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Effects of Wheel Size/Weight on Performance

Old 02-03-2005, 09:34 AM
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Effects of Wheel Size/Weight on Performance

I recently updated the orgy of unsprung weight links and decided to share it with a variety of forums. Feel free to keep, chuck, yell at, or do whatever you want with it. I figured since it took so long to gather all these damn links, it might be worthwhile sharing. Hopefully this won't offend anyone. Its just an orgy of available information for those interested in investigating it.

Articles

Size Matters
http://www.wam.umd.edu/~greghess/sizematters.pdf

Finding Free Power
http://www.nerocam.com/SCC_TAPnew.asp

Bicycles and Unsprung Weight
http://www.softride.com/bike/cornering.pdf

Fixing the 350Z: Why Lawyers Want Everyone to Run Staggered Setups
http://www.sportcompactcarweb.com/pr.../0404scc_350z/

Picking the Right Wheels For You
http://www.grmotorsports.com/wheels.html

Big Wheels, Big Trouble?
http://money.cnn.com/2004/12/15/pf/autos/w...day_big_wheels/

Wheel Weights Can Effect Your Vehicles Show and Go
http://www.tirerack.com/wheels/tech/...el_weights.jsp

The Danger of Dubs
http://www.edmunds.com/insideline/do/Featu...rticleId=104526

Automobile Ride, Handling, and Suspension Design
http://www.rqriley.com/suspensn.htm


Threads

17 vs 18, Drag Strip Comparison
http://forum.mazda6club.com/index.ph...0&#entry541857

How much does wheel weight really matter?
http://corner-carvers.com/forums/showthrea...rung+and+weight

Are 18" wheels and tires bling bling or a performance advantage?
http://corner-carvers.com/forums/showthrea...heel+and+weight

How much will 17" wheels slow you down
http://www.sccaforums.com/cgi-bin/ul...gi/topic/7/303?

Effect of Lighter Wheels?
http://www.sccaforums.com/cgi-bin/ul...gi/topic/7/301?

Bigger Wheels and Tires?
http://www.sccaforums.com/ubb/ultimatebb.p...ic/7/863#000004

Rotational Advice
http://forum.miata.net/ubb/ultimatebb.php?...=3;t=002795;p=1

If larger wheels are bad...why do sports cars have them?...
http://forum.miata.net/cgi-bin/ultimatebb....ic;f=3;t=005169

Wheel Weight, Who Cares?
http://forum.miata.net/cgi-bin/ultimatebb....ic;f=3;t=007412

1 Lb of unsprung weight =?? Static weight
http://forum.miata.net/cgi-bin/ultimatebb....f=3;t=006390;p=

Wheel Weights....Can They Make a Difference?
http://forum.miata.net/ubb/ultimatebb.php?...t=010655#000000

33.5 lbs/Corner Too Heavy??
http://forum.miata.net/ubb/ultimatebb.php?...t=010570#000002

Don't Small Wheels Mean Heavier Tires?
http://forum.miata.net/ubb/ultimatebb.php?...t=010479#000009

Whats With Huge Wheels?
http://forum.miata.net/ubb/ultimatebb.php?...t=010436#000002

18" Wheels too big? Take a Look!
http://forum.miata.net/ubb/ultimatebb.php?...t=008412#000031

I'm Finally Completely Convinced About Lighter Wheels and Tires
http://forum.miata.net/ubb/ultimatebb.php?...t=010379#000000

Do Wider Tires REALLY Provide More Traction?
http://forum.miata.net/ubb/ultimatebb.php?...t=010206#000034

Unsprung Weight 101
http://forum.miata.net/ubb/ultimatebb.php?...t=010206#000034

Unsprung Weight Effects Performance?
http://forum.miata.net/cgi-bin/ultimatebb....ic;f=3;t=008986

WO! The Joy of Lightweight Wheels!!!!
http://forum.miata.net/ubb/ultimatebb.php?...t=010108#000033

