Semi truck tires
Semi truck tires, semi trucks are usually set with 3 axles, the
front axle having two wheels, and each of the two rear axles having a
pair of "dual" wheels on each side. The most commonly set semi
truck has 10 wheels. The cargo trailer usually has two axles at the rear,
each of which have dual wheels, there are usually 8 wheels on the trailer.
Although dual wheels are most common for most semi truck tires, use of
a single, wider tire on each axle is becoming popular, particularly among
bulk cargo carriers and other freight operators. The United States also
allows 2-axle tractors to tow two 1-axle 28-foot semi-trailers known as
a set, doubles or a set of joints. Some places also allow towing up to
three 28-foot trailers known as road trains or triples.
It is important to understand the codes on the side of the tires you
intend to purchase, especially if they are used commercial truck or trailer
tires. For example if the tire sidewall reads 295/75R22.5 then in this
case this low profile tire has a width of 295 millimeters. On Tall profile
tires the reading will be in inches like "12R23" where "12"
is inches.

The second number is the aspect ratio but typically on tall 90 and 100
series tires the aspect ratio is not shown at all as part of tire size.
The DOT number is broken down with digits one and two being the manufacturer
and plant. Digits 3 and 4 are the tire size code whereas the last 3 digits
are optional information fields. The last one digit of the last 3 digits
indicates the year the tire was produced. If the last digit here is 8
for example then the tire was manufactured in 1998. This would mean that
if you were purchasing this tire in 2004 it would be considered past it's
useful life and should not be used for anything more than a spare or backup
tire for emergency use only.
There are many safety issues associated with changing commercial truck
tires, with inflation amounts, and explosion warnings. I recommend that
100% of your contact with tires be jobbed out to a commercial specialty
shop and you eat the cost. Pay for this service. No matter how expensive
and beautiful your big rig tractor trailer is, there is only rubber between
you and the road and between you and an accident if not properly installed,
built, maintained, and inflated. Note all of this when purchasing semi
truck tires.
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