Corner Balancing specifics

Forgive me as I know very little on the subject myself, but I thought that the best was to add real weight (lead) to even out weight, and to jack or unjack the spring to correct ride height. I thought I also recall guys putting twist into the sway bar rod by moving one arm in or out from the other or changing the pushrod length (thought some were ever cockpit adjustable?) to be able to alter cornering power.

 

Hi Sean,

Here are my numbers from my second crossweight adjustment, ( with 150 pounds in the drivers seat and anti roll bars disconnected):

714 705

915 886

This is within 20 pounds, across.

IIRC, i then rechecked the ride heights, the front was too low so i cranked up the spring perches the same amount on each front corner, so as to not change the balance.

hth,
chris
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Hey Sean,

I can move the weight diagonally but cannot alter the side to side totals. Don't forget, I stuffed 150 pounds of sand, (in bags) in the drivers seat to approximate my lardash, (150 lb, i wish).

There is more than a bit of chasing one's own tail here, alter the corner weight and the heights change - adjust the height and the weights go off.

Maybe someone who has done this 10 or 20 times will offer a bit of time saving advice - please???

best,
chris

 

Sean,

most critical issue is to remove suspension stiction when corner weighting the car. That means using slip plates or roll off ramps. If you are just jacking the car onto pads or using your lift without slip plates you are wasting your time. Cross weight is what is important and being within 30lbs is ok, 20lbs pretty good, 10lbs is about the best you can get with a streetcar/racecar and only a dedicated purpose built racecar can get in the single didgit lbs and make a difference. We on track are 99% of the time under 150mph so the aero of rideheight is not critical for our very few turns of a coilover. each turn is only 1.5mm height change times the motion ratio so even less actual height change. For us rideheight is more about controling weight transfer which effects your braking. Also remember to disconnect sway bars and if you are serious on corner weighting you will have at least one adjustable heimlink for one side of the sway bar so you do not put any "wedge" into any one corner i.e. spring weight. Corner weight is about mechanical grip. To setup a car you always setup for bets mechanical grip then work on Aero. You never use aero to fix mechanical grip problems. You can use rideheight to "help" front rear balance i.e. oversteer/understeer + braking stability and would prefer to have a car setup with mechanical grip oversteer and aero understeer at car's/your limits.

 

The total front # should always be the same, as will the rear unless you physically move some weight around. The center of gravity is fixed. By altering the perch you will transfer weight from side to side, altering the front affects the rear as you have seen. Puzzling that your first figure gave a total which after adding 150lbs increased by more than 150lbs! Inpossible to create mass. We normally look at the diagonal total trying to keep that as equal as possible, works great on porsches. 15-20 front cross is very good with driver/fuel etc. If that repeats I would leave it. FWIW I always adjust all 4 perches at once, learned to be precise so much that I could add/subtract front cross weight during practice sessions on ovals just by the perch, it would show accurate when checked on the scales later in the paddock. It's more difficult on single seaters trying to maintain ride height/chassis rake and tilt. Road courses are a doddle though, equal perches pretty much, so much so that we change springs and can keep the ride height consistent. It's also hard with road cars using rubber bushings, ideally you would loosen the bolts at each adjustment, very time consuming. Once you settle on a setting, drive around the block, if the numbers repeat, then you have GOT IT!

 

Correct, the total all 4 will always be the same, as will front and rear, left and right. Only way to change those would be by moving weight (hence the moveable weights in F1, Nascar etc.). many folk forget that they may have an instructor/passenger on track and that throws all this out the window..... If you are likely to carry people most times, set the weights empty. My corporate Pcar racer has a professional driver in left seat and anywhere from 100lb woman to a 270lber, that does affect the handling/performance, I set the car without driver.

You are really only interested in the front, let the rear fall as it may. 25lbs or less on the front will be very good, if you look as a % it is a very small amount. You may have to adjust the left side front and rear to keep an even ride height, although that is not too critical, within 10 mm will do. Adjusting all 4 perches should keep them close side to side. Adjusting both fronts or rears for a ride height change should have little change to crossweight with stock spring rates.

 

I have string bars for all my cars, quick to fit and you can roll back and forth, jounce it whatever. As accurate as anything, I do use my Dunlop guages as a quick check before and after. A bubble style for caster/camber is fine, the digitals will have you running back and forth chasing 1/10s which don't matter.

 

Others have mentioned it but I'll reinforce. Wheel has to be pointed straight, swaybars disconected, tire presures set, scales level to each other left to right, Front to back is not as critical but having all four level would be nice. Get ride height and corner wts where you want them and then reconnect sway bars and check again. Roll car back and forth and bounce on both ends after making any changes before reading corners.