0-60 simplified wheel physics and garfield's wheel test
http://www.mini2.com/forum/showthread.php?...3730#post279748

Spreadsheet blows lid off lightweight wheel debate!!!
http://www.mini2.com/forum/showthrea...threadid=14738

Lightweight Wheels
http://www.mini2.com/forum/showthread.php?...unsprung+weight

In Defense of 17's
http://www.mini2.com/forum/showthread.php?...unsprung+weight

16 or 17 Inch Wheels?
http://www.mini2.com/forum/showthread.php?...ht=wheel+weight

18 or 19 Inch Wheels?
http://www.mini2.com/forum/showthread.php?...ht=wheel+weight

Effects of Wheel Size on Acceleration (TimeSlips)
http://forum.mazda6tech.com/viewtopi...t=1762&start=0

6tech Article
http://www.mazda6tech.com/index.php?option...id=16&Itemid=32

Wheel Weight and Performance
http://forum.mazda6tech.com/viewtopic.php?...der=asc&start=0

Some Wheel Weight Sites
http://www.wheelweights.net
http://www.wheelspecs.com
http://www.miata.net/garage/garagetires.html

Last edited by crossbow; 10-25-2005 at 11:15 AM.
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Old 02-03-2005, 09:39 AM
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Thanks for your hard work bro!
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Old 02-03-2005, 01:51 PM
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You guys worry too much about a few pounds here and there.

From my roommate who is a professional drag car builder (for Inline Pro) "If its a street car, don't worry about weight, worry about making power".
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Old 02-03-2005, 02:12 PM
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Weight is power. Ask a drag racer which they'd rather have. Minus 50 lbs, or 5 hp.

Its all about power to weight. Increase your weight, and you have to increase your power to compensate. Increase your rotational mass, and the power increase required to maintain similar power levels increases by a factor of 2.2-3x.

Its all in the orgy of urls...but nobody can force you to look at them.

http://www.nerocam.com/SCC_TAPnew.asp
2.0 seconds off the 1/4, and they didn't increase power at all. :D

Last edited by crossbow; 02-03-2005 at 02:18 PM.
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Old 02-03-2005, 02:44 PM
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Originally Posted by cretinx
You guys worry too much about a few pounds here and there.

From my roommate who is a professional drag car builder (for Inline Pro) "If its a street car, don't worry about weight, worry about making power".
Your roommate may be an incredible drag car builder, but it's apparent he doesn't know dick about sports cars! Perhaps HE should read those links above.

Excellent summary, crossbow!

Regards,
Gordon
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Old 02-03-2005, 04:09 PM
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A bullseye for crossbow great info

cheers
michael
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Old 02-03-2005, 04:14 PM
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Excellent compilation. Drag racing carries different priorities than turning the wheel. If I had a choice of losing an extra 100lbs or making an extra 10hp, I would take the 100lbs.

HP helps with acceleration.

Weight helps with acceleration, turning, stopping, and wear.
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Old 02-04-2005, 01:51 AM
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Can we get this to be a sticky?
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Old 02-04-2005, 08:21 AM
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I guess you guys didn't understand my post

I know weight is power, he does too, on his drag cars they save every pound they can.

HOWEVER - there's a point of diminishing returns, and on a street car, its really not worth it to sweat a few pounds here and there for rims or amenities - if you have two identical looking rims, one that weighs 20 lbs and costs $205, or a rim that weighs 16.5 lbs and costs $495, there's little justification for spending the extra money unless you're professionally racing.

I see little to no point to stripping down a daily driver or a street car and worrying about weight when making power is so much easier and cheaper.
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Old 02-04-2005, 08:30 AM
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Nothing really justifies buying an RX-8 over a Hyundai Elantra either.
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Old 02-04-2005, 09:13 AM
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I think the fundamental problem with the whole rim/size/weight thing...is people hate to think that their multi-thousand dollar investments in their cars appearance subtracted power. They like to be under the firm belief that there isn't anyway you'd notice a few extra pound difference on each wheel, and that it doesn't matter whatsoever.

