Here's the thing: everyone scoffs at heavy wheels, and everyone seeks light, strong wheels, claiming that a decrease in wheel weight equals free horsepower, etc, etc.

Is this REALLY true? Has anyone done a test, where they've taken the same car to the track on the same day, slapped on different wheels of different weights (with same tires) then let the acceleration timeslips be the judge? No butt dynos, no "boy, I put them on and they feel great," but hard and fast numbers?

It seems to me that such a test, if one exists, would go a long way toward resolving the endless weight questions that crop up on this board. Heck, if someone wants to do it, I'd be more than happy to donate my old-school P1s to the party (Chicago-area test, of course).

Kevin

Hi,

Its different from a real-world situation, but take a look at this link that was posted last month.
Wheel & tire rotational intertia (http://forums.i-club.com/forums/showthread.php?s=&threadid=215952&highlight=tire+and+weight+and+acceleration)

~Cheers

Yes, it is REALLY true, but like you, Kevin, I think the effect is blown out of proportion by many people on this board. Every time somebody asks about or posts pictures of a new wheel, the first questions in reply are, "How much does it weigh?" and, "How strong is it?"

My street wheel/tire combo is a set of 17x7" UK WRX wheels with 215/45-17 Toyo T1-S's. The UK wheels are supposed to weigh around 17.5#, and the Toyos weigh 20.1# (according to Toyo's website), so we get roughly 37.5# together. My auto-x/track wheel/tire combo is a set of 15x8" Volk TE-37s with 225/50-15 V700 Victoracers. The Volks are supposed to weigh 9.5# each, and Kumho says the V700s weigh 23.8# each - for a total of 33.3# all together.

Not only is the race setup over 4# lighter at each corner, but I also get a 4.7% gearing advantage by using the shorter tires. Guess what? I can't feel any sort of acceleration difference with the ol' butt dyno. I think someone would have to be really in tune with their car to feel a 4 or 5# difference.

Pat Olsen
'97 Legacy 2.5GT sedan

Interesting. Thanks, Pat. I figured this question needed to be asked, for precisely the reason you state. It seems to me that even before offset (an important question) everyone wants to know what a wheel weighs.

One of my favorite posters (for you cycling geeks) is of Laurent Fignon, sitting on the ground, with a crankarm/pedal combination attached to his shoe. His Campy titanium bottom bracket sheared off during a race. I've since forgotten the manufacturer that was touting their "ours doesn't break" product, but it really got me to thinking about the whole weight vs. durability equation.

I know that with a bicycle, you can really feel the rim weight, as opposed to the wheel weight. My Ksyriums don't weigh any less than my Rolfs, but the Ksyriums are much faster, because they're stiffer, and there's less weight at the rim that you have to accelerate.

At any rate, I hope this post stimulates some interesting debate, and maybe somebody will head out to the track with their buddies and a bunch of wheels.

Kevin

Originally posted by Patrick Olsen
I think someone would have to be really in tune with their car to feel a 4 or 5# difference.

Pat Olsen


Oh, I'm sure there are plenty of people on this board that do. Just yesterday, I think, someone sworn that his front strut tower bar totally eliminates body roll and understeer. ;)

-Ray

The rotational interta thread says it all if you ask me.

Also, Pat's example (a difference of 4 pounds per corner) isn't what the typical i-club rim snob is reacting to. They're reacting to people taking the stock 16" 16.5lb WRX rims off and putting on 22lb 17" rims. There's 5.5lbs right there. Now wrap the outer perimeter of those rims with a set of lead-filled Kumho Ecstas and you have the i-club special.

EDIT: If you're racing, who cares if you can feel the difference? It's there. You can't evade physics :p

Originally posted by rkkwan


Oh, I'm sure there are plenty of people on this board that do. Just yesterday, I think, someone sworn that his front strut tower bar totally eliminates body roll and understeer. ;)

-Ray

It DOESN'T!!?? :eek: Now what am I going to do... :lol:

Kevin

Originally posted by gtguy
It DOESN'T!!?? :eek: Now what am I going to do... You need to install a set of my special 3" (76mm) sway bars to get rid of your body roll. Paypal me all you money and I'll mail you a set.

Originally posted by jblaine
EDIT: If you're racing, who cares if you can feel the difference? It's there. You can't evade physics :p

That's fine. If you're racing, you should really only be using forged mag wheels. ;)

Meanwhile, the rest of us who use our cars as daily drivers would prefer to get whatever wheels we can afford that are both strong enough and give us the best handling we can get on street tires.

