If you’re a regular follower of CB-Net’s ‘Brill Biking Inventions’ you’ll surely know that – most of the time – we road bike riders get the positive trickle down from our friends in racing.
Yup, whether it’s the beam frame, disc brakes, powervalves or radial tyres, most of the hard work developing these things happens out on the race track as our very own ‘proving ground.’ And so it was with the monoshock.
Now, we still love our classic twin-shocked beasts of course, but most modern classics that we ride today have a single shock absorber and spring set-up connected to the swingarm at the rear of the bike: but how did this come to pass?
Well, many feel that (once more) it was Yamaha that started this trend, as they did with ally beam frames and powervalves, but the truth could be more prosaic than that… Why? Well, because it is thought that a Belgian engineer by the name of Lucien Tilkiens was helping out his son Guy who was racing off-road bikes in the very early 1970s. It seems that Tilkiens felt that his boy was crashing more due to the failure of the suspension and its twin-shock layout and how it reacted to stresses and strains as well as how it was linked to the bike’s frame, giving less suspension travel than was needed.
Being an engineer, he reasoned that it would be better if the stresses were transmitted through a single shock absorber, rather than two. Having designed and built a suitable system, Guy raced and developed the new layout in 1972 under the watchful (and covetous) gaze of Suzuki’s motocross GP team along with star rider Roger DeCoster.
Soon Suzuki and DeCoster were testing their own system and got Tilkiens involved in its development, but the rumour was that the Belgian was – quite rightly – holding out for some sort of deal from the Japanese giant. And, while Suzuki were pleased with the feedback they got from their own monoshocked machine, they were confused as to where the improvement came from as the new bike also had greater suspension travel at the rear, itself a result of using that single shock…
Legend has it that Suzuki kept Tilkiens hanging for around three months, by which time Yamaha had covertly approached the Belgian, secretly agreed on a deal and slapped a raft of patents on the system. Yamaha then revealed to the world ‘their’ new single-shock system called (drum roll please) ‘Monocross’.
‘Monocross’ clearly worked, taking Håkan Andersson to the 1973 250cc World motocross title. Old hands would say it was down to the Swede’s superior skill or the Yamaha’s superior power – but it was a championship nonetheless.
In suspension, it’s often the off-road which innovates while road-racing follows (think also inverted forks) and so it was with the monoshock. Once more, Yamaha had the patents and were quick to apply it to road-racing. In 1974 the OW-20 YZR500 was the first Tarmac racer to use the Monocross system. Smaller capacity race machines would soon follow as would road machines…
Out on the roads, we had to wait until 1980 until the first monoshock-equipped bike we could buy in the shops. Again, it was a Yamaha: the super-cool RD250LC. With the later release of the bigger 350 ‘Elsie’, in a flash, the likes of Kawasaki’s KH250 and Suzuki’s X7 (as well as Yamaha’s own RD400) looked old and dated…
Since then the monoshock has taken over and been used on most new machines since 1980 – apart from ‘retro’ styled modern classics, of course.
Interestingly, one notable engineer would persist with twin shocks into the early 1990s: step forward Brian Crighton. He was the lead engineer in the Norton race scene and later split to form his own, Norton equipped race team.
The ‘Roton’ or Crighton Norton, took on the Japanese AND the monoshock-equipped JPS-backed Nortons in the early 1990s. His main argument was that the single-shock’s proximity to the hot engine (the rotary was notorious for this) would lead to suspension performance not being linear or predictable as the single rear shock got hotter and hotter… Instead – he argued – it was best to have twin shock, hanging out ‘in the air’ where they could perform more predictably.
Was he right? Well, clearly in part… did you know that the last ‘twin shock’ British road-racing championship was won by a Crighton Norton (the Duckhams Norton team) in the hands of Ian Simpson in 1994?