Trailing Arms
Putting 275 tires on the trailing arm requires relocating the parking brake brackets. I use a piece of wire to mark the distance from the bracket to the parking brake actuator. It was about 10.5".
Here's the first bracket I moved. This bracket has to be moved to the top of the trailing arm, which increases the angle on the cable as it passes through the second bracket.
Here's the second bracket. I removed the weld material so it could be repositioned.
I use a wire to determine the bracket position. The end I put in the parking brake actuator is twisted around a nut to keep it from slipping out. I bent the wire at the brackets original position so I would know where it goes on top of the trailing arm. I moved the second bracket until the wire was straight as possible without getting too close to the trailing arm. I marked these positions with a scratch awl.
Here's a trailing arm with the relocated brackets.
Here's a trailing arm painted and ready for installation. Stay tuned to see whether the set-up is correct. I should be mounting the brake hardware and tires within the next year or so.
SUMMARY: I'd give this a 4 out of 10. It is a little harrowing taking a grinder to your trailing arms. Once you get past that, it's easy to determine where to relocate the brackets, but the pictures don't really convey that.
To give credit where it's due, I must confess that my friend welded the brackets in the new locations. Thanks Corey. I want to learn to weld...but not on my trailing arms.
Strut Rods
About four years ago I upgraded to the Heim-joint strut rods. I was very pleased with the slight improvement I felt in handling as well as the increased durability. I had been having trouble finding stock strut rods that lasted more than a couple years. I looked at polyurethane but decided against it after reading many posts on the forum indicating mixed results.
After disassembling the strut rods, I noticed there was some wear on the the heim-joint ball. Though very minor, these are expensive and worth protecting. I assumed it was from dust getting trapped between the ball and socket and decided to use some protective covers.
The procedure is straightforward. I ground additional material from the spacers and after ensuring everything fit snugly, I added some graphite to the socket channels and worked it around the perimeter.
I've included this picture to show where I put the graphite. The socket channel is the dark portion in the center of the picture. I shot some graphite in four locations around the edge and worked the ball in the socket. It really loosened it up a lot. On the left edge of the socket, you can see a slight discoloration of the ball. That is the wear I mentioned earlier. There was not any movement of the ball within the socket, so I think everything is OK at this point.
The two slides at right show the fit checks for each end of the strut rod. For assembly, I put both heim-joints in the strut rod bracket and will install that as a unit. The rest of the strut rod will be installed during rear suspension assembly because of the shock mount. These heim-joints will be lubricated at that time.
Finally, I had a spacer fabricated at the local machine shop. They used the bracket as a template and made the spacer from aluminum. It is one half inch thick, which I believe was the recommended thickness to provide better suspension geometry.
SUMMARY: This was a 3 out of 10. The hardest part was removing equal material from both spacers so the heim-joint remained centered in the gap.
Differential Tabs
The differential tabs are supposed to reduce flexing at the junction between the differential and cross member. The picture shows them installed in the cross member. I used blue loc-tite on these.
SUMMARY: Easily a 1 out of 10. If you can operate a torque wrench, you can install this upgrade.
This walk through continues on the next page with the Differential Cross Member Cushion Modification.
After reading up on what constitutes a good suspension for handling, I opted to keep the stock spring rates to maintain height and softness, but upgrade to an anti-roll bar to increase stiffness and steering response. Ninety percent of my driving is commuter or back roads touring, so handling and comfort are primary. I don't want the suspension so stiff it's like riding in an ox cart. Things I considered for this project:
REAR SPRING: The 79 Stingrays came with two spring choices: the standard nine-leaf all curved spring rated at 196 lbs, and the seven-leaf heavy duty spring rated at 305 lbs that was included with the Gymkhana suspension package. My car has the standard nine-leaf spring. A softer suspension relies on good high performance shocks with adjustable rebound to prevent the rear end from lifting, and adjustable shocks perform best with a constant rate leaf spring. Since steel springs do not have a constant rate, I'll be changing them out for a composite mono-spring. Composite spring rates are different than steel, and the vendors sell a 315 lb spring is intended as a stock-rated replacement. UPDATE: After a discussion with the VB&P technician, I went with the 330 lb spring. Unfortunately I lost the part number.
