Extreme Machines.

Memorable Motorcycles 1958 Ariel Square 4G.
Ariel Motorcycles were advocates of the four cylinder powerplant since 1930, with its unique Square Four.
Looking back at history through a rose-tinted visor is often a dangerous exercise. Yes, we did have limitless freedom when I was a kid - but we also had our house heated by one paraffin stove and my bedroom window was covered in ice - on the inside - for much of winter!

Although I am a proud Englishman, I try to be objective regarding the British bike industry and the truth is that much of it was a tribute to mediocrity. Appalling management, dire products and short sighted, militant unions all worked happily together to destroy British motorcycle manufacturing.


But in the midst of the chaos there were, occasionally, missed opportunities which still bring tears to my eyes. One of the best examples of what should have happened, but didn’t, was the untimely end of the Ariel Square Four.

Let me begin by telling you what it is like to ride a “Square Four”. No other classic bike - British or from anywhere else in the world - gets within a light year of the sophistication and elegant grace of riding the big Ariel. The sales tagline for the “Square Four” was: “Ten miles to a hundred miles an hour, in top gear.” And it is absolutely true.

1958 Ariel Square 4G
Ample power and small size made the 1958 Ariel Square 4G a pleasing experience.
The softly tuned, 1000cc motor produces only 42 hp - probably less than the comparable 650 Triumph of the day - but whilst the Meriden bike is all snarls, vibration and coarse power the Ariel is the epitome of gentility. Even today, there are few more satisfying motorcycling experiences than the magic carpet ride of the burbling, softly spoken “Square Four”.
Ariel had been advocates of four cylinder motorcycles since 1930 when the first “Four” was shown at Olympia. This had been drawn by Edward Turner, later of Triumph fame, and it was a neat, 500cc overhead cam design. In typical Turner fashion, there was nothing radically innovative about the motor but rather good, practical engineering. The engine was effectively two Parallel Twins linked together on a common crankcase. The engine was small and light enough to fit straight into existing single cylinder chassis.

Turner said: “'I wanted to provide a four-cylinder engine small enough for use in a solo motorcycle, yet producing ample power for really high performance without undue compression, racing cams or a big-choke carburetor. I was aiming at the ultimate reliability with the minimum of attention.”

In 1937, Turner’s engine was given a complete redesign by Ariel. It became a 1000cc motor - now with the valves operated by push-rod rather than OHC - but still combining the key advantages of the Square Four design: all the smoothness of a four-cylinder motor but with the width, and mass centralization of a Twin. With the firing order at 90 degrees, no classic engine got near to the smoothness which the “Squariel” achieved.

Finally, this motor became the iconic Ariel 4G with four exhaust pipes and all alloy from top to bottom. Not only did this engine function very well but it was one of the most beautiful motors ever to reach production.

Although Ariel always made good bikes, like many of the smaller British motorcycle manufacturers they were permanently under capitalized and lacked economies of scale. Take the magnificent Square 4 as an example. During the whole 26-year production run Ariel made only 15,641 examples of the bike - about the same as Honda were producing during the British factory’s morning tea break.
Ariel’s one big chance was to be taken under the mighty BSA banner - which they were in 1944. At first, Ariel were left alone to do their own thing but even BSA’s ultra conservative management must have seen that - the Square 4 apart - almost everything that Ariel produced was replicated in the BSA model line-up. Even worse, many of Ariel’s products were re-badged BSA products and were just as conservative as BSA’s dull offerings. Even the color schemes of maroon and black were modest in the extreme.

1958 Ariel Square 4G
The Ariel Square 4's odd rear suspension was delicate and required far too much maintenance.
This left the Square Four as the star of the range - but it was a star isolated in its own galaxy. The problems were numerous. In 1956, when every other manufacturer was using conventional swinging-arm suspension, the “Four” clung to the complex and expensive Anstey link which had been designed in house by Ariel’s Frank Anstey.


Theoretically, this complex system provided constant chain tension but this benefit was crushed by the lack of damping and its horrendous complexity. Ariel recommended greasing the numerous pins and bushes every 250 miles. Take a long trip to the beach with your girlfriend - and stop on the way back for roadside maintenance. How attractive was that?

Although the engine was sublime when it ran well - it often didn’t! The two rear cylinders have very little exposed cooling area. This causes them to overheat, warp the cylinder head and leak. Almost worse, the front two cylinders, being cooled by turbulent air caused by the Squariel’s generous front mudguard, also run white hot. Things are not any better with the induction system which threads its way through the center of the engine and causes the charge to run hot before it gets near combustion: hence the low power output for a 1000cc engine.

Finally, the gearbox was separate to the engine and was a special unit supplied by Burman. With miniscule sales, Burman were never keen to keep making the ‘box just for the “Four”.
This brings us to the bike in our test. In 1957, Ariel produced two Square Four Fs. These were modernized Four Gs and were intended to keep the Square Four alive. The bike we are showing is a faithful replica of the “F” model which never made production. Now housed in a swinging arm frame, the “F” model is undoubtedly the best looking of all the Square Fours - but was it too little too late?

The big Ariel’s needs were numerous. Yes, the concept is perfect but the 1000cc Four demanded water-cooling and it badly needed to be unit construction, to reduce its length. This would have given a huge leap in performance at which point the woefully inadequate brakes would have had to be replaced by much more powerful, twin leading shoe units. The crude front forks, which had only compression damping, would have needed upgrading. Was the mighty BSA empire ever going to give its adopted child this sort of tender loving care? Not a chance!

So why should you sell your first born son to own a Squariel now? Primarily, because, as I said at the start of this article, nothing gives such an imperial riding experience.

1958 Ariel Square 4G
The Square 4G is an admirable example of practical engineering.
Robin James Engineering, who are one of the world’s leading classic bike restorers have mixed feelings over the Ariel. Robin said: “We have done a number of successful restorations of the “Four” but we insist on fitting a high capacity oil pump. The Square Four’s cooling is simply ineffective and the only way to keep the engine at a safe working temperature is to use a high oil flow as a coolant.

“If the owner wants to ride the bike regularly then we insist on having an oil cooler fitted. With a high capacity oil pump, and an oil cooler, the engine will be reliable - but only if the bike is ridden sensitively.

“Care needs to be taken with the handling too. The Anstey link rear suspension and the basic front forks, combined with the Ariel’s weight, mean that the “Four” is no Manx Norton. It needs be ridden thoughtfully and with respect for its handling limitations.”

So, a sublime riding experience - but with a container load of challenges not the least of which are current asking prices. Expect to part with at least $15,000 for a nice Square Four - and another $10,000 on top of that for a stunning example.