<== On "heavy" 18" P1s and proud of it. :lol:

22lb Speedline 2116's (Chrono,SuperTurismo..) Yeah, baby,yeah...
you know what they say about fat bottom girls;)

Fire away:cool:

Originally posted by jblaine
EDIT: If you're racing, who cares if you can feel the difference? It's there. You can't evade physics :p
I agree whole-heartedly, a car with heavier wheels will be slower. However, the question is how much of a difference does it really make. The point I was getting at is that if I can't even feel a difference, then it's probably something that would barely show at the dragstrip. That's just a WAG, of course.

I'd love to see some actual testing of this - identical tires on a variety of wheels. I'd also love to know how much of difference my shorter racing tires really make as far as acceleration goes.

Pat

you could just put a car on a dyno (the type with rollers)

Here's some testing.
The 17" rims are 25 pounds with Pirelli runflats. The 16" rims are, I think, 17 pounds with Azenis (I think this is skewing the braking results a bit):
Here's the results:

All testing was done in the same location, 78 degrees ambient, same direction, 3 runs each

I made the comparison even more accurate by swapping my father's 17" S-Spoke wheels on to my car instead of driving two different cars.

17's
-----
0-60mph = 7.37, 6.74, 6.85 seconds
60-0mph = 127, 125, 133 feet

16's
-----
0-60mph = 6.57, 6.67, 6.52 seconds
60-0mph = 115, 111, 113 feet

Interestingly, but not surprising, it took more power to launch the 17/run-flats. I was launching the 16's around 3200rpm to get the perfect run while it took about 4000rpm to launch the 17's. It's obvious to me that the rotational mass was the factor to get moving quicker (this is also why the first run on the 17's was significantly slower, it bogged a little at just above 3000rpm).

I ran the 17's first to insure that brake fade would not favor the 16's. Turns out the brakes cooled plenty in the tire change, although they were very hot when I changed after I was finished.

It is VERY easy for me to now see where the magazines could get higher 0-60 times. I've launched this car MANY times and it's well broken in, two factors that magazines do not have right now.

I was extremely happy to see the 111 foot braking number, that's quite impressive.

Again, take these numbers for what they are, a comparison via a G-Tech.


__________________
H Stock for Pro Solo's
D Stock for National Tours in 2002!


Here's the whole thread:
http://www.mini2.com/forum/showthread.php?s=&threadid=10982&perpage=15&pagenumber=1

The McRaes and Schumachers of the world would notice a 4lb/wheel difference immediately. But mortals - not in a month of Sundays! A bloody WRX with an average driver and full tank of fuel weighs over 3300lbs. Right, now lets take 16lbs off that and ...wow. I'm a second a lap quicker - in your dreams!

I'm still saving for a set of GC06s though - strong and light...OOPS! Just kidding.:lol:

Originally posted by HoRo1
The McRaes and Schumachers of the world would notice a 4lb/wheel difference immediately. But mortals - not in a month of Sundays! A bloody WRX with an average driver and full tank of fuel weighs over 3300lbs. Right, now lets take 16lbs off that and ...wow. I'm a second a lap quicker - in your dreams!

I'm still saving for a set of GC06s though - strong and light...OOPS! Just kidding.:lol:

the weight savings in relation to the car's weight is insignificant, but the issue isn't accelerating the wheels in a straight line, it's accelerating them rotationally.

Originally posted by gtguy
One of my favorite posters (for you cycling geeks) is of Laurent Fignon, sitting on the ground, with a crankarm/pedal combination attached to his shoe. His Campy titanium bottom bracket sheared off during a race. I've since forgotten the manufacturer that was touting their "ours doesn't break" product, but it really got me to thinking about the whole weight vs. durability equation.

I know that with a bicycle, you can really feel the rim weight, as opposed to the wheel weight. My Ksyriums don't weigh any less than my Rolfs, but the Ksyriums are much faster, because they're stiffer, and there's less weight at the rim that you have to accelerate.



Kevin -
Yeah, Laurent was using the old campy ti BB! The big issue was that BB was manufactured before they really understood the difference between alpha and beta titanium alloys. "The Professor" learned a lesson that day!

These days, bicycles have come a long way and breaking a spindle is almost unheard of, but on the topic of wheel weights...
My mtb has a set of the Spinergy SPOX (vectran spokes - ULTRA lite) and they make a HUGE difference over a basic Mavic/Shimano/DT wheel. They also have the benefit of being MUCH stronger than the wire-spoked wheel and the spokes tend to be kind of supple, which makes them superb mtb wheels...

now my road bike has a nice set of Open Pro Ceramics with DB spokes... they feel just fine, but when I tried a pair of road SPOX on it, it was horrible, not because of the weight, but because of the lack of stiffness and the fat profile of the spoke - it's not aerodynamic, which on a bike that averages 20+mph, is bad.

The Ksyriums are truly amazing wheels and the SL's are even more spectacular with even more weight shaved off the rim. Can't beat that aero-profile on the Al spokes either! Happy pedaling!

