INTRODUCTION
The series of articles in Classic Motorcycle Mechanics called the MIRA Files originated from an idea that had been germinating for a couple of months towards the end of 2000.
My archives of material from when I’d worked for Motor Cycle, the weekly newspaper, in the 1970s contained data from the performance testing I’d carried out at the Motor Industry Research Association’s proving grounds near Nuneaton in the Midlands.
While this data had been used to create the performance panels that were part of the road tests, there was much that hadn’t been used and more importantly hadn’t been put into much of a comparative context. So why not publish a series of articles that featured how the motorcycles of the 1970s, the lifeblood of Classic Motorcycle Mechanics and its readership, actually performed when they were new?
Editor at the time Bob Berry liked the idea as an extension of my previous contributions, and so the first of the series appeared in the January 2001 issue, featuring one of the most celebrated superbikes of the era, the Honda CB750 Four.
And the series continued, month by month, supported by pictures of the motorcycles of that period, providing an alternative insight into the classic period when the Japanese factories were becoming dominant in every sector of the industry. I’d joined Motor Cycle early in 1972 as a trainee reporter and amazing though that was to me – the office was in Fleet Street, centre of the newspaper world – it was even more dream-like to be getting paid to ride new motorcycles and report on their performance and behaviour.
I found that I’d stepped into a tradition for publishing road tests that were steeped in detail and supported by the use of rigorously-obtained performance figures. More to the point, these figures were measured in a way that offered repeatability, so that sensible comparisons could be made. If that sounds almost scientific, then that was probably the intention.
One of the mementoes from the period that I still have is the check list given to me by editor Harry Louis of the items that were necessary to be mentioned in every test report, right down to ease – or otherwise – of day-to-day maintenance.
In the 21st century, the most potent motorcycles have maximum speeds that are almost impossible for the average rider to achieve, and even performance testing them has its challenges even with the use of GPS and compact data gathering equipment. In the 1970s, the proving ground at the Motor Industry Research Association (MIRA) provided a huge expanse of test tracks including a triangular circuit with banked corners. For measuring speeds, we used the timing straight, 1000 yards long across which near either end were located pairs of light beams, which when passed through by a vehicle would trigger the electronic equipment in a tiny hut next to the middle of the straight.
It seemed like you had an immeasurable amount of space so that even at 130mph or more, most machines felt like they could be faster. It provided a tough testing regime in which you’d wind the motorcycle’s engine to the redline through the gears and hold it, flat out in a racing crouch, until it was necessary to slam on the brakes to avoid ending up in the sand traps. Weak clutches and braking systems would be exposed.
The repeatability of the figures came from measuring the top speed and acceleration in both directions, the ‘mean’ top speed being an average, that I found to be pretty accurate despite variations in wind speed. That tradition had come from the days after the Second World War when MIRA was set up in 1948 at the former aerodrome of RAF Lindley to provide research and development facilities for the British automotive industry. Factories could become members of the association, as did the motorcycle manufacturers of the day, and so did Iliffe, the publisher of The Motor Cycle, to exploit the facilities. From the style of the road tests from the early 1950s it’s clear that the performance was assessed at a test strip, which was more than likely to be MIRA.
One of the joys of being at MIRA was that you’d meet up with the factory testers from Norton, Triumph and Dunlop who were the hardest and most skillful riders I’d ever met, not to mention having the sharpest of wits. After leaving Motor Cycle at the end of 1978, I moved to Which Bike?, the monthly magazine where I angled again to get access to the facilities at MIRA. During the 1980s, speeds of the superbikes increased to more than 150mph so it was necessary to use the nearby parallel straights with 70mph connecting curves at either end.
They had no timing equipment so the early radar guns were used. In time the timing straight at MIRA became irrelevant for testing even 600cc motorcycles that could reach 160mph or more, and other locations such as the two-mile straight at Bruntingthorpe in Leicestershire provide the space. Since 2001 the facility has been called MIRA Ltd, and the operations are a £-multi-million business that mostly offers its members design consultancy although the proving ground gives a range of conditions for testing.
The timing straight is no more, though it returns to me as a vivid memory whenever I hear a skylark like those that would rise from the fields between the tracks, singing its plaintive song as a motorcycle crackled and pinged while it cooled in the summer heat. I like to think the MIRA Files series is a valuable invocation of those classic machines from the 1970s and 1980s.
And now that the series is in its 11th year the time is right to reproduce them in a book. I hope you enjoy it. - John Nutting
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132 Pages | Edited by Steve Rose | 