But it does. It matters so much that most people can notice as little as a 3 lb difference in unsprung weight in just a few minutes of driving ((3 lbs less per corner). More substaintal differences can change the entire feel of the vehicle, to the extent that you think you've bought a new car.

Of course this is possible to explain or get across to individuals, cause in their head (12 lbs is absolutely nothing). Its only when those individuals finally try something drastic, that their tunes change, and suddenly you'll see them posting on how to fit the smallest lightest rim possible, and still have rotor/caliper clearance.

I'm almost positive that if you added up all the current available NA mods on the 8 (pullies's, intakes, catback's, midpipes), it still wouldn't match the difference going to 17x8 SSR comps, with lightweight rubber on them. (36.6 lbs with 245/40/17 T1-S) [Especially if you look at the overall effect on acceleration, handling, braking, and gas mileage increases]

I don't think its that we didn't understand your post, I think its just that you have don't understand the effect of unsprung weight on a car...which is the whole point of the orgy of urls...with over a THOUSAND testimonies on the effect...with drag slips, autox times, road course times, g recordings, articles, and statements to the fact.

Last edited by crossbow; 02-04-2005 at 11:23 AM.
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Old 02-04-2005, 11:04 AM
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Originally Posted by cretinx
HOWEVER - there's a point of diminishing returns, and on a street car, its really not worth it to sweat a few pounds here and there for rims or amenities - if you have two identical looking rims, one that weighs 20 lbs and costs $205, or a rim that weighs 16.5 lbs and costs $495, there's little justification for spending the extra money unless you're professionally racing.

I see little to no point to stripping down a daily driver or a street car and worrying about weight when making power is so much easier and cheaper.
There is a big difference between weight in the car (seats, insulation, speakers, etc) and unsprung weight like wheels and tires. If you think there is no noticeable difference between 20 lb wheels and 16 lb wheels, then it's obvious that you've never tried it to see what the difference actually is! I just posted that there really is a definite noticeable improvement in ride and responsiveness due to my lighter winter wheels. Adding power will NOT provide that improvement in ride and responsiveness!

A point of diminishing returns? Yes, but going from 20 lbs to 16 isn't there yet - it will be a very noticeable return. You really ought to experience it yourself before you dismiss it!

Regards,
Gordon
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Old 02-04-2005, 02:59 PM
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As stated by others, your buddy has lived with drag cars too long if he thinks a lightweight sports car wont benefit from losing 4 pounds unsprung weight per corner.

I dont race professionaly and I dream of getting some SSR's on my car, just to lose those 8 pounds per corner.
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Old 02-04-2005, 11:44 PM
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Look at it this weigh
Assume you have the GReddy turbo kit installed, ok.

You can spend $200 / wheel on some 23 lb Kazera KZ-As, for $800
OR you can spend $500 / wheel on some 16.5 lb SSR Comps, for $2000

Now, you guys can all get your SSRs, I'll spend the remaining $1200 on a custom 3" exhaust (making it safer to increase boost) and a boost controller, safely raising boost to 9 psi (where the stock fuel system should start getting challenged) and enjoy blowing you away, on the circuit, strip, or street. The place where you'd see the big big benefit of saving a few pounds per corner of unsprung weight would be the autocross.

Weight consciousness is a disease I see drivers of underpowered cars get sucked into repeatedly- it just starts to consume you - seen it with the Civic drivers, Celica drivers, and I'm seeing it with the hardcore RX-8 racers.

If weight were the real concern, you'd be on 16x8 rims all around, and you would ONLY buy the base model, without DSC or leather or nav or any of the things that made me buy an RX-8 instead of build a 3000GT VR-4 to 500 awhp for the same price, or get a 420 rwhp turbo S2000, again for the same price.

