Running tires at max sidewall pressure?

[Grog]

I came out of the dentist this morning to find a flat tire on the mustang. (I think all fords need to be recalled and the company investigated because of the missing air in my tire. My tire air has been cleverly camouflaged and hidden within the surrounding air by Ford. Anyway, I installed the mini spare and went to a Les Schwab's tire center, because they fix flats for free. They refused to fix it because the tire was worn past legal limits. I knew they were getting thin and have been tire wheel shopping for a few weeks now. I just ordered Bullitt wheels with 255 45 18"'s. Back to the reason for the post. I get home and plug the flat, pressurize it up to 30 psi, car sticker says 36. The rear tires are wearing in the middle, the fronts look even. Car says 36 front and rear. Install repaired tire, go to other rear tire to reduce pressure to match and find it at 44psi. Last week I aired them all to 36, check the fronts and they are also at 43, 44psi. I have 2 digital gages, both read same. About a year ago I had a flat on the X5, same story took it to Schwab's and it came back with 45 psi n each tire. I call them and ask what is up with pumping my tires up to max rating. I get a story about how I will get better gas mileage and longer tire life. I tell him the car manufacturer recommends 36. He says its probably ok to lower them back to 36, but doesn't recommend it. The guy I talked to was not a kid, he is the asst manager and has been there for years. I told him the max press on the sidewall is just the max the tire is rated for and the car manufactures tell you the press you should run based on the weight on each tire and vehicle handling. He still told me I would be better off running at max psi. Am I messed up? is there some new info about running max air?

[kaisen]

The manufacturers spend a lot of engineering hours calibrating tire pressures. The pressures listed from the factory are what you should follow unless you deviated substantially from the factory tire.

[porsche4life]

Based on the wear pattern you describe..... Max pressure is TOO MUCH....

[krystar]

u always go by the door jam. 30-35 is somewhat norm. i've seen upper 30's too. but 40+ is overpressure.

effects of boosting tire pressure is it can support more if you have a alot of payload. like if yer going fully loaded in your minivan on a road trip. it also decreases the contact patch and thus your rolling resistance since there's less contact patch to friction. this goes wonders for your straight line gas mileage, but messes with your braking distance. side effect is that your center tread wears but your sidewalls don't wear as much

[Oh Haha]

You ARE checking them cold, right?

Follow the specs listed on the door.

[Vern Lyle]

When I bought my Trailblazer with 15k miles, the dealer put 45psi in the new Michelins (35 or so recommended). Said it would be OK with cross rotation at 5k. Slightly hard ride, but it IS a truck. I have since avoided several hydroplaning adventures while towing, when others around me did not. Now, dead even wear on all four, still 3/32; turned 100k miles today. YMMV.

[trekkor]

How could the 'door jamb' psi be taken as the ultimate recommendation ?
Safe guideline, I'd say.

You could set any tire in any application to 35 psi and be OK.
No optimal, but definitely safe.

Tires pressures vary by manufacturer.



KT

[john70t]

I'm wondering the same.
Just put new tires on the gf's ride, and changed from max35psi to max44psi. The installer filled them to 35psi.

The new ones have good grip, but I feel like there is too much effort needed at 35psi while making slow speed turns. Wonder if that affects the power steering system and/or mileage.

I go by the tire rating, instead of the door sticker, as it is supposed to determine the area of the contact patch.
-Summer is usually 38-42 for a smaller contact patch(and less heat), and winter is 34-38.
-The result from a blowout is greater, and greater wear on the suspension, but mileage is #1 for me.

Also contrary to industry standards, I prefer the bald tires in the back because oversteer and a rear blowout is safer. Rebel

[Noah930]

Originally Posted by Grog

Am I messed up? is there some new info about running max air?

Les Schwab guy is an idiot.

[dhrcr911s]

Worn in the middle = TOO Much pressure..

Simple - Reset the pressures and ask LS to set them per the Manufactures suggestion in the future.

[Grog]

Originally Posted by Noah930

Les Schwab guy is an idiot.

My thoughts exactly.

