Car Myths

I have ceased to be amazed at the “myths” that surround cars. Here are a few...

Cars are most economical at 56 mph.

This myth stems from the old way of measuring a car’s fuel economy, where manufacturers were obliged to produce fuel consumption figures for the Urban Cycle (running the car from rest up to 30 mph), at a constant 56 mph and at a constant 75 mph. Consequently, some manufacturers deliberately tuned fuel injection systems to “lean out” the fuel:air mixture to coincide with this speed in top gear, so as to produce good Government fuel consumption figures.

However, this merely flattered the economy figures at this speed (or, between 50 and 60 mph). It does not mean that 56 mph is the most economical speed.

Generally speaking, in any one gear, fuel consumption is proportional to the vehicle’s speed. The general rule is that the higher the engine revs, the higher the fuel consumption. However, at very low engine speeds, this is sometimes reversed, because you are labouring an engine. You may well find that fuel economy at 30 mph in top gear is noticeably lower than using fourth gear, or perhaps even third. Or you may well find that the car is more fuel efficient at 40 in top than 30.

Power steering makes a car handle better.

This is, for the most part, nonsence. Powered steering helps the driver chuck it about - ordinary steering can weigh up so that it is very heavy when cornering at high speed - but it does not, in itself, magically improve the grip from the tyres. Indeed, if anything, one could argue that power steering can isolate the driver from the road conditions - not all systems tell the driver that there is an absence of grip, for example.

Some models available with or without power steering have additional suspension changes between the two cars. This can change the car’s handling a little, but is usually more associated with the steering feel.

Lowering and stiffening a car always improves the handling

This is a very broad, sweeping statement to make, and it’s not always true. As a disclaimer, lowering and stiffening the car usually improves things for many cars, for at least some of the time. However, combining modifications to the suspension together with larger wheels wearing lower profile tyres can have quite a dramatic influence on the car in question.

The technicalities are detailed, probably rather dull, and certainly beyond the scope of this document. As you progressively lower and stiffen the car, so you make the ride harsher. If care is not taken with suspension settings, the car can become too firm, which in turn can reduce grip on a rough road as the wheels lose contact with the tarmac. Given that most entertaining roads I know also happen to be rough, bumpy, hilly and twisty, a standard car can often be a better drive.

The car designers have invested a lot of time, effort and money in to the suspension settings of a particular model. A poorly designed modification, which reduces the ride height without any other adjustments, can upset things.

CDs jam speed detection radars.

Who thought this one up? Have you ever seen a car with a CD either pressed up against the windscreen, or perhaps mounted in front of or behind a grill? And if you have, ever wonder what that CD is there for?

Well, the story goes that it’s there to confuse speed detection equipment. Unfortunately, this is utter, utter nonsence. Speed detection radar and laser systems work on the dopplar system - that is, the system knows the speed of the radar or laser wave, and it measures the difference between the return signal and what it expects. If the target is coming towards the radar, the returning electromagnetic waves will be at a higher speed. If it is moving away, the returning waves will be slower. The system calculates the speed of the vehicle by measuring the difference between the expected and the actual return speed.

A CD, mounted vertically, will present an excellent target for radar and laser beams (rather than the curvy, or angled, bonnets of most cars). For the most part, it is the number plate that provides the strongest return from a radar gun. The CD will also provide a strong return, but it won’t bend or distort the electromagnetic wave!

Fitting wider tyres means I can corner quicker

Under optimum controlled conditions (smooth, dry tarmac) this may well be true, but there are many more factors and variables in determining a car’s grip. As far as tyres go, a wide, cheap quality tyre may well provide less grip than a smaller, but better quality one. Tyres also have different designs and wear rates: the softer the rubber compound, the faster their growth rate.

However, under less-than-ideal conditions, it’s entirely possible that a wider wheel and tyre combination will provide less grip. The lower the pressure on the road (pressure being a factor of weight and area), for a given tyre design, the more likely the car is to aquaplane.

Driving a Ford Ka does wonders for your pulling power.

Oh, hang on, it does!