The Speedway Bike and How To Ride It
Following is a brief and simple account of how a Speedway bike works. For many years I was the Licenced Trainer at Oxford Speedway. I have also assisted Lew Coffin and Barry Thomas during their training sessions.
A Speedway motorcycle is both a simple and yet a complex thing. Those who have read the article on Ronnie Moore's Nightmare season will know the new replacement rear frame for his ESO was no good. To get some semblance of speed and control he was forced to use a damaged and much welded one. Situations like this still happen in Speedway and as far as I know there is not a satisfactory answer as to why.
In the early days ordinary motorcycles were used, stripped down for lightness. As the sport progressed success was dependant on having competitive machinery. By using a frame from one model, forks from another and the OHV engine from another model, Douglas made the first Speedway bike that sold in large numbers.
It is clear that the Douglas DT model had steeply raked forks and a long chassis. The steeply raked forks gave the front wheel grip, the long chassis allowed extravagant broadsliding in the leg-trailing style. Rudge followed, using their punchy 500cc four valve engine in a much braced frame with standard forks. The bracing was soon removed and Webb Speedway forks fitted. Again, these forks were steeply raked. The Rudge chassis was far shorter and allowed the foot forward style.
It is too complex to explain here, but forks with a shallow angle, like a chopper custom bike have great stability and do not wobble at high speed.
Bikes with steeply raked, more upright forks, as used on Speedway bikes give good front wheel grip but can wobble at high speed. Speedway bikes do not do high speed, so front wheel grip is the thing that matters. It is all to do with castor angle and what is known as trail. If a line is drawn through the headstock to the track surface and another vertically through the front wheel spindle, the distance between them where they meet the ground is measured. This is the trail or castor angle. A different angle for either the headstock or forks will alter this important measurement.
Over the years empirical experimentation has given the best range for this, but believe me, the search for a better frame and fork angle continues.
Other important issues is weight distribution, where the engine is mounted. The early bikes were soon replaced by those using the JAP Speedway engine. For many years this produced the most HP per pound of engine weight of any engine.
Weight - or lack of it - is a very important factor in a speedway bike.
Companies like Excelsior, OEC and Victor Martin were the largest suppliers of Speedway frames and complete bikes from 1934 to 1939 when WW2 stopped production. The frames used on these machines were dimensionally good but were of Brazed Lug construction, like road bikes and were quite heavy.
After WW2 Excelsior used up their pre-war parts and built some bikes. Everything was hard to get, rationing was in place for raw materials so new designs were hard to produce in quantity.
The basic design and dimensions were by now clear. To get a bike to slide on a loose surface steep forks, a short frame and a punchy and powerful engine set well rearwards were required. Improvements could be made by substituting lighter materials. The instigators were Australians who made all welded frames from lightweight bicycle or aircraft steel tubing. In the hands of riders like Vic Duggan and Grahame Warren they proved very, very successful.
Excelsior built a MK2 bike, not many were made. The tubing was heavy and the steering head was still a casting.
British builders started making lightweight frames, Mike Erskine perhaps the most prolific. His 'Staride' frames were really successful.
Mike Erskine's frames became the standard, the complete Speedway bikes sold in quantity and offered as a prize at the Wimbledon 'Internationale' meeting, the Rotrax Jap, were derived from Erskine's frames. A story for another day.
I was never a great rider - I never held a Speedway Contract - but I have taken a few scalps along the way and have the odd pot in the trophy cabinet.
The best description of how to slide a Speedway Bike is printed in 'Crystal Palace Speedway' by Lionel Crossley. I met the now late author, at Crystal Palace, when displaying the late Len Coles Douglas Dirt Track models.
Lionel tells of his early laps and how he got the bike to slide.
He said he gradually built up speed, shutting down less and less so as to carry more speed into the corner. He kept this up, little by little until he felt the front wheel lost grip and started to slide away. At this point he pulled the right handlebar back and gave it lots of throttle. In his words "This causes the bike to stand up a little and the rear wheel to slide out under power, tightening the turn of the bike. Once this point is reached throttle control can increase or decrease the radius of the turn. It really is as easy as that! On paper at least. On the track a bit different on a 50 HP brakeless bike weighing less than 200LBS! The skill, of course, is doing this with three other riders trying to win the race and staying aboard, but no one ever said it was easy."
Lionel is right. That remains the best explanation of how to induce a controlled slide on a Speedway Bike I have ever heard.
Even the latest 80HP laydowns work the same, and novices find exactly what Lionel found, get the front wheel losing grip, pull back on the right handlebar and whack open the throttle. The result is a controlled slide.
The big money, of course, is earned by those brave enough to take the next steps and push the limits further.
I can't tell you much about that, perhaps Tai Woffinden might.
This article was first published on 16th January 2022
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