Steel belted radials appeared in the early '70s and quickly became the
standard. There were two other competing (if you can call it that)
technologies at the time: belted pias ply tires and unbelted bias ply tires.
The fuel economy saving of 10% would be over the unbelted bias ply tires.
The only things the bias ply tires had going for them were that they were
easy to make and therefore cheaper, at least back when. The spread in price
between basic bias ply tires and the comparable level of radial tire was
often more than half again as much. Now bias ply tires of any sort are very
rare, if they are made at all. The handling of bias ply tires was far poorer
than the handling of radials, and the way the tire squirmed on the road made
bias ply tires wear much faster and use your gas to scuff the tires.
All radial ply tires are belted to provide tread stability. Most are steel
belted, but there are some tires belted with exotic fibers. As the others
say, it is very likely your current tires are steel belted radials.
To you all,
I am serious, and I am not afraid to ask any questions (even it may
sound/seem ridiculous to you) that I have no knowledge, esp. the questions
are related to gadget which you guys have tons of knowledge.
I came from the country where a car is a symbol of wealth, a measure of
political power and that country is far behind the U.S. about 500 years in
Oh, by the way, thanks Mike and John for your detailed explanation.
Michael Pardee wrote:
Message posted via CarKB.com
Someone must have written that article 30 years ago. It is amazing how
living long enough lets one see the cycles.
In 1972 the most popular passenger vehicle in the US was a body-on-from
Chevrolet Impala weighing around 4,500 lbs. with a big V-8 and getting
around 12-14 MPG.
In 2005 the most popular passenger vehicle in the US was the Ford F150
weighing around 4,500 lbs. with a big V-8 and getting around 12-14 MPG.
In the 1970s the arab nations decided to use their oil supply as a
strategic weapon to hold the western world hostage and attempt to have
it's way visa-vis Israel. By the late 1970s you couldn't give away
that Chevy Impala. Will the same happen for the F150 and it's ilk?
How to get better fuel economy articles were all the rage and switching
to radial tires was one of the common suggestions. About.com seems to
have simply picked up some of that old information.
In the end the only thing which is going to change the oil consumption
habits of US consumers is for prices to go high enough. How high is
high enough? We shall see.
Your question isn't weird at all. I'm not sure how much gasoline
economy can be attributed to radial ply tires, but tire technology has
advanced a lot in the last few decades. Two features are prominent in
design advancement. Radial plies and belts on the inside and rubber
composition on the outside. This link will get you to a picture of a
radial tire showing these features.
Because the cords which strengthen the construction plies of the tire
run "straight" out from the center of the tire, around the outer
diameter and back toward the center on the other side, they are called
radial. This configuration reduces cross-cord flexing which keeps the
tire cooler when turning under a load and puts all the strain parallel
to the cords which is their strongest direction.
Radial side walls can be made thinner than bias because of the strength
inherent in the design which makes them lighter and more flexible.
Lower unsprung weight makes the vehicle handle better and feel more
If the wear surface of the tire (inside the tread) were not stabilized,
the tire would squirm and roll from side to side around the metal wheel.
Steel belts are laid down around the circumference of the tire to
provide this stability, add puncture resistance and improve tread contact.
In addition, tire rubber compounds are so much better now that it is
common to drive properly maintained tires more than 65,000 miles and
80,000 mile warranties are not rare.
One of the coolest things about radial tire design is that it allows
significantly smaller sidewalls. Bias ply tires used to be about 80% as
tall as they were wide. 70, 60, and 50 series tires are common today
with even lower profile tires available for higher performance.
If your tires have lettering on the side that includes a "R," like
195R60x15 or 225SR50x17, you have radial tires
Hope this helps. Happy driving
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