Looking for more real world feedback on C4 conversions

[chevynut]

Brian, have you ever driven an early C4? Is there a noticeable difference in handling compared to your late one? They had various springs available even in the late C4s.

I've heard the early C4s ride rougher than the later ones, but that may be due to the Z51 suspension that was used in 1984. The Z51 spring is a lot flatter and thicker than the later springs and is sought after by C4 autocrossers. I have seen a few that have a lot more curvature to them indicating they're softer springs (lower rate) and they were used in later C4s. The springs tended to get softer in later years so not all cars are the same. All the rear springs are interchangeable, but the front springs apparently are not.

And you're right about tires contributing to the ride quality. However, my Porsche has 225/35-18 and 275/30-18 tires and I think the ride quality is excellent, for a sports car. It's firm and responsive, but not rough imo. A 4" sidewall height is about as short as I would go.

[Rick_L]

Cnut, how about the springs on a 91 Z51? A friend of mine had one a good while ago - I thought it rode very rough.

[chevynut]

Rick, any Z51 suspension is a "sport" suspension and they ride rougher than the standard FE-1 (or other) suspensions.

According to the spring charts I have there was no Z-51 suspension option in 1991, but there was in 1990 which was the last year for it. A 90 Z-51 had a front spring with a rate of 660 lb/in and a rear spring rate of 327 lb/in. In contrast, the FE-1 suspension (and some others) had a 522 lb/in front spring rate and a 228 lb/in rear spring rate.

So it's clear that you can't just ride in a C4 and make judgements on it without knowing the suspension option it has. Some guys like a stiffer ride and some guys like a smoother, softer ride. It all depends on how you want to use the car too.

[Custer55]

I have only driven our 90 Vette so I don't know how the ride is compared to an earlier model. Ours is just a base model also, not a Z51 option. I have heard the 84's had a really rough ride compared to the 85 and up.
Brian

[rockytopper R.I.P 5-13-2017]

Cnut does your frame design allow the customer to use the stock springs but allow a change over to coilovers if they decide they want more adjustability and can afford upgrade down the road or do you need to know up front one or the other just curious?

[Rick_L]

I am not clear on the year, may have been a 90. I do know the car had the "sport suspension" option, which I thought was Z51 on all years.

The owner was a coworker, and we'd occasionally go to lunch in it. A couple of the roads near our workplace were pretty rough and that's what formed my impression of the car's ride. The rough ride was dramatic compared to just about any other vehicle on one particular road.

[rockytopper R.I.P 5-13-2017]

I found this info. I read customer feed back made GM soften the ride after the first year. Factory racing increased it in latter years of the C4.

http://www.corvetteforum.com/forums/...84-96-z51.html

[55 Rescue Dog]

Whatever set up I go with, if I had a 55 that worked as good, or better, than my 96 Impala SS, I would be all over it! They just missed it by not looking like a tri five. The best full sized GM car they managed to build, and then they switched the assembly plant to trucks. My 97 C5 is ok too. Looking for the best of all three.

[chevynut]

Turns out the 1991 Z-07 suspension option used the same springs as the 1990 Z-51 and they were the stiffest springs used on any of the C4s with the exception of the '84 Z-51 which had a 500 lb/in rear spring and a 583 lb/in rear spring. By 1996 the base suspension (FE-1) had a rear spring of 149 lb/in with a front spring of 343 lb/in.

[chevynut]

Cnut does your frame design allow the customer to use the stock springs but allow a change over to coilovers if they decide they want more adjustability and can afford upgrade down the road or do you need to know up front one or the other just curious?

Yes, our shock mounts are designed for eyes on both ends so coilovers or standard shocks can be used front or rear. You can go either way with it.