Lowering the C5 Corvette
using the "ride height adjustment bolts"

 
Based on various postings on various forums the prevailint opinion is that you can lower the rear of your C5 up to about 1" and the front to 3/4" safely with the stock bolts if you have the Z-51 suspension.  If you have the base suspension (FE1) or the Continuously Variable Real Time Damping (F45) suspension, opinions on the net (not backed up with any facts) suggest that damage to the suspension may occur if FE1 or F45 suspensions are lowered this far.  Some kind of undefined, serious damage can occur if an F45 car is lowered.  No one has said what kind of damage or how serious or where it occurs, etc.  Could be an urban legend, I suppose.

I checked with automotive author and C5 guru Hib Halverson who said: "Both Delphi and the Corvette Team people told me that F45 has a problem with lowered cars and increased damping, i.e.: the car rides more stiffly." and "I think you can use the spring jack screws to lower the car as much as that will allow. Then road test the car, if you don't like the ride, simply crank up the adjustment again."  Followed by: "There won't be damage to the shocks. What I was told is that the F45 system "sees" the decrease in ride height and sometimes increases damping during normal driving where ordinarily there would be no increase."  Keep in mind that F45 cars have base springs. Softly sprung cars may have more of a problem with lowering than will Z51s.

So, based on my research, it appears that you can lower the FE1 and F45 about 1/2" in the front and rear safely.  Adjusting both front and rear bolts to their maximum will give you approximately 3/4" in the front and 1" in the rear (this will vary from car to car).  While this does not sound like much, it makes the car look and feel a lot lower.  My air dam was 2" off the road after the procedure.  I am considering either cutting off the lower one inch of the air dam or raising the car about 1/2" so it won't scrape so much.
 

Before starting, measure the height of the front and rear wheel wells from the ground through the center of the wheel.  It should be somewhere around 27-3/8" in front and 28-5/8" in the rear.  Remember these numbers.  Some suggest that the rear lowering can be done without raising the car - well, I'm too big to get under my car unless it is raised - so, the procedure is outlined below.

 
Lowering the Rear:
 
1.  With the car on a level surface and the front wheels blocked, jack the rear of the car and support with two jack stands.  It is actually easier to do the lowering if the wheels are removed, especially when it is time to measure the bolt height to ensure that the car will be level (you might want to remove the wheels now also).

 
2.  At each end of the transverse leaf spring, locate a long bolt, with the threaded up pointed upward. You should see about 1 inch to 1-1/2 inches of exposed thread on the bolt (this is on the top of the leaf spring). Using an 18 mm socket and ratchet on the bottom of the bolt, loosen (counter-clockwise) until there are only two or three threads exposed on the top part of the bolt.  Use an 18 mm wrench to hold the top nut in place as you turn the bolt.

 

Rear Before

Rear After
3.  Leave two or three threads exposed before it contacts the nut. The nut has a small "C" clip on it so it won't back out.  It takes about 5 minutes per side to lower the rear about 1".  It is a good idea to measure the exposed threads on each side to ensure they are the same.

Lowering the Front:  The front, the car definitely has to be raised.
 
1.  With the car safely raised and on jack stands and the front wheels removed, find the end of the transverse leaf spring next to the shock. Locate the 10 mm end of the ride height adjustment bolt. It has a retainer clip.

Front Before
2.  With some suspensions (like the F45) it is easier to get at the top of the bolt if the lower shock absorber bolts (13 mm) are removed so the shock can be moved out of the way.
3.  Using a 10 mm socket on the top of the stud, turn counter-clockwise (like unscrewing - even though you are not, you are just on the opposite end of the bolt so it looks that way) until tight.
4.  Back off the bolt about a 1/8 to ¼ turn to ensure it does not freeze in place in case you want to raise the car at some future date.

 

Front After
5.  Re attach the lower shock mounts, put the wheels back on and remove the jack stands.


At this point, the car may not appear to have been lowered very much. Take it for a drive around the block and allow things to settle (and it *will* settle quite a bit).  Then, with the car parked in the same spot, re-measure the height of the wheel wells as above.  The difference between the two measurements is the amount the car was lowered.  Make sure that both sides of the front and rear measure the same.  Adjust as necessary.
 


Drive the car for a week or so then have the alignment checked by a good shop.  Align as necessary.  If the car feels like the suspension is riding on the rebound bumpers, you may be too low - The best fix is to raise the car by about ¼" and test driving again.