Are lighter wheels really better?

Good timing with this post. 

I'm thinking of getting some 15x8s, and was trying to go as light as reasonably priced wheels would allow, in part because I thought it might help a bit when I auto-x.

At 12lbs per corner (!?), only between a 1/4 and 1/2 second, I shall seek out wheels I like the look of and worry a lot less about weight. 

I'm not competitive enough at this point to worry about a couple lbs a corner. 

Every time this topic comes up, I relate the story of basically revalving the Koni's in my Neon IT car by going from stock wheels with RA1's to Slipstreams with Goodyears.  Lost about ten pounds per corner, and the shocks were perfect after that.

Lap times may be one thing, but ride quality on the real world streets are another. Heavy wheels make for a less compliant ride when it comes to the daily drive. However, with less weight, one also should consider strength of design. If you sacrifice rigidity for less weight, you might be risking bent wheels if you happen to catch the wrong piece of road debris or an unseen pothole.

Perhaps the biggest thing I notice is steering effort and quality are much better with a lighter setup. Also, lighter wheels are easier to change, for what that's worth. I store my off season wheel / tire combos in the basement, which means a flight of stairs, one trip per corner. Less weight is better in that case!

All I know is when I went from the original steel wheels to miata alloys on my 90 miata the ride vastly improved.  I lost almost 10 lbs per wheel and it really made the car feel better in rider comfort.  I guess the lighter wheels have less gyroscopic effect because steering effort into tighter turns also decreased.    This car was a Club model with no frills like A/C or power steering, I think it weighted 2100 lbs,  so weight changes were very noticeable.

Awesome test!

We’re braking distances tested?

Great article, thanks for quantifying. This topic while much discussed in digital and print almost never includes test data. In fact I don’t recall ever seeing any data contained in the many thousands of words written on this topic until now. So once again GRM for the win!

My main want for light wheels is to get my wagon as far away from it's original 4,000lbs self as possible.

Being ever so slightly faster w/ improved MPG is also a big bonus in my eyes.

It depends on the type of racing. On circle track for instance where contact is a normal thing, I've found the mid weight wheel offered the best performance.  Ultra light spun shells deformed to easily with light contact and having an out of round wheel was just as bad as the flat that might also happen.  A heavy weight or (stock junk yard steel rim) wheel made it harder to turn slowed the cars reaction time and tore up the front end and bent frame rails if you tested the wall that day.  Mid-weight wheel had better on-track resistance to damage but lessened the damage to other components when You got in to a nasty wreck like testing concrete wall strength...

Reading between the lines, I'm thinking my fatass losing 40 pounds is good for about 15 hundreths on my 0-60 times.  

To cheeseburger, or not to cheeseburger for lunch...  

Just throwing wider tires on the same wheels adds a lot of weight something some might want to consider. I went from 195s to 215s and gained about 10 lbs per corner (same aspect ratio which meant a taller tire by an inch, so that effects things further). Ride comfort and cornering grip, braking seem improved but gas mileage and power suffered

I was wondering how much difference a pound or two makes in performance and feel. 

The 11lbs per corner is  LOT in my mind.  But going from 14lb wheels to 11 or 12 probably isn't going to be a huge difference, at least based on the test.  Looks like it averages a little over a tenth of a second per couple pounds in change.

I suspect the car would ride better with lighter wheels, on the inane theory that wheel inertia plays a part - kind of like the difference between a 3lb sledge and a 5lb sledge - when the 5lb hits, it hits with more force given the same rate of motion.  Of course, the opposite might be true in that it's harder to start moving 5lbs than 3.  My ignorance shining through.

In any case, since I'm not starting with 20lb wheels, and given that I'm just not that competetive in auto-x at this point (and probably won't ever be, really), might as well focus more on what I like than how much it weighs.  Current 15x7 wheels are 14lbs, and between the 15x8s I'd like to get, 6UL's, Hypergrams, S1 Storms, Dial-ins, etc, it's 2-3lbs a wheel.  Probably not setting my world alight.

