Calgary's Ethan Barkley made history at the CMDRA's most recent round at Mission Raceway Park, becoming the quickest Canadian Pro Street racer in history after a 7.505-second quarter-mile lap at over 187 mph.
The cool, dense sea level air at Mission combined with a smooth sticky racing surface allowed Barkley to finally begin turning up the boost on his turbocharged Suzuki GSX-R1000. Out of the box in early testing Saturday the bike ran a nice clean 8.0 at a mere 170 mph with a mild "off the trailer" tune. After a soft 7.7@185 in the first qualifying session, Barkley made some slight chassis adjustments and the engine tune was left the same. The Gixxer, dubbed 'Eleanor' shot off the line with the front tire hovering above the track. The result was a historic 7.505 @ 187. Barkley couldn't go quicker in the final qualifying session.
Monday, 20 August 2012 14:58
(BOWMANVILLE, ON – August 17, 2012) The championship titles will be up for grabs as racing at Canadian Tire Motorsport Park’s final major event shifts to the two-wheel variety when Canada's top motorcycle riders compete in the Superbike Doubleheader Weekend, August 24-26.
Headlining the weekend is the Mopar Pro Superbike class, where seven-time champion Jordan Szoke will look to claim an unprecedented eighth national title.
The Brantford native, who is riding a BMW Motorrad S1000RR this season, has now won three consecutive races and holds a commanding 66-point lead in the Championship standings heading into the season-ending doubleheader at his home track. A race win is worth 50 points and there will be two full points races this weekend.
Friday, 17 August 2012 14:19
In my last couple of blogs, I've talked about trail and how it changes as a motorcycle moves about on its suspension or leans into a corner. Trail gives a motorcycle its steering characteristics; in general, more trail is better for stability while less makes steering easier. Combining what we know about static and dynamic trail, and what changes affect each, it's possible to make subtle adjustments to improve rider feel and feedback in almost any given situation.
When a motorcycle is turned into a corner, there are a number of forces acting on the front end that are, in effect, trying to steer the motorcycle for us. Tony Foale's book "Motorcycle Handling and Chassis Design: The Art and Science" goes into the details of each of the forces, which include slip angle, camber thrust and longitudinal forces, but what we are concerned with here is the net result: oversteer, understeer or neutral steering. In an ideal world, these forces sum to zero and the rider never has to input a steering correction, no matter the speed, lean angle or pitch - the bike falls into a turn under braking, holds a perfect line in the middle of the corner with no input to the handlebar, and lifts from full lean of its own accord under acceleration. But the reality is that the rider has to intervene in many cases; the bike may have to be forced into a corner under braking, the rider may have to exert a constant pressure on the bar to hold a line or physically lift the bike out of the corner.
In many cases, it's rider preference that determines the goal regarding steering characteristics. Manufacturers generally design street bikes to give light, neutral steering and good stability in a wide variety of conditions. But some riders are willing to sacrifice that stability for low-effort steering quickness, while others prefer to use brute force and need more stability to do that. Additionally, deviating from stock components can quickly upset that balance the manufacturer worked so hard to attain - simply replacing stock tires with a grippy set of race tires that have a different profile changes how all the forces on the steering interact, in turn upsetting feel and feedback.
Here is where static and dynamic trail, and the differences between the two, becomes important: Small adjustments in trail can affect how those forces acting on the steering combine, altering feel and feedback to the rider and changing the steering/stability balance. And by making specific changes that affect only dynamic trail, those characteristics can be affected in very specific circumstances. For example, when a motorcycle is generally unstable or turns too easily, usually only static trail needs to be adjusted - a change accommodated by adjusting ride height or triple clamp offset. But if it's a problem only when the bike pitches on acceleration or braking, dynamic trail can be changed through fork springs, oil level height or the rear suspension linkage. Changes to how the bike acts in steady-state cornering can also be made by altering dynamic trail; this would be accomplished by changing tire profile, either through more or less pressure, a different tire, or a wider or narrower rim.
There are so many combinations and variables that it's easy to get lost when making adjustments that - intentionally or unintentionally - alter static or dynamic trail. But knowing exactly what those different adjustments actually change and how those changes affect handling is the foundation to understanding motorcycle setup.
Thursday, 09 August 2012 15:18
It seems like just the other day I was bragging to someone about how amazing it is in China. Heck, the few rules that they did have in place were not even enforced. A good way to describe it is probably like “The good ‘ole Days” that our parents always told us about…except with scooters and 200hp Superbikes at our disposal!
