There are many coilover kits for the C6. Most, if not all, owners who replace their leaf springs with coilovers state an improvement in vehicle dynamics, and some rave about the results.

Inspection of the factory C6 suspension reveals that the spring load is borne by the subframes to which the springs attach. The force is transmitted into the C6's frame where the subframe attaches to it. These forces are high.

Coilovers apply spring load to a completely different part of the C6's frame: the upper shock mount. When coilovers are in place, the force applied by the spring is the full corner force on the wheel, which has greater or lesser magnitude depending upon the load incurred due to maneuvering. This force is *much* greater than the force applied by a shock absorber, whose job is to dampen the natural oscillations that would occur in the spring-mass system inherent in the coupling of the suspension and body.

I admit that the first time I saw coilovers on a C6, I thought "Is that shock mount designed for that load?" User experience suggests it works because we don't have any cases of users bending or breaking the upper shock mounts due to coilovers, right? (I've not read any.) Do we have any intel that says Chevrolet designed those mounts with spring loads in mind?

 

This is a good observation, I will be curious to what answers you receive.

Ive been considering coil overs for my next upgrade, so will follow your thread here.

Like you I have not read any horror stories yet of catastrophic failure…

 

technically the shocks will see close to what the springs see with heavily valved shocks. I think theres two trains of thoughts - LG has a video out that shows coilovers taking a pretty good impact (IIRC, running over a 4x4 at speed?) with no damage to the shock perch. I also think another coilover manufacturer offers springs only as "helper springs" and requires the use of the stock spring.

I'd be willing to bet most people will be fine with a coilover setup even if you occasionally track the car. If you race the car, you might need to reinforce the perch but I know a lot of other sports cars that need shock/coilover reinforcements too.

 

you guys are a decade and a half late to the party. There was a big argument between LG and Pfadt back when the aluminum frame cars came out , and yes the narrow topped Pfadt busted through the perch when literally driven over a railroad crosstie at speed. HOWEVER I have yet to see a failure during any sort of normal usage, and we have been running coilovers on c5 and c6's for 25 years now.

TLDR I have zero concern about steel frame cars, aluminum frame cars....don't run over 6" obstacles

 

For real; there was videos and everything of them running over things with coilovers.
My take is that coilovers are fine for the track. The use you see there is very predictable.
On the street, it is entirely different and you never know what you will find in the road. For my daily driver, I have no troubles with the leaf springs and good aftermarket shocks. If my Corvette was dual purpose, normal car and track car, I would run coilovers with no hesitations.

 

 

Stop overthinking it honestly.
Coilovers matched with the correct swaybars are TONS better at cornering performance. Other than producing a harsher ride ie comfort, there is really no downside.

 

My question is a risk assessment, motivated by a principle I employ: all mods create risk, so it's useful, perhaps prudent, to quantify the risk prior to a purchase decision. My question is also practical, since I just agreed to purchase a C6 Z06 with this kit. This car will be a daily driver for me, so street suspension inputs are the primary stressors, not the loads experienced on a smooth track.

Another example of this principle: I knew I didn't want an LS7 with modifications to the valvetrain. First, 500 HP is way, way, WAY more power than I can use and (b) higher lift, higher valve speeds, and increased spring pressures (if applicable) surely won't lessen risk. In effect, a cammed LS7 is all risk and no benefit, *in my case*.

I readily agree that the cornering performance is enhanced. The owner from whom I'm purchasing the car disagrees with you about the reduction in comfort. He says the coilovers and Penske shocks have improved the street ride quality of the car despite the aggressive springs. He's attuned to the nuances of driving, so I'm inclined to believe him.

Probably not. But since (a) the coilovers constitute a significant change in the place on the frame that bears sprung weight and (b) we lack information about the load limits of the shock mounts then we need real-world experience. I'm grateful to posters who have provided some. I particularly enjoyed the LG video.

Asking and discussing the question isn't overthinking it because...

...this isn't true. I hadn't thought through the problem so Mike's assertion forced me to be more detailed. I'll show below how and why a heavily-valved shock doesn't apply a force nearly in magnitude to what the springs can delivery. And while the comparison between spring load and shock load is interesting, it's also irrelevant because the shock-only load isn't what the mount in a coilover-equipped car sees. The mount sees the spring PLUS the shock load.

