Tire Pressure
- Thread starter Warstud
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Another factor to consider is front / rear pressures. Very few cars are at 50 / 50 weight distribution. Most FWD car are up at 60 + front / 40 - rear. So, a 3200 pound car has roughly 1920 pounds on the front axle, but only 1280 on the rear axle. Or, again roughly 960 lbs per FRONT tire , and only 640 lbs per REAR tire. Big difference.
Most placard inflation pressures assume a full load, and spec pressure accordingly. Some car makers do make load dependant recommendations, but that seems to be less common.
I always run tire pressures much higher in the front, unless I plan on carrying a full load of passengers / cargo, which I almost never do in my personal car.
Most placard inflation pressures assume a full load, and spec pressure accordingly. Some car makers do make load dependant recommendations, but that seems to be less common.
I always run tire pressures much higher in the front, unless I plan on carrying a full load of passengers / cargo, which I almost never do in my personal car.
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Kestas
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I can provide one data point that shows manufacturers are on the ball with their recommendations. I ran a set of tires on my 1991 Mercury Grand Marquis from start to finish (11 yrs) at 35 psi, with tire rotation. Recommended pressure is something like 29 psi. After they wore out, I noticed the tires showed slightly more wear at the crown than at the corners.
Originally Posted by geeman789
I always run tire pressures much higher in the front, unless I plan on carrying a full load of passengers / cargo, which I almost never do in my personal car.
Why do you run higher pressures in the front tires?
If your answer is because there's more weight in the front tires, again, I ask, why does that mean you should run higher pressures in your front tires?
I always run tire pressures much higher in the front, unless I plan on carrying a full load of passengers / cargo, which I almost never do in my personal car.
Why do you run higher pressures in the front tires?
If your answer is because there's more weight in the front tires, again, I ask, why does that mean you should run higher pressures in your front tires?
My car is fwd, and specifies a higher pressure at the front. They built the car, I'm pretty sure they knew what they were doing.
If I do not bump the front tires from the factory 29psi front 26 rear to 38 front and 34 rear I get the outer edges of the tread destroyed really quickly while cornering hard in my FWD car.The ride stiffens a lot,which is bad in poor quality pavement but good in changing direction feel and fuel economy as well as extending the tire life.It also gives me some piece of mind regarding the rims geting bent when going over road bumps or broken tarmac.
Originally Posted by CapriRacer
What this all means is that S and T rated tires can have 35, 44 or 51 psi listed as the max pressure, and it is relatively arbitrary which of those 3 is chosen - that is, the tire's construction is NOT specifically designed around that pressure - AND - there aren't any vehicle manufacturers who specify pressures for their vehicles higher than 35 psi (36 psi for metric tires), with some notable exceptions.
Exceptions? German based vehicle manufacturers who specify H or higher speed rated tires, because Germany has the Autobahn with no speed limit, so the vehicle MUST be designed for that and that means the tires have to be capable of handling the top speed of the vehicle - hence the higher specified pressure for THAT condition. However even those vehicles don't specify that higher pressure for normal use.
Why would a H tire (sidewall max 51 psi) that is rated at 210 km/h speed is being recommended by German vehicle manufacturer having a vehicle top speed of 260 km/h ?
Is H metric tyre with rated speed of 210 km/h to be interpreted as a minimum speed, and not maximum speed allowable ? ...... and hence permitted by tire manufacturer (or is it Standards Organisation ?) for use in vehicle approaching top speed of 260 km/h.
Quote
Where all this leads to confusion is that H and higher speed rated tires (The ones that MUST have 44 or 51 psi max pressures!) must also have constructions capable of passing their respective speed rating tests - and many folks interpret that to mean the tire is designed for the higher pressure and that's not accurate. More accurate is that the tire is designed to pass the speed rating test and the construction reflects that.
So I call the pressure listed on the vehicle tire placard as a "Specification" - sort of like the oil viscosity is specified for the engine. You can do something different, but you have to be aware that the vehicle manufacturer doesn't endorse it.
Let's say 35 psi (36 psi for metric tires) was recommended by vehicle manufacturer , endorsement would likely not apply for 34 psi and below, right ?
