wheel balance effect on MPG / fuel economy

[MetroMPG]

I just took the first highway trip on a set of "new to me" Michelin winter tires 185/60r14.

There's a fair amount of vibration from being out of balance, and it had me wondering how much it affects fuel economy.

It has to affect it some, after all... a bit of the fuel being burned was being converted into shaking the whole car up/down/around, rather than just propelling everything smoothly down the road.

The crappy winter mileage of this trip (compared to warm spring temps) had me wondering how much of an effect it was. Probably not huge, but these are the things a fuel economy geek thinks about while tooling down the road.

So I wondered: how much power would it take to shake the car around to the extent I saw? 100 watts seems a reasonable estimate. So, roughly equivalent to running with headlights on vs. off.

That's my WAG, and I'm sticking to it.

100 watts represents about 2.2% of my car's power requirement for going down the road at 45 mph in pleasant conditions. (In "stock" configuration, according to our aero/rr calculator.)

[nemo]

Balancing of the tire/wheel assemblies has no measurable
effect on fuel consumption

From
http://counteractbalancing.com/Fuel%...ce%20study.pdf


Different on lighter vehicles?

[Philscar]

Darin
I have a static wheel balancer from Harbor Freight that you can use if you need it.

Phil

[Frank Lee]

I had a very unbalanced wheel on my Tempo once- ice and snow build-up on the inside of the rim, on a brutal winter night. It made me drive slower, so that probably saved fuel. However, it made me stop several times to hack away at it so that probably wasted fuel.

[MetroMPG]

Frank: ever practical.

=-=

Phil! Thanks - I may just take you up on that... if I ever get the ice & snow chopped out of the driveway so I can get in the garage and fiddle with it.

=-=

Originally Posted by nemo

From
http://counteractbalancing.com/Fuel%...ce%20study.pdf

Different on lighter vehicles?

Thanks for that link!

I'd bet it would be different for my ~1830 lbs Firefly vs. a 80,000 lbs transport. It makes sense that it would come down to the ratio of the power consumed by the vibration vs. the overall power requirement of the vehicle.

I did find a link that says it's an issue for passenger cars, but for an odd reason: it says the inefficiency is only due to traction loss & slippage.

WHEEL BALANCE AND MPG
GOAL: To understand how properly balanced tires can improve vehicle mpg.

... A tire 1 ounce out of balance and traveling at 60 mph exerts 7.73 pounds of excessive force each revolution! Energy is lost!

... The greater the imbalance and the greater the speed, the greater the loss of traction and a corresponding loss of fuel economy.

Source: Wheel Balance and MPG

The page also says that unbalanced non-driven wheels won't affect efficiency. Doesn't make sense to me -- the vibration costs energy regardless of which wheel it's on.

[user removed]

The wheel may spin on a rear axle (e brake off). If so then you can balance it with just weights.

It will drop the heavy part to the bottom. Add enough weight (opposite to the heavy spot) so that point moves to close to 90 degrees to the left or right, then add weight until the wheel will not stop in the same place when you spin it to check final balance.

You should have to add weight only on one half of the wheel and probably within 120 degrees between the weights. I have found this to work very well if you don't have the capability to spin balance them. If the first (heavier) weight is perfect, then the second(if it needs one) will be exactly 90 degrees from the first. Any wheel with weights opposing each other is not properly balanced. Seen weights added without all weight removed.

regards
Mech

[Frank Lee]

I did that before on my Tempo with the oil-filled hub. Worked OK but I think the spin balancers can do better- they can tell if the weight needs to go inside or out too.

[user removed]

True Frank, but if you want to get more precise, then just try the weights on both sides. I think 4 tries max for 2 weights. in-out, in-in, out-in, out-out. That is getting more dynamic as far as balancing, but still requires only some used weights, just crimp the clip portion that holds onto the rim.
You can also have someone watch for the bouncing wheel to possibly fix the problem with only one wheel if only one needs to be balanced.
Did the same thing with my 37 Ford with an extra hub, spindle and bearing. They would not fit on my Sanp-On balancer.
I do my motorcycle wheels with a rod sitting on two nails on the beams that support my garage steps.

regards
Mech

[roosterk0031]

I just use counteract balance beads, for all of my cars(Oriely's $25/lb and reusable, 2-3 oz should do), only cars with TPMS give me a slight problem, occasional vibration, I should have left the factory weights opposite the valve stem on all of them. Don't even need to dismount your snow's put it in thru the valve stem.

[aerohead]

If we could simulate both conditions back-to-back in a calorimeter we could measure the actual heat gain.
The inertia which must be overcome to set up the cyclical motion is certainly absorbing power and the tire is deflecting somewhere during the transition,with hysteresis of the rubber generating heat (entropy).