Car Tyre Technical Questions and Answers

The world of car tyres is awash with technical terms. You don’t need to know them but they sometimes come in useful. So try answering the following questions, each of which has only one correct answer. The answers are at the foot of the list and for those planning to scroll down and cheat - we’ll know what you did!

1: What is BS AU159f?

A: The British Standard for puncture repairs to car tyres.
B: The British Standard for puncture repairs to Australian car tyres.
C: A code to access holiday discount vouchers on the Internet.

2: What do the initials RWL stand for?

A: Reprogrammable Warning Lights.
B: Right Wheel Latitude.
C: Raised White Letters

3: What is an aspect ratio?

A: The number of attacks per bird experienced if you bend over in a chicken run.
B: The ratio of a car tyre’s height to its width expressed as a percentage.
C: The ratio of tyre pressure (in lbs per sq. in.) to tyre life (in miles).

4: What is a car tyre’s bead for?

A: Holding it on the wheel rim.
B: Keeping it in balance.
C: Threading on a string.

5: What is a butyl liner?

A: A rubber cruise ship.
B: A fine layer in a tyre that prevents sudden deflation if a puncture occurs.
C: A fine layer in a tyre that makes fitting it easier.

6: What is calendaring?

A: The method of assessing tyre wear per month.
B: Adding markings that denote when a tyre was made.
C: Part of the tyre-making process.

7: What is carbon black?

A: The measurable polluting content of a carbon footprint.
B: The marks left on a snooker table by the last ball to be potted.
C: A filler material used to make grey rubber into black tyres.

8: What is de-vulcanisation?
A: A process of mechanical and chemical decomposition that affects tyres.
B: The post court-martial execution of the first officer of the Starship Enterprise.
C: The final process in tyre manufacture.

9: What is a contact patch?

A: A damp chamois leather pad used with the electric chair.
B: The area of a tyre’s tread in contact with the road at any given time.
C: A place where you go to meet with business associates.

10: What is deformation?

A: An offence you can be sued for?
B: The flexing of a tyre in response to the forces acting on it.
C: The distortion a tyre undergoes during fitment.

11: What is an E Marking?

A: A marking all post-June 1997 tyres carry to show they comply with European requirements.
B: A marking carried by all post-May 1986 tyres to show they may be sold in Yorkshire.
C: A marking all post-July 1990 tyres carry to show their sell-by date.

12: What is a sipe?

A: A medium sized, skulking wading bird with short legs, a long straight bill and poor spelling skills.
B: A tyre-fitter’s contraction of the words ‘stand pipe’.
C: A narrow slit between two blocks in a tyre’s tread, designed to dispel water and enhance grip.

Answers
1A
2C
3B
4A
5B
6C
7C
8A
9B
10B
11A
12C

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

The Specials: Tyres for Unique Tasks

All car tyres may seem to be the same but they aren’t. Road tyres have different characteristics designed to maximise their performance for specific types of use. However, these differences pale into insignificance when you consider the different tyres offered for competition use.

Take rally car tyres. These must cope with a huge array of surfaces in innumerable different climatic conditions. In addition, rally car tyres usually have to be road legal and must last longer than racing car tyres.

Examining two types of rally car tyre in more detail gives an idea of how the various factors in the tyres interact. Gravel tyres have to clear away the top coating of soft dirt or loose gravel, just as car tyres must clear away rainwater. To do this, they have big, chunky blocks that are made of relatively soft rubber. This lets the tread’s blocks grip while protecting the reinforcing plies that lie beneath them. The tyre tread and carcass’s being rigid enough to resist tearing while being sufficiently elastic to return to their initial shape guarantee toughness and a long life.

Snow/ice tyres can boast an effective grip-enhancing addition. Some can have up to 380 carbide-tipped studs in their tread. This is tough on the surface beneath the tyre but the surface can be tough on the studs themselves. At 75mph, each stud hits the snow or ice 17 times…per second! The impressive part – other than that (most of) the studs are still present when the car stops – is that the car is running on a total of about 50 studs at any one time. The total area the studs offer is about the size of a postage stamp.

In some instances, the tyres have no tread at all. Such tyres are called slicks and are used in drag racing. ‘Top Fuel’ dragsters are the fastest and can reach 330mph in less than 4.45 seconds – the time it takes them to cover the quarter mile. Accelerating faster than the space shuttle launch vehicle or a catapult-launched jet fighter requires as much grip as can be found.

It’s common for all kinds of dragsters to do something memorable. The driver places the car so its rear tyres are sitting in two puddles of water laid down near the start of the drag strip. The driver then applies power, spinning the rear wheels in the water. The immediate result is huge clouds of rubber smoke and steam around the tail end of a car that’s standing virtually still at practically full throttle. Yet this isn’t for show. After a ‘burn out’ like this, the tyres’ tread surfaces are extremely hot and sticky – and therefore grippy.

Often, drag racing car tyres look distinctly soft as the car approaches the start line. This is unsurprising, as the tyre pressure used is around the 12 to 15 psi mark. Why so soft? For two reasons. Soft tyres give better grip but they have another benefit. As the wheels rotate faster, the tyres enlarge. This is like putting bigger wheels on the same car; drivers get a higher top speed from the tyres’ radial expansion.

As you can see, even from just these two forms of motor sport, specialist car tyres are essential. They do what’s asked of them and in doing so, they increase the performance of the car involved in whatever sport is concerned. Think about this the next time you find yourself believing car tyres are all the same!

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.