OT - Rotations of a low tire?

carl mciver wrote:


The cage is to catch the split ring, not pieces of the tire.
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wrote:

Even tubeless tires (no split ring) are required to be placed in a cage.
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| > | > Even tubeless tires (no split ring) are required to be placed in a | > cage. | | Perhaps now, but not when I was in the business. | In any case, the discussion is about semi tires | which have a split rim that can do grievious | bodily harm if they pop out and hit you. I've | known of 2 people seriously injured that way, | and nobody injured by flying rubber.
If it was a long time ago, perhaps there was just bias ply, and now everything is steel belted, and they do deflate rather explosively. The rubber of course carries lots of steel wire with it, and for all those who've had wire brushes lose strands into your skin you get the picture. I'll agree that the risk on passenger tires is a lot lower, but there's lawyers everywhere, spoiling all the really cool accidents we can laugh about later.
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wrote:

I don't know when you were in the business. Tubeless truck tires have been around for 30 years or more.
Fact: Very few new big trucks have tube type tires (split ring/lock ring). Almost everything except roadable cranes have tubeless tires. Reason for placing the tubeless tire/wheel in a cage is to restrain the big pieces if one lets go.
More and more truck tires have steel body plies; not just belts. When one is run under inflated or flat, there is a tremendous amount of flexing in the sidewall. This flexing is just like bending a piece of wire until it breaks. Except in this case the broken or weakened wire is concealed by rubber. When the tire is inflated, as pressure builds the sidewall lets go in what is known as a zipper failure. A ragged rip in the sidewall that is parallel to the tread. It may be a foot long. That sudden release of air can send a tire and wheel flying.
Next month will mark 40 years in the business. Twelve with Goodyear and 28 for myself.
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Jeff
I wonder if it would be legit to consider the distance from the axel center to the pavement becomes smaller when the tire is underinflated. The tire is free to flex and scrub as it wishes. The important parameter would be the "rolling radius", wouldnt it?? The picture gets pretty clear if you'd allow the underinflated tire to get thrown off. Then it would really have to turn alot faster to keep up with the other wheel with the good tire.
Jerry
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On Thu, 18 Aug 2005 11:52:04 -0400, Jeff Wisnia

First, you have to realize that you can't pressurize a tire enough to not have some deflection when weight is placed on it. Even solid rubber forklift tires compress in the contact area.
Here is the data from a popular sized truck tire; overall diameter 40.84", loaded radius 19.20"; revolutions per mile 509; max inflation 110 psi.
Before belted tires, not just steel belted radials, but any belted tires, the tread of bias tires created a tread wave in front of the contact patch. And sometimes continued into the contact patch, depending on speed. This was caused by the arched tread having to assume the nearly flat profile of the road surface. The wave was simply tread rubber waiting to be compressed as it went through the weight bearing area. All this flexing heated up the sidewalls of the tire and the scuffing of the tread as the compressed rubber exited the compressed area caused the bias tires to not last long.
ABS brakes and indirect pressure monitoring systems have made it hard for hotrodders to put different size tires on the front and rear.
There is more to come as our government tries to protect us as we get dumber, read lazier. All 2007 model year vehicles under 10,000 GVW will have direct pressure monitoring. (The public will feel they are absolved of maintaining their tire pressure)
Each tire will have a pressure sensor mounted in the tire. Most are attached via the valve stem. Price? Between $175 and $300 each. Bumping a curb and breaking that non-replacable valve is going to be very expensive. Some high-end vehicles have them now. Corrosion is already a problem because of the brass, stainless, aluminum and steel components of the sensor, stem, core, nut, washer and wheel.
And what do we get for this expense? The law already passed states that the monitor must alert the driver when a tire is 25% below its recommended pressure. That in itself is absurd but the monitor has 20 minutes to determine if a tire is low and alert the driver. The law is pushed by auto makers and monitor peddlers. They want to be relieved of any responsibility such as the Ford Explorer rollovers. ( As an aside, the same Firestone tires were used on F150 pickups. Recall a rash of pickup rollovers? Me neither.)
Let's assume you have just checked the air in your tires at the corner self-serve-pay-for-air station. You were careful not to damage that valve, right? As you pull onto the freeway, you hit a piece of glass that cuts your tire. A cut that will deflate your tire to zero, not 75%, in 5 minutes. But it is 20 minutes before your high priced monitor comes alive. Another shredded tire, another irate motorist cursing the #&%* no-account tire. Or maybe, another casualty.
The Rubber Manufacturer's Association, several tire companies and many consumer groups have sued the feds to either require tighter monitoring (less pressure loss and quicker detection) or scrap the law until such is available. They feel a false sense of protection is more dangerous than no protection.
Changes you can expect. Who will check the air in your tires for free when exposed to the risk of $1200 of damage? Roadside assistance will no longer repair tires. They will mount your spare. But then who is responsible for reprogramming the computer to tell it where that spare is now. And what will it cost to repair the flat tire when simply taking the core out of the valve can cost $300? I'm guessing $30 to $50.
For this kind of money, I feel a system could be developed to inflate the tires while traveling. There could still be a caution light or whatever. Maybe with suspension height sensors to detect load and air regulators, proper pressure could be maintained constantly.
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Hummer has had a central tire inflation system for almost 10 years! All tires can be inflated or deflated at the push of a button. They can be inflated as a pair (front/rear) or all together. It also has alarms for high and low pressure.
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I'm not sure if this applies but on the newer Chrysler products they have a tire pressure monitoring system that works by having a transponder located in the valve stem. There is a sensor located in the fender.
If you are not familiar with transponders, they are common in several applications like injectable little pellets for dogs and cats that can be scanned to help a lost pet.
Newer cars also have them molded into the head of the key. if an unauthorized duplicate is made or the lock is forced the car will not start.
Perhaps the car in question had a tire pressure monitoring system.
--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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On Thu, 18 Aug 2005 11:52:04 -0400, Jeff Wisnia

This is about as plain as it can be. Jeff, would you hand out those DNRs for those who can't understand this?
http://www.desser.com/tech/centrifugal.html
Want more? Google for tire traction wave.
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On Mon, 22 Aug 2005 12:38:41 -0400, Jeff Wisnia

Yes, I caught that "behind" the tire thing also. I was positive I remembered the wave being in front of the tire. Dug into my notes; couldn't find the photo but found the notes. It was the right rear wheel of a 1962 Pontiac on a dyno. Perhaps the drive/free-rolling wheels are opposite. One other possibility is because the tire wasn't belted.
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