Lighter Weight Wheels --- Worth It?

[therealtime]

Originally Posted by Christ

Secondly, the engine does not SEE the inertia required to spin the non-drive tires.. it only sees them as dead weight. The fact that they roll means nothing.

Just so everyone knows; I am unbiased and not attacking anyone, just trying to clarify for the knowledge of others who read this. For normal driving, where traction is maintained (no wheelspin) the non-drive tires are in fact mechanically connected to the drive tires. think of the road surface as a huge belt and the front and rear wheels as pulleys. They are easier to rotate because they are directly on bearings with only the brakes attached, but the same rules of physics involving rotational inertia apply.

If you put 50 lbs of lead wheel weights on the edge of the rear wheels of a civic, it take more power to accelerate than a stock car or a car with 50 lbs in the back seat and it would glide farther from the same speed. It would also ride rougher and take longer to stop.

just my $.02

[instarx]

Originally Posted by Christ

Secondly, the engine does not SEE the inertia required to spin the non-drive tires.. it only sees them as dead weight. The fact that they roll means nothing.

I disagree. There is no free lunch. Non-driven wheels are not easier to turn than driven wheels. The non-driven wheels are being rotationally accelerated at the same rate as the driven wheels. It makes no difference whether the wheels are accelerated by a drive shaft or from being pulled along the ground - it takes exactly the same amount of energy to accelerate each wheel to the same speed.

A thought experiment: After accelerating a car, immediately lift it off the ground - the non-driven wheels will still be spinning. So where did the energy come from to spin those wheels if, as you say, it took no energy to spin them? How did they get spun? You could generate some electricity or accelerate a flywheel with them. That my friend, would be a perpetual motion machine - energy from nothing.

[Curly1]

Drag racers use the lightest and narrowest tire they can. There is a noticeable difference in putting the "Skinny's" up front. You can even tell a diffence when just pushing the car around in the staging lanes. The car also steers much lighter and easier eliminating the need for power steering saving more weight and horsepower. I think a big part of it is the lighter weight but also a big part of it is the narrower tire for less rolling resistance.

If you are going for the best mileage then the same thing applies to your car. Use the narrowest, lightest wheel / tire combination you can and it will make a noticeable difference.

[basslover911]

I may go with some Konig Daylites in 17" (14.7 lbs!) which are the lightest and most affordable wheel I can get ($150 shipped each.).

I am also strongly considering removing the power steering in my car but I don't know... it IS 3,000lbs!

[Vwbeamer]

Here's my other car. The front wheels weigh less than 5 lbs each and mount 145 tires.

I picked up about 2 tenths by switching from a heavier cast aluminium wheel as seen here-

.



On my 2001 Jetta, I switch from the stock 195/65/15 to a 225/45/17 and LOST
two MPG.

What would happen if I mounted a 165R15 on the Jetta, think I could pick up 2 MPG?

That would be great.

[justinschmidt1]

Hey,

Im new here and drive a supercharged 96 mustang but its also my daily driver and have been checking out ways to improve gas mileage.

The car surprisingly does very well on the highway....probably knocking down 25 mpg or so cruising.

Anyways, I am switching from heavy 18 inch rims to 15 inch lightweight drag wheels.

I will be saving somewhere around 95 lbs of rotating mass in total!

I will do some tests and report back....I would expect a solid 2-3 mpg gain.

[basslover911]

That would be awesome! Please do some well thought out testing and let us know how that comes out!

[justinschmidt1]

Originally Posted by basslover911

That would be awesome! Please do some well thought out testing and let us know how that comes out!

I have kept track over the past years and usually averaged anywhere from 18-20 mpg to a tank with mostly city driving.

But recently had a long trip where it was about 75% highway and averaged about 23 mpg-24 mpg.

I will test some straight highway mileage with the new wheels when I get them and of course I would expect my miles per tank to increase a noticable amount.

[Sean T.]

I had it easy. I chose the wheels I wanted and then after I agreed to buy them I found out they were the lightest factory-produced wheels meant for a Taurus.

[alohaspirit]

I got Si Alloys (16 lbs each)

EDIT:
I went outside and weighed them.
Theyre 16 lbs each.
With tires theyre 31 lbs (15 lb tire)
Ill make the correction above


They are semi-aero

(ignore the purple, its not mine)




Now lets say I would get a pair of Slipstreams (14 lbs each)

So despite that theyre less aero than the SIs

theyre better for mpg because you save 8 lbs total

(a difference of 16lbs looked so much more worthwhile before the edit)



right?