So, Why use the 1984-’96, C4 Corvette Suspension?
And Why replace the entire frame?
Here we’re going to explore the how and why we believe that the C4 Corvette Suspension swap with the Nerd Rods Frame for the TriFive Chevy is the best performance per dollar upgrade you can make for your Classic Chevrolet.
One of the hardest parts is understanding why to do all of this. Most of the hot rod industry is trained to think in catch words. Its not just you, it’s everyone. Having catch words we can throw out is like dropping someone’s name mid conversation to impress others. It only really shows a superficial understanding of the part of the car we are talking about even if that wasn’t what we meant by it.
Disk brakes, coil over shocks, tubular control arms, drop knuckles, and so on.
One quick example.
We all know you can bolt on Corvette disk brakes to our beloved shoebox’s but it doesn’t perform the same as a the Corvette we pulled the brakes from. Why? We didn’t bring over the suspension geometry to handle the additional negative G Forces these new brakes bring to bear. This suspension design consideration is called anti dive. This is why when you see modern road racing cars hit the brakes and their 15” rotors turn glowing red the front just barely dips. When you hit the brakes on a TriFive with big brakes the bumper almost hits the ground. It dose hit the ground if the road is lousy, and we think that’s good braking. Its not. That’s what happens when you have a suspension designed for drum brakes and you slap on parts it wasn’t designed to handle.
So when we say the Corvette Suspension has disk brakes, it really has so much more that this one catch phrase. It has the brakes but it has a suspension that can handle the brake as well. It just doesn’t cover or encapsulate everything that’s going on. This happens over and over again when considering the upgrades and, more importantly, how all these systems work together.
The rear pushes the front, and the front turns the rear. They have to cooperate. So lets dig in.
Table of Continence
- What are you trying to accomplish ? And why you need to make a list of things you hate about your hot rods
- Ride Quality
- Handling
- Racing
- Stance
- Wheels and Tires
- Why the Corvette Suspension?
- Front Suspension
- Rear Suspension
- Why the new frame?
- Modifications, Required and Suggested
- Reasons to not use the C4 Corvette Suspension
- Why don’t use use the C5, C6, or C7 Suspension?
What are you trying to accomplish?
Do you want a driver? Do you want a show car? Do you want a drag car or maybe an autocross toy?
These are some of the questions you should ask. All are important to what the finished product will be and just the tip of the iceberg. To help us figure out what the end goal is to make this car our own we have to establish some hard goals. After building Hot Rods for almost 20 years and TriFive’s specifically for 15 of those you hear the same thing over and over
I want to drive it. I want it to ride good. I want it to handle.
Pretty generic when you think about cars but not really complete picture of what YOU think is acceptable. It doesn’t really tell us what YOU want in the finished product. Do you want it “to ride good” like a Rolls Royce? Or do you drive a 1 Ton pick up and a modern sedan rides good enough for what you want to do. Do you want it to handle well like your new SUV or do you have experience driving full bore race cars and expect that level of precision handling in your Classic Chevy when its done.
However, it’s easier for people to establish a list of things they hate and don’t want the car to do. Easier than the exact image of what it should be when finished. This is pretty common in all of human psychology. Bad things, or things we don’t like get us killed so we avoid and remember them. On the opposite side things we like, or the good things that have happened to us we tend to forget or just not remember. I learned this trick from the guy who designed the McLaren F1, Gordon Murray.
So lets establish what we want in a TriFive. Then we’ll talk about how we get there, where bolt on parts are typically used and the problems they create but the Corvette Suspension takes care of.
I hear this all the time followed shortly by “But why can’t I just use bolt on parts”. For this we’re going to discuss what each of these “bolt on kits” are supposed to accomplish but also the problems they create by only solving some of the problems they are supposed to solve.
Why the Corvette Suspension?
Why the New Frame?
Modifications, Required and Suggested
Reasons to not use the C4 Corvette Suspension
Why don’t use use the C5, C6, or C7 Suspension on the TriFive’s?
The Nerd Rods frame is designed around the C4 Suspension, 1984-1996. Because of that we get people asking for a frame for the 1997 and up Corvettes, often.
1997-2004 – C5 Corvette | 2005-2013 – C6 Corvette | 2014-2019 – C7 Corvette
All basically the same car as far as “we hot rodders” are concerned.
2020-Current – C8 Corvette
The Mid Engine Car, Completely different and we’re not going to talk about it here.
There are a number of problems with the C5/6/7 Corvettes when it comes to using them as a donor for the TriFive Chevy’s. I’m going to start by listing some of the problems here specific to swapping them to a TriFive but it might apply to a number of other cars in the era. I hope to have more time one day to go into the details about it. For now I’ll just try and dial in some general ideas about the problem areas, why they are problems, and ball park prices it cost to make work. That being said, we have done several C5/6/7 swaps, so these numbers are from experience.
