vasu

I was wondering if anyone had any stats of figures as to what kind of performance gain can be expected from shedding weight from the wheels.

Since there will be less weight on the wheel, there will be less rotational intertia, which should increase acceleration times and decrease breaking distance, both good things.

But how big of a gain can we expect? Looking at different wheels and different tires, depending on my budget it looks like you can get wheel/tire combo that will be anywhere from 6-15 pounds lighter at each wheel.

How much faster could this make the car? .1 seconds? 1 seconds? Anyone got any ideas?

-vasu

fdl

There was a really good post a while ago at the other place by someone..named stevevtec i think. He ran different variables through some "car data" software and it showed that lighter wheels made a significant diff in 0-60 and 1/4 mile.

Not sure if steve has moved here but he may have some more info on the matter.

larchmont

I'd be worried about the DOWNSIDE. Any?

TinkySD

There is no downside to using lighter wheels/tires. The gains are two fold. First you get better handling as the light wheels makes the suspension quicker to be able to adjust to the road, secondly the decrease in rotational mass makes the wheel easier to turn/stop which makes braking and acceleration better. Couple that with stickier tires which improve handling/braking/launch traction more and you are talking about a lot of upside.

The amount of gains one can expect aren't an exact science but let me give you some of the info. The old addage is for most street cars 100lbs is equal to .1 in the 1/4 mile. The only "real" scientific test I've seen was for drag race cars in which it showed dropping 1lb of axel speed rotation mass was equal to shedding 3lbs of statics mass in terms of acceleration. Note, however, this is for high torque motors. this discussion ties into the tq/weight ratio so it makes sesnse that cars with lower torque output(tsx @ 180lbft) stand to gain more relatively by shedding weight. SteVtec who is an admin at v6performance.net has done a observational study of weight reduction/timeslips and has noticed a trend that shedding 1lb of rotation is about equivalent to 8lbs of static. If you can drop 10lbs of weight per corner Stevtec estimates an effect ~ 320lbs off the car. That would give you a .3 gain in the 1/4. If you couple this with stickier tires allowing you to get a better launch you could very well see a bigger gain than that.

I'll post a little more on the subject in a couple minutes, but an interesting annecdote form Ste regardarding maximas is that the older body style with the 190hp engine stock for stock is just as fast as the last generation 3.0 with 222hp. The main difference between the two? Bigger and heavier wheels/tires on the newer generation.

vasu

There's only 2 downsides I can think of...

1) price.. it's going to cost a decent ammount to replace wheels and tires. I'm looking at a bout a grand to shave 7 pounds off each wheel.

2) From a physics perspective, shedding the weight will result in energy being able to move the wheel easier. However it will also require more energy to keep the wheel moving since it weighs less. In theory (and again i'm just speculating here), your fuel economy might go down a bit because the engine needs to expend more effort the keep the wheel going at the same speed?

TinkySD

Ill give that to you: theoretically if you maintain a CONSTANT speed for a long time you could see a decrease in gas mileage. But if you tend to accelerate or slow down on the freeway because of traffic/passing etc that should negate the effects.

In day to day driving where you do a lot of acclerating and slowing down you should see a mileagle in increase if you drive in the same manner; you should be able to be lighter on the throttle/revs to get to the same speeds.

larchmont

Sounds right. At first blush it seemed ass backwards -- how could less weight require more energy to keep it going? -- but I guess the idea is that heavier wheels would have more momentum, so it would take less to keep them going. (Right?)

Great posts from Tinky too.

vasu

larch, exactly. If something is heavier, it's more resistant to change in velocity, so once it got to speed X it'd want to stay at speed X.

Tinky, if what you're saying..rather if what Steve is saying is right, that it's almost a 320 pound loss from 10 at each wheel, that's a huge gain!

I just ran some numbers using Car Test using that reduced weight and I got numbers of around 6.5 seconds and 7.5 for the manual and auto respectivly in a 0-60..

That's pretty substantial, can it be that good? Is it too good to be true?

Tinky, whatcha think about this?

TinkySD

Part two of effects of light wheels:


For the Average Joe:
So are light wheels going ot turn your car into a burner? Not really, but it will make it significantly quicker and much more driveable which is the key for me. Handling benefits aside the biggest gain to light wheels is in higher gear acceleration. Some of you may or may not know that the gearing in a car has a huge effect on torque output at the wheels. In lower gears the tranny is geared in such a way as to amplify torque to the wheels.(you might be able to get 200+lbft to the wheels when the engine is only cranking 180) In higher gears the tranny is geared for economy and the tallness makes the effective max torque less than what the engine is producing.(maybe only 110lbft to the wheels even though the engine is still cranking 180) in low gears with torque amplification you may find the effect of the light wheels not terribly great as the effective tq/weight ratio is impacted less. But while cruising around in a higher gear(low rpm) you will find the car much more responsive and able to accelerate. The effect of the decreased weight has relatively greater in tall gears. For me this is huge. Sometime 5th gear in the auto just doesn't have enough go for me if i want to make a pass.
Another annecdote from mattg at a-cl. He says with centerlines on his cl-s the car accelerates much more crisply in the top gears. Seeing as how the tsx auto is geared nearly the same and has a much lower torque output you can expect much more significant gains.