In reply to xflowgolf :

Adding 40 pounds of sprung weight would require another test :-)

We ran "Factory Fours" on a "split 8" oval at http://www.racesandia.com , and our Mitsubishi MightMax/ Dodge D50 came with the heaviest steel wheels I had encountered short of an E-350 Class-C RV. When we switched to Toyota 4X4 alloy wheels we went from running 7th place to winning. The butt dyno didn't register the increase in acceleration, though it did notice the extra traction in the turns which are a bit bumpy. I was able to carry more speed through the center of the turns, and pick up the throttle about half a car length earlier. Big difference.

Several thoughts:

1 - Wow, the difference between the light and heavy wheels is greater than the weight of each (bare) 15" RPF-1 I mounted on my last Miata.

2 - Is there anyone here wouldn't sell his or her grandmother for half a second per minute? 

3 - I recall, from the old autox list on Team.Net a billion years or so ago, that somebody quoted the mathematical formula for calculating accelerative performance improvements from reducing rotating mass. ...No, no, it was more recently, when I was writing the PRI feature on cooling systems and in particular, C&R Racing's new Hustler fans for classes that require engine-driven fans. This Web site has a few JavaScript calculators for those who want to estimate for themselves:

http://hpwizard.com/rotational-inertia.html

Though it basically concludes by saying that, when it comes to handling effects, math is hard. I'll stick with half a second per minute as a rule of thumb.

sfisher71 said:

2 - Is there anyone here wouldn't sell his or her grandmother for half a second per minute? 

Me.  Half second won't help.  I suck.

Thanks for the great test!

In reply to xflowgolf :

I keep hearing words to the effect that the most effective modification is driver improvement.

...And I, too, have 40 lbs I could live without.

I’m wondering how the “butt Dyno” feels it? And I’m not talking “sear of the pants acceleration”, I’m talking “wow, my steering wheel feels incredibly light and the whole chassis seems to respond to my every flick!”

sfisher71 said:

2 - Is there anyone here wouldn't sell his or her grandmother for half a second per minute? 

I think the interesting thing in this test is that that 1/2 second came with wheels that are 12 POUNDS (!) heavier per corner.  When most of us look at wheels that size, almost all the options are in the 10-12lb range.  If the difference is linear, a 2lb weight difference is probably averaging in the 0.05second range - which would probably fall in the noise on a test like this. 

In reply to Trackmouse :

Steering effort gets noticeably easier the lighter you go, in my experience. Kinda figure it's like trying to hold a hammer out at arms' length. The lighter the hammer, the easier it is to move it around where you want it. =)

Lighter wheels/tires give the biggest benefit on the driven axle.  The reduction in rotating mass produces an improvement EVERY time you accelerate.

200mph said:

Lighter wheels/tires give the biggest benefit on the driven axle.  The reduction in rotating mass produces an improvement EVERY time you accelerate.

 

This affects the wheels / tires on all axles, driven or not.  They all have to spin up the same as you accelerate regardless of whether they're directly powered or not.  

rslifkin said:

200mph said:

Lighter wheels/tires give the biggest benefit on the driven axle.  The reduction in rotating mass produces an improvement EVERY time you accelerate.

 

This affects the wheels / tires on all axles, driven or not.  They all have to spin up the same as you accelerate regardless of whether they're directly powered or not.  

Not if you lift them off the ground :P

sfisher71 said:

2 - Is there anyone here wouldn't sell his or her grandmother for half a second per minute? 

Sell? No. Rent?... Possibly.

What about braking data. 60-0 distance and maybe 3 or 4 hard stops then measure for heat soak.

Having done a lot of research on this topic for both cars and motorcycles, I found several evaluations on both applications with light wheels. One interesting item that surfaced a few times was the comment that pulling one pound out of unsprung rotating mass has an overall effect similar to taking FOUR pounds of sprung mass. 