-Nick (All Star Bike Shop, Raleigh NC)

You might call me crazy but I actually did feel a difference between my normal wheels (17x7.5 Rotas w/Kumho 712s) and my stock wheels/tires when I put them back on for a rallyx. I didn't feel much of a difference once the car got going but it did seem that it was easier to get going with the stock wheels. I found that the car would start rolling with less rpms/clutch slip. Also, on hills I would roll back more than I do on my 17s. It's not a night and day type of thing, but I definitely felt it. After putting my 17s back on things were back to normal so I was able to confirm that there was a difference.

Originally posted by yonrin kudo
Hi,

Its different from a real-world situation, but take a look at this link that was posted last month.
Wheel & tire rotational intertia (http://forums.i-club.com/forums/showthread.php?s=&threadid=215952&highlight=tire+and+weight+and+acceleration)

~Cheers

I went thru and put in 2 wheels on that spreadsheet -

a 20lb 17" wheel with a 225/45R17 tire
a 15.5lb 17" wheel with 215/45R17 tire

The torque difference needed to accelerate the car in a straight line with the lighter wheels is about 1.05 ft-lbs...

the difference needed to accelerate the wheel rotationally is between 2.29 and 4.6 ft-lbs... which is like losing 44-76 lbs from the chassis.

If you add the linear + rotational, you get a difference made by going with lighter wheels of approxkimately 3.3-5.7 ft-lbs of torque freed up.

That's not huge, but it's noticeable by those who are "in tune" with their cars... It's about the difference you might feel from an underdrive pulley or a light flywheel.

A notable additional benefit of lighter wheels/tires is the reduction in unsprung weight, which should make the suspension work better!

Eh...double post :rolleyes:

A little off topic but...

gtguy, you said time and time again that your STi suspension is better than the coilovers you used to have. How exactly did you come to this conclusion? Do you have any lap times to support your argument?

The reason I ask is because this thread just screams pot, kettle, black.

get back to me after physics 101

16lbs of weight saved on a wheel which must acceleration in its rotation is not the same as adding a 16lbs dumbell to the back seat.

look at th hard data up above, thats "noticeable"
if you don't FEEL the difference, you might SEE it when you lose by a couple tenths =)

Originally posted by HoRo1
The McRaes and Schumachers of the world would notice a 4lb/wheel difference immediately. But mortals - not in a month of Sundays! A bloody WRX with an average driver and full tank of fuel weighs over 3300lbs. Right, now lets take 16lbs off that and ...wow. I'm a second a lap quicker - in your dreams!

I'm still saving for a set of GC06s though - strong and light...OOPS! Just kidding.:lol:

And with a lighter wheel mass you'll get better cornering. Less rotational mass= less of a gyro effect. Just like if you take a bicycle wheel and spin it while you hold it... Food for thought;)

This is my experience with differing wheel sizes and weights:

I used to have 13" steel wheels with super crap tires before I bought a set of WRX rims with RE-92's. I think the stock WRX rims are 16.5 lbs, not sure what my stock wheels were. Anyway, increasing the wheel size by 3" and adding a few pounds at each corner made a noticeable difference in acceleration. I'll trade some straight line speed for being able to maintain traction when it's raining though.
13" to 16" would be like a WRX owner going from 16" to 19", which of course would be a big difference. I can't see how a slightly heavier 17" wheel could make much of a difference.
Also, how much do you think my speedometer is off with 16" wheels?

I just got my wheels about 3 weeks ago. They weigh 12lbs, are single piece forged, and are 17". I wish I could say that the car felt faster in any way shape or form w/ the lighter wheels, but I cannot. The car does corner better, but I feel it's mostly b/c of the much better tires...I went from stock RE92's to S03's in 225/45/17...nuff said.

FWIW, SCC did a wheel weight/acceleration test a couple of years ago on a civic (same size wheels if I remember correctly) and there was a difference in acceleration. The lighter wheels did do better...but not a huge difference.

Also, I don't think that comparing two different sized wheels is in a weight test is fair, because even if the wheels weigh the same, theoretically, it should take less effort to spin the smaller wheel. Just my $.02

Originally posted by dj_noose
And with a lighter wheel mass you'll get better cornering. Less rotational mass= less of a gyro effect. Just like if you take a bicycle wheel and spin it while you hold it... Food for thought;)
This effect is small compared to the effects of the narrower sidewall of a tire on a 17 inch wheel compared to that of a 16 inch wheel (assuming the same overall outside tire diameter). My experience with 17 inch wheels is that while they do take more power to accelerate, they corner better.

Rich

the total weight of the larger tires + lighter wheel probably comes out about the same.