STRUT RODS AND BRACKET: After going through two sets of strut rods in three years, I switched to Heim-jointed strut rods. I have been pleased with their performance and will keep them. Based on recommendations from the 'Vette Improvement Program (VIP) by John Greenwood, I will install a half-inch thick spacer between the strut rod bracket and differential to improve suspension geometry.
SWAY BAR: The VIP recommends a 5/8" - 11/16" rear sway bar for a 1" front. This is a ratio of 1.45 - 1.6 front to back. As I mentioned in the Front Suspension section, the factory anti-sway bars have the best geometry, and I upgraded to the 1.125" FE7 (Gymkhana) factory sway bar in the front. The stock rear sway bars were 7/16" and 9/16", with the latter offered only on big blocks. These are too small for the suggested ratio. A 3/4" aftermarket sway bar with the proper geometry is available. This gives a front to back ratio of 1.5, which falls in the range suggested. I will install this sway bar.
BUSHINGS: The rotational motion of the trailing arms is best suited to rubber bushings. I'll install polyurethane bushings in the spring ends, sway bar mount and linkage, and differential snubber.
SHOCKS: I'm still researching this. Of course, the QA-1s are very attractive, but also very expensive and probably more than I need. I'm leaning towards Koni, and Bilstein gets good reviews also. Either way, I need a shock that has good adjustable rebound to keep the rear end out of the air.
U-JOINTS: Not much to say here. I'll be installing Moog solid u-joints in the half-shafts. However, because I am increasing the horsepower and torque significantly over what the stock engine was capable of, I also purchased the billeted steel u-joint caps from Dragvette.
STABILIZATION: I'm installing the cross member stabilizer disc kit from Dragvette. There are various opinions on the utility of this upgrade, but I was unable to form my own opinion based on the information I got. Thinking through the mechanics of how the differential moves, I can understand how this imparts some stability, I'm just not certain it makes much difference. But for the reasonable price of $40, it's worth a try.
SAFETY: I've seen pictures of several broken half-shafts, some from guys running 400 hp engines. I'm not a drag racer, but I would like to take the car to the track once in a while and see how it does. It just gives me piece of mind knowing that if I dump the clutch and break a half-shaft, the safety loops will be there to keep carnage to a minimum. At $133, it's cheap insurance.
WHEELS & TIRES: Since I'm keeping the classic look, I'll stay with the 15" rim. I will probably have another set for auto crossing. I am putting some 275 / 60 R 15 tires on the back, which requires some modifications to the trailing arms.
Modifications: One
- Relocate parking brake bracket and guide to accommodate larger tire width
Upgrades: Eight
- Install cross member tabs (No P/N available from Dragvette)
- Install cross member stabilizer disc kit (No P/N available from Dragvette)
- Install half-shaft safety loops (No P/N available from Dragvette)
- Installed strut rod bracket spacer (No P/N, had piece fabricated by machine shop)
- Install OEM style 3/4" rear sway bar and linkage (Eckler's # 25-110351-1 (sway bar with frame bracket and bushing), 25-101929-1 (polyurethane rear link bushings) ; Zip Corvette # SU-331 (Rear sway bar link), SU-330 (Rear sway bar link bracket), SU-138 (rear sway bar link bracket plate), and BL-351 (sway bar bushing link hardware))
- Install heim-joint strut rods and dust covers (Eckler's # 25-112725-1 (strut rods) and Seals-it # WS6250 (dust seal))
- Install stainless steel trailing arm shim kit (Zip # SU-525 (shims) and SU-826 (front bolt kit))
- Install composite rear mono-spring (Vette Brakes and Products Inc # 42303 (300# spring, bracket, hardware, and poly bushing))
Rear Suspension