Page:Popular Science Monthly Volume 90.djvu/126

 110

��Popular Science Monthly

��When wheels are out of alinement, as above, the con- dition illustrated at the right results, caused by improper adjustment of the steering apparatus or a bent knuckle

���At left: Fabric de- terioration and blis- tering of the tread resulting from neg- lect of two small cuts. Note the two prominent "knuck- les " or " bumps "

���Above: The result of running a tire too soft, that is, under-inflated. The waves of the tread are due to loosening

��one of the many excellent rubber prepara- tions supplied by tire makers and repair- men.

Taking Care of the Inner Tire

The inner tube is the air-container of a tire. Because it is very thin, very elastic, it must be protected by outer casing. It is evident that the casing will fail to act as an armor; that the inner tube will be cut, if pebbles and gravel work their way through an external cut. Cleanliness means tire- money saved.

An inner tube must not be too large or too small. If it is too large it must fold itself to fit the confined space within the casing. The rubber is sure to crack in the creases. On the other hand, if the tube is too small, it must stretch inordinately, which means that it soon loses its liveli- ness.

Tire manufacturers treat the inside of their casings with a white solution which prevents the tube from sticking to the fabric. Lubrication is always necessary. Talc, powdered mica, and soapstone should be used from time to time. But the lubricant must be applied evenly with a

��soft rag. Dumped into the case, it will merely collect at one point, where it will heat up and burn the rubber of the tube.

��Wheel Irregularities

Wheels that do not track, unevenly tighten- ed clamping-brackets of demountable rims, loose hub-disks, bent axles and bent steering rods, all lead to excessive wear on the tires. The front wheels of most cars are wider than the rear wheels by three-eighths to one-half an inch. A variation greater than this means that the wheels are out of aline- ment. The cause of wheel irregularities is generally to be found in a short or bent drag-link between the steering arms. Wheels can be tested at the branches of nearly every important tire manufacturer and at any garage. Since excessive wear may also be due to poorly adjusted brake drums or unevenly clamped demountable rims or bent axles and rods, do not content yourself with a mere test for parallelism.

Effect of Brakes

A car weighing over a ton, traveling at forty or fifty miles an hour, has about as much striking energy as a twelve-pound artillery projectile. Some disposition must be made of that energy when a car is Tires were not made Apply the brakes sud- denly while your automobile is running at high speed and the wheels will lock so that the tires are scraped along the road or pavement. You know what would happen to your trousers if you were scraped along in that way. A tread, thick as it is, can endure much, but it cannot withstand that. It will be ground off, and some of the fabric plies may even be broken. Locked brakes will not stop a car more quickly than brakes rationally applied.

Carelessness in driving against curb- stones may wear away the side walls of a tire. If the practice is indulged in too fre- quently, the fabric will be exposed and the

��stopped suddenly, for that purpose.

�� �