‘100 years later they are back to using design cues from BMW’s early days ’
‘The layout has remained true to the R5 from 1936’
clutter and allow greater airflow across the cooling fins. This was achieved by placing the camshaft under the crankshaft. Weight-saving aluminium was now also used for the barrels but with cast iron sleeves. The gearbox, meanwhile, was a new four-speed, three-shaft unit bolted onto the rear of the engine. During 1970, 12,346 examples of the /5 series were sold – the best overall production figures since 1955. Over the next 24 years, the 247 engine steadily grew in capacity until the R1100RS was launched, powered by the new R259 oil-cooled 1085cc engine.
Birth of the ‘oilhead’
The 259 ‘oilhead’ brought with it some big changes, most notably the use of fuel injection and fourvalve heads but there were other changes too. The central camshaft was chucked in favour two small camshafts that ran under the cylinders, operating the valve train via small pushrods – a set up that remained until the dual-overhead camshafts arrived with the 2010 ‘twin cam’ update. Even through the water-cooled update and into the ShiftCam, the general layout has remained true to the /5 from 1969. Until, that is, the new R18 arrived, which has cherry-picked various bits from their engine history, with a few modern extras, to create something really special.
In simple terms, not only is the styling of the R18 heavily based on the R5, the engine layout is also broadly the same. In the new R18 the crankshaft once again sits lower in the engine block, with two camshafts above acting on the valve gear, so the classic over-thetop pushrod tubes have returned. Interestingly Sepp Miritsch, Head of Air Cooled Boxer Series (who designed the HP2 engine) says half the reason BMW went to a single cam back in the 1960s was to save money. Unlike the R5 though, the R18 has four valves per cylinder, operating off two pushrods (a sort of R5, /5 and R1100 hybrid). It’s also a pioneer of new tech for BMW, with the fuel injectors placed in the head firing fuel straight past the intake valves into the cylinder for a cleaner burn. So there you have it. One hundred years of development and we’re back to using ideas from the 1930s. Some things just never change.