Effect of wheel weight

Posted By: Wedgeman

Effect of wheel weight - 05/28/13 03:26 AM

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

Posted By: 70AARcuda

Re: Effect of wheel weight - 05/28/13 03:32 AM

http://www.bigblockdart.com/techpages/rotatingweight.shtml

dont know if this what you are looking for..but..

Posted By: Wedgeman

Re: Effect of wheel weight - 05/28/13 03:42 AM

NOt sure I totally understand......wheels 15 pounds lighter in the back is worth .6 mph ?

Posted By: Wedgeman

Re: Effect of wheel weight - 06/01/13 01:23 PM

I have heard that for 1 lb off the Wheel is like 80lbs off the body....

67 Barracuda
best 6.75 1/8 mile

Posted By: MR_P_BODY

Re: Effect of wheel weight - 06/01/13 01:30 PM

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

Posted By: CHAPPER

Re: Effect of wheel weight - 06/01/13 02:51 PM

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.

Posted By: John Brown

Re: Effect of wheel weight - 06/01/13 02:53 PM

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.

Posted By: MR_P_BODY

Re: Effect of wheel weight - 06/01/13 02:55 PM

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

Posted By: StealthWedge67

Re: Effect of wheel weight - 06/01/13 05:31 PM

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.

?????

Posted By: MR_P_BODY

Re: Effect of wheel weight - 06/01/13 07:09 PM

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

Posted By: Duner

Re: Effect of wheel weight - 06/01/13 07:43 PM

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!

Posted By: Wedgeman

Re: Effect of wheel weight - 06/01/13 07:44 PM

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 ?????

Posted By: MR_P_BODY

Re: Effect of wheel weight - 06/01/13 10:06 PM

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

Posted By: Wedgeman

Re: Effect of wheel weight - 06/01/13 10:33 PM

Interesting to put that to the test !

I'll keep you informed as I am changing for M/T Pro 5 rims soon.........

Posted By: nss guy

Re: Effect of wheel weight - 06/01/13 11:58 PM

I've run heavy stock steel rims 15 x 10 vs 15 x 10 weld drag lite rims on the rear and 15 x 6 stock steel vs 15 x 3.5 weld drag lites on the front, can't remember the exact et difference but less than a tenth. and we're talking probably +50lbs difference

Posted By: jcc

Re: Effect of wheel weight - 06/01/13 11:59 PM

Posted By: CHAPPER

Re: Effect of wheel weight - 06/02/13 12:52 AM

Quote:

Quote:

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

The number I always heard tossed around was losing 1lb of rotating weight is approx same as losing 3 lbs static weight.

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..??

Posted By: autoxcuda

Re: Effect of wheel weight - 06/02/13 12:53 AM

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.

Posted By: B G Racing

Re: Effect of wheel weight - 06/02/13 01:27 AM

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.

Posted By: John_T_Brown

Re: Effect of wheel weight - 06/02/13 01:35 AM

Rotating Inertia

Posted By: jcc

Re: Effect of wheel weight - 06/02/13 02:29 AM

Quote:

This topic can be debated untill the cows or sheep come home.

Stating the obvious?

Posted By: Wedgeman

Re: Effect of wheel weight - 06/02/13 02:52 AM

Very interesting answers !

A good thinking tells me that a lighter wheel is easier to turn than a heavier one...which means more energy is transferred to the body to break the inertia..

It takes energy to break inertia of the rotating parts, and again some energy to break inertia of the body and keep the rotating going

Hard to quantify !

Posted By: autoxcuda

Re: Effect of wheel weight - 06/02/13 03:33 AM

Quote:

Very interesting answers !

A good thinking tells me that a lighter wheel is easier to turn than a heavier one...which means more energy is transferred to the body to break the inertia..

It takes energy to break inertia of the rotating parts, and again some energy to break inertia of the body and keep the rotating going

Hard to quantify !

Actually easy to quantify. With measurement tool or calculating.

Maybe tedious to calculate depending on the physical features of the part and the changes in accelerations.

Getting your findings, if small, to corralate perfectly 100% with measured ET's is tough.

Posted By: polyspheric

Re: Effect of wheel weight - 06/02/13 04:52 AM

http://victorylibrary.com/mopar/sprung.htm

Posted By: bill_greenwood

Re: Effect of wheel weight - 06/02/13 06:51 AM

Think of wheel weight in this fashion: You're not just accelerating the wheel/tire from 0 mph to trap speed in 1320 feet, you are accelerating that rotational assembly from 0 rpm to trap speed axle rpm in the span of your ET. If you're running 120 mph with a 30" tire, that wheel is turning 1200-1300 rpm. It takes a lot less energy to get a 10-12 pound assembly to accelerate from rest to 1200 rpm in 11.5 seconds than it does a 20 lb wheel.
I've been told, for example, that torque challenged small block stockers can easily pick up a tenth just by changing to tubeless slicks and losing a couple pounds per tire.
I've also seen anecdotal evidence that the 03-06 Ram pickups with the 20" rims (the heavy suckers) get noticeably poorer fuel economy in urban driving than ones equipped with lighter 17" rubber.
When I used to run a lathe all day long, I was very aware that it took less effort for my lathe to spool a 75 lb solid bar that was 6" dia up to speed than a 75 lb ring that was 20" in dia.

Posted By: Tig

Re: Effect of wheel weight - 06/02/13 10:58 AM

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

Posted By: Rapid340

Re: Effect of wheel weight - 06/02/13 01:35 PM

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.

Posted By: jcc

Re: Effect of wheel weight - 06/02/13 02:42 PM

Posted By: MR_P_BODY

Re: Effect of wheel weight - 06/02/13 03:15 PM

Quote:

Quote:

Quote:

Quote:

Quote:

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

Posted By: OUTLAWD

Re: Effect of wheel weight - 06/02/13 04:29 PM

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.

Posted By: Sport440

Re: Effect of wheel weight - 06/02/13 04:49 PM

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.