flashlaru

My 1985 I just aquired has been sitting for a long time..... 5 years or more and now I have it back on the road. Rides extremely hard. will new bushings and or insulators help that ride any? What are some other options or fixes? Ball joints?

jmgtp

Kevova

No it's a Corvette not a Cadillac. Ride is going to be firm to rough. 92-96 ride got softer with the 96 the softest. 84-87 have a slightly different suspension than the 88+. The front suspension doesn't share anything with the 88+ so no retro fit. The rear spring interchanges but handling probably will suffer after installing softer 96 rear spring. The "balance will be off. Aftermarket springs are limited and normally stiffer not softer.

flashlaru

Car was stored on its wheels. I had a 94 for a few years, and this rides nothing like it. I also had a 72 and a 73 but it's been so long I can't remember how they rode, but I'm sure they were stiff. Just wasn't sure how stiff an 85 roed. Thought is was a little rough but I guess it's normal, thanks for your help and insight.

MatthewMiller

In short, I doubt new bushings (even if rubber) would change much. Check your shocks to make sure they still are free to move - i.e., not rusted into solid pillars. Also, look underneath and make sure the rear swaybar isn't installed upside down. If it is, then the bend is facing upward and hitting a piece of the aluminum frame, which means you effectively have a solid rear suspension (please don't ask me how I know about this!).

That said, if this 85 is a Z51, it will be a lot stiffer riding than your 94 was just due to spring rates.

zachaeous

I have a 1984 and I just replaced all the bushings with poly bushings. It definitely did not soften the ride one bit. It rides rough and that was the way the cars were when new. I had a new 84 non-Z51 and it was a stiff ride when new. The poly bushings made the car ride stiffer than a new one did back in the day. I traded the 84 for a 86 Z=51 car and it rode softer than the 84 when it was new. They were intended to ride that way and I still love the feel of driving the 84 even if it is stiffer.

VenkmanP

If they're hardened from age they can make a difference, but the biggest determinant of ride quality is the springs.

When I moved to PA from CA my 94 was unusable. After switching to the softest springs available for the late C4 it was reasonable again. It turned out that I wasn't stock to start with - someone had switched in a stiffer rear spring in the past.

gerardvg

Hi
Firstly check what suspension you have Z51 or base, the wrong shock absorbers make a big difference.
Go for some base Bilstein shock absorbers, the back ones is what you are almost sitting on so they will make a difference.

I can confirm that poly bushes will only firm up the ride, not make it softer.

flashlaru

How can one tell if it has the Z51 suspension? VIN #?

drcook

Find the RPO codes sticker, either in the glovebox or the on one of the doors in the back. If it is a Z51, it will be listed there.

flashlaru

On the Service Parts identification sticker in rear box, Z51 is listed. This means I have the z51 suspension? Thank you.

Z51 listed here.

MatthewMiller

Yep. Although spring rates were reduced quite a bit from 1984, your 85 Z51 has the stiffest rear spring that came in any C4 after 1984. And because we sit almost on top of the rear axle line, the rear suspension compliance (spring rate, shocks, bushings) is what determines almost all the ride quality of a C4.

flashlaru

Ok, so other than changing the spring, there is little or nothing I can do? Put some good shocks on it? Thanks for all the info.

MatthewMiller

Shocks are actually more important to ride quality than springs, believe it or not. On fast suspension movement (i.e., going over sharp bumps) the shocks can put brief loads into the frame that are far higher than the spring rate. That's what our butts and kidneys feel. For best ride quality, the ideal shock has a strong "knee" in its damping curve so that the damping rate increase vs damper velocity rises a lot less above a certain damper velocity. IME, Koni Sport (yellow) single-adjustable dampers set toward their low end are really good at doing this well, and provide a comfortable ride. At least one forum member used the Ridetech HQ dampers and got similarly good results, and either damper can be firmed up with an adjustment when more handling firmness is desired. If you don't ring your car out on the street or track, you might consider the Ridetech RQ shocks, which are cheaper and not adjustable but are targeted toward better ride quality.

Beyond that, if you really want to try a softer rear spring, you could get one from a later car. All C4 rear springs are interchangeable, and the rears are easy to swap out. You can probably find a softer one pretty cheap.

C409

….. Please check the 3 alpha code on your spring … you will find it on the bottom at one end near where the bolt goes through it … if you have a BMF or BMH , I will trade you even up for an NYR that I have on my shelf … the NYR is fairly soft as C4 springs go …..

flashlaru

The letters are NYU, what does that tell you?

1984c4z51

on my 1984 z51 car it is stamped in the lower control arm next to ball joint

MatthewMiller

It has the correct rear spring for your 1985 Z51, with a rate of 57.2 N/mm (326lb/in). The BMF and BMH that C409 asked about are the two rear spring options for a 1984 car, and would not have come on your car. They are stiffer than yours.

flashlaru

Thanks for everyone's help,...... I see the z51 uses a different shock from the standard C4. I'm thinking maybe the previous owner put the wrong shocks on. but unless I want to spend big money on shocks I think I'll just deal with it. It does have Bilstein Delco shocks with a #4360228W00. I don't know if that's the shock number or just the part number, also a white "KA" sticker. It does have the 3Z51stamped on the control arm. All the bushings seem to be still a little bit soft, along with the bushings in the shocks, and not seized up.

cv67

YEs reseach shocks, you need something softer. I bet a generic base napa shock may soften thigns up
Edlbrocks are supposed to be "smarter"...may wanna get ahold of bilstein and see if they can rebuild a set that will work for you.