Originally posted by Dori Dori
I just got my wheels about 3 weeks ago. They weigh 12lbs, are single piece forged, and are 17". I wish I could say that the car felt faster in any way shape or form w/ the lighter wheels, but I cannot. The car does corner better, but I feel it's mostly b/c of the much better tires...I went from stock RE92's to S03's in 225/45/17...nuff said.

FWIW, SCC did a wheel weight/acceleration test a couple of years ago on a civic (same size wheels if I remember correctly) and there was a difference in acceleration. The lighter wheels did do better...but not a huge difference.

Also, I don't think that comparing two different sized wheels is in a weight test is fair, because even if the wheels weigh the same, theoretically, it should take less effort to spin the smaller wheel. Just my $.02

Also with the 17's with 225/45's tires the accuracy of your speedometer will be the closest to the stock set up. 834 rotations per mile for the 17's and 837 for the 16's. If I can remember corectly. 18" wheels with the 225/40 setup is even more off. Can't remember off hand for thoughs right now...

Originally posted by dj_noose
Also with the 17's with 225/45's tires the accuracy of your speedometer will be the closest to the stock set up. 834 rotations per mile for the 17's and 837 for the 16's. If I can remember corectly. 18" wheels with the 225/40 setup is even more off. Can't remember off hand for thoughs right now...

Aha, that also depends on the tire you use. If you check Tirerack's web site, you'll see the Subaru 205/55VR16 RE92s are 830 revolutions per mile, exactly the same as the Michelin Pilot Sport A/S 225/40YR18s 830.

Originally posted by ElDuderino
A little off topic but...

gtguy, you said time and time again that your STi suspension is better than the coilovers you used to have. How exactly did you come to this conclusion? Do you have any lap times to support your argument?

The reason I ask is because this thread just screams pot, kettle, black.

Both at Gingerman, and through my neighborhood test facility, yes, indeedy. And that doesn't take into account intangibles such as suspension feel, etc that go into making a car more fun and confidence inspiring.

If you don't test both on the same course and corners, with the same car/wheels/tires, how else are you to know if something works better or not? Seems to me there's no way of knowing otherwise.

And, the whole, synergistic STi package is better. Strut/spring for strut/spring, give me DMS (NOT Tein) any day of the week!

Actually, this is a holdover from my days as an audio geek. I would always test things with a blind A/B test. It's one thing to say that a $500 per meter speaker cable sounds like heavenly hosts...it's another thing to back that up with a blind test. We once did a test of interconnects, and found that RG8-U coax (the BIG stuff) from Radio Shack, sounded better than any of the expensive audiophile snakes that we had, on three different systems! :eek: Curiously, it also had by FAR the lowest capacitance. It caused quite a stir at the local audio emporium, let me tell you.

But ever since then, I've always wanted to know, in the same situation, A for B, how something works compared to its competitor/predecessor.

Kevin

Originally posted by gtguy
Both at Gingerman, and through my neighborhood test facility, yes, indeedy. And that doesn't take into account intangibles such as suspension feel, etc that go into making a car more fun and confidence inspiring.

So do you have track times to support this?

If ya mean posted slips, a la the drag strips, no. With car club stuff, you don't get stuff like that (you do with some, however). Only my own information. Mind you, I still haven't taken the full STi kit to the track, since Gingerman days have been on Tuesdays of late (some of us have to work). That's what the old neighborhood, late-night test track is for.

For example, there's an increasing radius bend that, in the stock car (these are all with 17" P1s/Dunlop 9000s), the max speed available is 35 mph, before the car starts getting squirrely, and the back end steps out. Not cool.

With the DMS, that same corner can be taken quite literally 10 mph faster, with no back end skittishness or instability. This does (did...they're gone now) happen if you mashed the throttle hard at the apex, however. Entering at a lower speed allowed you to apply throttle mid-bend, and the back end would behave predictably.

The STi struts and springs only were almost as fast as the DMS, wtih the same apex throttle application bugbear/caveat. We're talking 45-ish vs. 42 (not paying full, unblinking attention to the speedo when handling car, y'know).

Now, the addition of the STi link setup to the equation, makes that same curve a comfy 45 mph, but with increased stability and turn-in performance. Getting on the throttle at the apex, the car just goes faster, with no untoward behavior. It tucks into line better, and just goes faster with less drama.

I have a host of tests that I use: 90-degree bends, gentle sweepers, more abrupt sweepers etc, in addition to speed bumps and rough stretches of pavement.

It's all in the name of fun, but it's nice to be able to quantify efforts by slapping the stuff on the car, then rolling out of the driveway to see how it all works. It's getting to that at 2 a.m., the cops know that it must be me. :D

But suspension stuff is a no-brainer. You put it on, take the corners, see how it works. Wheel weight vs. acceleration is another matter. It's a simple question of straight line over a given distance, with two different setups. Either one is faster, or it isn't. We know the physics, but what about the reality. Some people have posted the results of their own tests, which is cool, and interesting, and feeds the spirit of experimentation/debate that makes this board a helpful place to be.

