Spare Tires and Run-Flats

The spare tire is still called a Stepney in India, Malta, Pakistan and so on. It originated with the Davies Brothers (it’s weird that so many innovations come from brothers). But it’s not what leaps to mind when you think of a spare tire.

Cars started out as a luxury item. They came pretty stock and were much more likely suffer mechanical failure then even to have a wreck. Prior to 1898 car wheels were basically wagon wheels, which didn’t go flat. Because wheels were usually made of wood or iron it was hard to keep a spare wheel—its pretty heavy to carry around and could even make a car top heavy and unstable.

In 1898 Charles Goodyear created vulcanized rubber and began wrapping wagon wheels in rubber, with an inflatable tube in it, like a bicycle tire. Then in 1904 the Davies brothers, of the Stepney Rubber Co. in in Llanelli, Wales, imagined a spare tire. The tire simply clamped around your existing tire and then was inflated by hand pump. Much like a modern donut spare it was only intended to get you home, then needed replaced. The nice thing is that you didn’t have to jack the car up to put it on.

It was patented in 1907. They tried to sell it to the US by their ideas were unfortunately stolen.

After only eight months they sold about a thousand without having to resort to advertising. A version of the Stepney Tire can be seen in the British Museum.

Where to Store a Spare

Carrying an entire spare tire came about later and was instantly popular. Sometimes there were a pair of tires behind both front fenders, sometimes they were in the cargo space, sometimes above the engine itself.

Nowadays the tires are generally stored in a well, a recess in the trunk, sometimes with a bolt and wing but fastener and covered by thick cardboard. They might be stored underneath the trunk in a “cradle” which allows you to change the tire without emptying the trunk. Unfortunately. it’s no good for four wheeled drive vehicles as the axle will get in the way of the cradle. So most 4-wheel-drive vehicles mount the spare to the front or rear of the vehicle.

In the case of rear engine cars and mid-engine cars (such as the F type Jaguar) have the tire at the front.

Run Flat Tires

The latest innovation to keep you from being stranded by a tire puncture is called a run-flat tire. These tires fill the inside air chamber with a honeycomb of stiff rubber that prevents the tire from completely loosing shape when it losses air pressure. Most vehicles that have run flats still carry a regular spare.

The first run-flat tire was created in 1935 as a rubber tire with inner fabric tire designed for trolleys and commuter trains. It was used for military vehicles as it was said to be bullet-proof. It wasn’t until 1958 when the costs came down that Chrysler and Goodyear teamed up to create a suitable vehicle tire.

In order to check the tires properly you need to invest in a tire monitoring system. A run-flat tire that has lost pressure is hard to recognize. If you think the tire has been punctured, you should the vehicle to see if it’s safe to drive. It’s not clear how slow you should drive a car with punctured run-flat tires, Audi suggest 20-30 mph, while BMW suggest less than 50 mph. It’s a good idea to stick to the back roads.

Opinions seem to be divided on whether it should be repaired or replaced when the “sidewall” has been punctured. The probable route is that you will have to replace the tire as it’s hard to find someone to repair the tire.

Increasingly, cars are coming with a small spare tire, called a donut, which is not meant to replace the tire for any length of time. It’s more crucial to replace the donut if it’s in the position of power (the rear of a rear wheel drive, or front of a front wheel drive) as the donut will cause your differential to fail.

There seems no real alternative to the spare tire as yet…

What has truly killed the need for a spare is road-side assistance. Most people prefer to sit and wait for help, over getting out on a rainy night and changing a tire.

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