Ariel Square Four
Undoubtedly, the most famous bike produced under the Ariel marquee was the Square Four. It was produced from 1931 till 1958. Its powerplant, effectively a geared together set of parallel twins, was designed by Edward Turner shortly after the future Triumph boss joined Ariel in 1928. The four's engine size started off at 500cc and soon was increased to 600cc and then 997cc. Often called the "Squariel", the powerplant was supremely smooth but suffered from overheating of the rear cylinders. Although the biggest model was capable of more than 100mph (160kph) it's performance was severely handicapped by it's excessive weight.
After WWII the Square Four was updated dramatically. First with a lighter aluminum engine, then in 1954, with a new cylinder head and a breathtaking four-pipe exhaust system. By this time Ariel had added telescopic front forks and plunger rear suspension. Despite all these marked improvements, the heavy Four was still a cumbersome handler. Even in its final sohpisticated guise, the engine was prone to overheating. But its redeeming factors of smoothness, comfort, and looks made the bike much treasured by those who could afford them.
1948
1954
1958
