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Originally Posted by orange4boy
Two ways of saying the exactly the same thing.........
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While this may be similar, it's not exactly the same thing. I'll explain that below.
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Originally Posted by orangeoy4
.......The chart then has the note that the tire engineer can increase the pressure up to max psi without increasing the load and this difference is what the engineer has to work with when determining recommended pressure. ie, NVH vs performance......
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It's the vehicle engineer, not the tire engineer that selects the tire size and the inflation pressure.
The vehicle engineer uses the table, knowing the load that the tire must endure, to select a tire size and inflation pressure combination that not only will carry the load - and knowing that over specifying that combination, a lesson emphasized by the recent Ford /Firestone controversy a few year back - but also have some over-capacity. How he does this depends on the design standards for each vehicle manufacturer. Notice that almost without exception, the pressure specified on the vehicle tire placard is not above 35 psi - and this would include the over capacity (in the form of over-specifying the pressure).
On the other hand, the tire engineer is designing the tire to the table without regard to over specifying by the vehicle engineer. I had a college professor cal this "Over-design / Under-utilize".
The tire engineer generally picks the 35 psi load - for passenger car tires - and uses 35 psi as the test condition.
NVH - for a tire engineer's perspective - is about tread generated noise, since most ride vibration are about "roundness" (a manufacturing issue), and ride quality is more or less controlled by the inflation pressure (which requires a vehicle for testing).
Quote:
Originally Posted by orange4 boy
....Please note they call it recommended pressure not required pressure.......
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I'm going to call what is written on the vehicle tire placard a specification - which it is - much like oil viscosity and bolt torque are specified.
Quote:
Originally Posted by orange4 boy
......If there was you can bet the NSHTA would have long ago had a placard with that in big bold letters. ......
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That's kind of a weak arguement because look how long it took for NHTSA to deal with the issue of inflation pressure BELOW the placard. There weren't any bold letters for that and that was a known quantity for decades. Besides, there isn't a lot of information about what happens in the real world when tires are inflated above the vehicle tire placard - mostly because actual usage inflation pressure information is rarely available from accidents statistics - which is what NHTSA is using to drive what they look at.