I have been tracking my 2006 Elise for over ten years and recently went from a set of Rota Slipstreams (a great wheel for the money, in spite of comments by some) to a set of 15/16 Volk CE28's. The effect on acceleration and ride quality is noticeable. The effect on turn-in or cornering is harder to feel, but must certainly be there. With two piece rotors and the Volks, I think I have pulled about 36 pounds out of unsprung weight. Also, by going 15/16, they are a little lighter than a 16/17 setup. I like 15/16 for several other reasons, as well. There is a wider variety of DOT legal competition tires available like the RA1 and it allows me to run the car at a bit lower ride height without having bumpsteer issues from the stock steering rack. 

Now, if I could just get a set of wheels for the Lotus like I just bought for my KTM 950 SuperMoto! 

On a motorcycle, the difference is astonishing as the gyroscopic effect from the wheels is greatly reduced at turn-in.   All fun stuff!

OldGray320i said:

sfisher71 said:

2 - Is there anyone here wouldn't sell his or her grandmother for half a second per minute? 

Me.  Half second won't help.  I suck.

Mine are all dead sooooooo....

From flipping around at Ecomodder, it seems wheel weight makes a signal difference in mpg.

I suppose that could factor into racing but maybe not until you get into the more expensive type racing where the rules are tighter?

OldGray320i said:

I was wondering how much difference a pound or two makes in performance and feel. 

The 11lbs per corner is  LOT in my mind.  But going from 14lb wheels to 11 or 12 probably isn't going to be a huge difference, at least based on the test.  Looks like it averages a little over a tenth of a second per couple pounds in change.

I suspect the car would ride better with lighter wheels, on the inane theory that wheel inertia plays a part - kind of like the difference between a 3lb sledge and a 5lb sledge - when the 5lb hits, it hits with more force given the same rate of motion.  Of course, the opposite might be true in that it's harder to start moving 5lbs than 3.  My ignorance shining through.

In any case, since I'm not starting with 20lb wheels, and given that I'm just not that competetive in auto-x at this point (and probably won't ever be, really), might as well focus more on what I like than how much it weighs.  Current 15x7 wheels are 14lbs, and between the 15x8s I'd like to get, 6UL's, Hypergrams, S1 Storms, Dial-ins, etc, it's 2-3lbs a wheel.  Probably not setting my world alight.

The effect is linear, as the 'm' term in pretty much any acceleration/Force equation is linear.

So for their 'average' driver in this particular test the difference is ~ 0.03 sec/lb.

Going from a set of Giovanna wheels from 1998 to a set of Kosei wheels would make a pretty good difference.

Going from the Kosei to Volks is definitely going to net diminishing returns for your money.

Reducing the diameter is a whole different story, though....

How much does speed influence the impact of weight?

The faster you're traveling, the more the wheels are accelerated upward over every bump, and the faster they have to accelerate to contact every dip.

I imagine from a grip and suspension-performance standpoint, wheel weight matters more in road racing than in autocross.

I might also wonder whether in testing this you actually need to twiddle damping to test for improvement from a meaningful change in wheel weight?

I'd like to redo this test on a bumpy surface. I think that will reveal a few things, too. 

I recall when I began road racing someone mentioned that in a competition engine we get rid of that heavy steel flywheel for a light aluminum one so the engine will spin up faster.
And the light bulb went on that I basically had four flywheels on the corners of my car. That's when I dropped the coin on new wheels. As for the old heavier wheels, now I had something to mount some rain tires on! 

So you're saying that the 17" RPF-1s on my soon-to-be running Frankenstang are a double whammy improvement over the 18" SN-95 Bullitt style wheels? There is surely no way that that extra confidence will end up with my rear end on top of another tire wall....

Very cool test.

I have two Mazda2s - one has a reverse stagger set of 15x9 - 15x7.5 Konig Dekagrams with 225/195 Hankook RS4s, the other has 15x7 Advanti Storm S1s and Conti ECS. The steering feel is world's different between the two cars. Also of note, the wide front tires seem to have caused a ~4mpg drop or so vs a normal 15x7.5 all around with 195s. 

With only 97whp, I suspect I'll be buying some 15x8 wheels and 205 whatever slicks for track use in the future until more power is added.

