How much does wheel weight matter?

[johnh]

So how much does wheel weight matter?

I understand there's a bunch of rotational mass, intertia and all that good stuff...but what's the difference in performance both straight line (1/4 mile) and handling/ride.

Lighter is obviously better, but how much makes a difference:

20# vs 30#
25# vs 28#

Would going to a 5# lighter wheel make any difference at all?

[G8GXP4now]

Good question. I await the expert answers.

['02 ws6]

I know that I helped a friend when he was dynoing his car. Going from a 17x10.5" rim with 315s to a 16x8.5" rim with 255s picked up 8rwhp. So more rotational mass is actually detrimental to performance.
BlackBerry8830/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/104

[VegasNate]

When my car was being dynoed, just for grins we pulled my heavy ass 20's and put some light 18" wheels on. The difference was only 2 HP. The tire width was the same though. 275's

[majesticix]

I'm no expert, but for track racing my brother who auto-crosses (and is a suspension engineer for Chrysler, for now anyway) it makes a HUGE difference. He special ordered what I believe was either a 12 or 14lb wheel from New Zealand for racing his old ACR Neon. Won many auto-crosses and was the President of the SCCA for Detroit last year, though now he just is in charge of the auto-crosses as it was too much work. So he knows his shit.

That's about all the help I can be though hahaha.

[PerfectD3]

When my car was being dynoed, just for grins we pulled my heavy ass 20's and put some light 18" wheels on. The difference was only 2 HP. The tire width was the same though. 275's

Lighter wheels don't add alot of HP (that's not the intention, just a piece of icing on the cake). Lighter wheels change every other parameter though. Less rolling resistance = faster acceleration. Every 1lb of unsprung weight is equal to 8lbs of sprung weight. 100lbs is approx. equal to .1th in the quarter mile. So for

30# vs 20# (per tire) = 40*8 = 320lb reduction from the car

28# vs 25# (per tire) = 12*8 = 96lb reduction from the car

Biggest setback is if you go with 10lb lighter wheels but at a wider width, you can easily offset the weight gains because a wider tire will be heavier than a narrower tire.

Ex. (just a generic tire)

245= 17lbs
275= 26lbs
You are now killing any gain from a lighter tire and possibly making the new tire setup heavier than the one you are replacing. It's a fine line alot of people don't care to consider in when buying rims/tires.

[Chewy]

Copied and pasted from Mazda Forums

Articles

Size Matters
http://www.wam.umd.edu/~greghess/sizematters.pdf (http://www.wam.umd.edu/%7Egreghess/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/ (http://www.sportcompactcarweb.com/projectcars/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/ (http://money.cnn.com/2004/12/15/pf/autos/wednesday_big_wheels/)

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

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

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


Threads

How much does wheel weight really matter?
http://corner-carvers.com/forums/showthrea...rung+and+weight (http://corner-carvers.com/forums/showthread.php?threadid=7019&highlight=unsprung+and+weight)

Are 18" wheels and tires bling bling or a performance advantage?
http://corner-carvers.com/forums/showthrea...heel+and+weight (http://corner-carvers.com/forums/showthread.php?threadid=3661&highlight=wheel+and+weight)

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

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

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

Rotational Advice
http://forum.miata.net/ubb/ultimatebb.php?...=3;t=002795;p=1 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=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 (http://forum.miata.net/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=005169)

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

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

Wheel Weights....Can They Make a Difference?
http://forum.miata.net/ubb/ultimatebb.php?...t=010655#000000 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010655#000000)

33.5 lbs/Corner Too Heavy??
http://forum.miata.net/ubb/ultimatebb.php?...t=010570#000002 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010570#000002)

Don't Small Wheels Mean Heavier Tires?
http://forum.miata.net/ubb/ultimatebb.php?...t=010479#000009 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010479#000009)

Whats With Huge Wheels?
http://forum.miata.net/ubb/ultimatebb.php?...t=010436#000002 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010436#000002)

18" Wheels too big? Take a Look!
http://forum.miata.net/ubb/ultimatebb.php?...t=008412#000031 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=008412#000031)

I'm Finally Completely Convinced About Lighter Wheels and Tires
http://forum.miata.net/ubb/ultimatebb.php?...t=010379#000000 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010379#000000)

Do Wider Tires REALLY Provide More Traction?
http://forum.miata.net/ubb/ultimatebb.php?...t=010206#000034 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010206#000034)

Unsprung Weight 101
http://forum.miata.net/ubb/ultimatebb.php?...t=010206#000034 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010206#000034)