Monday, 30 July 2012 09:00
In my previous blog, I talked about how rake and trail change as the motorcycle's suspension moves through its travel. But I also alluded to the fact that trail changes as the motorcycle leans from side to side. This is something non-intuitive, but a very real factor that must be considered when discussing handling. Vittore Cossalter's book "Motorcycle Dynamics" goes into comprehensive detail with several pages of equations required to calculate trail based on a long list of variables.
One important distinction that Cossalter makes is between mechanical trail and normal trail. In general, when we discuss trail we are referring to mechanical trail - the distance the front tire's contact patch "trails" the imaginary point where the steering axis (drawn through the steering head) intersects the ground, as mentioned in my last blog. But where mechanical trail measures that distance along the ground, normal trail measures perpendicular (or "normal") to the steering axis and is a better indicator of what the rider actually feels and experiences through the handlebars. The difference between the two measurements is subtle, but must be considered in conditions where the motorcycle is leaning.
Cossalter's formulae take into account the usual factors that determine trail - triple-clamp offset, rake and front tire diameter - but then add a number of other variables: front and rear tire width and profile, wheelbase, lean angle and steering angle. As the motorcycle leans and steers into a turn, the front tire's contact point moves in relation to the steering axis an amount calculated from those additional variables. Crunch the new contact point into more equations (15 in total) and you get results for mechanical and normal trail. The combinations of variables are almost endless, but there are some interesting trends that can be seen from graphs of the data.
In general, Cossalter summarizes, mechanical trail and normal trail decrease with more steering angle. As the motorcycle leans into a turn, mechanical trail increases, but normal trail decreases. From the rider's point of view, steering becomes sharper and lighter, with less stability, at increasing lean and steering angle. Consider a typical middleweight sportbike: mechanical trail is approximately 100mm, with a normal trail of approximately 110mm - slightly more than the mechanical trail. When the bike is leaned at 45 degrees in a turn that requires a few degrees of steering input, mechanical trail increases to roughly 120mm. But normal trail <i>decreases</i> to almost 80mm, a significant reduction.
One other aspect to consider is that the contact point of the front tire also moves as the bike goes over a bump or through a dip in the pavement. As an extreme example, imagine running your bike up a curb; the front tire's contact point goes from its usual spot (on the road) to a point far forward (on the curb) instantly.
A large bump or deep depression can reduce trail significantly, and a large dip at the entry of a turn can bring all these aspects together: the front suspension is compressed, reducing trail. The front tire's contact patch moves forward, further reducing trail. The bike is leaned in the turn, with the steering angled in - yet even more trail gone. It's small wonder that those scenic tracks with multiple rolling hills can quickly turn a sharp-handling machine into a wobbly mess, and almost all my setup notes over the years show correspondingly more relaxed settings with increased trail at hilly tracks such as Atlantic Motorsport Park or Mid-Ohio, compared with more aggressive settings at flatter tracks such as Shannonville.
Friday, 27 July 2012 10:03
In two conversations I had this week, the topic of dynamic geometry came up, and how trail changes as the motorcycle pitches and leans its way around the racetrack. In the first conversation, I was talking with Bernie Broderick about his and his son Javelin's adventures at the Barber Motorsports Park AMA round. They had changed to stiffer fork springs in their Yamaha R6, and after the change it was difficult for Javelin to change direction in Barber's transitions. What happened?
Most riders are familiar with the basic geometry characteristics of rake and trail. Rake is the angle of the steering head with respect to vertical, while trail is the distance the front tire's contact patch "trails" the imaginary point where the steering axis (drawn through the steering head) intersects the ground. In general, it's trail that gives a motorcycle its steering character and what we feel through the bars when we ride. Trail is dependent on rake, front tire diameter and the offset from the steering axis to the front axle. More trail usually gives better stability and heavier steering, while less trail tends to reduce stability but make steering lighter. Rake and trail measurements published in specification sheets are static numbers, measured or calculated with the motorcycle at rest and with a fixed load.
But a motorcycle is not a static piece of machinery. As the front and rear suspension compresses and extends, rake - and hence trail - can change significantly. On most sport bikes, an adjustment in front or rear ride height of 4mm will change trail by approximately 1mm, a change that an experienced rider can feel on the track. Ride height can be changed by raising or lowering the fork tubes in the triple clamps or changing the length of the rear shock or a rod in its linkage. Your front and rear suspension moves through much more than 4mm of travel, however; if the front suspension is fully compressed and the rear fully extended - as is the case under heavy braking - trail can decrease by as much as 30mm from static, a huge amount.
