Tom Johnson

1971, 350/270, Automatic, Air Conditioning, I am using the 71 Chassis Service Manual. In the specifications 5 using their diagram for points of measurement I come up with an average of 3.20. It should be 2.29 give or take .38. Doesn't this indicate the spring is not sagging? If the spring is sagging shouldn't the measurement be less than 1.91? The z measurement(2.29) minus the allowance(.38) equals 1.91. Going to Front Suspension 3-6 Figure 9-Checking Ride Height the diagram shows a different point of measurement for the corvette. The problem is that my lower control arm, near the lower ball joint, looks nothing like the diagram. Where, on the control arm near the ball joint, do I measure from using this diagram?

Tom Johnson

If I measure from the lowest point on the steering knuckle to the center of the lower control arm bolt I get 2.62. The measurement I come up with (2.62) minus the z measurement (2.29) equals .33 which is in the give or take allowance (.38).

flynhi

You must adjust the factory numbers for tire height. If you are using tires with different diameter than F70, you must adjust the factory spec appropriately.
Also, see the Vette Improvement Program series of articles in the archives. The one on suspension addreses Z and D heights.
Try this and post the results. I went thru this a couple of years back and can probably help you figure this out.

Tom Johnson

I could not find any data for z and d heights in the archives. The z dimension is not affected by tire height. Only the j, k and d are. My first post I was measuring from the bottom of the ball joint stud which I think is incorrect.

flynhi

look under Vette Improvement Program.

Stingy74

You can also check the z heights in the Chevy Power manual. They list them for SCCA type race cars so I don't know if they'd be the same or not.