Hence vehicle manufacturer endorses 35 psi and higher , not exceeding sidewall maximum pressure of 51 psi , am I right in saying so ?
What this all means is that S and T rated tires can have 35, 44 or 51 psi listed as the max pressure, and it is relatively arbitrary which of those 3 is chosen - that is, the tire's construction is NOT specifically designed around that pressure - AND - there aren't any vehicle manufacturers who specify pressures for their vehicles higher than 35 psi (36 psi for metric tires), with some notable exceptions.
Exceptions? German based vehicle manufacturers who specify H or higher speed rated tires, because Germany has the Autobahn with no speed limit, so the vehicle MUST be designed for that and that means the tires have to be capable of handling the top speed of the vehicle - hence the higher specified pressure for THAT condition. However even those vehicles don't specify that higher pressure for normal use.
Why would a H tire (sidewall max 51 psi) that is rated at 210 km/h speed is being recommended by German vehicle manufacturer having a vehicle top speed of 260 km/h ?
Is H metric tyre with rated speed of 210 km/h to be interpreted as a minimum speed, and not maximum speed allowable ? ...... and hence permitted by tire manufacturer (or is it Standards Organisation ?) for use in vehicle approaching top speed of 260 km/h.
Quote
Where all this leads to confusion is that H and higher speed rated tires (The ones that MUST have 44 or 51 psi max pressures!) must also have constructions capable of passing their respective speed rating tests - and many folks interpret that to mean the tire is designed for the higher pressure and that's not accurate. More accurate is that the tire is designed to pass the speed rating test and the construction reflects that.
So I call the pressure listed on the vehicle tire placard as a "Specification" - sort of like the oil viscosity is specified for the engine. You can do something different, but you have to be aware that the vehicle manufacturer doesn't endorse it.
Let's say 35 psi (36 psi for metric tires) was recommended by vehicle manufacturer , endorsement would likely not apply for 34 psi and below, right ?
Hence vehicle manufacturer endorses 35 psi and higher , not exceeding sidewall maximum pressure of 51 psi , am I right in saying so ?
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Originally Posted by zeng
Let's say 35 psi (36 psi for metric tires) was recommended by vehicle manufacturer , endorsement would likely not apply for 34 psi and below, right ?
Hence vehicle manufacturer endorses 35 psi and higher , not exceeding sidewall maximum pressure of 51 psi , am I right in saying so ?
No, if 35 is the spec, then it is 35, not 35 and above. You are altering the performance characteristics of the tire by going above the spec pressure, why would they endorse that and the liabilities it potentially brings with it?
The only exceptions here would be the German cars with multiple pressures listed for various loads and operating speeds, but that's due to the heat generated in use. When My M5 had the tires inflated to "fully loaded autobahn" pressure (which was still WELL below sidewall), it was extremely twitchy and would break loose the rear tires with only moderate throttle input because of the much narrower contact patch. The car's behaviour was significantly improved with the lower pressures indicated for how I was operating the vehicle.
Let's say 35 psi (36 psi for metric tires) was recommended by vehicle manufacturer , endorsement would likely not apply for 34 psi and below, right ?
Hence vehicle manufacturer endorses 35 psi and higher , not exceeding sidewall maximum pressure of 51 psi , am I right in saying so ?
No, if 35 is the spec, then it is 35, not 35 and above. You are altering the performance characteristics of the tire by going above the spec pressure, why would they endorse that and the liabilities it potentially brings with it?
The only exceptions here would be the German cars with multiple pressures listed for various loads and operating speeds, but that's due to the heat generated in use. When My M5 had the tires inflated to "fully loaded autobahn" pressure (which was still WELL below sidewall), it was extremely twitchy and would break loose the rear tires with only moderate throttle input because of the much narrower contact patch. The car's behaviour was significantly improved with the lower pressures indicated for how I was operating the vehicle.
Originally Posted by zeng
Originally Posted by CapriRacer
What this all means is that S and T rated tires can have 35, 44 or 51 psi listed as the max pressure, and it is relatively arbitrary which of those 3 is chosen - that is, the tire's construction is NOT specifically designed around that pressure - AND - there aren't any vehicle manufacturers who specify pressures for their vehicles higher than 35 psi (36 psi for metric tires), with some notable exceptions.
