Quote:
Originally Posted by TEiN
How much difference do you think it makes that the tires in this test are all rated at only 32 psi, yet, all current tires in this size (215/75x15) are rated at higher pressures? Although a few are rated at 35 psi, the majority are at 44 psi, some at 50 psi, and some at 65 psi. I'm no tire engineer, but these pressure rating differences say to me that some advances may have been made in tires since this test was conducted, and the results may not necessarily apply to the tires that are available today.
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Just to be clear.
The tires tested in this study were rated at 32 psi. Passenger car tires today are rated at 35 psi. However, the maximum pressure on the sidewall (which isn't directly connected to the rating pressure) can show a wide variety of pressures depending on 1) how the tire manufacturer reads the regualtion that covers what is to be imprinted on the sidewall, and 2) how the tire manufacturer reads the tire standards that cover that particular type of tire (meaning passenger car, light truck, etc, and not all season, winter, etc.)
In other words. you must be very careful how you conceptualize these pressures. The technical meaning of each is different and way each should be viewed (in the context of how a tire reacts to pressure) is going to be different.
So the assertion that the maximum pressures imprinted on the sidewall of modern tires must mean there have been technical advances isn't true. (There have no doubt been technical advances, but the pressure isn't any indication of advancement.) In fact, when this study was conducted, the tire standards that are applicable today, were applicable then - and further, tires was labeled in much the same way then.
When I brought up the link to Tire Rack that you provided, there are a mix of tire types (meaning P metric, metric and LT metric), and this is no doubt creating confusing. Tire Rack doesn't publish the letters that go in front of (or behind) the numbers in the tire size and those letters are sometimes important. (Just for reference, if the Load Index has a dual number, then the tire is an LT metric and not a tire designed for use on a passenger car.)
OK, so to answer your question, inflation pressure has a profound effect on the way a tire reacts, and pretty much all of the results of the study are applicable today. What will be different will be the levels of - oh, say - RR or grip, or impact resistance, not the way pressure affects that property.
One of the things I think is really important from this study is how far back I had to go to find ANY information about the effect pressure has on a tire when it is operated HIGHER than the rating pressure. There is very little data for tires operated in these region. My concern is for tires operated above the placard pressure and the further away from that value, the greater my concern - AND, I'm really concerned about tire operated over the max pressure.
And - again - just to be clear, the rating pressure for passenger car tires is 35 psi, and NOT what is written on the sidewall. In some respects you could say that since the rating pressure is 35 psi, then 44 psi is "pushing the envelope" - but one that has been recognized by the tire industry as an acceptable "pushing of the envelope".