So how much is too much tire psi?

AnthonyGS (Forum Supporter) said:

In reply to Toyman01 + Sized and :

Try 100 psi now or even 110 in a skinny bike tire.  

Some race tubulars can run as high as 180psi. Almost never recommended, but ~130 isn't unheard of on a velodrome.

This summer I had the oil changed on my E250 and the tech was checking the tire pressure and was alarmed by the 82psi (it was hot out), noting that's over the max of what the tire can handle. But that's exactly what the door jam recommends. These are LT tires and am carrying quite a bit of weight all the time.

Do I really need to be cross rotating the tires every 3k miles?! What a pain in the ass that would be.

This is pretty common. The pressure on the door placard is capable of the max load for the vehicle. Normally on 3/4 and 1 tons the recommendation is 80 in the rear. The problem is when the truck is unloaded or not towing you are running way more pressure than needed, so they ride poorly and in most cases wear the center of the tire out considerably faster than the rest.

A few manufacturers have a light and heavy load spec (dodge did for a short while and TPMS even worked) but most dont. So if you want the light off you pretty much have to run the door placard. If you want good tire wear drop the rears a little, and deal with the light, and air them up when loaded.

Also: as was said earlier. Lawyers.

We made another turn and almost rolled again. The Coupe de Ville is not your ideal machine for high speed cornering in residential neighborhoods. The handling is very mushy. . . unlike the Red Shark, which had responded very nicely to situations requiring the quick four-wheel drift. But the Whale -- instead of cutting loose at the critical moment -- had a tendency to dig in,  which accounted for that sickening "here we go" sensation.

At first I thought it was only because the tires were soft, so I took it into the Texaco station next to the Flamingo and had the tires pumped up to fifty pounds each -- which alarmed the attendant, until I explained that these were "experimental" tires.

But fifty pounds each didn't help the cornering, so I went back a few hours later and told him I wanted to try seventy-five. He shook his head nervously. "Not me," he said, handing me the air hose. "Here. They're your tires.  You do it."

"What's wrong?" I asked. "You think they can't take take seventy-five?"

He nodded, moving away as I stooped to deal with the left front. "You're damn right," he said, "Those tires want twenty-eight in the front and thirty-two in the rear. Hell, fifty's dangerous, but seventy-five is crazy.  They'll explode!"

I shook my head and kept filling the left front. "I told you," I said. "Sandoz laboratories designed these tires. They're special. I could load them up to a hundred."

"God almighty!" he groaned. "Don't do that here."

"Not today," I replied. "I want to see how they corner with seventy-five."

He chuckled. "You won't even get get to the corner, Mister."

"We'll see," I said, moving around to the rear with the air hose. In truth, I was nervous. The two front ones were tighter than snare drums; they felt like teak wood when I tapped on them with the rod. But what the hell? I thought. If they explode, so what? It's not often that a man gets a chance to run terminal experiments on a virgin Cadillac and four brand-new $80 tires. For all I knew, the thing might start cornering like a Lotus Elan. If not, all I had to do was call the VIP agency and have another one delivered. . . maybe threaten them with a lawsuit because all four tires had exploded on me, while driving in heavy traffic. Demand an Eldorado, next time, with four Michelin Xs. And put it all on the card. . . charge it to the St. Louis Browns.

As it turned out, the Whale behaved very nicely with the altered tire pressures. The ride was a trifle rough; I could feel every pebble on the highway, like being on roller skates in a gravel pit. . . but the thing began cornering in a very stylish manner, very much like driving a motorcycle at top speed in a hard rain: one slip and ZANG, over the high side, cartwheeling across the landscape with your head in your hands.