vinceg143

i drive an 1998 integra and was thinking about getting dia alloys monza 16 inch which are 14.5 lbs how much of a diffrence will it make if i get these other rims that weigh 12 lbs preformance wise

toyomatt84

iTrader: (1)

It depends on the tires being used.

rclark

"if sprung weight is evil unsprung weight is the devil"

katzenjammer84

Truth. In both weight of tire and type.

nsxtasy

While every little bit of weight helps/hurts, as a practical matter you'll never feel the 2.5-pound difference on the wheels. If this is for competition where you're looking for hundredths of a second per lap and it's part of an overall weight reduction program, by all means go for it! But if it's for street use, don't bother; any difference will be insignificant, and you'll get a much more significant improvement simply by buying stickier tires.

Dogginator

^ This. And...

It makes a difference in rotational inertia. Lighter wheels typically remove mass at the outer ring, where it is most critical to rotational inertia. Lighter tires make a more significant difference.

jdmztrane

I read in a couple of articles, that 1 lb. of rotational mass is equal to at least ten times that of static mass.

So, basically, the heavier the wheel, the more torque it takes to move it. Honda's don't have torque at all, so go for the lightest wheel you can afford.

Dogginator

I corrected the quote. Engine torque <> wheel torque. A transmission and final drive are torque multipliers. HP rules the acceleration world. A lighter wheel will help any vehicle.

nsxtasy

I've read people quoting figures anywhere from an equivalent of 1.5 pounds to four pounds. Ten pounds? You can believe whatever you want. Most opinions are clustered in the 2-3 pound range. Which means that the 2.5 pound difference per wheel is equivalent to a difference of 20-30 pounds in sprung weight. That's like a difference of 3-5 gallons of gas in your tank. You would never be able to feel it. But if you're in competition, racing for points or prizes, by all means go for it!

jdmztrane

True, but once the mass is in motion it takes less energy to keep it in motion than it did to start it due to the object's inertia. Hence the need for more initial torque for a heavier wheel.

You could be right. I'll have to look for the articles I have on my desktop when I actually get back to the house to use it. I could always talk to my physics prof and see what he says. But yeah, the lighter the wheel the better, regardless.

Dogginator

I'm not being mean. But absolutely not. Mass and rotational inertia only come into play during acceleration. An object in motion will stay in motion unless acted upon by an outside force.

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

For the real world, the rolling resistance of a tire is not going to be affected by the mass of the wheel.

jdmztrane

FRICTION my good friend. Friction is what is going to keep the wheel from continuously moving. Since you are accelerating until you reach a constant speed, it does come into play. Friction slows down the vehicle, otherwise, you'd be able to get up to speed, pop the trans into neutral, and completely let off the gas on flat ground. Since the tire and wheel are connected, the rolling resistance will be affected. The heavier the wheel is, the harder it is to make it move and keep it moving.

The wheels wont loose all their weight at speed.

Read the end of the explanation of the second law. All objects accelerate at 9.8 meters per second squared. Anything faster than that will exceed earths gravity, and if it continues on that acceleration, will eventually leave the earths atmosphere.

Dogginator

Wheel weight (mass) has nothing to do with rolling resistance (friction, outside force). Please stop trying to preach physics. You can choose to believe what I wrote and be smarter for it or choose not to and continue on a path of ignorance. No offense intended.

old man neri

I am not going to get into physics and start arguing but put it this way. Ever been on ice? How long does it take your speed to reach about 80 if you are on ice? Basically no time.

It can effect steering feel from what I have heard however due to gyroscopic effects.

As for what jdmtranze said....no.

jdmztrane

I don't get what you are saying. Are you saying that once a wheel is in motion it should stay in motion? And that wheel weight has nothing to do with it?

The wheel wont stay in motion because of the force of friction. Thus needing power to keep the wheel moving. A lighter wheel will require less torque to move. Acceleration will be quicker because the wheels will require less to make them move. This has all been proven numerous times. Otherwise wheel companies wouldn't make cast aluminum wheels and make cast steel because they're stronger, cheaper, and weight wouldn't matter.

old man neri

Basically, yes.

Yes, friction is a big deal to keep a car in motion at a constant speed. The primary drag on a wheel is the tire. In simpler terms the wheel needs torque to accelerate but horsepower to keep it at speed.

Weight of wheel doesn't really have effect on the frictional force. The primary factors will be tire design, tire width/dimensions, tire pressure, and car weight. If one really wanted to reduce this drag they would do what airplanes do, get very skinny high pressure wheel/tires on there. However there would be a lot of other down sides. Basically drag vs grip.

As for this whole 9.8m/s^2 thing and escaping the earth's gravitation. It's really cool that you are studying/researching things of science and I implore it. As always though, there is a lot more to it. I certainly don't pretend to know all of it. But it's cool that you are seeking more knowledge.

Dogginator

jdmztrane, I apologize for coming off so harsh. You have mentioned some concepts that were not quite correct. In the simplest terms, wheel mass affects the dynamic response (accelerating, braking, turning, handling*) of a vehicle, not the steady state (cruising).

* handling over bumps and so forth.

seannabend

if the wheels are the exact same dimensions and you will be using identical tires on each rim then you probably won't notice much difference

I've got a BS in Mechanical engineering so I've had the same physics 1 and 2 classes that these other guys have had

if you are really concerned with wheel weights, look at going with a lightweight 14" wheel