What PSI are your tires? (Poll)

Haha, that visual image made me crack up "Where'd my tire go?"

I've usually ran 38psi cold pressure. After reading this thread I'd like to try 44psi. I got my SGII a couple days ago so I can see if it makes a difference. The tires on my 99' Accord are SHOT so if it wears them out quicker no big deal.

My only question, has anyone tried a chalk test at max side wall pressure? This is where you paint a section of the tire with chalk, then drive in a straight light 100 feet. Get out check the chalk line. If it wore off the tire evenly you're good to go. If it wore off in the center only, then you've got too much air. If it wore off on the edges only then you have too little air.

 

We've done even better than a chalk test (which is a crude approximation at best) - we've run tens of thousands of miles at these PSI's.


Note: My Tire Manufacturer list 50PSI on the sidewall as max pressure, why would I go any lower ?

 

A few years ago, I read the police article recommending 50 PSI for training tires and figured that was a pretty safe bet. I normally park in the garage, there can be a 30°F difference to outdoor morning temps and 10°F roughly equals 1 PSI, so I've been using 53 PSI cold in the garage.

 

Well, that max psi also comes with a max load rating. For instance on my tires it's max psi 44 max load 1279 lbs. So that 44psi is for max load according to all the tire people I've talked to. I even called TireRack.com and asked them, which in this case would far exceed the vehicles GVWR anyway as that would be 1279 pounds per tire of load.

I'm not saying to run the door jamb pressure, but I'm not sure max is right either. I'm not going to argue the point, just throwing some info out there for the debate.

I am going to experiment with tire pressures some to see what effect it has.

 

Door jam pressures are for a "comfortable" ride.

 

Speedy - you are most correct, but how many of us hypermilers - load up their cars ?


We are the guys musing about how much weight we'd save if we pulled the carpets out


Up t 3-5 PSI at a time - My gut tells me I get 3-10% better MPG right off the bat @ max sidewall.


Also - max sidewall isn't what people here consider extreme pressure - look at the poll a healthy minority are above 60 PSI - these guys tell us that they didn't start feeling reall benefits until they went to 65 psi.

 

I just pumped up to 50... I hardly notice a rougher ride at 44... and my car is empty, so not worried about loads...

 

My spare tire just got taken out of the trunk and the tires are going up to 65 from 60 in the morning. I was worried about how I would keep that piece of cardboard that they call the floor of the trunk from buckling if I had to put something in the trunk, like groceries, but then I realized, "You Dummy" just take it out and there is more room and even less weight. Of course I still have my can of fix a flat in the car just in case and road side assistance on my insurance. LOL

 

I read the tire as the max pressure being what you should use at max load. For instance you would only put 44psi in the tire if your carrying 5,000 pounds of cargo (1279 x 4).

Maybe I've misread the tire info?

At any rate, I aired up to 42psi cold tonight from 36 just to see how much difference it makes.

The door jamb states 30psi front and rear up to GVWR.

Tires are GoodYear Regatta 2s 195/65/15s.

I'm going to replace these soon with some Yokohama H4Ss.

 

Yes, you've misread the tire info.

Passenger car tires come in 2 varieties - Standard Load and Extra Load.

For Standard Load tires, the max load rating occurs at either 35 or 36 psi. The difference depends on whether you are looking the US tire standard which uses English units - psi - or the one listed in metric units - bar or kPa - there's a round off error problem between the 2 systems.

For Extra Load tires, the max load rating occurs at 41 psi - and the round off error is small enough you get the same answer regardless of the measurement system.

There is a government regulation that covers what is to be put on the sidewall of a tire - and there is a bit of difference about what the regulation says. Some folks - notably the Michelin group (Michelin, Goodrich, Uniroyal) - read the regulation in such a way that the load rating and the pressure have to correspond. But pretty much everyone else reads it that the max pressure means exactly that - max usage pressure - and it isn't connected to the pressure for the max load rating. This makes using the sidewall pressure as a reference point for inflation pressure a bit iffy - unless you know which way they are reading the regulation.

 

Interesting.

 

I think CapriRacer needs to go back and investigate the problem with the Ford Exploder.

He says "....but it is also true that lower tire pressures tend to decrease the propensity for the vehicle to tip over." That disregards the inherent qualities of a radial tire.

Actually, a low pressure will help a vehicle wallow and cause the driver to lose traction. It was Bridgestone/Firestone's argument that Ford specified "too low a pressure," which caused the tires to heat up too much and the sidewalls to collapse from the increased wear due to excessive flexing of the sidewalls over time.

In almost every case of a Ford Exploder roll over, the cause was traced to an overloaded vehicle with underinflated tires, traveling at too high a speed.

 

I just got a tire gauge today and talked to my girlfriend about airing up the tires to about 40 psi. She said she didn't care.

 

Just starting out on doing mods so I'm still at my dealership standard of 32psi. I'll be pumping them up into the 35-40 range though the next time I'm out... drive not, waste not.

 

kwj,

Sorry, but there were 2 issues concerning the Explorer:

1) Tires failing: If you'll think back, the tire was recalled, not the vehicle. There was an identifiable problem with the tire. There was much discussion about what role tire pressure played, but in the end the tire that was found at fault by the government agency.

2) Vehicle tipover: This had 2 different scenarios:

a) After the tire failed: In this case, the inflation pressure of the tire is of no consequence.

b) Before the tire failed: Ford argued - and apparently successfully - that specifying a lower pressure was actually better. Since that time, there have been numerous studies that show that stiff suspensions are more prone to tipover - and the would include stiff tires. Obviously, the height of the center of gravity, the wheelbase and the track widths are very important contributors - and according to the studies, more important.

So while inflation pressure is important for tire durability, too much is also bad - for other reasons.

 

Here is a good link about results of the the Tire Recall.

 

For those who run high pressure on the tires like 50 or 60 psi: do you see more wear of the suspension due to bumps and potholes? Thanks!

 

One of the advantages of higher than recommended pressure, is that it is a lot harder to bend/dent rims on potholes.

I am running ~50PSI in tires with 51PSI sidewall maximum. Coasting is great.