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Re: Effect of wheel weight
[Re: Wedgeman]
#1443260
06/01/13 09:30 AM
06/01/13 09:30 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Romeo MI
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Quote:
I have heard that for 1 lb off the Wheel is like 80lbs off the body....
67 Barracuda
best 6.75 1/8 mile
No way.... a heavy wheel does take more power to
accelerate it BUT you also have to take into account
how far from center line of the axle the weight is...
if its a big 20" vs a 12" wheel
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Re: Effect of wheel weight
[Re: MR_P_BODY]
#1443262
06/01/13 10:53 AM
06/01/13 10:53 AM
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Joined: May 2012
Posts: 1,841
South Bend
John Brown
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South Bend
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I read an opinion by Porsche Engineering years ago that decreasing the weight of a rim by 1 pound was equivalent to removing 1.4 pounds of static weight.
July 19th should be "Drive Like Rockford Day". R.I.P. Jimmie.
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Re: Effect of wheel weight
[Re: CHAPPER]
#1443263
06/01/13 10:55 AM
06/01/13 10:55 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Quote:
Quote:
I have heard that for 1 lb off the Wheel is like 80lbs off the body....
67 Barracuda
best 6.75 1/8 mile
8 lbs is a closer estimate. 
This is much more realistic ... but whats a 0 amongst
friends...LOL
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Re: Effect of wheel weight
[Re: MR_P_BODY]
#1443264
06/01/13 01:31 PM
06/01/13 01:31 PM
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Joined: Jul 2006
Posts: 4,319
Puyallup, WA
StealthWedge67
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8 lbs even sounds like an over-estimate to me. think about it: that means if you save 5 lbs per rim, that's equal to 160 lbs off the car??? no way. I think the post above that references 1.4 as the factor is probably closer to accurate.
?????
Last edited by StealthWedge67; 06/01/13 01:32 PM.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: Effect of wheel weight
[Re: StealthWedge67]
#1443265
06/01/13 03:09 PM
06/01/13 03:09 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Quote:
8 lbs even sounds like an over-estimate to me. think about it: that means if you save 5 lbs per rim, that's equal to 160 lbs off the car??? no way. I think the post above that references 1.4 as the factor is probably closer to accurate.
?????
That I understand but I was just saying that the
8# is more in line than 80#... the 1.4 might be real close..
I'm not positive on it
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Re: Effect of wheel weight
[Re: MR_P_BODY]
#1443266
06/01/13 03:43 PM
06/01/13 03:43 PM
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Joined: Nov 2003
Posts: 1,969
Chandler, AZ
Duner
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The factory Dakota wheels are HEAVY.
I dropped 25# per front wheel/tire and 14# per rear wheel/tire.
That's 78# at axle speed.
I'm really hoping it should be good for 2 tenths.
The link from BigBlockDart indicates that each pound at axle speed is worth roughly 3 lbs vs carried weight.
If I had a racetrack that was open I could find out!
Last edited by Duner; 06/01/13 03:48 PM.
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Re: Effect of wheel weight
[Re: Wedgeman]
#1443268
06/01/13 06:06 PM
06/01/13 06:06 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Quote:
Ok....
I was questioning the effect of a very heavy wheel on the loss of ET because of the rotating mass
For example start with a 20lbs rim, make a few passes on a 3200 lbs car with 570hp...
Then given the same car with a lighter rotating mass at the rear with 11 lbs rims.........any change in ET ?????
You should see some gain but its not gonna be much
and it might not even show if the weather isnt the same...
but lighter is always better
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Re: Effect of wheel weight
[Re: jcc]
#1443273
06/01/13 08:53 PM
06/01/13 08:53 PM
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Joined: Jan 2003
Posts: 27,471
So Cal
autoxcuda
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So Cal
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Stick each wheel option on a Spintron and measure it. Done  Due to moment of inertia, two wheels with the same weight can take different amount of torque to rotate and accelerate. You could computer model/draft each wheel and put it into other software and give you the calculated difference. It's plug and chug right out of the book. I'm afraid the difference is so small that variables in track testing may not give you a precise number of what is going on.
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Re: Effect of wheel weight
[Re: autoxcuda]
#1443274
06/01/13 09:27 PM
06/01/13 09:27 PM
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Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
B G Racing
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This topic can be debated untill the cows or sheep come home. What we were always taught that the difference in rotational weight that has to be put in motion or unsprung weight as opposed to carried weight or sprung weight is for every reduction of 1# of weight that has to put in rotation is equivilant to a reduction of 8# of carried weight.IE:A reduction of 20# of power driven rotating drivetrain is like removing 160# of carried weight.This is only a rule of thumb since fricton and other causes of parsitic drag play a part in the rotation of componants.IE: Brake pad or shoe drag. Some good examples of lightweight componants are spools,axles,brake rotors,alum.hubs,driveshafts,wheels,tires and always the lightened engine rotating assemblies as well as trans assemblies.
