Quote:
Originally Posted by IsaacCarlson
...... The DOT on the tires says 174 so they might be from 04.......
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Sorry, but they are NOT 2004 tires, they are 1994 tires:
Barry's Tire Tech
But you should check to see what your trailers tires say fro maximum inflation pressure. If they are ST type tires, they are more like LT tires and operate at higher pressures.
Nevertheless, they are 16 years old, and I'd recommend you replace them.
Quote:
Originally Posted by JacobAziza
The The International Tire and Rubber Association burst tests I linked to that found a minimum burst pressure of over 300psi was (mostly) of used tires, not new ones......
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I hope you are aware that medium radial truck tires are inflated to over 100 psi - many are higher - but they were designed for that. As a tire engineer, it is not surpising they burst at higher pressures, but remember, a burst test is not the same as an operating a tire at that pressure.
Passenger car tires are designed to operate in the 26 to 35 psi range, with the 44 and 51 psi being a permissible inflation pressure for certain operating conditions. Truck tires ttoo can be inflated above the maximum pressure on the sidewall - but under certain operating conditons, and over-the-road is not one of them!
Quote:
Originally Posted by JacobAziza
........The number is set not by the manufacturer or car maker, but by an independent organization that has permanent set standards based on tire size only......
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You have to be very careful how you say that. If by "the "number" you mean inflation pressure, then you need to look at one of those standards. Here is a page from The Tire and Rim Association's 2005 Yearbook for passenger car tires.:
Notice that the inflation pressure range is 26 to 35 psi. Those are the conditions that a passenger car tire is designed to operate against. These are the conditions a tire manufacturer tests against. They do NOT test outside that range.
Quote:
Originally Posted by JacobAziza
......It was set once, by law, and never altered (as far as I can gather from the DOT website) since 1948.........
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Sorry, but the DOT adopts the existing tire standards whatever they might be - not the other way around.
- AND -
The modern DOT regulations date from 1968 with recent updates. But they reference back to the tire standards like the page above.
Quote:
Originally Posted by JacobAziza
......I can't find any thing explaining what, if anything, the 'max' pressure ratings were originally based on - but it is clearly not anything to do with an individual tire's actual burst pressure, strength, or performance (since, as people here have pointed out, they aren't even tested at any higher pressure to see whether they preform better or last as long or are as strong).......
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So here is a page that explains where those numbers come from:
What you are looking for is the last thing on the page.
I am going to stop there are let all that digest a bit as I am sure there are going to be questions.