Feather-Bed Comfort for Motor Cars

A Consideration of the Growing Use of Balloon Tires

H. W. SLAUSON

OUR ancestors slept in feather beds—but they worked hard during the day. The present generation applies feather bed ease to its automobile equipment and rides in almost as great comfort over rough roads as that which marked the sleeping hours of our forefathers.

But the feather bed comfort now applied to automobiles is not obtained from geese, swans, or any other bird, but from the free air. In fact, about the only difference between a balloon tire and a standard tire is, that the former holds much more air than the latter.

We have really been using balloon tires for thirty years—but not on automobiles. When we were youngsters we had balloon tires on our bicycles, but we didn't know it. Actually, we were using more air per pound of weight carried on each bicycle wheel than the softest and largest of the balloon tires of today, when applied to automobiles.

In order not to sound too technical, we may measure the air-holding ability of a tire, not in cubic inches or in cubic feet, but in gallons—and it is said that, in recent years, many motorists, crossing the border line from Canada into the United States, know the exact capacity of their spare tires in liquid measure. Be that as it may, suppose that the normal capacity of each tire on your car is one gallon of air, and that in order to support the heavy load on the wheels, five gallons of air must be crowded into that space which normally holds but one gallon. To crowd so much air into so small a space requires effort, and the four excess gallons must be pumped in, with the result that your small tire is very hard. Now, if you have a tire with a capacity of two gallons and you crowd five gallons into it, you will have exactly one-half the pressure of the smaller tire, and your tire will be comparatively soft and easy riding.

This is the whole story of the balloon tire, and accounts for the wonderful cushioning effect and easy riding qualities of this latest addition to the luxury of our automobiles.

If the principle of the balloon tire is so simple, however, you may ask why it was not developed years ago. There are many reasons for the delay. I have already shown that the balloon tire principle had been applied early to bicycles. When automobiles were built, they were very much heavier than bicycles and carried greater loads; but tire manufacturing machinery had not been developed to build tires which were proportionately larger, and what the tires lacked in air capacity was made up for in pressure. Then, as tires were rapidly made better and better, manufacturers and owners alike became engaged in a spirited contest to see whose tires could be made to give the longer service. It was found that any excessive bulging of the tire seemed to separate the plies of fabric of the tire carcass and reduced its effective mileage. Consequently, tire manufacturers, in effect, said, "Ride on air, it is the best cushion known: but if you would have long life and good service from your tires, put in so much air that they will ride as hard as a rock." In other words, we could not have both riding comfort and long tire life.

Then you, the automobile owners, came along and said, "We want comfort and we don't want the car repair bills that hard tires impose on us. We are going to run our tires softer than the manufacturers' directions call for, and we are going to buy the tire that will give the best service when used in this way."

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The result of your threats was the development of the cord tire, which was more flexible than the old type of fabric tire, and which could therefore be run "softer" without damage to the tire. These tires were also made larger for the same marked size, so that they held somewhat more air. This was only a short step in the right direction, however, and it was not until a little over a year ago that the real balloon tire was first heard of. The idea of using so much air space that only a very low pressure is required, appeals so strongly to the average motorist that practically every automobile owner is now talking and thinking balloon tires—whether he is using them or not. The chances arc that he is not using them, however, for it will require many months of capacity production to replace even a part of the sixty million standard tires which are now in use.

The conservative automobilist will also naturally entertain some doubts as to the practical advantages of a seemingly over-night innovation. He may be convinced of the comfort obtained from the use of balloon tires inflated to only twenty or twenty-five pounds pressure, but he may well wonder if they will not have a tendency to puncture, and if so, what happens if the air should suddenly escape when travelling at a high speed.

