If I wanted to change the front springs, and the car was corner balanced, could I change the spring, and then adjust the height of the corners I changed to match the previous corner balanced heights? Would this maintain the same corner loads?

 

I was thinking about this the other day - swapping the springs and keeping the koni perches at the same adjustment
I don't think it'd affect it that much if its just 100lbs up or down on the spring, its not like my corner balance came out 100% anywways

 

Well, I know it will make a difference and my cross weights are within 0.1% of 50/50 so I will have to make some adjustment to get back to that, and I'd prefer not to go back and re scale the car.

 

I think the force is far too sensitive to the height for you to get a precise corner balance just from measuring the heights, even if the height was independent of the spring rate.

I also expect that the cross balance depends on the difference between the front and rear spring rates, based on a simplified model I worked out. If the left side an right side weights are equal (center of mass on centerline of car) then the front & rear spring rate difference drops out and you could change the front spring rates and not alter the cross balance.

I think the best you could do is to replace the springs, and then adjust both the front spring seats up or down by the same amount (number of turns) to get back to the rake you want. That could introduce a small change in cross balance, but not as much as you could if you tried to adjust cross balance by measuring the corner ride heights.

 

changing the spring will affect the corner weights. Especially if you change the rates. If you run stiffer springs then that specific corner will change in height obviously because the spring rate is different. You would have to readjust perches to set the ride height at the exact position it was originally at.

Anyways even if you were to change the springs with a different brand of springs because the characteristics of the spring rate curve is different the height can once again change.

Anyways I hope this helps.

 

You could specify exact ride heights for all four corners, and I could show up and set your diagonal weights to just about anywhere I wanted between 0% and 100% with the car sitting at the ride heights you specified. There is not a one-to-one relationship between ride height and cross balance.

 

Thanks, this was what I was looking for!

 

Of course, if you constrain things so that the rear spring seats can't be moved, then I believe that there is a 1-to-1 correspondence. However, as I mentioned above, the force is extremely sensitive to small height differences. Multiply your height measurement by the wheel rate to estimate how big your cross weight error could be.

 

Given that everything else is staying the same, then I think that *in principle* you could get back to the same corner balance by re-setting the front ride heights where they were.

However, I also think it'd be very difficult to get as close as you'd want to be using just a tape measure, string, or whatever. With 600-700lb springs, every mm you're off could be 10-20 lbs of cross-weight. Also, remember that your corner balance is not preserved when you're not in the car (it should have been done with you in the car), so you'd need a very patient assistant to help you... I think it'd very quickly become so much trouble that you may as well just pay to have it done right.

 

I agree

I do my own corner weighing and have found one turn or a bit less of the threaded perch is necessary to get the cross weights to the gnats ass accuracy that I want. I don't believe you will get that with ride height measurements no matter how you do it. If you think you are going to make other changes soon like a wing, wheels, FSB, BBK I would do the best you can with measurements until you get it all done then get it corner balanced.

I am sure you know this but others may not, if you do not have adjustable end links on your front and rear sway bars it is very likely that the bars are preloaded and your corner weights are off as soon as you reconnect them.