Lighter Weight Wheels --- Worth It?
 

Lets say I can drop 5-6lbs per wheel with new rims.

Do you think I would gain anything in city driving?

Anyone replaced their rims with lighter ones and noticed a MPG improvement?




Trying to see if its worth it or to just get "pretty" rims instead of lightweight "race" rims.

Personally, I vote for HEAVIER rims, but my opinion doesn't count because I mean in-wheel electric motors, which would certainly mean better economy. :D

One thing that I just noticed to consider thought, is how aerodynamic the rims are.. ?

#1- My stock rims;
http://www.autopartsfair.com/images/.../aly64857u.jpg

#2- Same weight as stock;
http://i197.photobucket.com/albums/a...31/intersa.jpg

#3- And the "lighter" ones;
http://www.tirerack.com/images/wheel...1_ts_ci3_l.jpg

Now, which one of all three would probably be the most aerodynamic? (Im thinking #2), and do you think the reduced weight would make any difference in overal mpg if they are less aerodynamic... ?

My guess would be that your stockers have the best aero, I would think more spokes = more turbulence. If you can save 5-6 pounds per wheel that's pretty good. Wheels have to be spun as well as moved forward so the weight counts twice essentially. You probably already know that.

For the savings of gas alone updating your rims to lightweight alloy wheels will probably never return a financial payback to you (Unless you can get a decent price for selling your old rims)

To get an idea of the impact of lighter wheels, take your vehicles weight and divide it by your HP. This will tell you how much weight each HP drives. Say you have a 100 hp car that weighs 2000 lbs. Works out to 20 lbs/hp. So cutting 20 pounds from your car would be the equivelent to improving your engine by 1 hp.

Now this isnt really a comparison of apples to apples because the wheels are rotational mass. I think the conversion is roughly 4:1 so if you cut 20 pounds of wheel mass it is the same as cutting 80 pounds off the car

As far as aerodynamics they are probably all horrendous and you can always slap a moondisk on if you dont mind the looks of them

So clearly it will help with performance (which is why racers use light wheels) and I am sure it will help with mileage some, but I dont think it would be very significant...perhaps one mpg maybe two.

I recall reading that reducing the weight of any rotating mass gets you the benefit of 3x that weight. I wonder if the actual number is 3.1416, pi.

Anyway, for what it's worth, the very fuel-thrifty Honda Civic HX has lightweight 14" rims that weigh about 11 lb. each. It's predecessor the VX had similar ones but I think they were 13". In other words, Honda thought it worthwhile to use lightweight rims on their fuel sipper, and racers now like to grab those rims.

Aside from the cost, I'm sure it's a boost for mpg.

Civic HX rim
http://i8.photobucket.com/albums/a36...Picture251.jpg

Rotational weight is twice, thrice, four times???
Anyone have a source to reference? ;)

This is a classic consideration in bicycle racing, where the formula is that the tire tread is twice as significant as the axle and other chassis parts. The rims matter more than the spokes, because they don't get up to full road speed in rotational motion.

That just applies to acceleration. Wheel weight is nothing special on a smooth road, but on bumps, it wastes momentum, so the real formula would need a lot of input about the number of potholes in your town.

I like heavy small, and larger light. Of course without engine counterbalancers necessary, anything goes. A heavy wheel or a light one would be trial and error on every other vehicle today aside from electric motors and 3 main boxers. :rolleyes:

One question: are you asking whether the fuel savings from new rims would pay back the purchase price, or have you decided to get new rims regardless, and are just trying to decide what?