What Makes Corvette Suspension So Cool?
One of the most sophisticated upgrades a builder can incorporate into their project vehicle is an independent rear suspension, or IRS. From classic street rods to pro touring muscle cars – from street machines to off-road sand rails – from kit-cars to exotics – almost no other modification screams high-tech as loudly as an IRS.
Although there are quite a few quality aftermarket manufacturers offering independent rear conversions, priced anywhere from $5,000.00 to well over $15,000.00, arguably the most 'bang for the buck' IRS systems on the planet are the factory offerings from the fifth-generation, or 'C5' Corvette, built from 1997 through 2004, and the 'C6' Corvette, built from 2005 through 2013
Where else could you hope to find a bolt-in, double-wishbone IRS with all four control arms and the spindles made from aluminum forgings, all bolted to a transverse cast aluminum cradle?
And let's not forget that the entire system was designed and built by engineers at the Corvette division of Chevrolet with a product development budget unheard of in the world of aftermarket manufacturers.
The best part is that an entire used C5 suspension assembly can readily be located on several Internet sites, or at the local salvage yard – typically priced under $1,000.00, complete with the transverse cradle, the upper and lower control arms, the spindles, axles, a composite spring, calipers and rotors.
They also come right out of the factory with a mid-mounted Tremec 6-speed or automatic transmission, bolted directly to a limited-slip differential - which will run an additional $1000.00 and up, depending on the condition and the miles. They even use the standard Chevy 5 on 4.75” bolt pattern for the wheels.
Taking another giant leap forward for automotive enthusiasts, Chevrolet also incorporated a very similar independent front suspension, or IFS, in their C5 and C6 Corvettes, which is the natural companion to their IRS systems.
Just as the rear assembly, the IFS utilizes double-wishbones with all four control arms and the spindles also made from aluminum forgings and again, all bolted to a transverse cast aluminum cradle. And, just like the IRS, this entire system was designed and built by engineers at the Corvette division of Chevrolet.
Luckily, an entire used C5 or C6 IFS assembly can also be readily located on several Internet sites, or at the local salvage yard – typically priced around $1,200.00 – which includes the transverse cradle, the upper and lower control arms, the spindles, axles, a composite spring, calipers, rotors and the rack and pinion. And they too come standard with the standard Chevy 5 on 4.75” bolt pattern for the wheels.
Only the C5 complete suspension assemblies are shown above, as both the C5 and C6 cradles are similar and designed to perform the same task.
The major difference between the C5 and C6 rear cradles is where the differential mounts are located. The C5 differential utilizes a single mount in the rear, whereas the C6 differential has dual mounts - one on each side.
Here at Dobbertin Performance, when we need to narrow a cradle for a specific application, we almost exclusively use the C5 cradles, because of the difference in the differential mounts and the placement of the additional bracing that is added by us.
With a total of 238,230 C5 Corvettes built from 1997-2004, and another 215,125 C6 Corvettes produced from 2005 – 2013, there are plenty of used components to go around, along with new and rebuilt parts such as ball joints, bearings, calipers and rotors available locally, when it comes time to replace or upgrade an item.
About one in seven C5 Corvettes were Z06 cars, so they're pretty hard to find. The Z06 versions came with upgraded springs, shocks and anti-sway bars, but the lower cradle, upper and lower control arms, spindles, calipers, rotors and axles are identical.
However, most of the C6 Z06 Corvettes used a different configuration than the base models for mounting the rear upper control arms – similar to the front upper control arm mounts – and will not bolt up to our adapters – so watch out for those.
Believe it or Not, There are Quite a Few Automobile Salvage Yards That
Specialize in Corvette and Other High Performance Auto Parts.
Below are a couple photos from such a yard with a dozen complete suspensions and scores of cradles,
already removed from the cars and pressure washed – ready to go!
Below is a complete C5 IRS from a Z06 Corvette, right out of a salvage yard.
There are several things to look for when purchasing a complete unit such as this:
Inspect the cradle, control arms and spindles for any obvious damage or cracks.
Bring a small level and make sure that all four mounting points on the cradle are parallel. If they aren't, that means the cradle is twisted – and worthless.
Check to see if the ball joints seem to have excessive wear.
Check the CV joints and see if they move freely.
Check the transverse spring for damage or cracks.
Don't worry too much about the calipers and rotors, as most of them should be rebuilt and/or turned anyway – just for safety's sake.
Also, don't worry about the presence of corrosion on the aluminum components. Since they're aluminum, they'll have it to some degree – just look them over to make sure the pits aren't too deep. Remember, small imperfections can be easily removed with a quick visit to the bead-blasting cabinet.