Weight transfer

[Billy Mac]

I want to get Gator's opinion on something.....(and the rest of you cast of characters can put your 2 cents in as well )

I'm curious....what with the fact that my engine setback is going to be so substancial (in excess of a foot from the axle centerline to #1)....is "conventional" wisdom going to apply to 4-link settings...or am I gonna just have to tinker with the adjustments?.....I don't "think" that my chassis is going to pitch rotate like a standard "stock location" engine combo would / does....Am I going to experience "issues" with this setup??

[Gator]

upper & lowers pretty neutral?
lower bar slightly downhill?
not to big a spread between uppers&lowers?

[Billy Mac]

without the motor in there yet, Gator, I am not sure where things will be placed, "yet"...everything is just there for "roll-around" purposes..........Perhaps I'm just getting antzy about wanting to finish this project and get it runnin' again.....and also trying to over-think things....but I guess I just don't want to go out and embarass myself....ya know? I figure if ANYONE knows about this sorta thing, You would.

[BillyShope]

So long as your CG height hasn't changed, the no squat/no rise (100% anti-squat) line is still in the same place. So, link settings aren't so much a concern as excessive wheelstands might be.

You might want to take a look at the page in my blog on weight transfer:

http://home.earthlink.net/~whshope

[On the Ground Performance]

The good thing about 4-link suspensions are their ability to work well with very little or no weight transfer. Your engine set back will only benefit you on the other end of the track. You will find the vehicle to be much more stable and even easier to handle throughout the run. The best way we have found to set the rear 4-link is to first make a set of blanks that will replace the coilovers, and drill them to the dimensions of the coilover @ ride height. That will make adjusting easier as well as giving you a visual of where the instant center will fall with the rear suspension at ride height. You should start depending on overall horsepower with your lower bars parallel to the ground @ ride hieght. The upper bar you want to intersect about 50-55 inches in front of the center of the rear. This would be a good starting point with that engine set back. If you are still pulling the front wheels up too high (no more than 1"-2" at most) the instant center should be raised in the car. Whatever you don't point the instant center much lower than the neutral line- you will most definitely have a screaming wheel stand. In the end weight transfer doesn't become an issue as much with a 4-link because of the ability to control it.

[BillyShope]

Weight transfer is a function of car weight, CG height, wheelbase, and acceleration. The only way a suspension adjustment can affect weight transfer is to change the acceleration. Naturally, you're more inclined to wheelstand with an increase in acceleration. To "fix" this with a suspension adjustment is simply to reduce acceleration. But, this is an example of shooting yourself in the foot. You want maximum acceleration, which means that you have to do something about the static weight distribution. You most definitely do NOT want to stop wheelstands with a suspension adjustment.

The fraction of static weight on the rear wheels should be no more than:

(L-2.5H)/L

where "L" is the wheelbase and "H" is the center of gravity height. The "2.5" is the coefficient of friction for a good set of slicks. The static weight bias should be determined with the driver in the car, of course.

If the rear weight percentage is greater, wheelie bar loads increase and rear tire loadings decrease. Again, the wheelie is eliminated, but the price is a decrease in quarter mile performance.

So, I'd suggest that you verify that the static rear percentage is not excessive and then you can start worrying about suspension adjustments.

And, when that time comes, I'd further suggest that you use a traction dyno (Pages 4, 5, and 6 below) for your suspension tuning.

http://home.earthlink.net/~whshope

[On the Ground Performance]

Wheelstands=Loss of Motion forward. You don't want to go up, you want to go forward. Watch a Pro Stock Car.

[BillyShope]

Wheelstands=Loss of Motion forward. You don't want to go up, you want to go forward. Watch a Pro Stock Car.

Absolutely! Any force on the wheelie bars means that much less force where it's needed. The fans might like to see both fronts in the air, but that doesn't win dragraces.

[Maritime Drag Racing]

Wheelstands=Loss of Motion forward. You don't want to go up, you want to go forward. Watch a Pro Stock Car.

Absolutely! Any force on the wheelie bars means that much less force where it's needed. The fans might like to see both fronts in the air, but that doesn't win dragraces.

Very true - except maybe for Stock and Super/Stock cars.

[BillyShope]

I'm sorry. I'm certain you're making some kind of joke, but it went right over my head. At my age, that happens a lot.

For the spectator, expecting a good show, a wheelstand adds to the excitement. For the dragracer, it's an embarassment comparable to missing a shift or running out of fuel halfway down the strip. Unfortunately, many think a simple suspension adjustment can make it "go away" without affecting performance when what's really needed...a forward weight shift...can mean some serious changes.