- Front Suspension is too wide.
- To narrow the front you need a custom rack and pinion, you can’t just shorten the arms. That’s a really bad idea. Also good luck finding the exact width you need.
- +$500.00-1,500.00
- You’ll also need a custom sway bar since you’ve brought the control arms closer together. You might find a stock on that will work from another car but probably going to need to make a custom unit.
- +$200.00-1,000.00
- To narrow the front you need a custom rack and pinion, you can’t just shorten the arms. That’s a really bad idea. Also good luck finding the exact width you need.
- Rear suspension is to wide.
- To narrow the rear you’re going to need a set of custom CV Shafts.
- +$1,500.00-3,000.00
- To narrow the rear you’re going to need a set of custom CV Shafts.
- The rear suspension is too tall.
- You have to remember, there is an upper A Frame on the rear suspension. That upper A Frame is going to hit most old car bodies. So you’ll need to do some custom metal work to make room for it to clear inside of the car.
- +$500.00-5,000.00 (sky’s the limit on custom sheet metal)
- You have to remember, there is an upper A Frame on the rear suspension. That upper A Frame is going to hit most old car bodies. So you’ll need to do some custom metal work to make room for it to clear inside of the car.
- The Trans-axle gets into the back seat.
- The transmission bolted to the front of the differential in these Corvette’s is going to get into your back seating area. So custom sheet metal, custom interior, and some tricky exhaust to get through there.
- +$1,000.00-10,000.00 (custom rear seats and custom sheet metal again, could go nuts)
- The transmission bolted to the front of the differential in these Corvette’s is going to get into your back seating area. So custom sheet metal, custom interior, and some tricky exhaust to get through there.
- Torque Tube and Drive Shaft length problems.
- The tube between the engine and transmission is the Torque Tube with the drive shaft inside. It is WAY too short to go from a Front Mid Ship car like a Corvette to a Front Engine car like a TriFive. So you’ll have to extend it a lot.
- +$1,000.00-3,000.00
- The tube between the engine and transmission is the Torque Tube with the drive shaft inside. It is WAY too short to go from a Front Mid Ship car like a Corvette to a Front Engine car like a TriFive. So you’ll have to extend it a lot.
- Torque Tube height in the chassis problems.
- A little noticed problem is that the drive shaft is on the top of the ring gear. Think about a normal differential. The pinion is on the bottom of the ring get going forward. The C5/6/7 is on the top of the ring gear. So right off the bat the center line of the drive shaft is almost 9″ higher in the frame. So more sheet metal modifications to clear that.
- +$500.00-2,000.00
- A little noticed problem is that the drive shaft is on the top of the ring gear. Think about a normal differential. The pinion is on the bottom of the ring get going forward. The C5/6/7 is on the top of the ring gear. So right off the bat the center line of the drive shaft is almost 9″ higher in the frame. So more sheet metal modifications to clear that.
- Coil over shocks are add to the cost.
- The Coil over shocks for the rear of these cars is really specific because it goes between the CV shaft and the toe in toe out control arm. So you have to either do push rods and cantilevers or buy the Corvette Specific coil over shocks. Because you narrowed it and you can’t run the stock springs, even if you wanted to.
- $2,000.00-4,000.00
- The Coil over shocks for the rear of these cars is really specific because it goes between the CV shaft and the toe in toe out control arm. So you have to either do push rods and cantilevers or buy the Corvette Specific coil over shocks. Because you narrowed it and you can’t run the stock springs, even if you wanted to.
- Can’t get the rear tire off once the car is low enough because you can’t unbolt the shock from under the car.
- This is a fun one people don’t think about. You want the car low. On a TriFive that means the body is covering a good bit of the tire and wheel. Well the shocks can only go so far down. So you have to take the shock loose. This is true even for our C4 swaps. Unfortunately you can’t get to the bolt on a C5/6/7 suspension. The wheel is in the way. So you have to make some kind of access port in the truck to get the upper shock mount loose to let the tire down far enough to get the tire off. One more thing to plan for an design around.
- +$200.00-4,000.00 (I’m rolling some of this price into the shock problem above.)
- This is a fun one people don’t think about. You want the car low. On a TriFive that means the body is covering a good bit of the tire and wheel. Well the shocks can only go so far down. So you have to take the shock loose. This is true even for our C4 swaps. Unfortunately you can’t get to the bolt on a C5/6/7 suspension. The wheel is in the way. So you have to make some kind of access port in the truck to get the upper shock mount loose to let the tire down far enough to get the tire off. One more thing to plan for an design around.