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Crosslaces weight??


alphagtp

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Its been discussed before, I believe it was 22lb with no rubber...

 

Jamie

 

I have had mine on a scale, and mine were also 22lbs.

 

Not too bad for a factory 16 X 8in wheel.

 

My co-workers IROC wheels (also 16 X 8in) are 24lbs...........

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Last I checked my cross laces with 225/50/16 all season tires were 45 LB, ridiculously heavy tires.

I've often thought about finding a set of steelies for track tires, but I dunno what the weight difference would be.

 

Jamie

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so that being said, it means that a set of wheels 18X8 with each wheel at 23lbs is very good correct??

 

I dunno! I've been thinking about that for ages... 23lb so its only 1 lb more, but at the same time its 2" farther out from the center of the wheel. And I don't know what effect that has on the rotating mass. I did some google searching once upon a time and couldn't find anything about rotating mass... I should see if the wife can talk to one of her friends with a physics major to find out (she has her chemical physics, but didn't know what to tell me when I asked)

 

Jamie

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what youre looking for is the rotational kinetic energy. The same weight that is farther out possesses more energy when rotating the same angular speed as a weight closer to the center of rotation. Or it can be said that it requires more energy to attain that speed. Making you accelerate slower.

 

Think of a figure skater when they get into those spins. They start out with their arms and legs out and are spinning at a medium angular velocity. They pull their arms and legs in and spin alot faster. This isnt a perfect example because pulling their arms and legs in is doing work on the system (Force X Displacement) which gives it more energy, but the rotational speed is still increased due to the skater reducing their moment of inertia (MOI).

 

Its late and I dont have time to explain multiple physics lessons, but this page should help you do some calculations:

 

http://en.wikipedia.org/wiki/List_of_moments_of_inertia

 

In reality wheels are a combination of many of those (spokes are rods spinning about an axis on their end and rims are cylindrical shells, you just figure out each part and they all add up). To most easily get the rotational inertial of wheels very accurately, you could solid model them and do some analysis. But its should be good enough to use those MOI equations.

 

Edit:

 

Oh yeah, rotational kinetic energy is expressed as follows (disregarding the linear motion the wheel has, because that can be calculated with your whole car included):

 

Ekr = .5 * (MOI) * (angular velocity)^2

 

but comparing moments of inertia for each wheel (you can include tire if you wanna get fancy, but i dont see disc MOI on that wikipedia page) is what really matters, unless you are upsizing your tire OD too, then kinetic energy is all encompassing.

 

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So in other words, lol, the bigger they are the lighter they should be. I don't have the know how (nor will I ever) to figure out how much lighter you should be looking per inch of rim...

 

Jamie

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Well its also a matter of where the weight is. Moreso actually. if you have a super thick bead area for some reason, then that will add alot more rotational inertia than bigger wheel whose weight is more in the spokes or lug area

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