What does the Wheel Weigh??

[David Beale]

No, the weight is constant. The rotational momentum or kinetic energy rises from 0 (at rest) to some value which increases with speed.

The stock rim -is- an aluminum alloy wheel. A lighter wheel will make a difference, if that is what you are asking. It takes energy to accelerate a wheel up to a given speed, and usually you can't recover all of that energy. A heavier or higher mass wheel takes more energy to accelerate. You can't get it all back because in the real world if you have to stop, you have to do so in some finite distance (before you hit the vehicles in front of you, for example). Therefore you must dump some of the energy in the rotating wheel. Even the Prius, with regeneration, can't recover all the energy. With regeneration, it's claimed about 50% can be reused, overall, with generation losses, battery charging losses, battery draining losses, and finally, motor losses. You also loose ALL the energy from about 7 MPH to 0, as friction braking takes over.

I'm waiting for someone who has purchased the Volk wheels to post whether they can notice the increase in fuel economy. There should be -some- improvement, it's just a question of how much. The carbon fibre wheels posted above -could- give even more improvement, but being 18", the tire may waste it in extra friction to the road. It -would- handle much better however, due to the tire contact patch being much larger.

Finally, there is one thing the OP hasn't talked about yet. Whether you can use the stock TPMS sensors in whatever aftermarket wheels he chooses. They -may- fit in the Volk wheels.

[usbseawolf2000]

Originally Posted by David Beale

I'm waiting for someone who has purchased the Volk wheels to post whether they can notice the increase in fuel economy....
Finally, there is one thing the OP hasn't talked about yet. Whether you can use the stock TPMS sensors in whatever aftermarket wheels he chooses. They -may- fit in the Volk wheels.

rluciano owns a set and he confirmed (in a PM) that OEM TPMS fits in the Volks Eco Drive. His post with picture of his Prius is here.

[David Beale]

Thanks USB. It's hard to keep up with all the posts. This forum is HUGE.
Thanks to Danny!

So the only thing keeping me from getting the Volks is the tuner nuts you need to use (they are junk!). Oh, and the $2200 and worry whether they will arrive.

[statultra]

i wonder if my accord hybrid rims fit on the prius, their 16 inch 5x100

[tecrench]

Originally Posted by NovaBimmer

here's the wheels You need to save weight

that's in kilograms, too, so they're a hair over 6 pounds... it's black carbon fiber, so don't know if that'll work for You or not

What wheels are these and $$$, TIA

[ronhowell]

Originally Posted by David Beale

You can also use the Volk Racing wheels previously posted about. They were developed -FOR- the Prius as mileage improving wheels.
weight comparison
ce28 ecodrives
15 inch: 10.1 lbs
16 inch: 10.8 lbs

Prius factory wheels
15 inch 14.3 lbs
16 inch 15.2 lbs

So you're saving just 4.2 lbs per wheel, or 16.8 lbs per car set. That is the equivalent to the weight of just over 2 gallons of gas; so you should get the same effect on MPG by not filling your Prius gas tank by more than say 9 gallons of gas, so that you are not accelerating a mass of gasoline equivalent to the wheel set weight at any given time.

OTOH you would presumably get a smoother ride due to the reduction in un-sprung wheel weight.

Just a thought from a different perspective.

[richard schumacher]

Certainly it weighs more when moving: m = E/c^2. But you'll never notice it.

[David Beale]

Originally Posted by ronhowell

So you're saving just 4.2 lbs per wheel, or 16.8 lbs per car set. That is the equivalent to the weight of just over 2 gallons of gas; so you should get the same effect on MPG by not filling your Prius gas tank by more than say 9 gallons of gas, so that you are not accelerating a mass of gasoline equivalent to the wheel set weight at any given time.

OTOH you would presumably get a smoother ride due to the reduction in un-sprung wheel weight.

Just a thought from a different perspective.

Not quite. Because of the rotational momentum you loose more energy accelerating and decelerating the wheels than you do if you were just carrying the extra weight in the car (as fuel, per your example). So it's more than just the extra weight.

And yes, the car -may- handle better due to the lower unsprung weight, IF the suspension is still adjusted properly (as in tuned for optimum dampening).

The combination effect of the extra weight you -could- drop with lighter wheels is:
1. Less overall weight of the car.
2. Less rotational momentum you have to increase and decrease.
3. Less load on the brakes, so they heat up less (in racing applications, not with the Prius, the difference in the Prius wouldn't be large enough to worry about).
4. Less unsprung weight, so you can make the car handle a lot better.

All the above combine to make it very tempting for racing, to spend "uber dollars" decreasing the wheel weight. Which is one reason "Volk Racing" is a company known for their light weight wheels. Off road racing is different, as there wheel/tire strength is king.

[ronhowell]

Originally Posted by richard schumacher

Certainly it weighs more when moving: m = E/c^2. But you'll never notice it.

No, Richard. The equation is M = Mo/(1 - v^2/c^2)^1/2 where Mo is the mass at rest , v = the object velocity and c = the speed of light. But you are right, the last term is as close to zero under normal circumstances as makes no difference. Everything is relative, is it not?!

[Flying White Dutchman]

wo those carbon wheels are light!
whats the price?