Quote:
Originally Posted by CapriRacer
We're talking Federal Regulations here. I doubt we could change them, but if we could, I just know they
would not want to get rid of the pressure on the sidewall - plus, they absolutely would want the max load - ergo, referencing the load
table. It's the same for everyone including the government.
Well, that's the system we have now. On light vehicles (cars, pickups, SUV's, trailers), they have a placard that's supposed to be on
the driver's side doorframe.
For other vehicles, the government has been reluctant to get into the mess. Over-the-Road Trucks, for example, are ordered
special - that is every truck is individualized for the buyer - and that could mean a variety of tire sizes. For many trucking outfits, they
have a tire rep that helps with issues - and one of those is setting pressure.
Not exactly. The problem was an odd one: A combination of the tread pattern and a peculiar way of processing rubber (which is
probably what you were referring to.)
Don't fall for the trap others have fallen into - that the unusual pressure spec is somehow the reason for the failures. If Ford had
specified a smaller tire with a more common pressure spec, there still would have been failures. The problem would still be there -
and Firestone wasn't the only tire manufacturer with the problem - albeit different versions.
(1) Ah ....... No!!
A wider tire with shorter sidewalls does NOT require more pressure to maintain an even contact patch with the road. Even
contact with the road is achieved by careful attention to a thing called the tread profile - and chief among those is tread radius.
Those things can be adjusted regardless of the aspect ratio of the tire.
(2) You mean the Bronco II?
An interesting tidbit is that in 1989 I saw protypes of the Explorer operating at Ford's Naples Proving Grounds with Bronco II badging.
Shortly after that, the Bronco II was lambasted as being unsafe due it's high CG, narrow track, and short wheelbase - all of which
that replacement vehicle was supposed to address. But it was too late to fix the name, so Ford opted to change it to something
untarnished - hence the "Explorer" name that had been used in the past. In retrospect, it's kind of ironic.
(3) I think it is called the certification sticker.
Again, don't fall into the trap of thinking that an unusual pressure spec means that it is somehow faulty. Larger tires require
less pressure to carry the same load.
So when you go to compare pre-2000's Explorers to post 2008 Explorers, you will find something kind of interesting.
Prior to the Firestone recall in 2000, it was common for pickups, SUV's, and Vans regardless of manufacturer to be spec'd
with tires that closely matched the GAWR's. In other words, the tires were the limiting factor for payloads in these vehicles.
One way of expressing this is that there was no tire reserve load capacity.
But after 2008, the vehicle manufacturers added reserve capacity by going to larger tires and more conventional inflation
pressures. (It did not go unnoticed that there was prejudice towards lower inflation pressures!) And I mean more than just
Ford - GM, Toyota, Nissan, etc.
(4) Between 2000 and 2008 was the transition as vehicle manufacturers introduced vehicles that had bigger fenderwells to
accommodate the larger sized tires.
Why 2008? Because that was when the new laws concerning tire placards, TPMS, etc. went into effect. Some vehicle manufacturers
were quicker than others, but everyone met the 2008 deadline.
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Re: Tread pattern and rubber processing.
I see. I wonder if the specific tread pattern arrived by the partners(Ford / Firestone) on the project might have produced oscillation issues that slowly led to the separation of the tread from the carcass.
Where I now live, off a state highway, I hear the 'RO RO RO RO RO' of a knobby tread outside the window. I look, and sure enough its a SUV, pickup, or other such vehicle with monster 'knobby' tread tires going by!
1) Lower profile tire pressure and "tread radius"
The reason I made this assertion is because a friend of mine and I both have similar year Honda Accords of the same generation.
She has a 2009 base(LX) Accord, specifiying 215/60R16 94H tires @30psi cold. (I may be off on that speed letter though)
Mine is an 2010 Accord EX, specifying 225/50R17 93V tires @32psi cold.
My specific tires, and most tires currently available for my car, are 94V, since that OEM 93V has become a scarcer combination than hens teeth. lol
Searching through sites such as tirepressure dot com, I noticed a similar pattern, of car trim levels with wider lower profile tires specifying cold pressures 1-2psi higher than on trims with the narrower tires.
So then why are they doing that?
And also, I would appreciate more info, hopefully from you, regarding concepts of the "tread profile" and "tread radius" you mentioned.
2) Bronco II / Ranger as the starting point for Explorer platform.
Barry, on-line I have seen both referenced as such, adding to my natural confusion. And in reality, the Bronco II of that era(1980s) was just a covered Ranger!
3) Certification Sticker. I will search with that term. Not expecting miracles!
I even called it the "axle weight sticker" or "GVWR" placard - no dice on Google. The sticker itself does not have a name or part no. on it.
4) 2008.
So around THEN began the industry-wide transition toward the ridiculously wide tires and hideously huge wheels we now see on passenger vehicles from Sentras up to Sequoias.
I still maintain that something could have been done for brakes without resorting to rim and wheel sizes seen normally on 10- and upward - wheel trucks not that long ago.
I may, Barry, be alone in this regard: But I simply do not like the feel/handling on vehicles with such large wheels and low profile rubber. I have been (teasingly) referred to as "pizza cutter" for my preference for narrower, higher sidewall tires! lol