[Saint J VT]

I run my tires by how the tread is wearing. I have found that the 32 front and 30 rear is too much air for my wife's car, she barely ever carries a full load. I measure the center tread of each tire and the end treads. If the tires are wearing more in the center, it means, like a balloon, they have too much air. I run about 28 in the front and 26 in the rear to make the tires wear even.

Now, if she is going to be hauling a full-load, I will go up to the door placard of 32/30.

The front takes more pressure to keep the tires the same height off the ground as the rear, as the front is a lot heavier.

If I ever need to bump the pressure up to, say, 36 front, 34, rear, I will do so, if I notice that the cornering (outside) tread is getting shallower than the middle tread.

Measure in various spots as there are typically high spots made across the tires (perpendicular to the tread lines) that are supposed to indicate when you need new tires (called wear indicators). Just don't measure where they are.

If you have a caliper, you can get really accurate readings.

I have been "Reading" my tire wear and adjusting pressure accordingly for over 40 years and it has always resulted in my tires wearing extremely evenly across the treads on all of them.

Some people think the numbers on the door post and on the tires are cast in stone and you should not alter that at all. Of course, they want you to buy new tires when you still have 1/4" tread depth in the center and your cornering treads have steel cords hanging out (I have seen it)!:gasp:

I HATE driving a car with maximum pressure in the tires, as every single little pebble in the road hurts my lower back problem - not to mention if you hit a pot hole! Not only that, all that hard hitting with hard tires has to wear the suspension parts faster (especially on any rough roads) than if the tires are more spongy!

I know, less air means not as good fuel mileage.

For how little it affects my fuel mileage, I will continue to keep doing what I am doing and NOT TRUST ANYONE who works on my car, as they typically automatically fill them to WHATEVER! When I get home, I re-check using an accurate gauge, most times having to let a lot of air out! Maybe I could sell the air.

Just remember, whatever the pressures, keep the front about 2-3 PSI more than the rear on these cars to help prevent torque-bind problems related to tires spinning at (a lot of) different speeds.

 

[1 Lucky Texan]

I maintain the difference, front to rear, but boost the 'door card' pressure by about 10%.

IF you are the type person that is going to check your tire pressures at every fill-up, try adding just 1 or 2 PSI to the door card pressures. If you tend to wait months - or - until a tire looks low, to check pressures, try running about 15% over the door card pressure to help even out tread wear. If you regularly take corners at speed, you should probably run 10-15% over the recomm. pressure. But most spirited drivers/motorsports guys are gonna experiment to find the proper pressure anyway. Some folks will measure temperatures at the center and edges of the tires after a 'fun run' to help decide about pressure changes. Even if you have a little uneven wear, I think you would want to err on the side of overinflation.

as said above, the numbers are guidelines, though, the max on the sidewall, particularly on an old/worn tire, is something i try avoid violating.

Also, if you ever fully load or somewhat overload, your car , and must drive on the highway, better to inflate to near the max sidewall number than overheat the tire.

 

[jp1203]

In my 2004 LL Bean, I run 35F/34R. Max pressure on my current all seasons is 44. I think the door says the same as yours--30F/29R.

It rides pretty well at that pressure. I think the pressure marked inside the door is awfully low. I've tried it at that and it just feels bad to me.

 

[1 Lucky Texan]

I think the pressure marked inside the door is awfully low. I've tried it at that and it just feels bad to me.

every car I've ever owned handled better with pressure above the manuf. recommended.

I think they pick the lowest reasonable number so the cars ride smooth and 'cushy' on test drives. i dunno. It might be personal preference.

 

[blackdogob]

Wow. That's some good info. Thank you all. OK. I'll try F36/R34.

Why do you think the tires I have state not to exceed 40 PSI but the load rating is at 51psi? Seems like the lawyer couldn't agree with the engineer so they printed both. But in court it would be hard to prove that they had provided the correct info to purchasers/ users.

 

[Saint J VT]

Wow. That's some good info. Thank you all. OK. I'll try F36/R34.

Why do you think the tires I have state not to exceed 40 PSI but the load rating is at 51psi? Seems like the lawyer couldn't agree with the engineer so they printed both. But in court it would be hard to prove that they had provided the correct info to purchasers/ users.

You should experiment, as everyone drives differently and most people drive certain types of roads more than others. What works for me might be terrible for you! As you are aware, check the tires cold, being sure one or more is not in the sun while one or more are cool in the shade -- I have found that will throw off the actual pressure by several pounds or more!