OldGray320i said:

I suspect the car would ride better with lighter wheels, on the inane theory that wheel inertia plays a part - kind of like the difference between a 3lb sledge and a 5lb sledge - when the 5lb hits, it hits with more force given the same rate of motion.

This analogy works if you think about swinging the hammer sideways. You move the hammer, but the hammer also moves you. You can swing the 3lb with less reaction in your shoulders.

You hit a bump and the bump pushes the wheel up. The suspension wants to push the wheel back down on the other side of the bump (gravity is too slow ffor good hadling and good ride). The distance the wheel has to go back down is the same whether the wheel is light or heavy, but how hard the car has to push the wheel back down changes a lot. Imagine standing on a skateboard and throwing the 3lb sledge to land in a bucket 10 feet away. Now do the same with the 5 lb sledge. It is pretty easy to see that you will roll back further when you throw the 5 lb. The extra amount you moved with the heavier sledge is the difference in ride quality. Wheel goes down over the bump, but the car is still going up with the effort of pushing the wheel down. Shock dampers complicate the simple analogy, but that is still the underlying principle.

Rigidity is super important too. 

I have a VW race car and I had two sets of "race tires" for it with two different kinds of wheels with different brands of DOT race tires. One set were RFP-1's at 9.2 lbs each. The other was something I can't remember but they were heavy! The difference in "feel" between the two sets of tire/wheel combo was easily noticeable on track. The car accelerated faster, stopped easier, and responded quicker. BTY the weight difference between the sets was on the order of 50-60 lbs total.

On a more poweful car a 50 lbs difference may not be that noticeable but when you have a light car with barely 100 HP, every little bit helps.

It's hard to put a number on "feel," but you're right that lighter wheels often do feel better. Will you notice a few tenths saved on the autocross? But you do notice the feel. (Spoiler alert: We might be discussing a follow-up wheel test.)

David S. Wallens said:

It's hard to put a number on "feel," but you're right that lighter wheels often do feel better. Will you notice a few tenths saved on the autocross? But you do notice the feel. (Spoiler alert: We might be discussing a follow-up wheel test.)

Probably depends on how bumpy your autox lot is.  

In reply to codrus (Forum Supporter) :

Have you been reading our e-mails? 

Carbon (Forum Supporter) said:

Rigidity is super important too. 

“That which we manifest is before us.”

I heard from a reputable racing company that they measured significant camber loss from super light wheels. So the lightest wheels weren't actually the fastest.

Wheel inertia will be important when acceleration rate is large, for example in autoX. For high speed driving with small accelerations the inertia will have less effect. I talked to a very reputable race engineer about this, he wasn't that bothered with large unsprung mass, as long as he could revalve the dampers to match it. It would be interesting if GM could talk themself into a shake rigg to do this test just to see how the system response changes with wheel weights, and if some adjustments could mask out some of the drawbacks. 

I recall reading about how the Corvette ALMS team, during the C6 era, switched wheel suppliers mainly for stiffness reasons. There are a few tests out there where wheels were track tested and the lighter ones weren't automatically fastest. There's one Japanese mag that took an Enkei GTC01 or something like that, lightened one set and ran one set stock, and the stock set was faster, as it was stiffer.

David S. Wallens said:

In reply to codrus (Forum Supporter) :

Have you been reading our e-mails? 

Heh.  Back before the 49ers moved to their new stadium, SFR SCCA used to use the Candlestick parking lot for autox.  That was truly terrible pavement, we used to refer it to "autocross with elevation changes" :)

RX8driver said:

I recall reading about how the Corvette ALMS team, during the C6 era, switched wheel suppliers mainly for stiffness reasons. There are a few tests out there where wheels were track tested and the lighter ones weren't automatically fastest. There's one Japanese mag that took an Enkei GTC01 or something like that, lightened one set and ran one set stock, and the stock set was faster, as it was stiffer.

Here's a link to where someone posted that Enkei test in another forum.  Interesting read.  Looks like they took a ton of material out of the hub area, which would definitley see a lot of stress and maximize deflection.

