Door Pressure Sticker Reading on V

LOL, I know Chicago is street tough but you don't want to fight in WV.

 

Don't worry. I'm only planning on SHOWING UP for the fight, not following through on it!

 

So the picture didn't help?

Perhaps I need to re-take the shot so there is more perspective. You definitely will not see it just by peeking down below the steering column. My hope was that the photo would make it easier to navigate just by touch.

 

The MAXIMUM pressure on the tire indicates the LOAD the tire can hold, not what your tire should be at. 51-52psi is the maximum pressure the tire can handle before the risk of blow outs. As you go up in pressure, you are also increasing the load that it can carry on the tire/suspension. With each pothole, you are sending more shock to the rim/tire and your suspension. I don't recall the exact amount per psi, but it is not linear and it goes up drastically as you go up past a point. The recommended pressure is a compromise between tire wear/load recommendation (I think the gross weight on the vehicle is about 3600lbs, the maximum tire load should be around 1100lbs per tire) and handling. Toyota did enough testing to know what the pressure should be at, you think they would tell you to run 32psi if you need to be at 51psi. You would overheat your tires so badly that it will come off the rim before you know it.

High pressures are unsafe for the following reasons. (I mean like 10psi over, not 1-3psi more than recommended)

#1 You have a lot less contact patch on your tire to the road.
#2 Risk of blow outs are higher due to the extremely high pressure/load. (If you don't understand why, go look at why off-roaders deflate their cars below 15psi for any rock/hillclimb. You want the tire to have some flex, not stiff as a board. Also think about popping a little ballon vs the same ballon at 2x the twice)
#3 Tire wear.
#4 Tire temperature being to low

You should only overflate your tires under the following condition (I mean like 5psi over, 2-3psi for normal driving isn't bad)

#1 High speed cruising, I think Volvo or Mercedes tells you that in the owner's manual. You need 5psi more if you plan to cruise at 100mph+.
#2 Heavily loaded car. At 32psi, your tire can let say handle 3600lbs in weight. At 37psi, you can handle up 4000lbs (my math is off, but you get the idea). As you go up in pressure, you increase the load the tire can handle.
#3 Autoxing and track days. Higher pressure will give you better steering response due to the decrease of roll, in exchange for ultimate grip. Also you want to go up to prevent the tires from overheating. For normal tires, the rule of thumb is 5-10psi over stock. The stiffer the sidewall, the less you have to do so.
#4 Tires too hot. Let say you are running the car for 10 hours straight in hot heat, you probably want to increase your tire pressure slightly to compensate.

 

You are right that you should adjust your tire pressure based on conditions or the tires you have. I agree with you on that, but the adjustment should be rather small. A daily driven normal car should not have to run 40psi+ on their tires unless they plan to haul 5 Oprah around doing 130mph for 10 hours straight. The car simply doesn't generate that much load for you to go up the tire pressure that much. When you increase it like that, you are simply going to risk more blowouts and the risk of losing ultimate grip due to the smaller contact patch and lack of tire temperature.

 

While I agree with your beliefs I don't buy all your arguments as supportive of the view.

 

The Max Sidewall Pressure is not the maximum pressure the tire can take at maximum load, but it is the max pressure at load that an acceptably high percentage of tested tires will reach before some unacceptable deformation or failure. I've read it before, but I can't recall the specifics. The fact is the manufacturer's lawyers certainly won't put a number on the tire above which failure is even likely, much less probable.

Your points about load and the effect on the entire suspension system are quite valid, though, and must be kept in mind when inflating tires on any vehicle.

#1 -- How much less contact patch are you talking about? A 20% loss? I have no idea. I assume there is some loss, but I don't know the amount.
#2 -- I just don't buy this argument. The harder tire simply means the force is redirected to a point of less resistance. For the most part, that means the rest of the suspension system. As far as the rock climbers are concerned, the lower pressures (significantly lower pressures!) allow tire deformity which grants more contact space (not just "contact patch" here, but wrap-around) to allow better "grab" by the tire. The balloon argument just doesn't apply.
#3 -- Post after post, plus my experience, shows that with the Prius the tire wear is much better and more even with higher pressures.
#4 -- Don't think I really understand this point.

These all make sense to me, though I don't see why these would be the only times to inflate above the manufacturer's representative.

The auto-cross and track reasoning is familiar. If it works to provide better handling there, then why doesn't it apply to normal use? I know the risks are different, but are racers going to take tires to the absolute edge and risk ultimate tire failure?

 

You can go as high as you want, but the risk of blowouts are substantially higher as you go up past a certain point. 51psi is a compromise point they came up with.

#1 You are riding on something like 410mm L and R side, 20% is a lot.

#2 You bounce a flat basketball and a properly inflated basketball, see what will come back faster. The job of your shocks are to keep the wheels on the ground, what do you think will happen if you put more force against it.

#3 That's right, that's why no warranty will honor a tire that wears unevenly.

For track and autox. You lose grip as you go up in pressure (due to the less contact patch) and it can effect how much heat it builds up. Autoxer increase their tire pressure in order to resist roll, not to increase grip.

 

Tire manufacturers are building their tires to certain standards. Very few tires are built that are not either 44 or 51 psi max sidewall pressures. The number is far from meaningless, but it also is not magical.

I would agree that 20% is a significant number, but that is one I just typed in my response. I was wondering whether you had any idea of the actual reduction in contact. I have no idea what the loss is -- I'm just asking.

This is an apples-to-oranges comparison. Basketballs do not have strong sidewalls or steel belts in them to help maintain shape.

More force? More reaction. I agree that a more highly-inflated tire will transmit more of the energy to the suspension. I lower-inflated tire will absorb more, but it will be turned into something else, such as heat. The transmission to the suspension is likely to be felt first by the shocks, next by the passengers. Some folks don't like the firmer ride or are concerned about having to replace shocks sooner, while others would prefer higher fuel economy.

I don't quite understand. Which warranty -- the auto's manufacturer or the tire's. The OEMs on my 2007 had uneven wear when I was using the Toyota-recommended pressures.

I'm not an auto racer, so some of this clearly is lost on me, but it seems to me that if you reduce roll, you are better able to handle the car.

 

You can run your engine at 275-325F oil temp all day, is it good for your motor? You decide. They have their reasons for listing operating ranges (in tire's case, maximum recommended pressure aka load). I will take my chances with engineers who spent money and time on R&D. I do not need my beads to pop running at highway speeds.

The amount of contact you lose would depend on the tire pressure, wheel size, tire type, the curve of the road and even your alignment. I don't have the exact figure, but 20% plus is definitely within reasons.

Steel belts can't support 1000lbs (per corner) for a long period of time, proper inflation gives it the strength to support the weight. Hence the higher the pressure, the heavier the load you can carry.

You get better fuel economy with higher tire pressure because of the lower drag resistance with a smaller contact patch to the road. By having less contact patch, you create less heat in the tire also. (think biking with skinny touring tires vs offroad tires)

Uneven wear comes from alignment usually, also it depends on where and how the car is driven. Most cars driven on the street don't even use the full tread anyway.

In racing situation, you have to find the perfect balance. Lower tire pressure gives them the grip, but too low of a pressure will also overheat the tires and cause the tire to roll onto the sidewall. I don't know if the OEM tires have it, but look for a little aero/triangle on the outside of your tire.