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Wheel Weight

Old 05-23-2005, 06:41 AM
  #26  
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Man this forum is dropping like mad lately...

Quick summary. Some 6 owners have done back to back comparisons on the track comparing 18x8 rx8 rims (with stock tires), vs 16x8 rx7 rims (14 lbs less a corner) with similar diameter tires...and have dropped as much as 0.5 off their 1/4 time. In almost all the situations, the rx7 wheels were usually in a condition which wasn't favorable for good results, but regardless, a significantly acceleration difference was noted.

The performance benefits from reducing unsprung weight and rotational inertia are far greater then they seem on paper. This is of course completely ignoring the additional benefits to braking and handling which results from dropping unsprung weight.

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://grmotorsports.com/news/012005...ls-for-you.php

Big Wheels, Big Trouble?
http://money.cnn.com/2004/12/15/pf/a...ay_big_wheels/

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

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

Do Wheels Cost More than Money?
http://www.turbomagazine.com/tech/0106tur_wheels/


Threads

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

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

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

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

Bigger Wheels and Tires?
http://www.sccaforums.com/ubb/ultima...c/7/863#000004

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

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

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

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

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

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

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

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

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

I'm Finally Completely Convinced About Lighter Wheels and Tires
http://forum.miata.net/ubb/ultimateb...=010379#000000

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

Unsprung Weight 101
http://forum.miata.net/ubb/ultimateb...=010206#000034

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

WO! The Joy of Lightweight Wheels!!!!
http://forum.miata.net/ubb/ultimateb...=010108#000033

0-60 simplified wheel physics and garfield's wheel test
http://www.mini2.com/forum/showthrea...730#post279748

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

Lightweight Wheels
http://www.mini2.com/forum/showthrea...nsprung+weight

In Defense of 17's
http://www.mini2.com/forum/showthrea...nsprung+weight

16 or 17 Inch Wheels?
http://www.mini2.com/forum/showthrea...t=wheel+weight

18 or 19 Inch Wheels?
http://www.mini2.com/forum/showthrea...t=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?...d=16&Itemid=32

Wheel Weight and Performance
http://forum.mazda6tech.com/viewtopi...er=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; 05-23-2005 at 06:28 PM.
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Old 05-23-2005, 02:51 PM
  #27  
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Right on crossbow...and WOW...that's one big list, lol

Also, not to question the weight...but I thought it was agreed that the rims on our 8's came in at 22.5lbs? What happened to that number?

Lighter rims is something I was looking to do in the future, because as Crossbow said, the real world difference is more significant than it looks on paper.

17lbs is my goal to keep the rims affordable...I just can't see myself spending over $500 per rim...heck, $200-300 per rim is enough for me.
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Old 05-23-2005, 03:49 PM
  #28  
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Originally Posted by Sputnik
[/b] I've never heard of a ratio THAT high. The highest that I've ever heard is 4:1.

And you're calculations don't take tire weight into consideration (whether higher or lower).
[/b] That's irrelevant.

---jps
Wow. In this thread we've seen 10:1, 6:1 and 4:1. Well, at least we're headed in the right direction. Can anyone tell me the correct ratio for power necessary to accelerate rotating vs. non-rotating mass as relates to wheels?

Anyone?

Anyone?

It's 2:1. And that applies only to the mass at the edge of the wheel. Nearer the hub the ratio is less. Center of hub is 1:1.
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Old 05-23-2005, 06:23 PM
  #29  
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The formula's don't work. Track results tend to report much better results then you get by calculating.

Check out one of the starter articles, by sports car compact magazine.
http://www.nerocam.com/SCC_TAPnew.asp

(This is also a hilarous article to read, and one of SCC's best)

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.

By the formula calculations it would seem that they'd only have about 104 lb weight loss...but the results indicate closer to a 200 lb static weight loss.

Last edited by crossbow; 05-23-2005 at 06:31 PM.
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Old 05-24-2005, 07:53 AM
  #30  
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Originally Posted by MrWigggles
Alright I did the math anyway and it is about what mentioned earlier.

Assuming that all weight reduced from a using a lighter wheel is coming from the outer rim of the wheel (i.e. reduces moment of inertia the most); for an 18inch wheel with 26 inch tires it works out that each pound you lose from the wheel is equivalent to 1.5 pounds of car weight.

So for a 3000 pound car, 4 wheels X 1.5 lbs eq./wheel = 6 lbs equivalent, and with HP/lb being the key to performance.

3000lb / 2994lb eq = X HP eq / 250HP

Solving for X gives 250.5HP equivalent or 0.5HP increase equivalent by using a 1lb lighter wheel, best-case.

The reason I say "best-case" is my analysis assumes that the weight is removed from the outer rim of the wheel and that the wheels are the only items in the car storing rotational energy. I neglected the flywheel, the crank shaft, etc, and even the weight of the original wheels.

But any estimate over 0.5HP per 1lb is not accurate, 0.5HP per lb reduced is best-case. (at least for 18 inch wheels and a 3000lb car )

-Mr. Wigggles
Just stating the obvious here, but taking a conventional wheel only upgrade (whatever tire to weigh the same as OEM) - SSR Comps at 16.8 lbs for 18x8.5 that is saving something like 3.5-6.5lbs (since we can't agree on what an OEM wheel weighs).

So x4 wheels that's 14-26lbs rotating mass. Using the stated conservative .5hp/lb that's a 'gain' (please note I use 'gain' in this way - it is actually a 'quicker release' to accelerating the car - as you just cannot 'gain' HP this way) of 7HP to 13HP, best case. Not too shabby even that - And esp. for a measily ~$1800 wheel cost; or $257-$138 /HP 'gained'.

Personally I might do it slightly differently, that is, Kosei K1 TS 17x8 ($239) at 15.4 lbs, saving ~5-8lbs/wheel - 20-32 rotating mass lbs/car for a calculated 10HP to 16HP 'gain' and a $100-$63 / HP 'gain'. Or do 17" wheels/smaller diam tires for more significant reductions.

These are are argueably worth doing IMO, not simply trivial pursuits when considering potential numbers in this area.

Althernatively, using the economies of scale a $4000 turbo gaining ~70 'real' RWH costs only $57/HP actually gained.
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Old 05-24-2005, 08:02 AM
  #31  
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3.7 lbs savings
x 10 static rule of thumb
x 4 wheels
x 6 horsepower rule of thumb
--------
about 24 horspower gain
Are you staying that if I lose 37 lbs in my gut.. I would have gained 6 hp on my 8! 37lbs that is about 18kg...

I set the alarm clock to 6am tomorrow morning, worth a run! (6hp, 6hp, 6hp... )

Thanks
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Old 05-24-2005, 09:55 AM
  #32  
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Originally Posted by crossbow
The formula's don't work. Track results tend to report much better results then you get by calculating.

Check out one of the starter articles, by sports car compact magazine.
http://www.nerocam.com/SCC_TAPnew.asp

(This is also a hilarous article to read, and one of SCC's best)

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.

By the formula calculations it would seem that they'd only have about 104 lb weight loss...but the results indicate closer to a 200 lb static weight loss.
Actually, it looks like they only had a 55 lb weight loss by my math (2762-2707)...

Of course, it should be noted that the 15-inch wheels are 4% smaller than the 19-inch baseline wheels. That's going to give it 4% better acceleration (give or take a bit).

Given the:
2% improvement in 1/4 mile time,
6% improvement in 0-60,
3.5% improvement in 60-foot times, and
?% Margin of error

I'd say it was pretty much a wash for testing. Not that they were "serious" about the this, but, hey...

--Massive
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