LOSS OF AIR

Evening Post, Volume CXVII, Issue 71, 24 March 1934, Page 17

LOSS OF AIR

LEAKS AND PUNCTURES

THE APPLYING OF A PATCH

•Provided the walls of the tires have not -weakened or their treads worn down excessively, the motorist seldom meets with two punctures in quick succession. He can, therefore, generally content himself with the spare wheel, leaving the ..repair of the damaged inner tube to the nearest service station. But those who tour in districts where public garages are few and far between should always carry one or two extra inner tubes and a puncture repair outfit. ' ■ :

111 the event of a blow-out or a puncture caused, by a large nail or otter sharp object the ■ tire' deflates suddenly, and there is no difficulty in tracing the source of the damage, but gradual deflation isoften deceptive and it. should not be assumed that the inner tube is punctured merely because the tire has subsided slowly overnight or during the.day's ran. The nipple of the tire valve should first' be inspected. A deformed or displaced washer in the head of the nipple, might have pressed down the plunger of the valve so that ttlere^is a slow but continuous escape of air. A. faulty valve "inside" is another likely cause. . It might be that the tire was inflated with a pump from whose attachment grit and dirt had not been driven by giving a few strokes with the handle before connecting .the pump, to the tire valve; so that a particle of grit lodges on the small valve seating,,-with a result that,:there is a slow leakage. Sometimes, too, the base nut of the tiro valve loosens so that the assembly is not a tight fit. When a tire has not'become deflated quickly it is often -worth while to reinflate it partially and. then test the valve by moistening a finger and smearing the valve orifice, when, if air is escaping, a bubble will form. Old inner tubes tend to become porous and there maybe a gradual drop in the inflation pressure not attributable to an, actual puncture For example, it often happens that if a well-used inner tube is inflated to, say, 351b, and the car garaged for,a few daysj the reading will drop to 251b or less.- ' ■ '" ■ '

If wayside repairs are necessary, certain precautions should be observed. After removal, tho inner tube should be carefully tested, preferably under water, to find, if the leakage is > from some part of the valve - assembly or from a puncture. If any perforation is detected, the spot should be marked with a pencil or by a scratch ..and the surrounding area carefully dried. The patch applied should be big enough to reinforce the tube in the neighbourhood of the puncture, but should- not be unnecessarily large. ■', A, vulcanised patch is naturally more satisfactory than one whic^i is merely cemented, but if the latter sort of patch is applied carefully it should withstand hard usage. ,The danger is that a'poor patch will lift when the tire becomes heatdd. ■>

When the area near the puncture is dry, the.. surface should. be wiped with petrol applied on a clean rag and then roughened with glass paper or the scraper, • which; will be found in most repair outfits. ' The cementing solution can be put on7"tsut it should not ;be applied thicKly andI'sh'ould always be

allowed to, dry for several minutes until .t becomes "tacky." To avoid any risk of greasiness, it is best to spread it with a penknife or match stick and not with a finger. Tho patch should be cut to size before its protective covering is peeled off and should then be pressed on the puncture. It is a good plan to stretch tho tube over some curved surface such as a mudguard so that it can be conveniently put on from the centre outwards; after'which it should bo weighted or clamped iv position for at least ten minutes while tho cement hardens.

Before a tube is replaced in a tire, a thorough inspection should be made to ■ see that tho original cause of the puncture has been removed, for frequently it happens that a deeply embedded nail or piece of metal which has not been noticed will soon puncture the repaired tube again.