The Birmingham age-herald., 1913-11-23

bumps which a fully inflated tire would
safely resist.
THE same condition occurs when a car
with its extras is not equipped with tires
large enough to properly support the load
and altho it bs properly inflated the
weight flattens it out where it rests on
the ground just as in the case of a tire
large enough but not inflated to the
proper pressure. The extra strain thus
imposed not only breaks down the side
walls but increases susceptibility to all
the various forms of trouble.
In the design of a bridge where the
factor of public safety is actively i'm
portant, there must be no possibility of
a breakdown. The strains and their COM
binations are carefully calculated. from
both theoretical and empirical data
When, in this way, it is determined that
bar quarter inch thick would be just
equal to the strain, bar an inch and a
half thick-six times the thickness ac-
tually necessary-is adopted. The extra
inch and quarter is a margin of safety
which insures the structure against any
unforeseen and unusual strain to which
it may be subject. The lack of this mar
gin of safety would be inimical to pub
lie welfare.
By the same token the tire which
gives good service, other things being
equal, is the one which not only pro-
vides the necessary strength to resist
the average strains but which also pro-
vides sufficient margin of safety also to
at times occur.
Proper attention to imitation will
usually insure good service For the man
who exercises care in this particular, bur
who is still unrewarded with the good
service usually returned by this precau-
tion, the solution lies in the use of the
oversize tire-the largest tire that fits
ooIa 1ifra pto ord CD oF
rim, there are two sizes of tire which fit.
Fors example, a 34x4 rim carries q 34X4
tire. Should the 34x4 tire, after the car
has been equipped with it's extras, PROVE
inadequate for the support of the load
the 35x41a tire which also fits the 34x4 rim
and is the regular oversize for the 34x4,
is the proper size to insure satisfactory
service. Also the 33x4 is the regular over
size for the 32x31A.
Usually. it is by experience that the
motorist discovers he has equipped his
car with tires that are too small. He
then desires to change to the regular
oversize tire for his rims. For making
this change, the manufacturer has pro-
vided every convenience. Not only does
the oversize fit the rim as perfectly
as the regular size, but it also takes the
same tube Tubes, like rims, are now
made interchangeable. Consequently the
change over to the oversize will not be re-
quire any changes or additions as to the
tube equipment.
'"rhe oversize tire contains 80 and 40
per cent more air capacity than the regu-
lar size. This extra capacity makes pos
sible not only more effective air
cushion to sustain the weight imposed,
but higher residence as well. An over
size tire naturally costs more than one
of the regular size because it is larger.
It's more effective air cushion however,
as well as the better distribution of
road wear because of its extra width,
insures still greater mileage in proper
tion to the initial cost. And so its use
decreases the cost per mile; and cost per
mile, rather tha3 cost per tire, is the
ultimate test of economy.
But its most important advantage re-
mains to be stated. Every motorist,
though he be peased with good mileage
at moderate cost, is still better pleased
Eif he can obtain this mileage without
tire trouble, and what is perhaps still
more important, with a feeling of conf
dence, engendered by actual experience,
that the possibility of trouble is SO re-
mote as to cease to be a factor. This
feeling of confidence, safety, and freedom
from trouble, as well as it's real economy,
is the advantage of the oversize tire