ME 109 wrote:For a long time I have thought that the gyroscopic effect actually benefits our older airheads handling.
I have thought this because of the difference in handling from say 40 mph to 50 and above mph.
The heavier, larger 19" snowflake seems to reduce rubbercowness as speed increases.
Is this the case?
Stability vs flick-ability:
Some, and cruiser riders come to mind as the extreme example,
are more comfortable with lazy geometry and massive gyroscopic effect.
Typically, they will not be so well equipped to round a corner easily and briskly, either.
We always filter our evaluation of MC chassis handling characteristics
through the fine-mesh screen of personal experience, expectation, desire, or need.
A balancing act:
For many riders, the expectation of a motorcycle's ultimate handling capability
has changed dramatically over the course of the past 30 years .
This phenomenon is due in large part to the advances in chassis engineering / design,
and tire / braking system technology.
Indeed, the airhead is an antiquated design, and the rider (or builder) must understand this fact
as his expectations of the old machine are formed and performance demands are made.
For example, the goal of retrofitting contemporary stopping power to the old machine may be a good one,
but in an absence of thoughtful consideration of the entire "chassis package" –
results could very well be disappointing if not disastrous.
Response to 18" vs 19" front wheel and "rubbercowness":
I have noted that many airheads used in vintage track racing duty will have an 18" front wheel fitted.
Sometimes the choice will be determined by class restriction,
but never will this choice be made to increase or induce
instability.
The move to smaller diameter front rims is, in large part, an effort to reduce unsprung mass
and gyroscopic effect, which, in turn, greatly reduces steering effort.
Keeping in mind that critical geometry such as trail can always be fine-tuned and adjusted,
and that tire circumference, wheel assembly mass and the distribution of that mass
determine gyroscopic effect, more so than rim diameter,
and that these will not be nearly all of the factors
which contribute to high speed stability or handling abilty ...
The resulting chassis geometry and dynamics of those track chassis
simply cannot be judged by noting the front rim diameter used.
What I am saying is that, in addition to the change of rim,
other factors that contribute to chassis geometry and dynamics may also be changed
in order to make that "package" work well.
Case in point:
The 1988 R100RS is fitted by BMW with a 2.50x18" rim.
Front suspension and rear suspension components used on this model
are, without any doubt, dramatically different than anything found on the early airheads.
Trail numbers remained surprisingly similar, however.
Kwinky-dink ? Me thinks not ...