I'm sure that having me explain my suspension testing methodology helps someone, and perhaps I'll start another thread asking how everyone does that, rather than derailing this one by doing so.

Kevin

Kevin

Originally posted by DoinkMobb
This is my experience with differing wheel sizes and weights:

I used to have 13" steel wheels with super crap tires before I bought a set of WRX rims with RE-92's. I think the stock WRX rims are 16.5 lbs, not sure what my stock wheels were. Anyway, increasing the wheel size by 3" and adding a few pounds at each corner made a noticeable difference in acceleration. I'll trade some straight line speed for being able to maintain traction when it's raining though.
13" to 16" would be like a WRX owner going from 16" to 19", which of course would be a big difference. I can't see how a slightly heavier 17" wheel could make much of a difference.
Also, how much do you think my speedometer is off with 16" wheels?

it shouldn't be off any, as long as you don't exceed or go below the 205/55/16 size...mine is dead on, according to the readout from the vehicle speed sensor, and the radar trailer speed limit sign i pass every day on the way home from work.

Originally posted by gtguy
Mind you, I still haven't taken the full STi kit to the track, since Gingerman days have been on Tuesdays of late (some of us have to work). That's what the old neighborhood, late-night test track is for.
Kevin
What neighborhood track you're talking about? Do you have something like a small Gingerman next to Highland Park?

SCC ran an article awhile back where they tested acceleration times based upon wheel size/weight. I just glanced through my magazines and couldn't find the issue. I belive it was a pretty good read.

-Jon
www.nothingserious.net

Originally posted by RafalW

What neighborhood track you're talking about? Do you have something like a small Gingerman next to Highland Park?

:lol:

That's why God made Sheridan Road, man!

Kevin

Will lighter wheels make you quicker - maybe at the strip, but on a road circuit... like I said, the Schumachers and McRaes would notice, but mere mortals...

You'd be better off with a variety of improvements elsewhere on your vehicle, especially making the nut behind the wheel better - then you can improve by many seconds.

GC06s - my choice of lightweight wheel (I wish) - at ~$1800/set, well that's many driving schools with many hundreds (possibly a thousand or more!) of laps of good instruction - that'll make me (and you) a lot better and quicker than a 4 or 5 or 6lb/wheel saving.

Originally posted by HoRo1
GC06s - my choice of lightweight wheel (I wish) - at ~$1800/set, well that's many driving schools with many hundreds (possibly a thousand or more!) of laps of good instruction - that'll make me (and you) a lot better and quicker than a 4 or 5 or 6lb/wheel saving.

you can go fishing with dynamite but people still talk about which lures work the best. :rolleyes:

Of course driving schools are going to make you faster, but that doesn't prevent us from still wanting the best our equipment can give us, especially when presented with the choice between:

a) will get the job done
or
b) will get the job done better

if it better to get a brand name wheels say "volk" with so-so tire, or a copy wheels say "rota" with best tire?
if they both 17" but different weight.

many people said that there car cornered better with the 17s on instead of 16 inch rims. true a bigger rim and smaller sidewall will help,, but the main issue is tires. you could corner just as good with 16 rolling with some high performance rubber. ;)

-aaron

btw, IMO bigger wheels are for looks, not performance. not that there is anything wrong with that,.

Originally posted by scubaracer
many people said that there car cornered better with the 17s on instead of 16 inch rims. true a bigger rim and smaller sidewall will help,, but the main issue is tires. you could corner just as good with 16 rolling with some high performance rubber. ;)

-aaron

btw, IMO bigger wheels are for looks, not performance. not that there is anything wrong with that,.

Bigger wheels have one other advantage besides (arguably) looks: More room for larger brake components.

With that said, I'm sticking with 16" rims for the forseeable future. Like you alluded to, I wonder how many of those people went from 16" RE-92s to 17" performance tires and are giving more than due credit to the tire size rather than construction.

coati, the brake thing is true. but, there are seveal kits that let you keep 16inch wheels.
such as:
-Ap racing 4pot
-subaru 4pot
-perrin/wilwood 4pot
I like 16 for everyday use and you can still go offroad rallying.

-aaron:)

Yes, Yes, Yes, heavier wheels=slower acceleration, but what if I go from a stock wheel/tire setup on my WRX to 17x7.5 SSR Competitions with 225 45 17 Falken Azenis tires?

This setup should be the same weight as stock if not a little lighter!

Will my acceleration suffer?

E

16" wheels or not, most 4pot kits will NOT fit under the MY02 WRX wheels. You will need pre MY02 RS wheels for that or aftermarket wheels.