I always go with the manf. suggested press + or - after watching the tread wear. I only raise the pressure when adding extra heavy loads to trunk. I add air all the time on my truck when hauling stuff or pulling trailers. The max press on the tire sidewall is just that, a max press, usually when at max load. The tire manufacturer can't possibly know what type and weight of vehicle their tire is going to be installed on. The rear tires on the mustang were worn in the middle, but still had tread when we bought it 1 year ago. I rotated them to the front and back again. I stuck with 36 psi on the front and 32 rear. I ordered wheels back in April from speed concepts in Cal. I waited a week without any emails saying they were processing or shipping my order, so I called them to see what the status of my order was, called a dozen times and emailed over a 2 day period without an answer so I canceled the order. I get an email 3 days later from some idiot telling me I was having a heart attack because I could not contact them on good Friday and they were allowed to take a holiday off. He also said he emailed me stating the wheels were on back order, never got the email. Don't buy from Speed concepts, bad BBB rating (checked after I ordered)

[jyl]

I pump the Prius tires to 44 psi for better gas mileage. They are wearing evenly and grip okay. If they were wearing in the center, I'd lower pressure.

[pwd72s]

Originally Posted by porsche4life

Based on the wear pattern you describe..... Max pressure is TOO MUCH....

Agreed...wear in the center means you're running too much pressure. FWIW, I run my Bullitt Mustang's stock BFG G Force TA's at 34 all around. That's cold, checked with a blue point gauge sold by snap-on. Cheap tire pressure gauges are for entertainment purposes only...

[masraum]

I can't imagine running at 40+psi unless you were specifically doing it for mileage reasons. Tire manuf are putting their MAX on the tire, that's max, not recommended. I think the guys at Les Schwab are idiots.

My opinion, I think you'll get the best compromise of performance, mileage, wear, etc... out of something in the 30-35 range or Ford's recommended specs.

[wdfifteen]

The Ford Explorer debacle makes me suspicious of car manufacturer's recommendations. Ford lowered the recommended pressure to 26 PSI to cover up chassis design deficiencies that made the car unstable. Firestone reluctantly OKed the change, even though the low pressure caused excessive heat and tire tread separation. You know the rest. Blowouts, crashes, deaths, recalls, lawsuits etc etc. I put 5 to 10% more than the car maker recommends and monitor tread wear and handling.

[Joe Ricard]

I run the RX-8 tires at 38F / 36R Tire wear evenly

F250 get 80F and 75R unless loaded then it 80 Rear. Tires wear evenly and the vehicles are way more stable.

[masraum]

Originally Posted by Joe Ricard

F250 get 80F and 75R unless loaded then it 80 Rear. Tires wear evenly and the vehicles are way more stable.

Wow, really? Is that the recommended on the tire or the vehicle, or is that something that you came up with via trial and error. I've never had a truck so I don't know if that's the norm or not.

[sammyg2]

You should use the pressure on the door jamb, MOST OF THE TIME.
There are exceptions.
My 2007 Tundra was one of those exceptions. With the pressure at OEM recomendations, the front tires wore terribly on the outer edge.
The alignment was right on but the wear was still there. A guy at the alignment shop said to kick the pressure up to 42 even though toyota said 33. I tried it and the truck handled better, rode better, got better gas mileage, and the tires lasted longer. No downside.

I'd say it's a case by case decision taking into account the type of vehicle, the design, the tire wear, handling, safety, etc.
But if in doubt, use the car manufacturer's rating.

[sammyg2]

Originally Posted by masraum

Wow, really? Is that the recommended on the tire or the vehicle, or is that something that you came up with via trial and error. I've never had a truck so I don't know if that's the norm or not.

Passenger car tires usually max out at around 35 psig, light truck tires usually max out at around 44, heavy truck tires (like the ones used on an F-250 or 1 ton truck or superduty) take gobs of pressure like described above. They are also way more expensive and heavier.

So no, not all trucks take that kind of pressure, only the big heavy ones.

[dtw]

Originally Posted by masraum

Wow, really? Is that the recommended on the tire or the vehicle, or is that something that you came up with via trial and error. I've never had a truck so I don't know if that's the norm or not.

Normal. Used to run 90 psi in my F550.