I am looking at aftermarket wheels and, for comparison purposes, I'm trying to find the weight of the stock hollow spoke twist wheels that come on the 996TT. Anyone know off hand?

Thanks in advance,

 

Aprox. 22 and 26 lbs. front and rear, respectively.

 

I wish they published the rotational inertia too. Two wheels
with identical weight might have different weight distributions
that would help or hurt acceleration. Maybe not as much
as for motorcycles for instance, but I'd be interested to know...
I once replaced one of the early cast 'mag' wheels on a Yamaha
RD400, with a custom spoked wheel, and the replacement wheel
+ sproket (nylon!) + tire together weighed less than the original
wheel alone!
Joe

 

Thanks Jack.

How do you measure rotational inertia Joe? Just curious...

 

racer63,
You don't exactly "measure" it. You would need measure the intricate dimensions of the wheel's cross section and then the rotational inertia can be "calculated" using appropriate "mechanics of materials" equations.
As a rule of thumb, the more mass you have closer to the outer diameter, the greater the rotational inertia (bad). The less mass near the outer diameter, the lower the rotational inertia (good).
This is why, in general, I prefer wheels that have tapered spokes that are widest near the hub and narrowest near the rim edge.

 

You would measure rotational inertia on a dynomometer
designed to do that. The test would be to measure how
long it took to spin the wheel from 0 rpm to XXXX rpm,
given a constant sourcce of power. Someone could probably
rig a test up with an axle on a stand, and an electric motor,
and the stuff to time-to-rpm. I'm not sure how much practical
info this will garner, but it would be of interest to know...