Advantages to lighter wheels?

[Groomz]

I would like to know if there is any benefit to running a wheel that weighs 17 pounds versus one that weighs 20 pounds? Would it have any performance advantage on the street?

 

[Eclipse96Ryder]

of course it has an advantage. 3lbs on each rim is 12lbs total. Thats weight that really makes a difference too, because its on the tire....the thing that needs to move in order for the car to go fast. A lighter rim is definately noticeable in acceleration

 

[CowPimp]

Those 3 pounds will make a difference, but it probably will be too small to notice or barely noticeable.

Also, if the wheels are larger in diameter, but lighter, it will negate some of the advantage of having lighter wheels. This is because less of the mass is concentrated towards the center of the wheel. This makes the wheel harder to turn.

The main reason to get aftermarket wheels, in my opinion, is so that you can put on wider tires and make the sidewalls less sloshy. Even widening the wheels without adding wider tires will make a noticeable difference in hanlding. Dropping some rotational weight at the same time is a good idea, but it's not the reason I got new wheels. Since you have a FWD car, this will also imrpove your ability to launch at higher RPMs.

 

[Groomz]

I plan on running a tire thats diameter is *slightly* smaller in diameter to compensate for any additional rotational mass. The factory tire diameter is 24.87 inches, while a 215/45ZR-17 tire has a 24.61 inch diameter. The best reason for a larger wheel, at least for me, is to install larger than factory brakes. You also get better cooling, and looks too

 

[CowPimp]

I think you should try and run a wider tire. I'm running 225s, and I kind of wish that I crammed more rubber on there. I think next time I have to get tires, I will run 235s. I will even go 245s if possible. As I said before, you have a FWD car, so it is even more important for you.

 

[Groomz]

I'm just gonna get slicks for the track.

 

[CowPimp]

Alright, I'm just saying you should run as wide a tire as possible because it's about the best thing you can do for handling. It improves braking, really hard acceleration, and handling greatly. However, do as you please; I'm just stubborn.

 

[Defiant]

3 pounds a wheel won't hurt anything, but you won't be able to measure the improvement. And if it's to go to bigger brakes, you might lose the gain.

 

[Groomz]

True. I can always switch tire sizes if this size doesn't suit me. I'm going to have to compromise between looks/weight/performance when I do get a set. The weight advantages would be lost if I upgraded the brakes, but the braking would greatly increase, so I guess it evens itself out. Can't win em all

 

[CowPimp]

I definitely support getting larger brakes. Despite the slight weight increase, better braking is just a good thing to have. In addition to the obvious advantages for autocrossing, you will also be happy you got them next time someone changes lanes into a car on the highway in front of you.

I upgraded just my rotors and pads, and I love the difference in feel. The initial grab is more significant. Fade is reduced drastically at high speed. Also, good rotors combined with low-impact pads leave your rotors in good condition for a longer time. The last rotors I had warped pretty badly after 20K miles (The traffic around here is the worst in the country). Don't forget that the right rotors can enhance the look of your car too.

 

[Groomz]

Going for some AEM upgrade rotors and swapping AWD calipers once I get the 17s. I think the AEM rotor upgrade should fit in my aftermarket 16x7s. Once I go for the AWD calipers, I will need some 17s for sure. Preciate the advice

 

[MrPikolo]

isn't rotating mass alot more than stationary? So infact you would be losing more than just 3 lbs? Or have I been misinformed

 

[igs]

Originally posted by MrPikolo
isn't rotating mass alot more than stationary? So infact you would be losing more than just 3 lbs? Or have I been misinformed

Correct. 3 lbs per wheel is like losing 30 lbs of dead weight. Wider tire = more drag and more rolling resistance.

 

[MrPikolo]

so thats about 120 pounds? A decent weight reduction isn't it?

 

[CowPimp]

It is indeed a decent weight reduction. However, some of the weight loss will be offset by the fact that the weight is less concentrated towards the center of the wheel. The difference will be there, but it won't really be noticeable. I lost 4 pounds per wheel when I got my rims, but I couldn't really notice a difference.

 

[igs]

Originally posted by MrPikolo
so thats about 120 pounds? A decent weight reduction isn't it?

3 lbs per wheel equals 12 total pounds of rotating mass which is roughly equivalent to 30-35 lbs of static mass not 120.

 

[CowPimp]

Someone on these forums told me that every pound of rotational mass removed is equivilant to 9 pounds of stationary mass. The person in this thread was saying the ratio is 10:1. Anyone else with better knowledge of the subject that can shine some light on this little dilemma?

 

[igs]

Rotational inertia = (1/2)m(R^2)

So it depends on how far away the mass is from the point of rotation. Rotational mass could be 2x or 20x that of static mass.

 

[igs]

Rotational weight is best described by example. Let's say you have 12" rotor on the front of your car. That rotor weighs in at 16lbs. To calcuate the amount of rotational weight that rotor has use this formula. r2 * weight= rotational weight. So in this example the r=radius of the rotor which is (6 * 6) * the weight, which is 16lbs = 576lbs. So in order to turn that rotor whether speeding it up or slowing it down, it is the equivalent of moving 576lbs. This is why racers try to limit the amount of rotating mass they have. It can make a big difference when accelerating and decelerating. Let's say you had a rotor that only weighed 6 lbs (same 12" diameter). (6 * 6) * 6 = 216lbs. So, for each rotor you are saving 360lbs of rotating mass. That could just mean that much less weight for your engine to turn or your calipers to stop.

 

[MrPikolo]

120 all total is what I was saying. Based on that 3 pounds of dead weight =30 pounds of static weight.