Here's the question. If I weigh my Moda R6 18x8 wheel with the tire inflated to 30 PSI I get 50 pounds. How much of the weight would you guess is wheel? (EX:30 pounds wheel/20 pounds tire). I'm asking because, I'm going to probably invest in new light 18" wheels but I need a comparisson number for what I've got. I basicly need to figure out how much my Moda's weigh. Any guesses?

Moda R6s weight 28.6lbs per wheel in 18x8.
www.wheelweights.net

-Spidey

Thanks for that link. Very helpful. I guess I didn't think that the tire would actually weigh 22 pounds! So even if I go to Volk TE37s, I'll only save about 10 pounds total on each wheel. Now I'm not sure if its worth it or not.

What you need is a smaller rim then you can really get the weight down. True though the tire will hurt it a lot in the long run, they are heavy bastards...

Can't do it. Huge brakes!! I may be able to squeeze a 17" on there but thats it. Otherwise, I'll have to ditch the brakes.

Lets get some pics of your brake kit, what kit do you have?

Baer pro kit, 4 piston Alcon calipers, 13" cross drilled rotors. Sorry I don't have any pics.

Damn!! I wish i had the money to afford that kit, it is soo nice.

Originally posted by Mike 99GSX
Baer pro kit, 4 piston Alcon calipers, 13" cross drilled rotors. Sorry I don't have any pics.

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Post pics or ban.

Originally posted by Rx3


Post pics or ban.

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Huh?

:laugh: Btw, 10lbs per wheel = 40lbs of rotating mass, it would definately help.

my 18x7.5 Tenzo R Passion 5's weigh 20 lbs each and my goodyear eagle f1 GS-D3 235/40/18 tires weigh 24 lbs... my tires weigh more than my rims, how nice

Originally posted by Mike 99GSX
Thanks for that link. Very helpful. I guess I didn't think that the tire would actually weigh 22 pounds! So even if I go to Volk TE37s, I'll only save about 10 pounds total on each wheel. Now I'm not sure if its worth it or not.

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If you save 10lbs / wheel, that's a lot for unsprung weight and rotating mass! I would think you should be able to feel the difference there. I know I felt a difference when I went from lame quantum tek alloys in 18x7.5" to Volk GT-Cs in 18x8". Even though they were bigger, the car felt lighter on its feet. Just imagine strapping 5 lbs of weight to your shoes and trying to run vs. holding 5 lbs in your hand and running. The difference in rotating mass makes quite a difference.

Plus if you want to accurately weigh the wheel/tire combo, you might want to completely deflate the tire first. I'm not sure if it will make much of a difference, but pressure in the tire will probably make it weigh more. Like the difference between a propane tank that is full vs. empty (if you ever lifted one up before).

Come on man you have to be kidding me....air weighs nothing. so your telling me if you could inflat that tire to 100 pounds it would weigh more than one with 10 pounds? pounds meaning pressure not weight:laugh:

I work at a tire shop and I can deff. say that a tire with air in it weighs more hands down than one without air in it.

Originally posted by Spidey
:laugh: Btw, 10lbs per wheel = 40lbs of rotating mass, it would definately help.

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Where did you get that number from? Rotational inertia increases with the square of angular acceleration and wheels dont spin fast enough to make that big a difference.

Originally posted by 2FST4U
Come on man you have to be kidding me....air weighs nothing. so your telling me if you could inflat that tire to 100 pounds it would weigh more than one with 10 pounds? pounds meaning pressure not weight:laugh:

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Have you ever picked up a cylinder full of compressed gasses? If not, do so.

Originally posted by igs
Where did you get that number from? Rotational inertia increases with the square of angular acceleration and wheels dont spin fast enough to make that big a difference.

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It still takes alot more energy to spin 40lbs than it takes to carry 40lbs on the chasis...

Originally posted by MNGSX
It still takes alot more energy to spin 40lbs than it takes to carry 40lbs on the chasis...

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It takes more, but not a lot more. It all depends on how fast you are spinning it.

Originally posted by igs

Originally posted by Spidey
:laugh: Btw, 10lbs per wheel = 40lbs of rotating mass, it would definately help.

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Where did you get that number from?

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Igs, I love you, man. So, I'm going to try to help you out.

Our cars have 4 wheels. (If you don't believe me - and this wouldn't surprise me, since you rarely listen to anything that I say - then go out and count the wheels on your car. Mark them with white shoe polish as you count them, to be sure to count each one exactly once.)

Spidey is talking about wheels that each weigh 10# less.

4 times 10# is 40#.

So that's where he got that number from.

Glad to help.

- Jtoby

^^^

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Originally posted by mrecl1pse
Plus if you want to accurately weigh the wheel/tire combo, you might want to completely deflate the tire first. I'm not sure if it will make much of a difference, but pressure in the tire will probably make it weigh more. Like the difference between a propane tank that is full vs. empty (if you ever lifted one up before).

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I don't know remember the physics but I do now from diving that 80 cubic feet of air weighs about 7 pounds. I don't think you have that much air in your tires. You could probably loose a couple pounds by filling your tires with helium but you would loose more by taking a laxative.

Since we're taking this issue of what's inside the tires seriously....

Much more important (especially when autoXing or road-racing) is the question of how much water is in your tires. You want the air inside to be as dry as possible. Not because of the added weight, but because of the effects of the water as the tire and wheel get hot. When water boils, for example, it gets a heck of lot bigger. So the more water in your tires, the more heating up the tires and wheels causes an increase in tire pressure.

This *is* an issue. Gizmos that will inflate four tires with <2% R.H. air are available from racing suppliers. They're more than $1k.

- Jtoby

Yup. When air is compressed, it has a higher density = heavier. And, moisture turns into water.

If you don't believe me, go to a computer store and buy one of those compressed air cans used for blasting dust out off of motherboards. Shake the can and you'll hear and feel liquid sloshing around in the can. Empty the can and you'll noticed it can is a lot lighter than when full.

Yes, kids, air does have weight.

Don't want to get way off topic but the canned air dusters don't use "air." It takes several thousand psi to liquify air (nitrogen/oxygen) so they pick a gas that can be more easily liquified and doesn't have too many harmful properties.