by Hib Halverson
A little-known feature of C8 Corvettes is the wide range of ride height adjustment on cars ordered with the Z51 “Performance Package”. Common reasons why a C8 Z51 owner might want to change the ride height would be to lower the car to enhance appearance or to improve at-limit handling, especially in a racetrack duty cycle.
From 1984 to 2019, Corvette suspension had glass/epoxy composite, transverse leaf springs with shock absorbers acting on the outer end of the lower control arms. For 2020 and later, coil springs with concentrically mounted shock absorbers, known as “coil-over-shock” assemblies, have replaced the plastic leafs and separate shocks.
All four coil-overs on C8 Z51s without the E60 “Front End Lift” option and the rear coil-overs on Z51s with E60 are engineered like those on many race cars with threaded collars near the bottom of their shock bodies which rotate but are fixed axially. The spring seat is threaded and can turn up or down on that collar. Once the adjustment is complete a locking ring on the collar below the spring seat secures the seat. The adjustment range is 38-mm or 1.5-in. and adjustment can be accomplished without removing the coil-overs.
On C8 Z51s with E60, the front-end lift actuators at the bottom of both front coil-overs preclude the threaded collars and adjustable spring seats. Nevertheless, the E60 front suspension can be lowered but not by methods covered by this article. It requires removal and modification of the front coil-overs, a procedure which will be covered in a future article on this web site.
The non-E60 front/rear ride height adjustments and the E60 rear height adjustments are relatively simple procedures. They can be accomplished on a DIY basis if the user has the ability to jack up each corner of the car and has a set of spanner wrenches specifically designed to adjust C8 Z51 coil-overs.
This 2020-2021 Z51 LPE Ride Height Adjustable Spanner Wrench Set (PN TL-183) is made by Lingenfelter Performance Engineering (LPE) and sold by Zip Products. The spanners are manufactured from black-anodized, 6061 Aluminum. Their size is optimized for good ergonomics and storage in a C8 Corvette’s glovebox. Their design prevents the wrench from slipping off the spring seat or locking ring during adjustment.
The wrenches have an integrated pin to hold the threaded collar while adjusting and an integrated scale to measure height before and after adjustment. They were engineered by LPE and are manufactured in the USA.
To change the adjustment, the coil-over-shock must be fully extended, so the first step in using the Spanner Wrench Set is to lift each corner of the car. There are three ways to do that:
Method 1: Install Zip Products C7/C8 Jacking Pucks (PN X-3197) and raise each corner of the car with a floor jack lifting on a jacking puck.
Method 2: Install four jacking pucks, then raise the car with a four-point, frame hoist.
Method 3: Lift each end of the car with a floor jack with its jack pad under the front or rear jacking points, then set the car on two jack-stands positioned under two Zip jacking pucks.
We suggest method 1 or 2 because they are the least complex. Method 3 is the most labor intensive because it requires removal of underbody panels before one can access the front and rear jacking points. For that reason, we’re not covering that procedure. However, instructions are listed on GMSi, GM’s web-based service data for dealer technicians, which is available by subscription to consumers from ACDelco’s Technical Delivery System. This article covers Method 1 in detail because that is the most likely method used by DIYs reading this web site.
01: Pick one of the two rear suspensions, then reach under the frame rail and insert a Zip Products C8 Jacking Puck in the slot on the rail which is closest to the suspension on which you’re working. Depending on the floor jack’s height, you may need to drive the car up on some Race Ramps in order to get the jack positioned under the jacking puck.
02: Maneuver your floor jack such that the jack pad is under the jacking puck, then raise that corner until the tire is off the ground with several inches between it and the ground. DO NOT put any part of your body under any part of the car.
03: Remove the tire and wheel assembly. The wheel nuts require either a 22-mm or a 7/8-in. 1/2-in. drive socket. They are torqued to 140-ft/lb. so a lug star with long arms or a 1/2-in drive breaker bar with a long handle will be required to break the nuts loose. Again, DO NOT put any part of your body under any part of the car. Once you have the nuts off, remove the tire/wheel and roll it out of the way.
04: On the shock, under the spring seat, is a threaded lock ring and below that a plastic sleeve which acts as a dust cover over the threaded collar.
05: Use the large upper half and the smaller lower half of the LPE wrench set to break the lock ring loose. In cases of fairly new cars or cars with exceptionally clean chassis, unscrew the lock ring and sleeve all the way down. If the coil-over shocks are a bit dirty, that sleeve might be difficult to move or, even stuck in place. Spray under the sleeve with WD-40 or brake cleaner to loosen/remove any dirt and then the lock ring and sleeve will move more easily.
06: If the car has not had any adjustment before, you should see the spring seat around halfway up the threads which leaves 19-25-mm or 0.75-1.0-in. of space to change the ride height.
07: Before you change anything, use the scale on the lower half of the Spanner Set to measure where the spring seat is located and record the number. In the majority of cases, the goal is lower ride height so, use the upper part of the Spanner Set to turn the spring seat such that it moves down. If it’s a rare case of wanting to raise the car, turn the seat the opposite direction. We suggest you start with a half-inch change. The geometry of the C8 suspension is such that the actual ride height change is approximately equal to how much you move the spring seat.
08: If the threaded collar is not in a position for the large wrench to be easily applied to the spring seat, use the smaller wrench with the pin to turn the collar so it’s oriented such that the spanner will engage the slots on the spring seat.
09: When making the adjustment, if the seat and the collar both rotate, use the smaller wrench with the pin to hold collar while turning the seat.
10: Once you have the adjustment “eyeballed” to the place you want it, use the scale on the lower half of the wrench set to measure the new spring seat location. Record that number. Then, thread the lock ring and sleeve by hand, upwards, until it is against the spring seat.
11: Using the two wrenches, tighten the lock ring.
12: Reinstall the wheel/tire assembly. Torque the wheel nuts to 140 ft/lbs. in three increments and in a star pattern. Then, lower your jack, remove the jacking puck and move around to the other rear suspension to make the same adjustment. After doing the rear, if the car is a Z51 without E60, adjust the two front coil-overs in the same manner. Remember, when you lift the other wheels with the floor jack, DO NOT put any part of your body under any part of the car.
13a: If the car has been lowered no more than 19-mm (0.75-in) in front and 12.5-mm (0.50-in) in the rear, suspension alignment will not be affected to any practical degree so no visit to an alignment shop is necessary. If you lower the car more than that, alignment may be necessary.
13b: For track use, alignment must to be changed and, at minimum, settings need to be adjusted for significantly more negative camber. If you are tracking, regardless of what you’ve done to ride height, you need to change alignment. Chevrolet has published a comprehensive Track Preparation Guide for C8s and it contains starting points for track alignments. This guide can be downloaded from www.chevy.com or mygm.com
DIY C8 Corvette Height Adjustment
Source: Zip Corvette Parts
8067 Fast Lane | Mechanicsville, VA 23111 | (800) 962-9632
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