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Wheels are the major 'unsprung weight' load on any vehicle. But they are also highly 'energy absorptive', and there are a number of theories as to how to reduce loading on a drivetrain by cutting the load right at the hubcaps. Any bicyclist knows well the difference between pumping big tires, and running on small diameter high pressure tires (road and touring bikes). The principle does not change just because we are looking at a truck instead of a bicycle - if anything, it brings to us a test sled on which to chase the idea even further...
We should explore this, especially now. What we learn and save could go right into the BANK!
The dynamics of a rotating tire are not what most people think they are. As a tire/wheel rotates, ALL of the mass it is made up of is constantly changing direction - and that requires an energy expenditure. THEREFORE reducing the total mass reduces the amount of energy required in order to just turn the wheel. This energy expenditure increases directly in proportion to increased RPM at the axles.
Bottom line here is that BIG tires should be reserved for slow going and off road use. For the highway - normal width, moderate sidewall, high pressure ('E' rated tires are pressurised to 80 PSI) tires on alloy rims are the best way to go.
NOTE: Taller wheels/tires have a lower overall rotation rate for a given speed of travel in miles/kilometers per hour.
Things to do today: Be Like Steve...
Last edited by Greywolf; 05-12-2005 at 01:41 AM.
Reason: Further clarification (definition)
Removing 10 lbs of rotating weight is the same as removing 100 lbs of dead weight. To feel a measurable difference in mileage, it takes 500 lbs of dead weight (or 50 rotating) removal to gain 1 MPG.
Not only would fuel mileage increase, but there would be less wear and tear on components, such as shocks, wheel bearings, brakes, etc. The vehicle would accelerate faster, stop shorter, handle better........ You get the picture.
Reducing rotating weight is a good start, but, it's proven that though the higher load range tires offer reduced rolling resistance, the increased weight of the tire negates any possible benefit in that department. If you were to develop a lightweight, low rolling resistance tire, with a moderate sidewall height, it, IMO, would not be fit for installation on any vehicle that hauls any amount of weight.
'02 Dodge Durango
"The voices in my head may not be real, but they have some good ideas!"
A tire company has re-invented the wheel recently. The wheel is plastic and is very light, the tires are non inflatable, the wheels structure produces the shock absorption. They will probably only be on small, light cars to start but maybe they will be able to make them strong enough for trucks. They debuted the wheels at one of the major car shows this year.
Also, magnesium wheels are much lighter than aluminum or steel wheels. A 45# aluminum wheel would weigh 30# made out of magnesium.
If you look through the pictures it shows them on a Cat front loader, so I guess weight carrying capacity wouldn't be an issue. It kind of weirds me out to see a car going down the road with those things on though.
ah yes, i think that they called them tweels in four wheeler or four wheel and off road.
so with two otherwise identical tires, one rated at 50 psi and one rated at 80psi, the one that takes 80 will get better mileage?
and does that also mean that 235/85's would do better than my 33/12.50's even though they are a big shorter (taller tires make the engine turn slower at any given speed)
also i have heard that over 40,45 mph air resistance is a bigger factor than rollng resistance.
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Intriguing topic... I'm of a mindset now to do anything (within reason) that I can to improve the efficiency of my vehicles. So, is it worth investing in lightweight wheels? Which ones have the load-bearing capacity needed for a truck?
Wolfus, I like your thinking on this. I don't know for certain about aluminium or magnesium wheels, however. Lots of the alloy wheels are heavier than steel ones. I would have to imagine this is because most of the alloy wheels seem to be designed for looks, rather than weight savings. But a carefully designed alloy wheel might be just the thing. Doesn't Alcoa make something we might could use ? I really like the high pressure tire idea. I went and looked at the wheels and tires on the UPS truck that comes every day to my shop. It had 9x19.5 tires on it. They were load range E, and were about 37 inches tall, with about a 6 inch wide tread face. If one could find some 19.5 wheels with a bolt pattern to fit our trucks, that might be a neat size to try. DF, @ his Dad's house
There was a time when Budd rims (for semi's) were illegal in the state of California. Trucker liked them as much for the looks and name as they did for the weight and rolling resistance savings. These days - there are a lot of big rigs with alloy rims, and there is good reason for it.
For a pure, solid enough to handle speed/load, straight-up road rim I would think centerline or some similar manufacturer ought to be ideal. Western is long out of business, but they were said to have some of the best engineered rims around. Budd may still be out there - I'll surf around and see in a minute.
Looks don't equal MPG, and in fact can reduce it a lot. The reason for cut-outs in early rim designs was to aid in cooling brake discs and drums on racing machines. There are better ways to do that though - Air-Dams on front ends had ports at the outer ends to duct cold air directly to the brakes using 2" - 3" flexible hose, many race cars still use this method today. Lighter duty vehicles ought to have no problem with a non-ventilated rim design or even "MOON" hubcaps. (Which I always thought were cool anyway)
There are dual-metal rims designed for show that are intriguing. A hardened steel hub area with a larger alloy circumferance composition might be a possibility (my thought). Corrosion would be the main drawback, because of dissimilar metals in the design.
Mainly I have thought that some of the "Joe Cool" 21" rims might be a good idea if they were solid center designs instead of being "Fancied Up" with alien looking spoke designs. Picture a 21" centerline racing rim with a narrow or modest sidewall...
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