design issues with tires (Google Firestone 721 radials) and explains how they became a division of Bridgestone.

2- The PSI numbers on the sidewall of your tires are MAXIMUM inflation rates, don't go higher than that. The Auto/Truck manufacturer recommends inflation pressure, and they should be okay with most tires of the same size and rating, change that and you're in new territory. Variation in tire design may change the pressure to get the ride/handling/fuel mileage compromise the manufacturer established when they set the tire pressure. On the early Corvairs GM set a funny tire pressure recommendation , this was a cheaper way to make the car behave decently on the road, folks ignored GM's recommendation and folks died and Ralph Nader got famous. GM eventually fixed the car in 1965 but the damage was already done to it's reputation.

3- For those who care about such trivia BFG or BF Goodrich tires are made by Michelin, General Tires by Continental Rubber. Uniroyal is made by by Michelin in North America but by Bridgestone in Australia. Most of the minor brands are subsidiaries of a big company and to make it even more interesting some brands are made by different big companies in different countries and some big brands (Goodyear) are made by different companies in different markets (Japan).

I know it's a worn and tired statment but tire inflation is as much about liability and lawers as wear,comfort and control. As some have already mentioned,different situations call for different inflations. Depending on several elements such as center of gravity,weight distribution,speed and tire desighn of course,there is a sweet spot for steering,one for tire life and another for ride along with others. Point being that even if the manufacture put all that on the door plate,how many owners would follow the instructions. Most drivers don't even own an inflation guage,much less desire or ability to use it.
My door says 50F/80R. I run 50F all the time,deflate R to 55 if I don't plan towing or hauling for a while. I ALWAYS increase R 10lbs for each 500lbs load up to 80psi max.

Fully loaded, the axles might carry different weights. Check your door sticker. Are the front tires listed at a lower ply rating than the back tires? Another alternative is they might have kept all tires the same and simply adjusted the air pressures to match the loads.

Lanse,

Good to see you're still around.

I don't care much for door stickers. If it's heavy, max pressure. If it's not heavy, then let your sticker be your guide.

Glad to se you in these parts....post more of your doings.

D

Good to hear from you, Lanse. Look at the recommended pressure on the sidewalls. Also, the more plies in a tire the more pressure they need to run. A tire with more plies heats up more than a tire with less plies if it squats a bit.

Every tire manufacturer has an inflation table for their tires. The pressure you put in the tire depends on how much weight you intend to carry, as already stated. Air pressure vs. load gives you the proper amount of tire/road contact so the tire wears evenly, gives you the best ride, and gives you the most stability.

Some manufacturers make their charts easier to get to than others. Here is Michelin's:

http://www.michelinrvtires.com/michelinrv_en_us/tires-retreads/load-inflation-tables.jsp

In reality, Michelin's is "close enough" if you choose a tire that's rated the same as what's on your truck. I've seen other inflation charts from other manufacturers, and when comparing apples-to-apples, that is, the same size tire of the same load range rating, the inflation tires are nearly identical.

The pressure shown on the side of the tire is the MAXIMUM INFLATION PRESSURE. Not a "recommended" pressure. Tire pressures are recommended by the manufacturer based on vehicle loading and handling characteristics. Most are tested extensively on test tracks to determine the "ideal" pressure that conforms to safety/ride/handling requirements.

be careful over-inflating your front tires - it may FEEL better, but you probably reduced your traction significantly. You wouldn't notice this till you really needed the extra traction - a bad time to find out.

Seems to me Frod's door sticker said to run the tires at 4 or 6 PSI under Firestone's minimum recommended pressure. Which doesn't sound like much, til you consider that 6 PSI under the 32 PSI minimum is nearly 20% under-inflated.

If you check the manual it may have a lower empty pressure for the rears.

Want the quick and dirty (and fun) way to find the correct inflation for the rears when empty? Find an empty parking lot, throw it in reverse, and do a burn-out (they are easier in reverse). Look at the black mark. Dark in the middle- too much pressure. Dark on the edges- not enough.

Yes, that sounds much more fun than the chalk method.

Of course once you've burned your tires off and have to buy a new set, you are back at square one to figure out what the correct pressure is for the load... Sorta... Maybe I'm just looking for an excuse to do more burnouts.