According to the gossip from social media single track vehicle dynamics authorities, I'm doing everything wrong! They don't know what I'm doing, so clearly I must not know what I'm doing! Right...
Roadracing motorcycle design has evolved itself into a dead end - they can't accelerate or decelerate any harder without flipping, or corner any harder without running out of clearance. Any changes to one or more areas to improve one aspect will result in an overall loss of performance. Tires are optimized to accelerate or brake, not both, leading to cooling events. Suspension has to be optimized for load transfer extremes. All the above leads to both slow roll response and high polar inertia about the roll axis. And that results in terrible aerodynamics. ALL of the above problems can be successfully addressed IF you discard the old configuration and derive a functionally superior new configuration.
Here are those problems (And causes):
- Stoppies (High CG, short WB)
- Wheelies (High CG, short WB)
- Lean angle limitations (Oversized rear tires)
- Roll rate limitations (High roll axis, high polar moment)
- Suspension sub-optimization (High CG, short WB)
- Tire sub-optimization (High CG, short WB)
- Aerodynamic sub-optimization (High CG, short WB)
- Long WB, low CG, linked brakes
- Long WB, low CG, 2WD
- 2WS, appropriate tire selection
- 2WS, low roll axis, low CG
- Long WB, low CG
- 2WD, 2WS, linked brakes, long WB
- Long WB, low CG
2. Also pretty obvious. Same as the above, but from the opposite direction - just a lot more difficult to implement. Doing it beats complaining about it. The ultimate solution to that problem is addressed near the end of this post.
3. Not obvious, at least with the 2WS part. The tire part ought to be obvious: With 2WD and linked brakes, a big fat rear tire is no longer necessary or even desirable. A narrow tire at both ends provides enough footprint area - more about that in #6, below.
With 2WS, cornering force deviates from perpendicular to the roll axis, thus reducing lean angle (Simple trigonometry, if you must). If 2WS is taken to an extreme, a single track vehicle dynamically transforms into a purely 2-tracked vehicle known as a "Di-cycle": NO lean angle required at all for cornering. That isn't practical for obvious reasons, but steering the rear wheel in the same direction of the turn at any proportion much over 25% (Ideally over 33%) contributes to the same effect, thus significantly reducing lean angle.
6. With 2WD, linked brakes, 2WS, low CG, and long WB, both tires are working all the time. There are no "Break times" for cooling down that then require warming back up to optimum temperature. And since extreme load transfer isn't happening anymore, much lower tire pressures (With the obvious benefit of a larger footprint) are both possible and desirable without developing stability and control issues. Having interchangeable front and rear wheels and tires is a welcome benefit. I doubt that existing tires are close to optimized for such implementation, but the choice of racing slick tires with different compounds and carcass stiffness is a huge help.
The rationale (And obvious physics) behind all 7 points guided the design of my next racer. All 7 points are necessary, if not convenient, to work. No, I don't expect said social media authorities to comprehend any of those points - nothing depends on the comprehension of those gossipers.
In the mean time, work is progressing nicely if not quickly on the next racer. Got questions? You know how to contact me. Got gossip? You know how to contact them.