Like I said, its your money, if you want to lose those 8 lbs per corner and beat a stock RX-8 by a a good second or two on the autocross, that's your deal - autocross is a lot of fun! Me, I'll settle for some "heavy" 23 lb rims and put the money into neck snapping acceleration, and a midrange response that doesn't remind me of stepping on a rotten tomatoe.
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Old 03-16-2005, 06:33 PM
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Lotus Elise anyone?
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Old 03-17-2005, 05:20 PM
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So whats the lightest tires one can get for the 8 ?
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Old 03-18-2005, 01:28 PM
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One analysis that I think should be placed above is the following:

https://www.rx8club.com/showpost.php...9&postcount=22

Through those equations I determined that the 1.5 lbs of non rotating weight is equal to 1 lb of wheel weight - worst-case. (Another forum member did it a different way and got the same answer.) Meaning that in terms of acceleration, having a 36 lb dumbbell in your rear seat would slow you down more than having wheels that weighed 6 lbs more each ( 36lb = 6lb X 4 X 1.5 ). At best the lighter wheels (or removal of dumbell) would translate into a 1/15th of a second improvement in 0-60 time.

I definitely don't think that straight-line performance difference is worth the $1200 difference in wheels. (It so happens I own KZ-A's and was seriously considering SSR Comps)

As far as handling, how much unsprung weight matters is going to be very subjective and no one has done blind or double-blind tests to prove otherwise to my knowledge. Instead of someone buying new lightweight wheels and knowing that they should feel a difference, it would be more interesting to put someone in a vehicle not knowing what wheels were on the vehicle and see how much their track time improved.

I wish a had more time to get into it but I don't think Miata is the ultimate comparison vehicle for determining the effects of unsprung weight. You are talking about a very light weight vehicle without a whole lot of power being driven on very tight test tracks. Those conditions amplify the role of weight. Miatas also don't need tires and wheels that have high load ratings either, so using light-duty equipment doesn't have as much downside as it would on a heavier higher power vehicle.

One last thing to keep in mind is that Tire Rack uses a BMW 330ci to do their tire comparisons (I wish they would do wheel comparisons as well) and there is very little correlation between tire weight and subjective and objective tire performance measurements. The S-03 by Bridgestone is a heavier than average tire and it does very well in the performance tests. Many of the lighter tires don't do well.

All cases for or against an idea should have both sides represented. Before people spend $2000+, they should have a better understanding of what to expect in terms of straight line performance and overall handling. There are two sides of the coin here. The first post shows all of the positives mainly in the form of subjective opinions which are possibly quite prone to the placebo effect.

-Mr. Wigggles

Last edited by MrWigggles; 03-18-2005 at 01:35 PM.
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Old 03-18-2005, 02:20 PM
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All I can say Cretenix about your argument that saving weight is a lost cause... is that a journey of 500 miles (or 500 lbs) begins with the first foot (or the first lb.) You say that people are all crazy spending their money to lose weight from their cars.

If you just throw up your hands and say "not worth it", well that's anyones choice.

But it's obvious, I think, that weight costs too, big time. The costs to 'makeup for weight' are exemplified in the need to add lots of HP to go faster, quicker, and bigger, beefier everything else to handle that weight and added power, extra wear and tear on it all, plus real world handling & performance suffers carrying extra weight both down the straight and around those corners - every single lap - no matter what.

It is simple physics. Weight consumes power, and impedes handling.

There is reason to try to lose 10, 20, 50, 100, 200 lbs, whatever the figure. Of course the BEST answer :D is to loose the weight, gain the HP, then go like a crazy person to the finish line.

It's not just about the money. But just saying loosing weight is a non-starter "so don't bother, just get a turbo" is wrong-headed IMHO.