The anti-slip paint bit was very interesting.  I've always assumed that tires stay pretty set unless you're cranking out stupendous levels of power.  I may have to put some indicating paint on my wheels to see what comes of it!

On the street my much heavier tire and rim combo on the miata ruined ride quality over bumpy pavement. I suspect I need a lot more damping that the coilovers im using can't provide. And they are probably matched to the cars weight.

For all the vast interest in wheel weight, no one ever seems to look at tire weight. 
 

It's hard to find sometimes, but it is a much bigger variation than most people realize. 
 

And THAT'S rotational weight that is much further from the axle center. 

SVreX (Forum Supporter) said:

For all the vast interest in wheel weight, no one ever seems to look at tire weight. 
 

It's hard to find sometimes, but it is a much bigger variation than most people realize. 
 

And THAT'S rotational weight that is much further from the axle center. 

True, Mazda worked with 'I forget brand' to supply lighter tires for the Miata. 

Great article. 

SVreX (Forum Supporter) said:

It's hard to find sometimes, but it is a much bigger variation than most people realize. 

Tire rack has that info for every tire they sell. I picked 245/40/18:

Competition class tires: Hosiers are 21-22lbs. Everything else 25-26lbs.

200tw: 25-28lbs.

I think the problem with picking tires based on weight is that a heavier tire may be faster than lighter one. There is info on which tire is faster. There is no performance, or even durability data on wheels, so the only thing people focus on is weight. In the Enkei test it's a .4sec difference on a road course with a non-viable wheel vs. a viable one. Is it maybe .1 between a decent wheel and a worst one?

BA5 said:

The anti-slip paint bit was very interesting.  I've always assumed that tires stay pretty set unless you're cranking out stupendous levels of power.  I may have to put some indicating paint on my wheels to see what comes of it!

 

Remember, your tires can only put down so much power, so it doesn't need to be that stupendous.  Also, almost all track cars can effectively put down stupendous amounts of power with their brakes.

RE: light tires, just like the wheel argument (maybe even moreso), stiffness is a factor.  200TW tires are typically heavier than other tires, but they also have stiffer sidewalls which helps performance.

I've commented on various posts before about running the smallest wheel & tire you can get away with BUT I'm racing cars that only have 100whp. 

In reply to OldGray320i :

At 12lbs per corner (!?), only between a 1/4 and 1/2 second

True, it's a small difference on the stopwatch, but a much bigger difference in the seat of the pants.  I have both factory steel and lightweight alloy wheels for my Miata, I think the difference is something like 8lbs per wheel.  The car is certainly driveable with either set of wheels, but you can definitely tell when one set is on vs the other.

Somewhere shy of forged aluminum, the cost-benefit curve goes crazy.  Just don't make the mistake of ignoring wheel weight altogether.  There are benefits in smoother running on the highway as well, less sensitivity to bumps, your shock absorbers are more effective, etc.

Snrub said:

SVreX (Forum Supporter) said:

It's hard to find sometimes, but it is a much bigger variation than most people realize. 

Tire rack has that info for every tire they sell. I picked 245/40/18:

Competition class tires: Hosiers are 21-22lbs. Everything else 25-26lbs.

200tw: 25-28lbs.

I think the problem with picking tires based on weight is that a heavier tire may be faster than lighter one. There is info on which tire is faster. There is no performance, or even durability data on wheels, so the only thing people focus on is weight. In the Enkei test it's a .4sec difference on a road course with a non-viable wheel vs. a viable one. Is it maybe .1 between a decent wheel and a worst one?

That may depend on what rules you are playing by. 
 

I brought a car to the Challenge a few years ago wearing Hoosier Road Racing bias plys.  (DOT legal is not required at the Challenge).  They were 14 lbs per corner. By the time we included the lightweight wheels, we saved 24 lbs per corner. 96 lbs rotational weight.  That's a lot!

The operating temperature was off. The road racing tires were intended for extended periods at speed, not short autocross.  We compensated by using smaller tires intended for a lighter car than we were running.