I found this document very helpful, especially the graph on page 2, which makes plain the following:

• The force applied by the shock in compression is relatively low. It doesn't need to be high because (a) the spring already opposes motion in compression, and (b) the vehicle body hasn't started moving much.
• The force applied by the shock in rebound is far, far higher than in rebound. This asymmetry is a key to effective damping because (a) the spring aids in the vehicle body moving away from the suspension; (b) the vehicle body now has velocity and therefore momentum; and (c) the shock has to counter the spring's force.
• We only care about the magnitude of the shock force in compression because any force applied in rebound is away from the mount, and is subtracted from the spring force. Stated another way, we care only about compression and can ignore rebound when asking "Could I break a shock mount with coilovers?"

Now we can do some basic math.

• If the car has a corner weight of 800 pounds, then the spring is applying 800 pounds to the shock mount when the vehicle is at rest. The shock applies 0 pounds to the mount when it isn't moving. Unlike springs, shocks only generate force when they have velocity. (I'm ignoring a shock's gas charge, whose force is negligible.)
• When the suspension is compressed, the spring force rises quickly. If a 1" input compresses a 700 lbs/in spring, the spring force on the mount is now 800lbs + 700lbs = 1500 lbs.
• Per the graph in the document, the shock will probably never apply more than 160 pounds of force to the mount regardless of its velocity. We should agree that 800 lbs > 150 lbs, and that 1500 lbs >> 150 lbs.
• BUT... the total force applied to the shock mount is the sum of the two: 1500 pounds from the spring + 150 pounds from the shock = 1600 pounds. This too is far in excess of the force the shock will ever apply to the mount.

We can see that there's no circumstance under which the shock-only load is remotely close to the peak load of a coilover-equipped car. And the peak load in compression is what would cause failure of the shock mount. The lone remaining question is "What is the load at which the mount fails?" We don't know, but LG's car wasn't damaged, and davidfarmer's experience suggests that so long as I don't drive quickly over parking curbs, I'll be okay.

I appreciate the stimulating discussion.

 

Let me mull over this a bit - I dont fully agree. I think the rebound (e.g. one wheel off the ground) can and will create a near opposite/equal force on the shock mount (obviously other direction). If the spring is fully sprung at 1600 lbs, weight shifts quickly and now unloads (or, it hops over a bump), the spring loads the other direction at the full force it was seeing, which the shock mount will need to take.

 

The factory C6 mounts were never designed for coil overs. If you sift through the many debates on this subject, somebody had a face-to-face conversation with a GM engineer, and he answered the question. That is why the race teams use coil overs designed to be used along with the leaf springs.
Now, will the shock mounts break if you use coil overs without the leaf spring? I highly doubt it. I daily drove my C6 on Aldans for years till they started leaking. I went back to stock, now going to the NEW QA1 redesigned coil overs. I never had an issue with the mounts.

 

I own a C6 (highly modified) with coil overs.
The word "harsh" is the best description I can honestly provide.
I've also run the same coilover setup on the street with runflats, a 35 profile as well as a 30 profile tire.

You will give-up TONS of performance attempting to minimize discomfort on the street. Unless you drive on perfectly smooth highways. At that point you might as well stay with the horizontal leaf/shock set-up. Drive/follow a performane vehicle with a coilover set-up and see for youself. There is no magic recipe.

If your concern is comfort, I'd keep the oem or similar set-up. If your concern is potential damage from impact, I wouldn't be concerned in the slightest as TONS of folks have run coilovers for years on a dd C6 with zero issues. I HAVE seen one C5 with Penski's crack the upper R front mount. A simple weld fixed the issue.

The shocks/leafs vs coilover set-up can be swapped-out faily easily on a lift and not very difficult even on jack stands. IF you prefer one set-up over the other. It's not a big deal.

 

What is strange is you never really see longterm feedback from those using hybrid setups (that keep the leaf spring) like the Eibach coilovers. On a daily driver, you would not want a more harsh ride.

 

You know that it isnt a problem, because if it was it would be like the LS7 dropped valve issue.
Every person who suffers a suspension related failure due to coil-overs would be in here screaming from the highest mountain and demanding reparations and a class action lawsuit against somebody.

 

Too true!
As for the harsh ride....
I have a C6Z with LG/Bilstein coilovers and fairly stiff, track-focused spring rates (forget exactly what they are off the top of my head).
Monoballs, JOC swaybars.
It rides soooooo much better than my stock C5.