-Jon
www.nothingserious.net

Curiously enough, I think that if I were to do it all over again, I might run a 225/50/16 on a 16x7 wheel, rather than 17s, for the stealth factor if nothing else. As subtle as the P1s are, whenever I roll into a gas station, or park somewhere, people gawk.

I do love those P1s, though...

Kevin

Originally posted by scubaracer
coati, the brake thing is true. but, there are seveal kits that let you keep 16inch wheels.
such as:
-Ap racing 4pot
-subaru 4pot
-perrin/wilwood 4pot
I like 16 for everyday use and you can still go offroad rallying.

-aaron:)

I hear you. If I ever upgrade from the stock rims, it will be to lightweight 16" Rotas. I didn't buy a dirt-capable car just to make it dirt-incapable, which is why the only upgraded suspension kits I've considered seriously are the DMS and (more likely) the whole SPT wagon kit. That Baer brake setup looked interesting, too.

However, I'm getting married in a few months, so car mods are out at least for the near future. I'll have to "suffer" with the stock suspension and 205/55-16 Azenis.;)

STimpy, swap the wrx rims for the 5 or 6 spoke older rs rims. those rims fit all three 4pot setups i listed.

coati, I just think 16's are way more practical and good choice with the 16inch rotas. also, when I get my 2000-01 rs pretty soon, I have also been thinking towards DMS.

btw, the azenis tires you have are good tires and congratulations on your coming marriage. best of luck;)

I have 17x7.5 Rotas on my car right now and a set of 16x7 RS wheels ( 6 spoke) sitting in the basement with dead rubber. Sadly, I think they are going to serve as snow wheels this year.

-Jon
www.nothingserious.net

It's not just the overall static weight; it's the moment of inertia (mass x radius squared). As you move the rim of the wheel and the tire further out, the increase is exponential. The issue is that straight-line acceleration is one thing but handling is another. Over uneven surfaces (street) you are asking the damper compensate for the increased rotating mass. On a race track this would be less important since generally speaking the dampening action is more linear since you are dealing with smooth sealed tarmac, the street is another matter. The only benefit to a larger wheel is the ability to fit larger brakes, there is no other benefit. You can argue that the detrimental effects are negligible but they are exactly that - detrimental. You are asking your suspension do more work than is necessary for no good reason. You don't need to be rich to keep your stock wheels. There are also 15 and 16-inch wheels that weigh as much or less than stock that are reasonably priced (raceline, enkei). I am happy for anyone if they like large wheels and if they feel that looks justify having them but if they are going to say that it doesn't affect performance in a quantifiable way, it's just not true. Not to mention, many modifications that people do to their cars don't always make it "feel" better but many of them at least move in the right direction and in some small way contribute to the overall performance of the car. If you like the way your wheels look on your car, just come out and say it, I’m fine with that but if you try and rationalize your decision from a performance standpoint you’ll have a very hard time.

(I know that people will say that a 17 inch wheel with improve “turn-in” feel because you have more metal where there was rubber but you could just as easily put a low profile tire on a 15 or 16 inch wheel.)

Originally posted by mtclaes
blah . . .

Dude, I have no idea what your point is. You contradicted yourself 3 times.

Time to chime in I guess...

Well, I got my SSR 17x7.5 and Falken ST115 215/45R17, end result is one pound heavier than a well worn stock RE92 + 00 rim. At that time, 16s Rota or SSRs aren't available, and I do get 4 lbs advantage from the SSRs over the Rotas. Now it's a know fact (or is it not) that a grippier tire is gonna be heavier. You can say that I went for the 17s because of looks, as I still wouldn't have got 16s even if they were available. I thought about running 225/50R16 on stock rims (or light weight 16s), but the though of having them rub the strut or fender + the 7" rim width makes me worry. Ultimately, the weight savings in the rim allows me to run grippier tires and maintain a close to stock weight wheel setup.

kgb, the Toyo T1-s are real lightweight and grippy, but they seem to be the exception.

Instead of wheel WEIGHTS (or along side said data) there should be a figure for rotational inertia... it'd be easy to figure out... entry level physics.

Originally posted by Frederf
Instead of wheel WEIGHTS (or along side said data) there should be a figure for rotational inertia... it'd be easy to figure out... entry level physics.

entry level if only we had a good enough model for the wheel.

Maybe it's my imagination, but I do feel the difference between my 17" wheels and my 18" wheels. At the track (and sometimes just for fun on the street) I run SSR Competition in 17x7.5 with Falken Azenis. On the street I run Fikse Mach V in 18x8 with Michelin Pilot Sport. My WRX "feels faster" with the 17" setup. Like I said, maybe it's my imagination, and I haven't done a "back to back" measured test or anything like that, but that's what I experience. Now, yes, the rest of my WRX has had extensive modifications, and yes I've been to 3 different driving schools in the last two years, and I'm no stranger to road course tracks. Just thought I'd chime in with another voice of personal observations to this thread.

