Hello all,

I have read that rotating weight can impact et more so than static weight.

I went from a Hoosier radial to the MT pro bracket radial. Pro bracket radial is supposed to last a lot longer. But each tire I about 5-7 pounds heavier.

So basically 10-14 pounds more rotating weight. Would you see a difference in et?

Thanks

While there might be some correlation; All cars will be affected differently. So unless someone has a very similar combo to yours - it's going to be hard to give you an exact.

When I put bead locks on my rims that added 4 lbs a rim it slowed .015 et .

I'd look at it this way if I were you.

If you got a lighter tire, that is slower than a heavier tire with better rolling resistance, less energy loss at all frequency's. Then the heavier tires lower energy loss at all frequencies, wins in performance (et) over the lighter tire with high energy loss.

This is what you're ultimately measuring, comparing the timeslips from each tire. High energy loss vs low energy loss.

If they et about the same, the heavier tire's low energy loss compensates for the additional weight it possesses.

This message has been edited. Last edited by: Mike Rietow,

quote:

While there might be some correlation; All cars will be affected differently. So unless someone has a very similar combo to yours - it's going to be hard to give you an exact.

That's my experience also, every car is different. I've played with a few different cars both bb and sb with different wheel/tire combo's and the sb cars seemed to notice the weight more. I doubt you'll see much difference at all.
I went from steel rally wheels to lightweight race wheels on my 11.50 bb Camaro and the car literally didn't know the difference.

I'd look at it this way if I were you.

If you got a lighter tire, that is slower than a heavier tire with better rolling resistance, less energy loss at all frequency's. Then the heavier tires lower energy loss at all frequencies, wins in performance (et) over the lighter tire with high energy loss.

This is what you're ultimately measuring, comparing the timeslips from each tire. High energy loss vs low energy loss.

If they et about the same, the heavier tire's low energy loss compensates for the additional weight it possesses.

These are the unbendable fundamentals of tires polar moment of inertia

This wheel with a 6.5 backspace makes for poor rolling resistance.

Put a beadlock on it and it's rolling resistance improves to the point it's performance (et), exceeds it's weight detriment.

Any time you hear anyone say beadlocks slow them down, it's weight detriment exceeded the potential for better rolling resistance.

Beadlocks don't always slow you down, that's wrong.

The gal who ran champion wheels was pretty slick, she called it before she sent the wheels back to me from Cali. She was very knowledgeable

I hope she got on somewhere, good business, very honest and smart as can be. Beadlock outside only.

This message has been edited. Last edited by: Mike Rietow,

old rule of thumb was 1lb rotating equal to 10 lb off car. Not scientific but just that a rule of thumb. Same as 100lbs off equals .10 off car. I have seen last one work cpl times. Thats all 1/4 mile. Now will 1lb off equal .010 in 1/4? Not sure what it equals in 1/8.

Figure adding will probably cost same but in slower et.

I know Jr. fuel guys swear by GY2525 tire because of its lite weight. I think its about 5lbs less than next tire of same size.

I have a model of a 700HP 3300lb car in Quarter Pro that runs a 6.07 1/8th. If I add the additional weight for the wheel and tire, it'll slow .01 in the 1/8th and .02 in the 1/4 which is in the ballpark of markemark's real data.

In performance formulas that I've researched, rotating mass is often manipulated into an "equivalent mass" and lumped into the vehicle mass. That may be where some of the 100lbs = 0.1 second comes from.

5-7 Lbs per tire sounds like a lot. I would expect it to make a difference. I bet some of the better Stk/SS/Comp Eliminator guys know more about this than most of us do.

I to have heard that 1 Lbs of Rotating weight equals 10 Lbs of static weight. I have not ever been able to see that.
I think if you get wheels 20 Lbs lighter (20 lbs x 10 = 200 Lbs and 200 Lbs = .2 tenths) I think you are going to be dissapointed.

Still you try to lose all the weight you can and it adds up. Rotating weight is probably better place to start but do not expect miracles. IMHO.

quote:

Originally posted by Curly1:
I to have heard that 1 Lbs of Rotating weight equals 10 Lbs of static weight. I have not ever been able to see that.
I think if you get wheels 20 Lbs lighter (20 lbs x 10 = 200 Lbs and 200 Lbs = .2 tenths) I think you are going to be dissapointed.

Still you try to lose all the weight you can and it adds up. Rotating weight is probably better place to start but do not expect miracles. IMHO.

Some old rules should be buried and this is one of them!

It's pretty simple, the lower HP combo you have the more things like this will impact performance. A typical 7.30's RED ( decent HP and relatively low weight) swapping from non bead locks to bead locks has no impact. This swap is about 7 to 8 pounds heavier per wheel.

Swapping tires is really doing two things, weight and the tire itself, both can impact performance.

quote:

Originally posted by TOP38:

quote:

Originally posted by Curly1:
I to have heard that 1 Lbs of Rotating weight equals 10 Lbs of static weight. I have not ever been able to see that.
I think if you get wheels 20 Lbs lighter (20 lbs x 10 = 200 Lbs and 200 Lbs = .2 tenths) I think you are going to be dissapointed.

Still you try to lose all the weight you can and it adds up. Rotating weight is probably better place to start but do not expect miracles. IMHO.

Some old rules should be buried and this is one of them!

It's pretty simple, the lower HP combo you have the more things like this will impact performance. A typical 7.30's RED ( decent HP and relatively low weight) swapping from non bead locks to bead locks has no impact. This swap is about 7 to 8 pounds heavier per wheel.

Swapping tires is really doing two things, weight and the tire itself, both can impact performance.

Well said.

There are many rules that should be buried.

All of the old "Rules" about alcohol come to mind.