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

WO! The Joy of Lightweight Wheels!!!!
http://forum.miata.net/ubb/ultimatebb.php?...t=010108#000033 (http://forum.miata.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=010108#000033)

0-60 simplified wheel physics and garfield's wheel test
http://www.mini2.com/forum/showthread.php?...3730#post279748 (http://www.mini2.com/forum/showthread.php?s=&postid=279748&t=3730#post279748)

Spreadsheet blows lid off lightweight wheel debate!!!
http://www.mini2.com/forum/showthrea...threadid=14738 (http://www.mini2.com/forum/showthread.php?s=&threadid=14738)

Lightweight Wheels
http://www.mini2.com/forum/showthread.php?...unsprung+weight (http://www.mini2.com/forum/showthread.php?t=58149&page=1&highlight=unsprung+weight)

In Defense of 17's
http://www.mini2.com/forum/showthread.php?...unsprung+weight (http://www.mini2.com/forum/showthread.php?t=10982&page=1&highlight=unsprung+weight)

16 or 17 Inch Wheels?
http://www.mini2.com/forum/showthread.php?...ht=wheel+weight (http://www.mini2.com/forum/showthread.php?t=63449&page=1&highlight=wheel+weight)

18 or 19 Inch Wheels?
http://www.mini2.com/forum/showthread.php?...ht=wheel+weight (http://www.mini2.com/forum/showthread.php?t=81973&page=1&highlight=wheel+weight)

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

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

Wheel Weight and Performance
http://forum.mazda6tech.com/viewtopic.php?...der=asc&start=0 (http://forum.mazda6tech.com/viewtopic.php?t=563&postdays=0&postorder=asc&start=0)

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

[Ktlplxm]

On a dyno, its just a numbers game. you can put a spare donut on it and pick up hp, but if you aren't racing that way its just a waste or stroking an ego. In racing, sprung and unsprung weight make a huge difference. It is more detrimental in drag racing than road racing (hence skinnies, less rolling resistance and weight). It makes a difference in class road racing because of chassis requirements, and a few lbs off in a supposedly even field puts you ahead.

[johnh]

Found speadsheet that calculates it.

Don't know how accurate it is, but looks interesting.

[JTG8GT]

[QUOTE=4GASEM;82200]Copied and pasted from Mazda Forums

Articles

Size Matters
http://www.wam.umd.edu/~greghess/sizematters.pdf (http://www.wam.umd.edu/%7Egreghess/sizematters.pdf)

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


ETC,ETC,ETC


WOW. Talk about a comprehensive answer. Well played sir. Thanks!!!

[daviddrift]

"A vehicle's rotational weight includes all parts that spin including everything in the vehicle's driveline from the engine's crankshaft to its wheels and tires. This affects the energy required to change speed as the vehicle accelerates and brakes. As you would guess, reducing the weight of any of these rotating components will enhance the vehicle's performance because less energy will be required to increase or decrease their speed" heres a total rundown on the posted articles above, in other words, every car parts (http://www.overnightautoparts.com/) contribute to the performance of your vehicle.

[TireDoc]

I can attest to heavier wheels affecting acceleration and braking performance to be sure, but only in certain situations; heavier wheels made my little 1.6L Miata feel even more underpowered than it was, and when we switched to 20" wheels from the OE 17" wheels on our Envoy it added 10 feet to a normal stop from highway speeds. On the Envoy a better (more agressive) brake pad fixed that issue, but I ended up selling the heavier Miata wheels and getting a lightweight setup. I think with the power our cars have, the primary concern would be the stopping distance issue.......

[familycaronROIDS!]

:watch:

[GT Drew]

I saw a Top Gear AU and they tested the supercharged Commadore.
Going to a smaller rim saved over three seconds on a lap time. Tall wheels and tire are for show ONLY.

http://www.youtube.com/watch?v=CIKQv_sW-Co

[96Prix]

Lighter wheels don't add alot of HP (that's not the intention, just a piece of icing on the cake). Lighter wheels change every other parameter though. Less rolling resistance = faster acceleration. Every 1lb of unsprung weight is equal to 8lbs of sprung weight. 100lbs is approx. equal to .1th in the quarter mile. So for

30# vs 20# (per tire) = 40*8 = 320lb reduction from the car

28# vs 25# (per tire) = 12*8 = 96lb reduction from the car

Biggest setback is if you go with 10lb lighter wheels but at a wider width, you can easily offset the weight gains because a wider tire will be heavier than a narrower tire.

