Weighted swingarms

[gschuld]

I?m doing some theoretical bench racing if anyone wants to jump in:

So first off, I?m talking about 1000cc classic modified.  160mph or so potential depending on aero/non and fuel type.

I?ve read and seen several examples of far faster sportbikes running swingarms with significant added weight for traction.  One with 73lbs of lead shot, and similar weights of various forms.

Most of these high powered sportbikes are running wide rear tires.  This presumably increases the, sorry for the incorrect terminology, float effect of the rear tire from the air pressure exerted from the extra tire width beyond the contact patch at high speeds.

Let?s say I?d be running a 130 series rear tire on a 3.5/18 rim.  The aero geek in me says that if I can extend the wheelbase by nearly 6? to the Modified limit, I?d do it all in the swingarm and have the rider position as fwd as possible in the racers tuck position to maximize the length of aero fairing behind the rider for partial streamlining.  It?s often said that the aero behind the rider is more important than the aero in front of the rider.

But this moves rider weight away from the rear tire.  I imagine it?s safer to keep the rider?s butt near the rear tire for traction over the potential aero advantage?

Could a weighted swingarm make up that loss in rider weight over the rear tire and improve overall front/rear weight bias?

Increasing overall weight doesn?t seem to be of much concern.  Aero, traction, and HP should by far be more important considering the extra weight is more a function of acceleration rather that top speed.  Slow acceleration is needed regardless on the salt because of limited traction anyway.

Thoughts?

Thanks in advance

George

[stay`tee]

wide tyres and floating have three parts of nothing to do with it,,
 Its all about "Driving Force", every action requires a opposite reaction,,
At speed one faces a opposing force (atmosphere resistance), you require a force at the driving tyres contact patch to mitigate this resistance,, once these two opposing forces are equal one has reached their maximum velocity 

[Stainless1]

Before you start adding weight...
What is the balance front to rear?
Are you experiencing tire slip?
Faired or open?
In our 1000 we fought slip with 67 lbs of swingarm internal weight, and added front weight to keep the balance.  We added more weight to counter slip as we increased HP. 
If you are not slipping, you don't need weight.   

[gschuld]

Good insight.  Sorry I should have been more clear.  This is currently hypothetical toward a potential new build.  A friend runs in the MC750 class with a 110 or 120 series rear tire with his butt near the leading edge of the rear tire.  He reports for the most part, he experiences traction issues in the lower gears, but not so much once up to speed. 

The power difference between the engines should be significant from the 750 to the 1000 engine.   He currently does not add weight to the swing arm.  I'm wandering if dropping a more powerful engine in his chassis would require added weight to have comparable traction.  I would guess his weight bias is around 50/50 currently.

Both open and partial Streamlining

George

[maj]

I would bring weight and add it if needed,
Dont think you will need a lot at that speed and power
try and keep the bikes COG similar to original , in both front/rear and height