Cheers,

GoodFinder :)

Originally posted by GoodFinder
On the street I run Fikse Mach V in 18x8 with Michelin Pilot Sport. My WRX "feels faster" with the 17" setup. Those Fikses must weigh at least 20lbs apiece, though, compared to probably 13-ish for the SSR's? If you're ever going to feel a difference, it should be between those two setups.

Next time I swap out tires (which should be this weekend) I'll do a weight comparison of the wheel-tire combinations. I'm assuming there's something like a 5 pound overall weight difference between the two combos. The Fikse wheels look beautiful on the WRX, but the SSR wheels are a bit faster, so I keep going back & forth in my mind regarding whether I want to reserve the Fikse combo for show and special occasions, and use the SSR as my primary wheels for both street and track. Plus, the SSR cost so much less money than the Fikse, and I put so many miles on the car (75 mile daily roundtrip to work and back), that it would be a lot less painful if something happened to the SSR than to the Fikse wheels. Good point, though, in this thread, to note that the wheel-tire combo weight has to be compared, and even then, a wheel with more of it's weight towards the center, should work better than similar wheel with more of it's weight towards the outer edge, all other things being equal.

GoodFinder :)

Originally posted by nhluhr


entry level if only we had a good enough model for the wheel.

This is a problem. Weight is one thing, but where on the wheel the weight exists is another. I read some tests of bicycle wheels in VeloNews a few years ago where Zinn did some extensive testing on this using some sort of acceleration/frequency test. Mere extrapolation will get us nowhere. You'd need some heavier equipment to test it for car rims.;)

From SCC Mag

Step 1: Baseline
Curb Weight: 2,762 lbs
1/4 Mile:16.3 @ 84.0 mph
60-foot:2.9 sec.
0-60 mph:8.6 sec.

Step 2: 15-inch Wheels
Curb Weight:2,707 lbs
1/4 Mile:16.0 @ 85.5 mph
60-foot:2.8 sec.
0-60 mph: 8.1 sec.




Basically the wheel tire combo saved 55 lbs of translational weight (and probably much more rotational inertia since they went from 19" to 15") and the car's 1/4 time improved .3 seconds.

0.3 seconds at around 85 mph is 37.4 feet! I think you can feel that. If not, you will definitely see it!

unspring weight vs rotational mass ....

wouldn't these curp a lot of people from getting the suby 4 pot calipers? those suckers are like 3-4 lbs heavier than stock

in fact, call me crazy but i felt the car dampened better with the additional unspring weight, cannot confirm this tho but it does feel better when i hit speed bumps

also, from the deduction : lighter rims=faster cars, we are talking about quicker acceleration correct? but not higher velocity/speed (hp/torque)

Follow this link to the COBB tuning forum. There's a post reply from Josh at COBB where he talks about doing back to back dyno runs with stock WRX wheels vs. COBB CT-One wheels.

Click Me! (http://www.wrxforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=4;t=000152;p=)

Yeah, i think the saying is 4 lbs of unsprung weight for every pound of sprung. (maybe more?) But that's talking about handling. If your springs are stiffer than stock, then maybe a little extra sprung weight would feel better? Of course what is "better" anyway :lol:

Originally posted by mtb_dude
Yeah, i think the saying is 4 lbs of unsprung weight for every pound of sprung. (maybe more?) But that's talking about handling. If your springs are stiffer than stock, then maybe a little extra sprung weight would feel better? Of course what is "better" anyway :lol:

Heh, you've got it exactly backwards. :o

I don't think it's my imagination (although I've been accused of having an active imagination), but my 16" Volk's- 11.4 lbs, combined w/ my T1S's (~1 lb lighter than oe 92's) feels quicker than my oe (winter) setup. Losing ~ 6lbs per corner seems to make a difference.

.2 seconds in the 1/4mi.

My stock wheels are lighter than the 18's I put on.They're kinda cheap 18's (heavy) but they look great.
I was curious one day and did it.
15.8 on stock wheels @ 85
16.0 on the 18's. @83

It all makes sense to me. More weight, further out is harder to turn.
Take it as you wish.

Dominic

Originally posted by Skyline


Heh, you've got it exactly backwards. :o


Which? That unsprung weight is "heavier" than sprung weight, or that more unsprung weight would feel better with stiffer springs? I didn't say that you would get better performance, just that it would feel better (to the drivability minded person, which basically means it performs worse.)

Originally posted by BIGSKYWRX
I don't think it's my imagination (although I've been accused of having an active imagination), but my 16" Volk's- 11.4 lbs, combined w/ my T1S's (~1 lb lighter than oe 92's) feels quicker than my oe (winter) setup. Losing ~ 6lbs per corner seems to make a difference.

