Lightweight Wheels - Does it really matter?
 

I was always under the impression that light weight wheels would make a significant difference in acceleration/braking/handling in general.. but I came across this post in the NSX forums that seems to prove otherwise:

http://www.nsxprime.com/forum/showth...-their-results

Long story short, there wasn't any significant difference between the heavy vs light wheels acceleration wise.... but of course that's just some guy on the internet. I didn't read the whole thread but braking/cornering wasn't tested I think...

Those of you who shaved off a lot of weight, say ~5 lbs at each corner with 17x7 RPF1s or something like that ... is there a measurable difference? Is it just 'feel'? Or just cuz you upgraded to stickier tires from the stock ones?

Lightweight wheels are meant to help lighten the car in general. It's like switching to racing seats, removing the backseat, or changing out the exhaust to a lighter one. That one part itself doesn't make a measurable difference, it's the weight saved altogether that will have the affect.

Say you buy lightweight wheels and save 5lbs a corner. 5x4 = 20. 20lbs aint much overall and you wont notice. Now say you add a lightweight full exhaust, there's maybe 10-15lbs. 20 from the wheels + 15 from the exhaust = 35lbs saved. Say you add a lightweight battery on top of that. There's another 11lbs. 35+11= 46lbs saved. Now remove the rear spare tire. 35ish pds? 46+35 = 81lbs saved. Now you're getting somewhere and you're going to feel the difference. It's not gonna be night and day, but you'll feel it.

You're going to feel the difference going from a 7" wide tire to a 9" wide tire more than you're going to feel the weight lost by adding lightweight rims. But shaving weight wherever possible does make a difference.

That NSX guy just added lightweight rims and expected a night and day difference in acceleration. That's not how it works.

Unless you are a seasoned track driver will you really notice the tenths or maybe second or 2 saved from weight reduction?

Also think, he said .05 was the result of the lightweight wheels? So if a track has 15 corners, can you multiply that difference by 15? If so then you are really getting somewhere.

In competitions where wins are decided by tenths, .0X is actually quite significant. But if you are just racing some guy on the highway 0.X is neck and neck...

Reducing mass is good.

Reducing unsprung mass is great.

Reducing rotational mass is brilliant.

Reducing rotational unsprung mass is golden.

Just because you have an NSX, doesn't mean you have a clue.


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+1 I believe every pound of rotational unsprung mass reduced is equal to 8 pounds of sprung mass. so 5 lb off per wheel would be more like 20x8=160. Prob isnt "8" though correct me if I am wrong.

It might not always make a huge difference in acceleration, but it makes a GIGANTIC difference in feel. Adding unsprung weight forces the suspension to work harder. It has to control the up and down motions of the wheel going down the road. Imagine lifting a 5lb barbell up and down over and over. It's light enough that your arms don't have much issue. You can do this smoothly without shaking or trembling. Now, up that weight to 10lbs or 15lbs...you can still do it, but probably not as smoothly or easily. Your arms fatigue sooner. Now, your arms might get used to it and build muscle but your suspension doesn't have that ability to change.

Same goes for rotational mass. Spin a weighted flywheel with your hands. Now stop that flywheel. Add a bunch of weight to it and spin it. It takes more work to get it started but once it gets going it's not a huge issue. However, now you have to stop it...ahhh it's hard!!!

You can feel it everytime you get on and off the throttle...it does not take a seasoned track driver to notice ~15lbs of rotating mass coming off the entire car (I saved ~4lbs/corner with my wheel/tire setup).

Grassroots Motorsports tested and 100% of their tests the heavy wheels were FASTER on their test course than light weight wheels. The lighter wheels helped with braking and acceleration but they also flexed more which ended up hurting cornering.

Just sayin......

It does make a difference in feel though if you go far enough. My tires more or less offset the wheel weight savings for me...

On my GTI, the stock "Detroit" wheels are 29 lbs. I switched to 19 lbs. aftermarket wheels and noticed some immediate differences.

- More road feel.
- More road noise (i.e., car was louder over rough pavement).
- Suspension reacted quicker to bumps and cracks (i.e., tires stayed in contact with the road better).
- Average fuel economy increased by a little over 1 mpg, as tracked by the onboard readout.

Take that for what it's worth. Also shedding 10 lbs/wheel is pretty extreme, so your results may vary.

Someone crunched the math once and the number was more like 1.7x for acceleration. Empirical test data seems to corroborate that as well.

So saving 5 lbs/wheel is more like 20 lbs x 1.7 = 34 lbs IMO.

Reminded me of this article:

http://www.m3post.com/forums/showthread.php?t=479110

We were always able to measure whp gains on dynodymanics from going to lighter wheel tire combo. Usually between 5 and 10 whp on evos.

I have done the math and got a multiplier of about 1.25x (or 5x if you are talking single wheel weight change) for acceleration. Of course the math is not exact, you have to make some assumptions about the moment of inertia of each wheel and the multipliers are only valid for a given tire/wheel diameter.

So if you save 5 lbs per wheel that is ~ equivalent for acceleration to saving 25 lbs of overall vehicle weight.

On the other hand, adding a pound of tire per corner is ~ equivalent to adding 7 pounds to the overall vehicle weight.

These numbers only consider the effect on acceleration, and not that lower unsprung mass allows your suspension to work better.

Here is my math

So what they should have said is that lighter wheels are faster, but shit wheels that flex are slower.

Light, strong wheels FTW.

GRM wasn't testing no name crap wheels.... Light = less material, there's no way around that given the same manufacturing process. Less material will mean less strength given similar designs.

So the real question is which design is the strongest for a lightweight wheel?