It worked perfectly. 

Can't wait to see the bumpy part 2 article. Great discussion here. 

In reply to Mangocats :

As a non racing gearhead the GRM site/forum helped me to recalibrate my value of time in a motorsport context.  '1/2 a second' (or some such) per lap (or whatever metric the specific performance motor sport is using) is allot in most time evaluations.  1/2 a second a lap on a short 60 second ish lap like this is ALLOT in motorsport terms.  Like in a 10 lap race you are nowhere to be seen at the finish if you are 1/2 a second a lap slower.   

I guess my answer to the title question would be yes, every time.

But is it worth spending up to get lighter wheels? That would be a personal and application specific decision.

I've got American Racing VR Rodder wheels on my car and am looking to make a change. I noticed that Torque Thrust ll wheel are 6 lbs lighter per wheel. That pretty significant for a budget wheel line like American Racing.

Rallye or racecircuit is gonna be a bigger difference 

Rallye or racecircuit is gonna be a bigger difference 

So is the difference in rotational mass between a heavy vs. light wheel setup something that can be easily verified on a chassis dyno as a difference in measured HP/TQ at the wheel?

You stated you are not that competive yet.  More rubber will help.  In the learning phase keep the cost down.  After you have done all the inexspensive things, and are now near the top gor the lighter wheels.  I recommend three piece wheels.  My 9`` RSR 2.8 clone car runs BBS Magnesium centers andaluminum hats.  With gears, it keeps the 3+ liters looking directly over there shoulder.

Remember lighter generallly means easier to damage.  For Autocross on parking lots stay away from pot holes, on the race track try not to drop the wheel off the track, any bend means end of the weekend for that wheel.  One must check the center of a 3 piece wheel if one damages a hat.

In reply to OldGray320i :

Yeah, but at least you'll suck less!

Tom1200 said:

I've commented on various posts before about running the smallest wheel & tire you can get away with BUT I'm racing cars that only have 100whp. 

My experience certainly bears out what you are saying as the truth. I usually manage one track day a year due to financial constraints and other competing interests but it is nonetheless important. Last year I took the devilwagon to VIR on 16" wheels with 225/50-16s as opposed 225/45-17s from the previous year. Obviously there are numerous things in play here, ride height is down some, so less weight transfer in corners and under braking, more favorable gearing allowing me to get nearly to the top of 4th gear and bump the rev limiter occasionally, the lighter wheels helped I am sure. At any rate in combination, I was better than 2 seconds a lap faster than the previous year. How much was track familiarity? Who knows? but I can tell you the lower ride height and the slightly shorter gearing were noticeable changes to me as the driver and made some positive difference in my lap times. The overall wheel/tire weight was about 5 lbs lower per wheel than when on 17s. Never mind I had gained a few pounds myself. :(

Still, the car was faster. I want to try a good 200tw tire this year in the same size 225/50-16 that will hold up for street use and see what kind of improvement I can get. I have no doubt that will make the car more predictable at the limit and thus easier to drive on the edge of the friction circle. Suggestions for a long lasting consistent performing inexpensive 200tw tire in the 225/50-16 size will be gratefully entertained.

In reply to livinon2wheels :

If you aren't testing things on the same day, lap times are pretty much useless.  It's amazing the times I've gone to Sebring and been two seconds off my regular pace, along with everyone else in Spec Miata.  Track temps, humidity, wind, oil on track, recent rains, did Indycar recently test and leave super sticky rubber down...  it all affects lap times.

I'm sure it's a tiny difference, but for the most part, fancy lightweight (well made wheels) tend to look much better. 

I ran one of my race cars on magnesium wheels but when I switched to vintage racing I went back to fairly heavy knock off peg drive stock steel wheels. I can't say that the lap times changed, but the feel certainly did - I preferred the alloys.  I also ran a race on some other steel wheels and under hard braking the car was twitchy - presumably the wheels were flexing. Fortunately that was not the case with the peg drive steel wheels (or the magnesium ones) - I could take my hands slightly off the steering wheel under full braking and no twitch!.