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#1 Posted : Thursday, June 6, 2019 3:59:12 PM(UTC)

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Hello- in your article rethinking dirt, you mention the formula for lateral weight transfer as (Weight x CGH / TW) x G (lateral). In another part of the article it states:

"How do we achieve maximum lateral traction? Keep the CGH low. Although some of this is controlled by the design of the car, we can raise and lower the CGH. By lowering the car we transfer less weight and keep the rear tires more equally loaded providing more lateral traction."

So if I understand this correctly- the lower the resultant number of the formula, the the less lateral weight transfer and therefore it will have more "side bite"? So if nothing else changes a car with a center of gravity of 20" will have more lateral traction "side bite" than a car raised one inch to 21"

For a non-wing car- This makes sense on a tacky track where the "bite' is built into the track itself and usually the G forces are higher too so loading the right rear is not the problem but keeping proportional weight on the left rear is the key. I understand the RR is larger and needs to be 20-30% loaded more than LR for maximum tire efficiency.

But when the track gets hard and slick- the G forces are lowered and the track is no longer providing the traction on the right rear, wouldnt you then need to raise the CGH to add weight to the right rear in order generate "side bite" or else the car would just want to slide and/ or spin out? Of course you still want some weight on the LR as well so its more advantageous to transfer weight (longitudinal) from the front to the rear if possible, but if the RR doesnt stick and not doing its share of the work its a lost cause so it becomes a balancing act how much you raise the car and where to increase side bite and forward drive. But in this case- raising the CG could increase side bite through increasing lateral weight transfer? Is this logic correct?

Mike Dicely  
#2 Posted : Monday, June 10, 2019 8:45:42 PM(UTC)
Mike Dicely

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Your thinking process is spot on! Well done.

If you do the math using the formulas, you can answer your question. Lateral Weight Transfer = (Weight x CGH / TW) x G (lateral).

Using an 800 pound race car with a 13-1/2" high CGH with 65" track width in a 2.5 G turn (a typical wet track), the amount of weight transferred to the right side of the car is 415 pounds. A little less than half of that is transferred off the LR and onto the RR (depending on the roll couple, you can easily calculate that too). So say 200 pounds.

On a really slick track which is about .8 g's, the weight transferred is 132 pounds and about 60 of the that is in the rear.

Typically we have about 490 pounds of rear weight, if we want to end up with 65% (318 pounds) of that weight on the RR (30% more than the LR [172 pounds]). So on a slick track we would want to start with 232 pounds of LR weight and 258 pounds of RR weight. Yea, kind of surprising isn't it? Of course there are more variables and factors to look at, but this really is the basics of what we are trying to think about. So it's weird how most people add LR weight to tighten up on a really slick track. And yes you can raise the CGH to get the weight to transfer as well instead of starting out RR heavy.

For your exact situation you would need to do you own calculations based on your own numbers. The G force is a big factor of course as you will transfer more than 3 times the amount of weight.

Good stuff!
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