New-York tribune., 1918-12-22
Holds That Tire Initiation
Depends Upon Cars Weight
What the Casing Carries, Rather Than Its Cross
Section Alone, Is the Proper Index, Contends
MIR. Manierre-OversizeB Best Answer to Problem
To the Automobile Editor of the Trib-

To the Automobile Editor of the Trib-
une
SIR, In these days when many peo-
pie have become their own chauf-
feurs, and particularly in view of the
very large number of those who have
but recently become interested in the
automobile. the subject of tire sizes
would seem to be still very much alive.
Even at this late day one may see
we'll made tires plainly stamped with
a direction to initiate them to def !
mite air pressure, when as a matter of
fact the amount of imitation needed by
tire has little relation to it's cross
section. The question is wholly one
of the weight which it is called upon
to support
The tire perhaps most generally
used on medium weight cars has here
tofore been the 34x4. 1t is actually
best suited to a car which with it's
full load of passengers and equip
ment, oil, water and gas, puts a load
of $50 pounds on each wheel, or in
all about 5000 pounds. Under those
circumstances, with an equal division
of weight, sixty-pound imitation is suf-
hclent. Or, if it is a cord tire, it may
be somewhat less The rule is that
when the tire has lost fifth of its
air pressure it should be renewed.
This size of tire, however, has been
generally placed upon cars that with
their complement of passengers weigh
considerably more than 5000 pounds,
the result being, even with careful
driving, frequent tire changes by rea-
son of tube failures and punctures, and
even with careful driving a matter of
1000 or 5000 miles is the probable
limit of ordinary life for the tire.
A one-half inch larger cross section
of tire would have done away almost
completely with tire road troubles of
all sorts, would have reduced very
materially the air pressure required.
and would have approximately doubled
the length of life of the tire
For touring purposes five of the
larger tires, i. e. one spare, would
much more than equal a set of six of
the standard size. They would weigh
the same and cost substantially the
same money.
1t is just at this point that the Afri
can IN the woodpile is dug out. The
difference to the automobile maker
between the cost to him of the larger
tires and those which will just manage
to DO amounts to between $40 and $40,
and the great majority of manufacture
ers save this difference, to the disad
vantage of their customers. Very few
manufacturers have refrained from
his saving at the expense of their
clientele
In buying new car it is generally
safe to offer to pay the difference for
oversize tires and to refuse to deal
with concern which is unwilling to
make the proposed change.
-, IT the inner tubes and the inside of
powdered graphite the oversize tires
will remain so long on the rim that
the only trouble the owner NAV ex
perlence IS that from being so long.
undisturbed it may become frozen to
the rim, and this may happen even
when the rim has been painted with
mixture of shellac and graphite to
prevent it.
So important has the matter of over
size tires been deemed that in cut
ting down the number of tire sizes it
was carefully kept in mind. and each
OF the sizes remaining has been fitted
with q corresponding oversize.
occasionally warnings have been pub
lished against undernf1aton. At first
thought this might seem to be directed
at one who takes a 41s-inch tire.
plainl y marked to be inflated to 90
pounds, and runs it on an imitation of
so pounds. But the simple truth is is
that with a light car SO pounds NAV
be full imitation 1t is a question of
| how much the tire is flexed in its run
ming by the weight which it is carry
ing. The oversize tire does not in
crease the rolling resistance of the
car. 1t does not heat up by reason of
the smaller air pressure, because it is
fiexed only in proportion to it's size.
The oversize tire is not only more
quickly inflated to the required press
ure, but it remains much longer at
approximately its determined imitation.
The higher pressure succeeds in max
ing its escape and is at the same time
very much more difficult to attain. It
requires an extra good pump, with it's