Spee-dee-D wrote:
>I would have to agree about the value added of doing this. I lifted my
>dismounted front wheel - without the tire - and it really isn't very heavy
>in comparison to the weight of the GTS.
<snip>
Judging be the appearance & shape, my guess is that the GTS front wheel is
an aluminum sand casting. Casting alloys tend to be 1) soft, tough & weak
or 2) hard, strong & brittle AND they have to be assumed to contain some
amount of porosity, which can severly affect fatigue life and impact
strength. The result is that they tend to be heavy because a high safety
factor is required to cover the worst case. Billet wheels, on the other
hand, are turned from plate (essentailly a forging) which will not have
porosity. Because you can better control the microstructure of the metal
plate you can achieve a combination of strength and toughness difficult to
obtain in a casting. The advantages of castings are cost and the ability to
easily make complex shapes. Because of the better properties of the billet
material you can significantly reduce the thickness but still have an equal
or better part. Essentially you are paying more for better performance.
However when you look at the cost of CNC machining (lots of competition)
versus the markup on replacement parts (only game in town) billet may not
cost more.
Reducing unsprung weight has a far greater effect than just reducing the
weight of the bike. The lighter wheels will track the road surface better,
increasing cornering, braking and acceleration traction, especially on rough
surfaces. Lighter wheels could reduce the stability since the "gyroscopes"
will be lighter but transient steering behavior - turn in - should improve.
I'll shut up now.
Bill