I don't know about acceration, but I feel my 16inch Volks(11~12lb each) provide good braking. I used to have 20lb Advan rims with TOYO TS-1,but it was scary.

Originally posted by nukeyfish


I don't know about acceration, but I feel my 16inch Volks(11~12lb each) provide good braking. I used to have 20lb Advan rims with TOYO TS-1,but it was scary.


with the same tires? that sounds very interesting...
If you have different tires, you're probably mistaking the brake quality between the tires for the wheels.

Originally posted by ImprezaRSX



with the same tires? that sounds very interesting...
If you have different tires, you're probably mistaking the brake quality between the tires for the wheels.

No. it was different tires. But, check this out. I have Volk TE37 with 16" Pirelli sport veloce(which is OK quality all-season tires) I had 20lb rims with 17" Toyo TS-1(which is known as hi performance tires). I feel TE37+pirelli tires have more stopping power.

I'm not sure if the ST115 would have more grip than the T1-S, but they are 3-4 lbs heavier per tire.

As for the caliper, since they don't rotate, it's less of a problem. So technically, for the same weight, it's always better to have lighter tires than lighter rims?

My friend got Wilwoods and they are feather light!

Originally posted by Coati


This is a problem. Weight is one thing, but where on the wheel the weight exists is another. I read some tests of bicycle wheels in VeloNews a few years ago where Zinn did some extensive testing on this using some sort of acceleration/frequency test. Mere extrapolation will get us nowhere. You'd need some heavier equipment to test it for car rims.;)

I've done one of these tests, not on a wheel, but on something similar (bit smaller, like a small plate). It's quite easy to do. You get better data with the stuff from a University 2nd year phys. lab... but even with a stop watch and a yardstick you'd get damn close.

The concept is easy.
Get a broom or a hammer.
hold it by the handle and swing it around.
Then hold it by the broom/brush/head end and swing it around.
which way moves easier?
simple, when you hold it by the brush/head end there is less weight further away from your hand. Simple lever/torque physics. The broom didn't change weight, but the location of the weight did; and it was easier to manipulate
Just like with wheel and tire combos. If a 16 inch wheel weighs the same as an 18 inch wheel, the 16 inch wheel WILL be faster; that's just the wheel. Since none of us what the harsh ride of just a wheel (or the sparks and poor wet weather traction) We add tires. If the 16 inch tire is significantly heavier than the 18inch tire the 18 MAY end up being faster.... isn't this fun?

So the answer is this:
If you can find a light wheel and tire combo, with the majority of its weight in the center of the wheel and not near the bead or the tread, YOUR ACCELERATION WILL IMPROVE.

Or if you're like me, you bought a cheap set of 18's with pirellis (from the tire rack for $1377) and lost 2/10 of a second in the 1/4, but gained a more rough ride, fender rubbing, worse gas mileage, poor treadwear, better handling and GREAT LOOKS.

Dominic;)

Originally posted by nukeyfish


No. it was different tires. But, check this out. I have Volk TE37 with 16" Pirelli sport veloce(which is OK quality all-season tires) I had 20lb rims with 17" Toyo TS-1(which is known as hi performance tires). I feel TE37+pirelli tires have more stopping power.


What was the Temp, Traction and Treadwear ratings on the tires? Usually a softer compound (when not overheated) will provide more grip and therefore more stopping power. The treadwear rating is a good indicator of the compound consistency. A lower number like 160 (my pirellis) is pretty soft and doesn't last very long. A higher number like 360 ( I think that's what the RE-92's had) is a harder compound and lasts longer. A rule of thumb is to multiply the number by 100-150-ish(depending on how you drive... for me its 90 :lol: ) to get the approximate life of the tire in miles. The advertised expected life of the tire is never right. The pirellis are probably a softer compound. Also, the extra side wall height could have changed the "feel" of the braking experience enough to fool you into thinking you had more stopping power.

I found the SCC article for those interested parties. The article is called "Power, Weight, Grip! Which Matters Most?". It is found in the January 2001 issue. It's a good read that applies well to this topic.

-Jon
www.nothingserious.net

There's always going to be disagreement about how much weight makes a difference. If you're talking 10-15% increase, you might not change the subjective or objective performance and handling at all. But I start wondering what happens when you increase the wheel wheel by 20-30%.

Getting light wheels is a diminishing return on investment, but you should keep weight in mind as one of the factors. You don't need to go overboard for a road car.

Certainly HEAVY wheels is a bad thing, I think we can all agree on that.

I had some anchor-class MOMO wheels on my car before, and the ride and handling suffered tremendously. Even my wife noticed the car's increased skittishness over the stock wheels. The MOMO wheel set was 30% heavier than stock.

SSR's and Toyo Proxe TS-1's baby. The only way to rotate =)