Exceptions? German based vehicle manufacturers who specify H or higher speed rated tires, because Germany has the Autobahn with no speed limit, so the vehicle MUST be designed for that and that means the tires have to be capable of handling the top speed of the vehicle - hence the higher specified pressure for THAT condition. However even those vehicles don't specify that higher pressure for normal use.
Why would a H tire (sidewall max 51 psi) that is rated at 210 km/h speed is being recommended by German vehicle manufacturer having a vehicle top speed of 260 km/h ?
Is H metric tyre with rated speed of 210 km/h to be interpreted as a minimum speed, and not maximum speed allowable ? ...... and hence permitted by tire manufacturer (or is it Standards Organisation ?) for use in vehicle approaching top speed of 260 km/h.
Quote
Where all this leads to confusion is that H and higher speed rated tires (The ones that MUST have 44 or 51 psi max pressures!) must also have constructions capable of passing their respective speed rating tests - and many folks interpret that to mean the tire is designed for the higher pressure and that's not accurate. More accurate is that the tire is designed to pass the speed rating test and the construction reflects that.
So I call the pressure listed on the vehicle tire placard as a "Specification" - sort of like the oil viscosity is specified for the engine. You can do something different, but you have to be aware that the vehicle manufacturer doesn't endorse it.
Let's say 35 psi (36 psi for metric tires) was recommended by vehicle manufacturer , endorsement would likely not apply for 34 psi and below, right ?
Hence vehicle manufacturer endorses 35 psi and higher , not exceeding sidewall maximum pressure of 51 psi , am I right in saying so ?
Many german models have speed limiters of either 210km/hr or 250km/hr (sometimes higher). The appropriate tires will be spec'd based upon the intended load and speed limiter not the individual model of car.
The rating is the MAX speed.
Originally Posted by CapriRacer
What this all means is that S and T rated tires can have 35, 44 or 51 psi listed as the max pressure, and it is relatively arbitrary which of those 3 is chosen - that is, the tire's construction is NOT specifically designed around that pressure - AND - there aren't any vehicle manufacturers who specify pressures for their vehicles higher than 35 psi (36 psi for metric tires), with some notable exceptions.
Exceptions? German based vehicle manufacturers who specify H or higher speed rated tires, because Germany has the Autobahn with no speed limit, so the vehicle MUST be designed for that and that means the tires have to be capable of handling the top speed of the vehicle - hence the higher specified pressure for THAT condition. However even those vehicles don't specify that higher pressure for normal use.
Why would a H tire (sidewall max 51 psi) that is rated at 210 km/h speed is being recommended by German vehicle manufacturer having a vehicle top speed of 260 km/h ?
Is H metric tyre with rated speed of 210 km/h to be interpreted as a minimum speed, and not maximum speed allowable ? ...... and hence permitted by tire manufacturer (or is it Standards Organisation ?) for use in vehicle approaching top speed of 260 km/h.
Quote
Where all this leads to confusion is that H and higher speed rated tires (The ones that MUST have 44 or 51 psi max pressures!) must also have constructions capable of passing their respective speed rating tests - and many folks interpret that to mean the tire is designed for the higher pressure and that's not accurate. More accurate is that the tire is designed to pass the speed rating test and the construction reflects that.
So I call the pressure listed on the vehicle tire placard as a "Specification" - sort of like the oil viscosity is specified for the engine. You can do something different, but you have to be aware that the vehicle manufacturer doesn't endorse it.
Let's say 35 psi (36 psi for metric tires) was recommended by vehicle manufacturer , endorsement would likely not apply for 34 psi and below, right ?
Hence vehicle manufacturer endorses 35 psi and higher , not exceeding sidewall maximum pressure of 51 psi , am I right in saying so ?
Many german models have speed limiters of either 210km/hr or 250km/hr (sometimes higher). The appropriate tires will be spec'd based upon the intended load and speed limiter not the individual model of car.
The rating is the MAX speed.
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I go 3-4 PSI above the spec. Why? because tires naturally lose a tiny bit of pressure over time and having the 3-4 PSI extra gives me a buffer for several months. BTW its also with in the natural temp induced seasonal varience. Zero issues.
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