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Re: Effect of wheel weight
[Re: bill_greenwood]
#1443281
06/02/13 06:58 AM
06/02/13 06:58 AM
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Joined: Jan 2003
Posts: 2,926
A shed in England
Tig
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Back in the day, our car was running mid 12's with steel chrome 5 spokes. We swapped to convo-pros on all 4 corners with a skinnier front. Went to the track expecting to pick up a tenth and it was still running mid 12's. No real change for us 
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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Re: Effect of wheel weight
[Re: Tig]
#1443282
06/02/13 09:35 AM
06/02/13 09:35 AM
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Joined: Sep 2004
Posts: 2,093
oberlin, Ohio
Rapid340
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The mass is more significant as it moves away from the center of rotation. This inertia effect increases with the square of the radius. But, the negative effect of inertia is perportional to change of rotational speed (acceleration). Anyone that spends big dollars on gun drilled axles will likely be disappointed and wont pick up more than the actual weight removed. Going from new street tires to close to bald (may drop quite a bit of weight in some cases) is weight where it is more significant. A pound of tread verses a pound of lug nuts has 38 times more effect one the overall inertia of the wheel/tire (given a 28 inch tire. and 4.5 in. bolt circle). In fact, the total weight of a wheel/tire combo could be less than another but still result in more loss due to increased inertia. Running a smaller/lighter converter or damper (or even paying the extra to have the crank turned down when you have a bunch of material to remove) could payoff. 
Last edited by Rapid340; 06/05/13 09:10 AM.
1971 Factory Appearing Duster 340 11.000 @ 122 mph
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Re: Effect of wheel weight
[Re: jcc]
#1443284
06/02/13 11:15 AM
06/02/13 11:15 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Quote:
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8 lbs even
The idea of testing wheel weight, would seem like a good and easy tech article for one of the car mags, just come up with a system to SECURELY bolt on some balanced wheel weight, and make runs.
Maybe fluid in the tires..??
Interesting idea for a test and worthy of a reply.
The first problem I see would judging how fast the fluid due to inner tire friction would match the actual tire revolutions, not likely very quick. Second problem would be the liquid would also likely due to its considerable mass distort the tire as it reached higher speed, which would change its rolling radius, and traction footprint, and last and likely not a real issue for drag use, but if temps inside ever reached 212F if using any water, you have steam related issues. I suspect the test would become a fluid in the tire test at the drags rather then test of wheel inertia at the drags.
All I see with this type of testing is a REALLY out
of balance tire and if enough was added you would
just destroy the tire due to bouncing due to balance
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Re: Effect of wheel weight
[Re: B G Racing]
#1443285
06/02/13 12:29 PM
06/02/13 12:29 PM
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Joined: Feb 2003
Posts: 1,942
Metro Detroit
OUTLAWD
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Not back to back, but I picked up ~.15 in the 1/4 by replacing my cop wheels with drag lites. Same tires, saved 15# per wheel.
Faster, Faster until the thrill of speed overcomes the fear of death...
71 Swinger - slowly collecting dust/parts
66 Belv. II - just a streetcar
88 Mustang - turbo LS beater
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Re: Effect of wheel weight
[Re: Wedgeman]
#1443286
06/02/13 12:49 PM
06/02/13 12:49 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
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Quote:
Can someone tell me the gain of going to lighter wheel on the back vs ET ?
...........I mean what gain in time for every pound lighter
Dan
I can tell you! The gain will will be equal to a dead weight loss rule of thumb .1 et per 100 lbs.
The rotational effect wont come into play because the tire will gain rotational speed the whole 1/4 mile. the car just sees the weight as dead weight.
I did the tests many years ago Hoping I would see 1# rotational = 3# of dead weight.
The theoretical gain never occured. The gain was that of the weight alone that was lost as per the old rule of thumb.
I also went as far as removing the rear drums and tested The drums were 40# Guess what 40# of rotational weight was worth ET wise. It was the same as 40# of dead weight.
I did that test over and over a few times.40# on ,40# off, The rotational gain never showed its effect, MEASURABLY!!!
My speculation again was that it was because the tire slowly gains rotation across the whole 1/4 mile ,thus the car sees the weight just the same as dead weight because of that.
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