19" wheel on a Mono?

[Deleted User 62]

Oh sure, you had me going there for a minute.... Next you'll be telling us the bullet holes aren't real!

No.......the bullet holes are real.
They were from a spitfire. He came out of the sun. True story.

[Deleted User 72]

Where are you finding 19" R1100R wheels? I can't find anywhere that lists that wheel. The R1100R was stock with either the 3.5 x 17" cast wheel, or the 2.5 x 18" Cross-spoke. The GS had a 19" wheel.

Also, earlier models did NOT use that size. They had a 1.85 x 19" front rim - same diameter, but very different from a 2.5 x 19" (or 2.5 x 18"). Making sure you have clearance for the much wider tire will be important, but the K75S had a 2.5" wide front rim, so those forks (including their triple clamps) should clear fine.

My GS has a 21" rim. I also don't like Por 15, AND I have used it!

[vanzen]

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 ...

[Major Softie]

Where are you finding 19" R1100R wheels? I can't find anywhere that lists that wheel. The R1100R was stock with either the 3.5 x 17" cast wheel, or the 2.5 x 18" Cross-spoke. The GS had a 19" wheel.

Also, earlier models did NOT use that size. They had a 1.85 x 19" front rim - same diameter, but very different from a 2.5 x 19" (or 2.5 x 18"). Making sure you have clearance for the much wider tire will be important, but the K75S had a 2.5" wide front rim, so those forks (including their triple clamps) should clear fine.

My GS has a 21" rim. I also don't like Por 15, AND I have used it!

BUT, there was also a 19" wheel available on the GS. My point was, I know of no 19" wheel available on the R1100R and wonder what wheel he's talking about.

[ME 109]

Thanks for your response Vanzen, some good food for thought.

My 'tests' in evaluating the gyroscopic effect of the front wheel have been to shake the bars at speeds of about 35 mph and feel the whole bike responding like a bowl of jelly with no real direction change.
Also shaking the bars at 50 mph and noticing a great reduction in jellyness.
At speeds of 60 mph and above, the jellyness has gone, with the 'bar shaking' producing firm, quick changes in direction.

It would be interesting to take a slow motion video of the bike sitting stationary on its wheels with the handle bars being shaken the same way as I've done on the road.
When I have done this 'stationary' shaking, the flexing of the whole bike is positively awful!
A video would show just what is actually flexing.
I think a lot of it would be in the forks.

[vanzen]

...My point was, I know of no 19" wheel available on the R1100R and wonder what wheel he's talking about.

Me neither, me too ...

[vanzen]

...My 'tests' in evaluating the gyroscopic effect of the front wheel have been to shake the bars...

I have often performed that routine myself.
Ride along, and at a given speed take both hands completely off of the bars,
and with the palm of one hand, whack the end of the H-bar smartly – to evaluate what happens next ...
But rather as an exercise to determine whether the instability induced by whacking the bars
will result in an increasing instability or a diminishing instability.
A "Primal" test with certain risk, to be sure,
but one that primarily addresses a given chassis propensity for (speed) wobbles
rather than any evaluation of gyroscopic effect.

[Nourish]

Major Softie - I've searched my E Bay feedback and found the wheel I bought and it was described as - BMW front wheel with ABS ring R850 R1100R R1100S and GS - but then maybe they were different options here in the UK?

Vanzen - what Disc and caliper set up are you going to use on 'Old Crow'

Thanks all for your input. Martin