Wheel Weight VS Performance

[300c Owner]

Someone shared some comments on relative wheel weight and performance impact ... now I can't find the comments. Anyone know the original link or could someone re: quote the comments / impact of weight on performance ... etc.

[jjs]

Originally Posted by 300c Owner

Someone shared some comments on relative wheel weight and performance impact ... now I can't find the comments. Anyone know the original link or could someone re: quote the comments / impact of weight on performance ... etc.

Among others that Google can find...

http://www.tirerack.com/wheels/tech/perform.htm

[DrDeville]

In brief, heavier and larger diameter wheels provide
improved cosmetics at the expense of reduced
performance in a number of areas:

1. Wheels are accelerated not only forward,
but in rotation. Heavier wheels have a greater
resistance to being "spun up" (this resistance
is called rotational moment of inertia), and
reduce acceleration and braking much more than
the same amount of extra weight elsewhere.

2. Wheels are at the end of the suspension
springs, and called "unsprung weight". The
heavier a wheel, the stronger the spring/shock
force needs to be in order to keep the tires
in contact with the road over bumps. Thus
heavier wheels will ride rougher (if the shocks
and springs are firmed up to handle them) and/or lose
contact during bumps (if the shocks and springs
are left stock). Some RT and 300c owners
who installed larger wheels report their cars jumping
sideways over in-turn bumps, due to this effect.

Being a performance nut, I would only change wheels
if the new ones had less weight and rotational inertia,
but that's just me. Now you can make your own
informed decision.

Best,

George Ferguson

[300c Owner]

After a little research I did find something else ...

http://forums.nasioc.com/forums/arch.../t-446090.html

[II kings 9:20]

Upgrade the brakes, why spend all that money on wheels for reduced performance. Baer will likely have a brake system by Nov. SEMA show.

[LWOOD]

Even if the wheels are as light as stock, or lighter, the larger diameter will increase their rotational moment, yes? There would have to be a significant difference in weight between an 18" and a 22" wheel for the 22" to offer the same accelerative/braking ability of the stock 18". Right??

[DrDeville]

Originally Posted by LWOOD

Even if the wheels are as light as stock, or lighter, the larger diameter will increase their rotational moment, yes? There would have to be a significant difference in weight between an 18" and a 22" wheel for the 22" to offer the same accelerative/braking ability of the stock 18". Right??

Greetings LWood,

Yes, and yes. You grasp the physics of the matter.

Its like when an ice skater pulls in her arms during
a spin. With her arms in, she has the same weight
but less rotational inertia so, with the same amount
of energy, she spins faster.

Best,

George Ferguson

[cmego]

If mass is the smaller part of the equation, why spend $$$$ on carbon-fiber wheels?

[jjs]

Originally Posted by cmego

If mass is the smaller part of the equation, why spend $$$$ on carbon-fiber wheels?

Some people want every little bit they can get out of an upgrade. Also, 'performance' is not just straight line speed and acceleration. Another aspect of performance is in the handling department. Reducing unsprung weight there can be a big benefit in that area.

[Gary C]

One extra pound in the wheel/tyre department is SIX LBS in the cab/trunk,,, so 10lbs (more per wheel/tyre) x 4 wheels/tyres x 6lb(for unsprung Weight)= 240 lbs in the passenger seat.