johntorg

I have been trying to adjust the corner balance on my 944Cup car and seem to have moved in the wrong direction. Here are the before and after weights. I am going to Roebling road this Friday and will be able to use their scales again.

BEFORE

LF 745 RF 668
LR 745 RR 708
TOTAL 2866
LF+LR 1490 RF+RR 1376
RF+LR 1413 LF+RR 1453
AFTER
LF 770 RF 631
LR 712 RR 731
TOTAL 2844
LF+LR 1482 RF+RR 1362
RF+LR 1343 LF+RR 1501

After looking at the BEFORE setup, I cranked up the RF coilover 2 turns. This added weight to the LF and RR, and my cross weights are now wider apart.

The car is heavier on the L side, due to a heavier driver (me) and removal of some ballast on the passenger side. I am planning on going back to the BEFORE setup, at least until I can shift some weight to the R side.

I have coilovers in the front and torsion bars on the rear and can easily adjust the front only. It appears to me that the BEFORE setup wasn't too bad.

Any and all comments on my logic (or lack thereof) are welcome, as well as suggestions for improvements.

Van

I use a spreadsheet that helps in the calculation of corner balancing.

First - I have to make an assumption... You *did* put weights in the driver's seat to equal your body weight and you have about a half tank of gas and all other fluids are topped off. I.e. the car is *exactly* in racing trim.

Now, I plug in your before #s..... and, to start off, your LF-RR diagonal is carrying too much weight (you're getting a see-saw effect). You need to either *lower* the spring perch on the LF or *raise* the perch on the RF.

Now, I plug in your after #s..... you've moved even farther away from your target. You went from carrying about 20 extra lbs on that diagonal to now carrying 80 extra lbs on that diagonal.

If you think you moved the spring perch in the right direction, you have some other variable that you're not taking into account, like:
-Scales not level
-Scales binding due to suspension movement
-Parking brake set
-Spring not squarely sitting on perch
-Weight in car changed
-Moved spring perch in wrong direction
-Confused left and right

2bridges

Hi John

Yes this is a tricky deal. If this is for a dedicated race car (as it sounds) then your ride height adjustments will help...... as I recall you get the drivers front ride height set higher to shift a bit of weight to the pass and rear.

The end resulting different front height side to side is aesthetic only
Also you can adjust the rears via the eccentric bolt. Kind of depends where you are in the eccentric now, but worth checking.

Lemming

Go back three turns.

In the before setup, you have 0.7% reverse wedge. The program I have suggests that wedge should be less than 0.5%, so you are not too far off.

HansB

You are correct, you went in the wrong direction.
Cranking your RF up ( I guess you mean you have rotated the spring perch so it went up) effective lowers the car RF, so it will take less weight.
A way to think about this is, that if your spring perch could be 1 ft higher, and your car would be very stiff, the RF wheel would have no weight on it.

Your original distribution is not bad at all, but by going back to your original setup, and cranking it one turn in the opposite direction you should be ok.

To do the best thing in your situation, you should measure the ride height LF and RF, to decide to go up on the L or down on the R

Lemming

It is my understanding that changing ride height will not change weight front to rear or side to side, it only affects the cross-weight. To change F/R and L/R you need to add or remove weight from different areas of the car.

Van

Hans, I'm not sure you're right about this... If you move the lower spring perch up, it will compress the spring more - which will make the spring push back more... which pushes back down on the scale more - which means that diagonal is now holding more weight.

If you crank that perch up 1ft, like you say in your example, it will lift up the front of the car, letting the other front wheel dangle in the air - thus, the diagonal you move the perch up on will be holding *all* of the weight, and the other diagonal will have *none*.

Van

Correct.

reno808

Van is it possible i can have that spreadsheet

2bridges

I wold love to take a peek also

theedge

I wouldnt mind a copy too

If you want, you can email it to me and ill host it.

johntorg

Thanks for the help. I am using a spreadsheet, but when I cut and pasted it it came out as shown. I will lower the spring perch 3 turns and see where I am on Friday. I can only adjust the cross weights with ride height adjustment. The car is about 120 lbs heavier on the driver's side. I am close to my minimum weight (2800 lbs) so I can't add weight to the Passenger's side. How bad is the 120 lb difference?

johntorg

I forgot to reply that I was in the driver's seat when on the scales and yes it is a dedicated race car.

Lemming

Here are two sites that discuss corner weighting, the second site has a calculator.

http://grassrootsmotorsports.com/art...orner-weights/

http://robrobinette.com/corner_weight.htm

Lemming

No, Hans is correct on this one. Lowering the perch increases ride height as long as you are not outside of the range of the spring.