adding lead and where?

[bluemod]

I need to add 40 pounds to car the drive was 260 and now 220 so where is the best place to place this weight to keep the %s the same. Under driver seat or high on left side where do i need to place this?

[LITE-INN]

same place you lost it lol

[bluemod]

same place you lost it lol

Better not never get in the car now. Wheres the best place to mount the weight.

[Racer111]

between driver and drive shaft.thats a neutral area.

[istock11m]

Around the drive shaft loop or in that area.

[autoshop]

high for wet track low for dry

[bluemod]

thanks for pointing me in the direction i needed ill be puting it on the scales soon.

[Confused?]

Find the center of gravity for the car and mount it as close to that as possible. This won't change the precentages.Depending on the rear and left side numbers, it may be mounted around the dash bar, above the transmission.

[juice87]

high for wet track low for dry

thats backwards.

[drtrkr244]

Mount it beside the driver, to his right.That will be as close to the center of gravity, for a dirt car,as you can get.

[DaveBauerSS6]

Put the car on scales, note the rear %, and the left side %. Get a 20# chunk, lay it on the roof move the weight front to rear until the rear % is the same as you started. Then move it right to left until the left is the same. That is the CG, and will have the least amount of change to the car. Vertical is something to tune with.

[speedbuggy]

To my knowledge, Dave is correct.

The only reason you have to do the raising of the car is to be able to calculate the true CoG height. Most just say your CoG is about the same height as the camshaft and it's close enough.

Another way to do it is take the wheelbase and track of the car. Let's say the wheelbase is 100 inches, and the track is 60 inches (just to make the numbers round). If your percentages say you have 55% left and 58% rear, then your CoG is (100%-55%) x 60 = 27 inches from the center of the left-side track and (100%-58%) x 100 = 42 inches from the rear axle centerline.

Dave's method should give the same result and a lot less math...

[speedbuggy]

thats backwards.

Agree....that sounds backwards to me, too.

[DaveBauerSS6]

Agree....that sounds backwards to me, too.

Agreed, High ballast for slow , slick tracks. Low ballast for tacky tracks.

[DaveBauerSS6]

That isnt how you locate CG. That would be neutral to left and rear but nothing to do with CG.

CG can be calculated on scales, mine came with directions which said something about raising the rear of the car 14 inches on the scales etc. Ive never done it.

When you add lead to the CG, the rear and left % will not change. That proves its in the center of CG. Longacre has that procedure for lifting the car on scales to find the CG height.
http://www.longacreracing.com/articles/art.asp?ARTID=22

[7uptruckracer]

Lead should be bolted roughly 16-20" on the race car from the ground. There is a formula for finding CG on your car I block mine up 24 inches but I've heard 14" too, the camshaft in the V8 is a used rough in sometimes but not precise. Low weight for Heavy and Tacky Tracks, A higher Position for slick. You want the weight in a common grouping never in front of the front hubs and never behind the rear axle. Try to get your polar moment in a tight central grouping but still maintain the correct percentages and minimize your weight being at far counteracting ends.

[powerslide]

I think you two are discussing different things. One person is concerned w/ the CGH(Center Gravity Height) and the other the CG(Center of Gravity).

Again posting the longacre link
http://www.longacreracing.com/articles/art.asp?ARTID=22

[DaveBauerSS6]

The CG of a 3 dimensional object like a race car includes the height, the link you provided again doesnt tell you how to find CG as if its different from the CG Height.

Ill erase my post so you guys can move on sorry for pointing out the obvious. My bad.

You are right about the CG being 3d. Moving lead until it has no effect on the %s is the 2 dimensional position. The vertical is a function of how much roll you want. The link was for finding the vertical height.

[7uptruckracer]

I agree with stock car finding your CG includes lateral and height. If you could suspend your car in a single wire from the side and the top there is one central location that would work to balance both

[speedbuggy]

I need to add 40 pounds to car the drive was 260 and now 220 so where is the best place to place this weight to keep the %s the same. Under driver seat or high on left side where do i need to place this?

So, bluemod....

in the midst of all this, did you get an answer that you can use?