LET us set your mind at ease on -Li these two points at once. It is true that the balloon tire is considerably thinner than the tire of the standard type—that is one of its advantages. Less thickness and strength is needed to retain air at twenty-five pounds pressure than at seventy-five pounds, and this thinner construction permits of greater flexibility, as we have already shown, with less wear. The low pressure makes the carcass so yielding, that it absorbs sharp projections and literally folds itself over and around those which would seriously injure a high-pressure tire; and, unless a nail be long and sharp, it will merely make a slight dent in the tire, and the load on the wheel will be carried by the portion of the tire which surrounds that nail and rests mainly on the road.

But, even if a nail should puncture the tire, there will not be the sudden escape of air that causes the rapid let-down or blow-out of the high-pressure tire. Air carried at low pressure docs not try to get out with the same energy as air carried at high pressure, and the flattening of the balloon tire will consequently be much more gradual. Furthermore, since a balloon tire is normally ridden "soft", the wheel will not drop through much more of a vertical distance than would be the case, were the car carried on fully inflated, standard tires.

While we arc on the subject of the supposed disadvantages or dangers of the balloon tire, we might point out the few actual objections to their use which we have been able to discover. Probably the most noticeable will be the increased difficulty in steering. The large balloon tire carrying air at low pressure will have over twice the surface contact with the road, and to turn this surface requires sliding a portion of it. To overcome this difficulty, the front tires may be carried at a slightly greater pressure than the rear, although the hard steering is principally noticeable when the car is running slowly and in "backing and filling" in a limited parking space. The new cars which are designed for the use of balloon tires as original equipment have specially-constructed steering gears which take care of this difficulty.

Another disadvantage, although one more annoying to pedestrians and occupants of other vehicles than to those who sit in the balloon-equipped car itself, is its mud-splashing and dust-throwing proclivities caused by the width of the rut which the balloon tire makes. This disposition of the balloon tire, however, can be turned to excellent advantage when negotiating mud or snow, for the width of its surface in contact with the road produces a snow-shoe effect which causes it to ride on top without the danger of becoming mired in the mud or stalled in the sand.

THE balloon tire is not absolutely free from skidding. It can be made to slide as easily as can a smaller, high-pressure tire—but possibly it will not slide as far on wet pavements, because the large surface contact with the road wipes dry a portion of it with a window-cleaning squeegee effect. The balloon tire, however, will hold its course better than the hard tire when taking a corner at high speed. There is thus less danger of side slipping, but the advantage of this feature should be used to promote safety rather than to make increased speeds possible.

But, when it comes to freedom from skidding or to quick stopping, put your trust in four wheel brakes. These apply their stopping effect to the entire weight of the car and not merely to the two rear wheels. With stopping effort applied to the front wheels as well as to the rear, the brakes on neither need be applied as hard as though the entire resistance would be applied only at the rear wheels, and in consequence sliding, slipping and skidding will not take place nearly so easily with four wheel brakes. Also, with double the stopping force available, a four wheel brake car can usually be brought to rest within half the distance of that required by a two wheel brake car under the same conditions. Obviously, an exceptionally effective contention is that balloon tires and four wheel brakes will reduce skidding to a minimum and shorten the stopping distance required.

The balloon tire is basicly the latest motoring luxury. You are accustomed to pay for luxury and therefore you may be pleasantly surprised to find that the ultimate cost of the balloon tire may be scarcely fifteen or twenty percent more than for standard tires having the same carrying capacity. The balloon tire is much larger than the ordinary tire, but a smaller number of plies is used in its construction and its manufacturing cost may be kept surprisingly low. Beware of the too-cheap balloon tire, however, for the very thinness of the walls makes the utmost care in manufacturing and design a matter of primary importance, if we would obtain our accustomed tire mileage. This accustomed tire mileage, by the way, may well be increased by the balloon tire, because the load carried by the wheel is distributed over a considerably wider area of contact, and the surface wear of the tire is less than is the case when distributed on a narrow ridge of the tire. We might liken the latter way to that of the pussy-footer who might walk around continually on the toes of his shoes and would wear that portion much more quickly than were he flat-footed and forced to distribute the weight of each step over the entire sole and heel of his shoes.