Best way to adjust rear coil overs for proper height on my SPF

[scottj]

Originally Posted by elmariachi

If the corner weights are not balanced properly and you have more weight of the car on one side versus the other, it will not go straight under hard acceleration. I would suspect its MORE likely the rear end setup as offered above, but go ask the drag racers why the worry about left and right weight distribution. Its because it affects straight-line launch.

EDIT>>

I just pulled my measurements. Before doing the corners my car didn't handle very well. It responded much differently in right turns than left, especially if accelerating. I actually thought it was the Billboards at first. We had already checked alignment and rear end setup and thought we were good there. Hurricanes have had some bump steer anomalies so we measured that as well and it wasn't too pronounced (once we got the right camber specs.) Then a buddy said "Hey come use my scales and let's set up your corner weights." Huh? So we put it on the scales and here were the initial measurements:

LF: 677 RF: 683 Total front: 1360 lbs Total left: 1367

LR: 690 RR: 650 Total rear: 1340 lbs Total right: 1333

This is almost a 50/50 front to rear ratio, and more weight on the driver's side (even before counting me). Quite a shock given the big FE up front. And clearly the axis from RF to LR was bearing more weight, 34 lbs more. Oddly though the wheel lip to floor measurements suggested the car was level left to right. So by adjusting the coils we got to this:

LF: 710 RF: 725 Total front: 1435 Total left: 1335

LR: 625 RR: 640 Total rear: 1265 Total right: 1405

This moved 75 pounds from rear to front, which yielded a 53/47 ratio. Much more towards what you would expect with the FE. But the diagonal values are perfect (1350/1350). We chose not to make adjustments with me in the car because the left was already 70 lbs lighter than the right, probably would be about equal with me in the car. This made a noticeable difference in how the car handles and steers. And amazingly, the car sits almost level (RR is 1/8" higher than LR) and has more of the a$$-low stance I wanted.

I didn't know squat about this beforehand but there is no denying the numbers and the resulting handling.

If your numbers show that coil over adjustments are moving weight from rear to front or from side to side, then you have bad numbers. Coil over adjustments only cause change to cross-weight percentage. You have to relocate mass to cause a change in F/R and L/R percentages.

[patrickt]

FWIW, here is my iron block FE/aluminum head/intake/WP/flywheel, Tremec/ERA custom outboard braked rear car with half a tank of gas and a small bag of tools in the trunk. This is with me in the car, and I weigh 195lbs.

[elmariachi]

Originally Posted by scottj

If your numbers show that coil over adjustments are moving weight from rear to front or from side to side, then you have bad numbers. Coil over adjustments only cause change to cross-weight percentage. You have to relocate mass to cause a change in F/R and L/R percentages.

Yea I was thinking about that after reading again what all we wrote down. You're right, we do have a mistake somewhere. We have made two changes to the car to lighten it since I took those readings so I think once I get the new Billboards on next weekend I'll do it again and see what it reads.

[patrickt]

Originally Posted by elmariachi

Yea I was thinking about that after reading again what all we wrote down. You're right, we do have a mistake somewhere. We have made two changes to the car to lighten it since I took those readings so I think once I get the new Billboards on next weekend I'll do it again and see what it reads.

I wouldn't even bother screwing with the coilovers. I'd just go down in the basement and get those old weights from high school and stack them in the corners of your car to make it all even out. Throw a sack of cement in to the trunk too, just for good measure.

[elmariachi]

Originally Posted by patrickt

I wouldn't even bother screwing with the coilovers. I'd just go down in the basement and get those old weights from high school and stack them in the corners of your car to make it all even out. Throw a sack of cement in to the trunk too, just for good measure.

No I am hell bent on re-measuring now. I do know the last measurement is right because its in my hand writing. The first ones were taken by my alcohol imbibed buddy.

Did read somewhere that your club owns a set of these scales?

[patrickt]

Originally Posted by elmariachi

Did read somewhere that your club owns a set of these scales?

The scales were owned by an individual in the club... who has since moved on to greener pastures. I know DCDoug was trying to find a set, maybe two years ago, because that set was no longer available. Then his wife started having babies, apparently in rapid succession, and we haven't heard too much from him. I would think most race shops would rent them to you for a reasonably modest fee, along with a hefty deposit for their safe return.