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market trends: Six gears are best

Car companies may be trying to reduce cost and complexity, but there is one area where there is no end to inflation: gearboxes.

A generation ago, the default gearbox had four gears if it was manual and three if it was automatic.

Ford did not introduce a five-speed manual until the 1980s and they did not become common on superminis until the 1990s.

Today you cannot buy a four-speed manual (the last one died with the original Mini in 2000) or a three-speed auto (the last one apparently fitted to the Suzuki Alto in 2006).

What is more surprising is that the five-speed gearbox could soon be overtaken as the default choice.

Since 2000, the proportion of cars fitted with six-speed gearboxes has leaped from 1.8% to 37.4% so far this year.

It fell back slightly in 2008 as the whole market downsized, but it is likely that six speeders will become the most popular gearbox within the next few years.

Even granny might have to get used to choosing between six gears –although she might do what lots of older drivers did 15 years ago and simply ignore the new top gear.

But what, apart from marketing, is driving this inflation (if you’ll forgive the pun)? Funnily enough, aerodynamics.

As cars first became more aerodynamic in the 1980s (e.g. the 1983 Audi 100 and Ford Sierra), their slippery shapes meant that they could pull a higher top gear, as less energy had to be expended simply shoving the air out of the way.

Before then, cars were often under-geared –they would have to over-rev slightly just to hit their top speed.

With a higher top gear, but the same first gear (after all, the car needed the same first gear ratio to get moving), there was a need for more intermediate gears. Today, the other factor is diesel engines.

With their massive torque, they can pull yet higher top gears and so yet more intermediate gears are needed.

Back in the 1980s a typical 2.0 litre saloon would pull 20 mph per 1,000 revs – today a 2.0 diesel can pull 30mph per 1,000 revs. With a top gear 50% higher it is no wonder we keep needing more.

However, the good news is that manuals have now reached their limit.

Most of us can handle gears arranged in three planes (first/second, third/fourth, fifth/sixth),
but with the four planes that a seventh gear would require, we would all turn into grannies.


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