KNOW YOUR PRODUCTS
Off-Highway Tires:
Colossal Performer
Paul Bunyan wrought mighty acts with the help of
Babe, his whopping blue ox. Pecos Bill took a stick and dug
the Rio Grande. John Henry—out to beat the steam drill—
drove steel ‘till his hammer caught afire.’ And many are the
incredible doings of Joe Magyarac. The legendary facts of
such as these in American folklore are no more spectacular
than the actual deeds of real men today.
A few years ago, what could for all phases of construction
have seemed so impossible as a
monster which scrapes up and
hauls away 5,000 tons of dirt in
a day? Or a 120,000-pound
“crasher” which clears an acre
of dense woods in 20 minutes?
Monslers Wiih A Purpose
The mythical human giants
and modern-day earthmovers
are both products of imagina
tion—the difference being that
today’s engineers have an eye to
the future so they create “mon
sters” with a purpose.
Heavy - equipment manufac
turers can endow their creations
with almost limitless size and
speed. That’s where Firestone
comes in. It becomes the job of
development engineers to keep
pace. Firestone men design and
build the largest tires in the
world, and this is only the be
ginning.
In the late 1940s all giant
earthmover tires were capable
of full-load operation at top
speeds of five miles an hour.
Today, larger tires carry much
greater loads at speeds nearing
60, and this upward trend in
. both speed and weight is contin
uing.
Spectacular improvements in
off-road tires are due largely to
Firestone’s research policy of
considering each construction
job as a separate problem, and
designing or recommending a
specific tire for the job.
Long Time The Leader
Firestone has long been the
leader in producing special off-
road tires for unusual jobs. The
experience has given the com
pany’s products excellent ac
ceptance in both original-equip-
ment and replacement markets
Super Rock Grip
Wide Base
Ground Grip
Wide Base
5
Super Hock Grip
Deep Trsad
Rock Grip
Excavator
work.
With the large expenses in
volved in big construction pro
jects, the important thing to any
contractor is to have minimum
“downtime” in which a piece of
machinery is out of commission
because of breakdown. Many
contractors figure downtime
costs at a minimum of $50 an
hour per unit.
Firestone representatives try
to see that such losses are not
due to tire failure. The company
has earned a large share of the
heavy-construction market by
having teams of preventive-
maintenance men on the job at
big projects to see that off-road
tires are cared for properly.
Trucks and personnel for field
maintenance, and service men
run regular cold-tire pressure
checks in the field, checks
for punctures, rim damage on
tubeless tires, valve failure,
breaks and separation. When
contractors use Firestone tires
according to recommendations,
they get good service.
For every operation, company
engineers establish certain max
imum oases on load and speed
at which tires are expected to
run. In making recommenda
tions, they must consider; Tread
design; compounding; and cord-
body strength, determined by
the surface over which the tire
must run.
Stockpile Against Downtime
After the type and size of tire
required for a certain job and
unit have been determined,
service men keep a stockpile of
replacement tires on the site, the
number governed by expected
tire life based on the engineers’
estimates of: Job conditions,
speed, overload conditions,
wheel positions of tires, main
tenance record of tires already
in use, and amount of existing
wear left on them at beginning
of operation.
Firestone’s specialized knowl
edge has produced many sizes
and designs of off-road tires.
The largest production models
are included in the “earth
mover” class.
There are two basic types of
earthmover tires: Rock designs
and tractor designs. The rock
types are for operation on harsh,
abrasive terrain; the tractor
type, for loose dirt and mud.
Many contractors use rock-type
tires all the time because they
Function adequately on loose
Super Ground Grip Ground Grip
Plain Tread Roller Compaclor
UPROOTER—This 60-ton Le-
Tcurneau Tree Crasher uproots
large trees and heavy under
brush with the aid of Firestone
48-68 tires. The tires, 10 feet
high and 4 feet wide, may be
deflated to only five pounds
pressure.
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soil, and expenses of alternating
on different jobs are eliminated.
Change in earthmover tires
came when earthmoving equip
ment went to self-powered units
from drawn units pulled by con
tinuous - tread tractors. Tires
must now provide pulling trac
tion as well as lateral stability.
They also need to take higher
loads and more speed.
Engineers' Big Problem
Heat is the chief problem with
which the engineer is confront
ed. Deep-tread tires are made
ioi xough terrain, but they also
run too hot to be used for long,
fast hauling. For long-distance,
high-speed earthmoving over
smooth ground, tires with thin
ner treads are made-to-order for
greater heat dissipation. For best
cooling, the treads are grooved
where temperatures run hottest.
For earthmoving jobs, wide-
base treads are more in demand
today because of their higher
flotation and better traction.
The same qualities which
make for cooler running also
make for fewer hours of wear,
so a compromise must be made.