For Racing:

The comment I made about gaining .3-.5 seconds in the quarter mile or probably more with good tires may sound like it doesn't mean alot but in the racing community .3-.5 is huge. A lot of people put all kinds of mods on their car, intake, exhaust + headers and don't gain that much time. The reason is those mods tend to only give gains in a small portion of the powerband while light wheels are a constant source of extra torque to the wheels at all rpm. Even though at no point is it going ot make your car feel like it has an extra surge of power, but the area under the curve adds up and you are going to feel like you dropped a few of your friends out of the back.

TinkySD

Those are similar numbers to what stevtec got. I think they are a little overoptimistic but not necessarily out of the realm. With the manual I think that going ot sticky tires will be more important while with the auto lighter wheels will be more important as it's geared much less aggresively. Both will have an impact in both cases though

ClutchPerformer

Is this a typo? The auto/manual part, I mean...

vasu

Wow... using those same numbers and going with those SSR's you were showing me, coupled wtih the Toyo Proxes T-1s, that's about 14 pounds lost at each wheel, or "effective" of 448 pounds.

Using those numbers in Car test I now get <drum roll please>: 7.2 seconds for the auto and around 6.3 for the manual.

WOW, couple this with a possible Hondata application, and without modding any of the engineering aspects, that's quite a big improvement!

If I can get into the mid to upper 7's with an auto with lighter wheels/tires, then I'll be quite happy

-vasu

vasu

Yeah i inverted it, it's now fixed

ClutchPerformer

Whew! Man, 6.3 0-60?!? That's incredible. Volk GT-Cs, here I come! (when I save up the money :P )

larchmont

Here's a Q that I'm surprised nobody has asked yet:

Why, then, doesn't Acura (not to mention every other higher-end brand) just make their stock wheels lighter?

I know it would increase the cost some -- but not that much in the grand scheme of things. Vasu says it would be maybe a grand to mod the car -- which I assume means it would be considerably less than that for the car to be made that way in the first place.

And, considering how much they bust their butts to make the cars lighter to help performance, they'd be getting an awful lot of bang for their buck in doing this, given the "mulltiplier" effect. You'd think they'd want to make the wheels absolutely as light as possible.

Which maybe gets back to whether maybe there are other downsides besides what's been mentioned?

TinkySD

To answer a few questions. I think knocking a whole second off is unrealistc. That's turbo territory. But .3-.5 seconds is HUGE + the increased drivability.

Larch: Costs for good forged wheels and tires more like like 2 grand to 2500. Performance cars like the nsx, 350z, some porsches among others to come with forged wheels. But only on true performance cars generally. Some claim that light weight rims tend to bend easier but I think that is more due to the fact that alot o fpeople that use them are autocrossers who reallys stress the wheels. Forged wheels are stronger for a given amount of metal so less can be used which is what gives it the lightness. Technically there should be no differences in strength... but i'm sure some companies light weight wheels are in fact softer.

Also note that the larger the diamtere of the wheel the larger the lip is away from the axel. This increases it's inertia and effective weight. As carmakers have gone to higher diamtere wheels over the years there has been a trend to decrease weight to keep performance from suffering. Over the years wheel weights have gone down a bit but you can only do so much with the casting process. one rule of thumb i've heard is that you need to known 5 lbs off a wheel to keep it effectively(inertia wise) the same as a wheel with an inch less diameter.

RogerPodacter

Yeah! Except that i heard hondata is not coming out for the TSX this year...

vasu

Well lets all hope for hondata next year

YBA

Maybe Acura is using heavier wheels because of the wheel strength... Maybe lighter wheels are not as pot holes resistant as the original heavier wheels...

Remember, they have to sell the car in many different countries including Canada where we have more than our share of road holes...

Just my 2 cents

Jason

Excellent thread. So do we have the weight numbers for the stock TSX wheels and tires? What would some recommendations be for decent lightweight wheels with a nice tire?

I am torn on the whole thing b/c I'd hate to ditch my stock wheels and tires and basically throw them away before they are even used. It seems like a waste. Then of course there is the summer/winter argument, so I guess I could use the stock wheels/tires for that. Ideas?

OldieTSX

the other beni from lighter wheels is less unsprung weight at each corner, which is directly related to the handling gains. It also reduces the stress placed upon your suspension components.

ClutchPerformer

I was thinking of putting winter tires on the stock wheels. Then buying a new/prettier/lighter set of wheels to put summer/performance tires on. That seems like the ideal setup. Don't want the good wheels getting messed up in the winter months anyway.

vasu

Yeah that'd be awesome, and so easy to swap out yourself