Ex. (just a generic tire)

245= 17lbs
275= 26lbs
You are now killing any gain from a lighter tire and possibly making the new tire setup heavier than the one you are replacing. It's a fine line alot of people don't care to consider in when buying rims/tires.

Yup. Unsprung mass is a big deal (at least in relation to mass in general). I had the ratio in my head at 7:1. Nice analysis.

[AVIDMOTION]

I am not sure about HP but lighter tires and rims definitely helped in my mpg, I proved it to myself several times. However It was only significant with a sizeable weight difference, directly related to the HP of the car. What I mean is: say 10 lbs each off a tire wheel combo on a 4 cycl Mazda made a bigger difference then the same 10 lbs of each tire wheel combo on my Mustang GT which had less effect, less noticeable mpg difference.

[hayabusa160]

my accord had super heavy steel wheels on it and i switched to a set of 12lb alloy wheels with the same tires and i felt a big difference. the mpg went up also.

[bowtiefan]

For our GT's, any advantage of using stock 18" wheels vs. the 19's? Looks like the G8 was designed to be used with both sizes, but would the 18's give better 0-60 and 1/4 mile times than the 19's?

[Napalm]

Some good info here.

If you are only drag racing, get thiner lighter wheel and tire up front, make up for the difference in the rear for grip. assuming you need grip. if not don't bother.

If road coursing/autox'ing: this is where the lighter wheel and tire will help the most. mostly due faster responses for the spring and shocks. yes lighter is always better assuming equal grip. However and the arms are flexing and moving with the ripples of the road, the lighter the end of the arm, the faster it can compensate. This leads to more track adhesion and lets you push just a little harder in the corners.

Also as people mention going to 18's. When you get to a 40 series tire or less, you can end up where there isn't enough tire flex to deal with the loads, and instead of flexing for grip the tires skid across. You will occasionally see where people will go back to smaller rims for lighter weight, and more tire sidewall.

[TCorzett]

Also as people mention going to 18's. When you get to a 40 series tire or less, you can end up where there isn't enough tire flex to deal with the loads, and instead of flexing for grip the tires skid across. You will occasionally see where people will go back to smaller rims for lighter weight, and more tire sidewall.
There are also far more compounds available for 18" and smaller tires than there are for 19" (or larger).

-Todd...

[hayabusa160]

had steelies on my accord. then i got a set of free wheels off an old infinity they were also 15s so i swapped the tires over.
not sure how much the steelies weight but the infinity wheels were only 12lb it might have been almost half the weight of the steel wheel. it was a night and day difference. also picked up a few mpg.

[Napalm]

There are also far more compounds available for 18" and smaller tires than there are for 19" (or larger).

-Todd...

This is changing very 2 months also. there are lots of 19 and 20 inch compounds available. since every performance car made now comes with either 19, 20 or 21 and even 22.

Honestly I would love to go back down to 17's. but you need to clear larger brakes now as cars weigh more now.


had steelies on my accord. then i got a set of free wheels off an old infinity they were also 15s so i swapped the tires over.
not sure how much the steelies weight but the infinity wheels were only 12lb it might have been almost half the weight of the steel wheel. it was a night and day difference. also picked up a few mpg.

I would say they were more like 2/3'rd the weight rather than half going AL from steel. but either way, as you mention less rotating mass is always a good thing. I almost bought a set of carbon fibre spoked rims for my GTO. was going to save me 18 lbs per wheel, and going to wider rubber in the back. course they were also going to be 8 grand. but I quite road racing my car so hard as I had a house to fix.

[I12XLR8]

There are a ton of articles here which I have skimmed through but can't find the answer to a question I have...I'm sure I've just overlooked it.

Is rotational mass an issue on all tires or just the drive tires. I know it might be a stupid question but I hear about people putting lighter tires on the back but leaving their usual front's on when at the strip. Is this laziness or because rotational mass issues only affect the drive tires?

My issue is that over all four tires I have a 28lb difference between my stock 18's and Camaro 20's. If the math in this thread is correct this would translate into 224lbs of vehicle weight which should add .2s to my 1/4 miles (?!?!??!!)

Does my math make sense?

[Napalm]

yes it does.

And yes that rotational mass or more importantly rotational inertia does affect the car even on the front wheels. Lower rotational inertia makes the wheel easier to tun over all.

Improves acceleration and braking (call it deceleration) and lighter rim weight is at the end of the suspension arm. Another benefit is faster suspension response to road imperfections. trade off, if you need more brakes, then you need bigger rims.