I know how 50 pounds rides as I have a work truck that can go up to 80 pounds max, and - I think for the OB, the max should be more like the labeled 41 PSI. You don't want to be riding on such a small footprint that the tire starts hydroplaning easily when without a FULL LOAD. You also don't want to feel every pebble, tiny crack and every ant you run over (kidding about the ant)!

I typically ALWAYS agree with what 1 Lucky Texan has to say!

 

[1 Lucky Texan]

I typically ALWAYS agree with what 1 Lucky Texan has to say!

well, i mostly repeat what I read, in this instance, i do have some experience with my own cars, but some of it was from the wisdom of others on the Forums and at a few track events.

I think all of those 'max' numbers associated with tires are conservative - it might take 3-4 times the sidewall pressure to actually burst a new tire.

But consider that somewhere out there, someone has a 9 year old tire that's been exposed to Mojave Desert type climate it's whole life, been patched 4 times and is worn bald. They are piling the grandparents into the van, then loading all 7 kids and about 11 cousins and the dog in next. About to highball it down the highway to the lake. That is what lawyers are concerned about when it comes to max inflation pressure.

 

[plain OM]

On my 04 OBW LTD, . . . Tires themselves have a disclaimer that, in part, says to never inflate to over 40 psi. There's also a load rating printed on the tire and the load is rated for max 51 psi. So that's pretty contradictory.

The door jamb label for the original OEM Bridgestones, says rear at 29 psi and front at 30 psi. What's up? What's the proper pressure to run these at?

Thanks

I think if you read the full text related to the 40 psi, it says something like:

"never exceed 40 psi . . .to set beads". This is when installing the tire on the wheel. It's to protect the installer.

The other data on the tire is the actual load rating and is found at a different point on the tire. This section will have wording such as:

"maximum load xxx pounds at xx psi maximum pressure". It's pretty well what it says -- the maximum load that can be placed on the tire at it's maximum pressure. Going beyond risks failure. (At lower pressure the load that can be supported is reduced.)

Both the above are determined by the tire manufacturer in accordance with tire industry standards and any related government regulations, and apply to the tire regardless of which car it's on.

The door jamb pressure data is determined by the car manufacturer, and as has been noted, is based on the designers' or engineers' choices for ride quality, handling, and tire longevity (wear).

So the specs are not contradictory. They deal with different aspects of tire installation and use.

 

[Saint J VT]

plain OM is correct, if the installer blows a lot more air than necessary to set the beads (when you see the sidewall suddenly pop into place with a loud POP), the result could be a sidewall blowout, or rim failure, right in the installer's face!

 

[1 Lucky Texan]

not many good videos but, look what the pressure gets to on this welding test;

but this is why folks should avoid violating the max sidewall number;

 

[upstairsdave]

Tire Cupping/Pressures/Vehicle Weight Balance issue???

I have a 2005 Outback Wagon and installed $500 Michlins on it. What great ride!!!!! I had the tires rotates at the first 5K mile recommendation time. The second time they were rotated I saw the cupping on the tires immediately, especially when I heard it singing down the highway. Very annoying sound. Of course the tire dealer tried to sell the cause as poor rotation, out of balance tire, out of alignment suspension....all of which is not the problem of a continuous tire tread cupping. It appears that the all wheel drive cars with most of the vehicle weight to the front of the engine and transmission, and steering systems, causes the rear suspension and tires to bounce along the highway. Each time the tire hits the road surface again it removes a little bit of rubber with the end result of lots of tread cupping. Some manufacturers have added weight to the rear suspension to help alleviate the problem. I modified my tires pressures to 30 up front and 24 in the rear just to see how things respond. It's the high speed highway driving, especially with concrete dividers, that does the damage.
Well, I just called the subaru dealer and he told me the same thing....front end alignment. Now I'll call "800 subaru 3" to see if I can talk to someone that cares.Well, the guy in customer service at headquarters was clueless too. I asked him for the weight ratio from front to rear. I don't thin he had any idea of what that meant. I'll let you folks know when I find out. I thought about putting softer struts on the rear to help prevent the irregular road contact at speed. Any suggestions???????? I hate to fill my trunk with lead....hmnmmm golf clubs might help!!!! If you load he rear of the car then the front end alignment is thrown off too. I'm telling you that the noise from the cupping is not tolerable. I'll sell the car.
Thanks