Do you inflate by manual specs or tire specs?

[skaughtz]

Just curious as to how people inflate their tires and what the pros and cons may be for filling them based on the manual (door jam) specifications or max psi tire specifications.

For instance, on my 2007 Camry, the specs for cold tire pressure front and rear are 30 psi, but my tires max out at 45 psi. Would filling them closer to, say 40 psi, yield better wear/lesser control/etc.?

 

[aquariuscsm]

I go by the values that's listed on a sticker in my middle console.

 

[Chris Meutsch]

3lbs. over the door sticker.

 

[Olas]

Depends how the car handles with that particular rubber on.

Higher pressures in the rear = prone to oversteer
Higher pressures in the front = prone to understeer

I'll tweak the pressures over the first week of having the new rubber to find a pressure I'm happy with.

 

[HerrStig]

Originally Posted By: Olas
Depends how the car handles with that particular rubber on.

Higher pressures in the rear = prone to oversteer
Higher pressures in the front = prone to understeer

I'll tweak the pressures over the first week of having the new rubber to find a pressure I'm happy with.
Higher pressure means (unless excessive enough to alter the contact patch) a LOWER slip angle which on the rear would keep the rear from moving OUT in cornering, thus causing UNDERSTEER. Higher pressure in the FRONT causes the fronts (with the same caveat) to run at a LOWER slip angle and thus cause the steering to become MORE responsive and closer to neutral, especially with Front WD where the fronts do so much of the work. IF you have been doing the opposite you must have some strange handling vehicles. The goal is neutral handling where both ends operate at the same slip angle. The safety Nazis, of course, want cars to understeer like pigs because it's "safer" than being tail happy, as they say. The sidewall pressure listing is for maximum load and speed use, the car maker knows a whole lot more about the proper pressure for the vehicle that what's on the sidewall of a tire which could be fitted to many different products with different drives and weights. I usually adjust UP from the "one passenger" listing on the sticker, but seldom by more than a few pounds, given the sorry state of our roads. 45 pounds in a Camry and you'll be buying a lot of suspension pieces over time.

 

[ccap41]

A lot depends on how the vehicle feels with the current set of rubber on the vehicle. Each tire will respond a little different to diferent pressures and temperature changes.

For me, I like to put about 10% over the recommended amount in. It feels like I get a little better "roll"(because technically they do).. It also seems to tighten up the ride a little bit, nothing drastic though.

Personally, I will never run at max PSI unless I'm tracking the vehicle and even then you will want to dial in the presure to what handles best.

Technically, the higher the pressure the less tire is in contact with the ground, less pressure and there is more tire contact patch and more tire flex. I'm pretty sure most OEM placards recomendations are a good medium of both comfort and optimizing the tire contact patch for safety/performance.

For my current vehicle my placard reads 35psi front/rear and I run them at 38psi. I haven't seen any unusual wear over the past 8,000 miles of ownership.

 

[Yah-Tah-Hey]

Inflate tires to manufacturer's spec listed on driver's door jamb or glove box. Also listed in operator's manual.

 

[ARCOgraphite]

Never run max pressure on sidewall unless you don't like your strut steering bearings to last

Also youll be riding on the center third of the tread. Nice way to hydroplane.
Never found it necessary to stray more than 2-3 psig from the door sticker..
Ran unladen truck rears lower, running my unladen Rogue compact suv rears 1 psi under the fronts. If your are getting pounded, lower it a bit. 1 psi changes can make a noticeable difference - if you are sensitive to these things.
Dial it in and you have a magic carpet ride

 

[Texan4Life]

I go by the tire sidewall. I usually go to max psi or a few under the max psi listed on the sidewall

 

[HerrStig]

There are graphs on the "net which show the relationship between tire pressure and rolling resistance, the break point us usually just a few pounds above the "suggested" pressures for most cars, beyond that the gas mileage improvement is close to non-existent and tread
distortion begins to affect handling, as well as the ability to survive a pothole hit. A crude way to tell....after a high speed blast if the tire is just warm to the touch it's got enough air. If it's really hot, that's energy which could have been moving the car being wasted. Obviously, don't stand on the brakes from 0 to zero when doing this as the extra heat will distort the crude test. Race teams make their tire pressure adjustments with the aid of a "tire pyrometer" with which they measure tread temps across the tire after a run.

 

[HerrStig]

ho a
Originally Posted By: ARCOgraphite
Never run max pressure on sidewall unless you don't like your strut steering bearings to last

Also youll be riding on the center third of the tread. Nice way to hydroplane.
Never found it necessary to stray more than 2-3 psig from the door sticker..
Ran unladen truck rears lower, running my unladen Rogue compact suv rears 1 psi under the fronts. If your are getting pounded, lower it a bit. 1 psi changes can make a noticeable difference - if you are sensitive to these things.
Dial it in and you have a magic carpet ride

Who at the factory where the number is molded into the sidewall knows what kind of car it's going on?

 

[HerrStig]

Originally Posted By: HosteenJorje
Inflate tires to manufacturer's spec listed on driver's door jamb or glove box. Also listed in operator's manual.
I've found that to produce more understeer than I like but a soft ride which I don't want as a tradeoff.

 

[Traction]

Still can't believe people still think sidewall pressure is correct! Some tires are rated for 51 psi. Just run the door placard pressure, and check more often would be best. When set to 30 cold they will come up from there anyway, 4-5psi on a hot day.

 

[Spector]

I run close to 40 in front 38 in rear. Why, lower PSI in the front results in both tires wearing prematurely for me on the outside edges. For me this results in longer life and a slightly harsher ride which I am willing to live with.

What is on the door is the manufacturers compromise between ride, comfort and handling, a compromise. As long as one does not exceed the cold PSI printed on the sidewall you will be fine, adjust to suit your needs.

remember for every 10 degree change in outside temp the PSI in the tire will change 1. So, winter summer pressures do need to be checked once in a while.

Whatever lets you sleep at night.

 

[Quattro Pete]

Originally Posted By: skaughtz
Just curious as to how people inflate their tires and what the pros and cons may be for filling them based on the manual (door jam) specifications or max psi tire specifications.

It's not like it's an option. If you're using an OEM approved tire size, there is only one correct starting point for your tire pressure, and it is the vehicle tire placard. You can experiment by going up a few PSI from there to see if it results in better steering response, possibly at the expense of less comfort.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=147

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=196


Quote:
For instance, on my 2007 Camry, the specs for cold tire pressure front and rear are 30 psi, but my tires max out at 45 psi. Would filling them closer to, say 40 psi, yield better wear/lesser control/etc.?

Take a look here for some info on disadvantages of both overinflation as well as underinflation:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1

 

[Doog]

2-3 psi over the door sticker.

 

[mclasser]

Originally Posted By: Doog
2-3 psi over the door sticker.

+1

 

[razel]

They don't put the word 'max' on a sidewall to confuse you. Run what's recommended by your car manual/glovebox/center console/etc. If you really want to test what's right for your driving needs, run chaulk across the tire. In my experience running chaulk it is often in the ballpark 3-6 PSI with what the car manufacturer recommends. You will need more PSI in the rear tires if you often have rear passengers or a truck and always have stuff in the rear.

 

[Quattro Pete]

Originally Posted By: HerrStig
Who at the factory where the number is molded into the sidewall knows what kind of car it's going on?

LOL! Precisely.

 

[skyactiv]

I have Cooper Zeon RS3-A's on my GTI. Those tires says max inflation 50 PSI on them. VW says 38 PSI on the door jam and that's what my car gets.