Note that even adjusting preload will change ride height, in turn changing trail on the track, and many riders attribute the result - lighter or heavier steering - to softer or stiffer suspension, when in fact it is the geometry that has changed and is affecting the steering. Going a step further, changing fork or shock springs also affects ride height when the bike is underway. But whereas a preload change affects trail uniformly through the suspension's travel, a spring change has an increasing affect. A stiffer fork spring may compress just a few millimetres less than a softer spring near the top of its travel, but the difference will be much more pronounced - with a correspondingly greater change in trail - further down in the stroke.
In the Brodericks' case, substantially stiffer fork springs made a significant change to ride height and trail on the track. The solution? A spring change is usually accompanied by an adjustment in preload or oil level, so that the desired geometry at a certain travel is the same as it was before the change. And this leads to the second conversation I had this week about dynamic geometry: Using suspension potentiometers and a data acquisition system, we can generate a math channel that plots dynamic rake and trail, and see exactly how they change when adjustments to the suspension are made. It's important to remember that changing one adjustment in your setup can affect may other settings, and these must be taken into account with each step in the process.
Thursday, 12 July 2012 13:01
When your entire trip is full of highlights, how do you write a story that fits onto just a few small pages? Jordan Szoke does his best to describe an unforgettable Rocky Mountain adventure — in 2,000 words or less.
Wednesday, 04 July 2012 10:27
In the current issue of Inside Motorcycles, I wrote about the 2012 MotoGP bikes and touched on chatter and chassis flex. I addressed chatter in my previous blog, and will go into more detail about chassis flex here. Chassis designers have long known that some flex is a good thing as it acts as the motorcycle's suspension at extreme lean angles. With tires getting grippier and wider over time, motorcycles are getting increasingly more lean angles and the importance of chassis flex increases accordingly.
Incorporating flex into a chassis is not easy, as strength and stiffness are still desired in some directions while flex is advantageous only in certain directions. Typically, manufacturers express chassis rigidity in three ways: vertical, lateral and torsional. The chassis is generally desired to be stiff vertically, to absorb braking and acceleration forces, while some flex is desirable in the lateral direction to act as suspension. Torsional stiffness keeps the wheels in line, but some twisting can also translate to lateral movement at the contact patch. Yamaha published a graph showing the M1's changing chassis rigidity over the past few years, with vertical stiffness increasing and lateral stiffness decreasing - just what you would expect as tires get stickier and the bikes lean further.
Changing flex can be accomplished in subtle ways. For example, the top triple clamp of the GP12 Ducati Desmosedici shown here has slots that allow the forks to move from side to side. The Yamaha M1's top clamp is similar, and the Suter BMW takes this to the extreme with just a small amount of material connecting each fork tube to the steering stem. Teams constantly experiment with fork tube inner and outer diameter to find just the right combination of stiffness under braking and flex while cornering.
In the frame itself, there are almost infinitely more variables. The height and width of the spars or individual tubes, and the material and its thickness, help to determine how much the frame flexes in each direction. The engine mounting design determines how much the engine itself contributes to stiffness in each direction. And even how the individual components are welded together can make a difference. Most teams machine each part of the frame - even the spars - from solid pieces of aluminum; four or five machined pieces welded together requires less welding and gives more consistency than a collection of extrusions or stampings.
At the back of the bike, the swingarm is usually constructed in a similar manner - individual components machined from billet aluminum and welded together - and it's here that some development has been concentrated over the past couple of years. Bracing has moved from the top of the swingarm to the bottom on most factory MotoGP bikes and World Superbike machinery, which reduces lateral movement at the tire's contact patch when the swingarm twists, improving feel and feedback. This is just one example of how lateral and torsional stiffness are related.
In the end, it all comes down to what the rider desires for that feel and feedback. Repsol Honda riders Casey Stoner and Dani Pedrosa each have frames custom-built to their requirements. The Ducati team has used carbon fibre swingarms on the Desmosedici since 2009, but recently tested an aluminum version with mixed results - riders Valentino Rossi and Nicky Hayden are divided on their preference. The finished chassis is as much a function of the rider's input as the engineer's computer, especially when it comes to flex and rigidity.
Thursday, 28 June 2012 18:42
Grand Bend, Ontario- Story and photos by Graeme Jones: 2012 marked the 9th anniversary of the Kevin Blackmore Memorial Quick 16 race at Grand Bend Motorplex in Grand Bend, Ontario. The annual drag race, held to commemorate the life of longtime Ontario dragbike racer Kevin Blackmore, was started in 2003 and routinely draws the most talented motorcycle bracket racers that the province has to offer, as well as racers from over the border in Michigan.
Wednesday, 27 June 2012 13:16
Monday, 25 June 2012 14:40