Lighter Weight Wheels --- Worth It?

[justinschmidt1]

I was purchasing the wheels anyway...the extra mpg is just kind of a bonus

[justinschmidt1]

Some people are arguing that heavier rims keep the cars momentum better at highway speeds but I was saying that the motor will have to work less to keep the car moving at a steady speed with lighter rims

I dunno, seems like people want to argue about it both ways...but i will have test data within a couple of weeks hopefully.

[chuckm]

For keeping a vehicle at speed, the rim weight won't matter too much. It is mainly when you are changing velocity that it makes a real difference. I would suppose that a heavier rim weight would cause you to coast further. However, and for the same reason, it would also take more energy to accelerate the vehicle.

[justinschmidt1]

Originally Posted by chuckm

For keeping a vehicle at speed, the rim weight won't matter too much. It is mainly when you are changing velocity that it makes a real difference. I would suppose that a heavier rim weight would cause you to coast further. However, and for the same reason, it would also take more energy to accelerate the vehicle.

Makes sense, even if it helps with accelerating it should save me gas since my car eats gas when accelerating, not so much cruising.

Should help with the overall averages

[tournapart]

Totally new here, just signed up, but I have read this 8 page thread and am in the same boat as the original poster. I have a Mazda RX8, which yes, its a sports car that gets horrible mileage, and for its mid price range is probably amongst the worst. That being said, I am an avid car enthusiast and am studying to be an engineer. To take it further, I did complete a vocational program at a community college for auto repair, and have been quite involved with rotary engines for years. I am interested in making my car a little more efficient. To filter the BS so to speak this is what I have taken from this specifically and a mix of what I have read in the past.

Talking strictly wheels

Lighter wheels will promote greatest fuel effciency in more urban/stop and go environments.

More aerodynamic wheels will promote greatest fuel efficiency in more highway/constant speed environments.

Now dipping into how much more efficient as you get more aerodynamic or lighter is debatable. I share the same sentiment as someone who posted earlier, not sure if its the original or not, as saying, I would get them anyways, the fact that they are more efficient is just a plus.

I wont sit here and say that my intentions are strictly efficiency, obviously if that were the case I wouldn't own a sports car. But it is a hybrid affair, fun/daily not gas/electric, and I think I can try to squeeze some more MPG's out and enjoy the car even more.

After reading this thread I was up in the air about upgrading my wheels once again. Stock, my rims were 23-24lbs each. When I discovered that one of the rear rims was slightly warped when I was getting some tires installed I went out and found a set of cheap rims to get me over. These turned out to be more like 26-27lbs each. The rims I am thinking (and now am definitely) of getting are 18.6lbs each (Enkei RPF1). I think there are many things to be gained having lighter rims, less wear and tear on wear components, such as brakes, tires, clutch, suspension, etc. Acceleration improvements will be the most noticeable and I think there is something to be said about being able to put less power out to get to accelerate as much as it did before the weight reduction (more of as a real world application versus a study of efficiency), everyone has different driving styles that make them feel comfortable when they drive their cars.

I am unclear on one thing. From my readings today, and of years past, there is always some heated and unproved debates of the equal ratio of unsprung to sprung weight. Some say 1:2, some say 1:3 I have read as high as 1:10. What are the exact variables that determine this ratio? and how could you apply these variable to any vehicle? I guess what I am getting at is, is there a fill in the blanks calculator that will tell me for my specific vehicle (curbweight, HP, etc) what my unsprung to sprung weight ration is? or is it infact a fixed ratio that is applied to all vehicles and everyone is just giving it they're best guess?

Thanks again to all who contributed to this thread, it has help me immensely and I hope to get to know some of you smart people out there.

[Bicycle Bob]

Everything I have ever read or understood suggests that the less unsprung weight, the better. The sprung mass is used to control the unsprung mass, and is upset if it has to react strongly.

[some_other_dave]

To my knowledge, there is no simple formula for the effects unsprung vs. sprung mass. There are rules of thumb that seem OK to a first approximation, and there are formulae that let you calculate specific effects for particular masses sprung in a particular way. The latter require more inputs than we usually have conveniently available to us (e.g., motion ratios, masses of the specific parts, etc.), and the former are about a half-step better than wild guesses.

-soD

[Christ]

Originally Posted by jabb

In my opinion MPG gain from lightweight rims might be small compared with purchase price however if rims do not get damaged there is only minimal loss in value in time. When you get rid of your car you can put your old rims on and sell lightweight ones for roughly the same price you bought them (if you're lucky).
Of course some investments are not there for making profit, some are just to make you feel better and that's not a bad thing either

heh... not around here. I buy "last year's" rims for nearly scrap value, even with minimal damage (paint nicks, no metal damage) and mount decent tires on them and sell them for only slightly more at times.

The retail market is there for used OEM WHEELS, but not so much for aftermarket ones.

[alohaspirit]

Originally Posted by Christ

The retail market is there for used OEM WHEELS,

aint that the truth

who knew huh

remember round 10 years ago when we didnt want that stuff

[Christ]

It gets bad when OEM wheels look better and are usually lighter than most aftermarket "bling"...