The First Mono Shock Rear Suspension

Front suspension has been commonly fitted to motorbicycles for the last 100+ years.  And some old bikes also featured rear suspension with one or two springs and a swingarm.  While Yamaha is remembered for their rear Mono Shock suspension, the idea was certainly not new in the 1970s.  30 years earlier, H.R.D. / Vincent had used a spring under the riders seat to provide travel to a swingarm pivoted on bearings behind the motor.  And Vincent did have some novelty to the design, but it wasn’t the first manufacturer to use such a layout.  In the years around the Great War, several bike featured rear sprung wheels.  The Matchless Model H used a design with two coil springs and a swingarm that would be very familiar to riders 50 years later.   Indian famously had their rear wheel sprung via two leaf springs.  But the use of a single spring, mounted centrally under the rider’s seat is what we’re after.  If you’d like to read about wheels with springs mounted inside them, click this link.

 

Flying Merkel had a very interesting rear suspension setup in 1909 using twin springs captive in the seat stays of the frame.  This one is a later version from 1913-1915 using only one spring unit under the seat.  Two struts take the spring force down to the rear axle, which mounts in a swingarm.  The pivot can’t been seen in this photo, but it is under the cylindrical oil tank.

 

Earlier, in 1910 the Perry Vale motorcycle, also known as the PV, used a swingarm that was sprung via compression and rebound springs that attached to the saddle tube.  The swingarm pivot was just ahead of the rear axle, so a small amount of wheel travel translated via the long lever arm to a big movement of the springs under the rider’s seat.  This photo is from the excellent book; Encyclopeadia of Classic Motorcycles by Richard Rosenthal of The Classic Motorcycle.  (It is the best old bike magazine in the world.  Buy a subscription!)  PV claimed to be the Pioneers of Spring Frame Design.  But if we travel back in time a bit further…

 

One year earlier, NSU introduced their version in 1909.  This one was restored by Stan Dishong.  So, by 1910ish, we have sprung frame swingarm motorcycles being made in the USA, England and Germany by multiple companies.  But did they all create these things in parallel?  Were they all independent inventors of the design, working without knowledge of the others?

 

The English BAT chose a slightly different route, and suspended the rider’s seat and footpegs on a subframe that was sprung via tension springs that allowed movement relative to the bike’s main frame.  Ixion wrote in his column that even the very best sprung seats still forced the rider’s legs to dance around on the rigid footpegs.  But the BAT rider could float somewhat above the undulations of the chassis.  It didn’t help to keep the rear wheel on the road surface, but it must have provided some comfort to a weary Pioneer rider.  This was a very interesting idea for the time, but it didn’t feature a swingarm…  (Another notable feature on the BAT is the magneto placed in the gas tank!  Be careful of leaks mixing with the sparks)

 

Still, we can go back further into the history of motorcycles and find earlier inventions for a rear swingarm:  The initials A.S.L. stood for Air Springs Limited.  And we can guess, they used pneumatic springs in their motorbikes.   Keeping the air in via the rubber seals was troublesome though, just as Dowty found out with their air spring front forks just after WWII.  Modern seal materials might allow for a good air spring system, but the ones used in the old days didn’t last very long.  Some books claim they introduced their very novel springing system in c1906, although the first reference that I have been able to authenticate is June 10th, 1908, with the following text in The MotorCycle, writing about the M.C.C. London to Edinburgh Run:

The competing machines represented almost every known make of motor cycle.  Several machines made their debut in open competition; the 4 1/2 h.p. A.S.L., ridden by Mr. A. Sharp, fitted with a 4 1/2 h.p. JAP engine, and possessing a distinctly novel feature for a motor bicycle, namely, a pressure fed JAP carburetter; the machine was also suspended fore and aft on Sharp’s patent air springs.

A 1913 advert for an A.S.L. single cylinder bike. 

 

We’ve traced the mono shock swingarm back to 1908, but Lurquin-Coudert offered a really nice bike in 1906 with rear suspension, but it was plungers, not a swingarm.  Still, that might be one of the very first plungers.  Here are two picks from the excellent French website  Z’humeurs & Rumors  and a link to the page.

 

And going back even further, to 1905 France, we have the Stimula.  Not much information is available on these bikes.  But they did feature a mono shock type rear suspension in addition to the early Traffault front end.  Here are two sides to a collector’s card that I found on eBay.  The bike is missing a few things (belts and pullies), but the suspension can be seen.

And that 1905 Stimula is the earliest bike that I have found that featured a solo rear spring and a swingarm.   Did it spawn ideas that were eventually modified and copied in the UK, USA, Germany and elsewhere, eventually even Japan?  Or was there an even earlier example?  I think that our readers may know of other early bikes that featured such a setup.  Please comment via the little Comment button and we’ll revise the article or write up a new one with any new content that can be found.

  

And of course we can dig a bit deeper and find that pedal cycles had suspensions in 1888, if not earlier.  Here is a Whippet, and an amazing step by step build up of a replica by Paul Brodie (he of the OHC Excelsior repops) can be seen at this link.

 

 

And while I was looking through old magazines, I found this great article from 1911.   Enjoy:

 

And a letter to the editor of The Motorcycle magazine, in which the writer describe the modifications he made to his Triumph to equip it with rear suspension.  It looks like the PV design, but using ASL springs.