Main changes from conventional
design required for production
of a cooler-running tire include:
Use of cooler-running tread
compounds, reduction of tread
thickness, modified tread design,
and use of a larger tire for a
comparable load to reduce heat-
producing overload.
Among earthmover tires the
most popular models are the
Super Rock Grip Wide-Base and
the Super Ground Grip Wide-
Base. The Rock Grip is intend
ed for use on e.'^tra heavy,
powerful self-propelled scrap
ers, wagons and bottom dump
units in work on rough, rocky
and abrasive terrain. It is com
pounded of Firestone’s super
tough Rubber-X, and has a
nylon cord body, tread bars ex
tended into the sidewalls for ad
ded protection against cuts and
snags, and a larger crosr. section
for greater flotation.
For Units On Loose Soil
The Super Ground Grip is for
lighter types of self-propelled
scrapers, wagons and bottom
dump units in general earth-
moving on loose soil. There is
also a regular Ground Grip
model. Both ground-grip types
have the same major construc
tion features as the Super Rock
Grip, except for the different
treads to match soil conditions.
All have extra-wide, rugged
tread designs for top tire life
and traction.
Akin to the earthmoving tires
are the mining types, especially
designed for operations on steep
grades and very rough ground.
Most important among these are
the Rock Grip Excavator and
the Super Rock Grip Deep
Tread. The Excavator is design
ed for scrapers, bottom and rear
dump units, and wagons. It is
nylon-corded, has extra body
strength, and features double
thick sidewalls and heavy scuff-
ribs, with a chevron tread de
sign for positive traction with
minimum vibration.
The Deep Tread has a 50 per
cent deeper tread design than
the Excavator, and because of
the increased running tempera
ture of heavy tread, is recom
mended only for short hauling
at speeds under 25 mph. It is
made chiefly for rear-dump
units.
The Deep Tread is the lowest
cost-per-hour design in the in
dustry, if used at the specified
maximums under tough-earth
conditions.
Some For Building Roads
Roadbuilding tires are differ
ent from earthmover types be
cause roadbuilding calls for run
ning on soft dirt and paved
roads, although the greater part
of such work requires good trac
tion on loose soil and mud with
heavy equipment. Most often
used are the Super Ground Grip
and the Ground Grip models.
Super Ground Grips are entire
ly new, with a curved-bar tread
design that gives top traction
with improved cleaning, as well
as smooth operation at all
speeds. The Ground Grip has
straight bars, and is used mostly
for pulling power.
Roadbuilding tires are not
much larger than regular large-
truck equipment and are best
used on graders, industrial tract
ors and similar heavy machin
ery.
Unusual tires used in some
roadbuilding operations are the
Plain Tread Roller and the Com
pactor. These feature the same
Tire$tone ssjuws
SEPTEMBER, 1961
PAGE 3
high-quality construction fea
tures as all Firestones, but are
designed for grade-compacting,
in which they perform much the
same function as the old-fash
ioned steam rollers.
Both the Compactor and the
Plain Tread are ,’un at a maxi
mum speed of only five miles
per hour, and are used on self-
propelled compactors and rollers
in gang-loaded, staggered axle
positions, so that no ground area
is missed.
Whoppers Built On Contract
Firestone builds some giant
tires on contract. Largest in the
world are the size 48-68s in use
on Army Transportation Corps’
LeTourneau Overland Cargo
Carrier, known as the “Snow
Train.” This monster has 13
self-propelled cars and is made
to cross the ice, snow, mud and
marsh of Artie wastes in
Alaska, and to operate on the
Greenland icecap.
The Snow Train tire is almost
10 feet high and 4 feet wide.
Each one carries up to 15,000
pounds at only 10 pounds pres
sure per square inch, and has
10-ply nylon construction for
maximum flexibility. Tread
depth is only little more than a
conventional small truck or
automobile lire, yet the as
sembled tire weighs 1,441
pounds. The Snow Train Tire
achieves top flotation with more
than 10.4 square feet of tread
against the ground at all times.
More heavily-built, if smaller,
is the 36.00-41, developed for the
Army’s amphibious “Bare”, built
to unload offshore ships and
haul the cargo inland. This tire
is 9V2 feet high and 3 feet wide
aiid weighs 3,318 pounds. It
carries 80,000 pounds of load at
70 pounds inflation, and con
tains enough rubber to manu
facture more than 150 popular-
size auto tires.
People who have read ab^ut
Paul Bunyan will recall that a
woman once told the hulking
logger: What you don’t finish
will be done with machines.
That’s just what is happening
today—and Firestone tires are
playing a big part in it.
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A 41,000-mile network of multi-lane, controlled-access
highways will be completed by 1972. The project completed,
it will link every major metropolitan center in the nation.
Already, nearly 12,000 miles of highway built under the In
terstate ror»d program are open. Playing a big part in earth-
moving and roadbuilding will be giant off-highway tires by
Firestone. This article, one of a series, is the story of these
tires, to help you "Know Your Products".