Last edited by Spin9k; 03-18-2005 at 02:38 PM.
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Old 03-18-2005, 04:48 PM
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wouldn't gas milage increase slightly with a lighter car? Over 100,000 miles you might see some of that 2000 bucks back into your pocket in savings on gas right?

someone should do that math on that!
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Old 03-23-2005, 12:29 PM
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Originally Posted by Jarred
wouldn't gas milage increase slightly with a lighter car? Over 100,000 miles you might see some of that 2000 bucks back into your pocket in savings on gas right?

someone should do that math on that!
If you guys are worried about gas mileage, you certainly got the wrong car, and you shouldn't modifying any car. You should be driving a stock D15 Civic or a Miata.
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Old 03-24-2005, 11:02 AM
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Originally Posted by cretinx
If you guys are worried about gas mileage, you certainly got the wrong car, and you shouldn't modifying any car. You should be driving a stock D15 Civic or a Miata.
Evidently you must be made out of money or someone else is paying for your gas. There is no way I would give up my '8 because of the poor mileage, but I'm all for saving some money at the pump if I can.

Also, for auto-x I went the light wheels route and smaller diameter. My wheel/tire combo is 7.6 pounds per corner lighter and I lost an inch in diameter. I agree that going a few pounds lighter for track day activities or general street driving is kind of a waste of money just like the lightwieght flywheel or rotors, all of which reduce rotating mass. But if you are actually competing where tenths of a second matter and the rules don't allow power adders like a turbo or nitrous, I say go for it.
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Old 03-24-2005, 12:41 PM
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I don't get this it's a waste of money arguement about buying lightweight mods for the 8?

People go and spend $2,000.. $3000.. $4000 or more on a plasma/LCD/DLP television.. is that a waste of money?...they could get by with older, heavier $1000 versions.

People go and spend $2,000.. $3000.. $4000 'making pretty' their cars in too many ways to count.... that 'pretty' is argueably in the eyes of the beholder..so is that a waste of money?... they could do noting...that's cheap... or worse do something and make it worse.

Money is meant to be spent, it gives you power to do what YOU think is right, what you want to experiment with.

Someone may go spend $2000 on lightweight wheels, $500 on a PPF, $1000 on a flywheel set, etc. "Because it is lighter" has value to some that others don't appreciate regardless of whether your turbo gets you their faster. [ I say that because the benefits are there and based on physics, whether one recognizes them or not ]

If you can accelerate faster than me, I applaud you. In turn if I can go through the twisties quicker than you, I'd expect the same. Last time I checked, moding personal cars wasn't a contest based on value for ????

Last edited by Spin9k; 03-24-2005 at 12:48 PM.
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Old 03-29-2005, 05:44 PM
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Like I said, "I agree that going a few pounds lighter ...... is kind of a waste of money ....." That's just my opinion. I have no problem with people dumping loads of cash into a car. To each his or her own - it's their money. Improving the looks and performance of one's car is a worthwhile endeavor.

I just hate seeing somebody throw an $800 lightened flywheel in their car and then stick heavy 19" bling wheels on negating the effect of the flywheel. I did the math and for me the added performance and cost savings of the 17" wheel/tire combo made sense. The $280 I save each year on tires will pay for the wheels in three years. And I'm also seeing the performance benefits of the smaller diameter tires and lower unsprung weight.
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Old 03-31-2005, 07:15 AM
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Originally Posted by Dark8
I just hate seeing somebody throw an $800 lightened flywheel in their car and then stick heavy 19" bling wheels on negating the effect of the flywheel.
90% with you on that thought, but I don't hate to see it, but I do chuckle a bit. I guess it is all a matter of what (and if) you have a goal. I applaud all who do mods for a quantifiable reason (speed, handling, acceleration, whatever). Who knows, perhaps the guy who would do what you mention has a goal - to have bragging rights like "Look at my sick (and heavy) 19" wheels AND I put in an $800 superlight flywheel!" For some, illogical as it may be towards any performance reality, that's enough for the $$ spent.

Me, I'm totally up for (light) 17" wheels, damn the cost (savings)!:D
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Old 04-21-2005, 02:59 PM
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If you want power and don't care about extra weight the best thing you can do is sell your 8 and buy a 350Z
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