I wanted to see what spring rates were being ran by others for autox and tracking with coil overs. I started out with 500lbs for the front and 400lbs for the rear.

 

Is this for a track or street car. I am really interested in putting coil overs on a street car. So that the suspension is truly independent. But, I do not want to get a harsher ride. Thank you

 

500lbs for front and 400lbs on the rear coil springs will give you a soft ride as long as you don't put too much compression in your shock settings. Also, you would want to run FE1 bars front and rear. And the car will still handle good, but not good enough for autox or track competition.

 

Thank you so much. I know that the stock Corvette suspension is really great for racing. But, I have always been so disappointed in the way the leaf spring translates bumps across the car. I always felt that a true independent suspension would improve its street or day to day performance. Thanks again

 

So....you're going to remove the front and rear sway bars? Because that is the ONLY way that you're going to get "truly independent" suspension. FYI, the rear is already as independent as it will ever get, regardless of which spring you chose.

 

Doh, I guess the swaybars would prevent it from being totally independent. But, I think the spring translates the shudder across the car. And how is the rear already independent. The left and right wheels are connected by the leaf spring and the sway bar. But, if you remove the leaf spring. I think you would be separating the left from right.

 

No.

You're making things up in your head. What does "translates the shudder across the car"...even mean? The car "shudders" b/c the structure isn't stiff. A C4 will always "shudder across the car" in some situations, b/c the frame isn't as stiff as we'd like it to be.

How is the rear independent? It's not...b/c of the sway bar...but if you remove the sway bar, it is b/c the mounting of the rear spring is in the center of the car. The mounting is such that action on one side of the spring, has no meaningful effect on the other side of the spring. Each side of the spring behaves just like a single, independent spring -like a coil spring.

The front mounting, which is widely spaced, produces some anti sway bar effect -the purpose being to reduce the requirements (size and weight) of the sway bar. If you change to coil overs that have the same wheel rate as the stock spring, you'll need to add more sway bar, or you'll experience more body roll.

The reasons that you think exist are not reasons to $witch to coil $springs. There ARE good reasons to switch. The reasons that you you're citing, or not legitimate reasons.

 

First I am not making things up in my head. It is possible that I am not familiar with the proper way to describe what I feel or think the car is doing. Even my 1969 seemed to shudder are slide over uneven road surfaces. I did see that someone was selling a bar to stiffen the cars chassis by connecting the windshield and cabin.

Thank you for the lesson in Corvette vehicle dynamics. Does the adjustable suspension offer better street ride.

I have old bushing and stuff. Will changing them improve the ride. I have new Billstien shocks for the Z51, which is the proper shock for this car.


Thanks again

 

I'm sure that you're NOT making up the way that the car drives. What I meant was, you're making up reasons why it's happening. It's not happening b/c of the type of spring.

I've never driven a C4 w/the adjustable suspension...and tried it on anything other than the "perf" setting. In that mode, it felt similar to my '92 which has Koni shocks.

Old bushings definitely do not help. Changing them and having GOOD/new shocks will help. Stiffening the frame will help. I have an RD Camber brace. It's helps.

 

Thank you for the update. I have the bushings I need to get off my *** and install them. Camber brace. I could not remember the name.

Thank you

 

The only person I know who is seriously competing in a C4 with coilovers is Chris CB Ramey in his early C4, which he built up for Optima events. But I don't know what rates he's been running, and I honestly doubt he's going to tell us. My guess is that they're pretty damn stiff, but that doesn't help much. Plus, with his car being an early car and having different motion ratios up front, I don't think the numbers will translate to your later-year car.

Jseremba, Tom is on point. A spring is a spring: it does the same thing no matter whether it's a coil or leaf or torsion bar. Honestly, trying to define "independent" suspension in the way you're talking is not technically correct, and even with swaybars or whatever, these remain fully independent. It's only not independent if the wheels are rigidly tied together, as they are with a solid axle. That is, in a solid-axle car a change in camber or toe on one side necessarily requires an equal change for the wheel on the other side, regardless of whether the body moves or not. This is not the case for any C4, regardless of what springs it has or whether or not it has a swaybar. The term "independent" was not intended to refer to wheel loads, which is what you're referring to.

The best way to think of this is to boil it all down to wheel rates and wheel loads: what is the total rate (spring plus swaybar rate multiplied by the motion ratios squared) at each wheel, and what happens to the loading on one wheel when the load changes on one or more other wheels? Regardless of what kind of springs you have, and whether you run a swaybar or not, the exact same thing happens. If the load changes on a tire on one side of the car due to cornering or a bump, it must change an equal and opposite amount on the other side. This cannot ever be any different. It's also the same regardless of the type of suspension. So it's impossible for a leaf spring to be harsher in ride quality or to handle differently than a coil spring.

Here's an article that explains more: http://www.route66corvetteclub.com/d...%20Springs.pdf

 

Hi Matthew. That article was excellent. Now there is a readily accessible doc to reference for threads like these.

If the doc is still editable, I'd suggest two things:
1. The C2/3 were actually 3 link rears; there was no toe-rod link since the trailing arm (sort of) set the toe.
2. When defining the coil spring, you were so close, but didn't mention it; a coil spring IS a torsion bar spring, wound up.

 

Thanks! Yeah, it's helpful to not have to repeat everything in each thread.

Oops, you're right! I'll have to see if that can be changed. Thanks for pointing that out.

I don't think this is accurate, but I'll have to ponder and research it a bit further. A torsion bar spring stores energy by twisting around the longitudinal axis of the bar, like a swaybar does. But a coil spring isn't twisting the coiled up bar, but rather bending it as if the bar were clamped at one end and a weight hung off the other end (like a diving board). This makes it even closer to a flat (leaf) spring, and in fact it can be made out of a flat spring instead of round bar stock (like a slinky). I've seen it referred to as a torsion spring before, but I don't think it technically is one. It's literally just a flat spring wound into a coil, and it functions identically to a leaf spring.

 

If you take a 500 lb/in coils spring, unwind it. How long is it? ~4'? Or so? Clamp 3" of one end in a vice and push sideways on the opposite end of the bar, to displace it laterally, (bend it) one inch. Are you going to get 500 lbs of resistance to your 1" of push? (no)

It was a mind-**** when I read that the first time....but as I worked it out in my head I realized that it was true. The bending of the bar isn't where the majority of the force is, in a coil spring. You actually are twisting the bar, when you compress the spring. Each part of the coil is perpendicular to another part of the coil (90* to any point in the coil wrap). Any given point in the coil is a lever arm, that is twisting the adjacent (90* away in the wrap) part of the bar. All the way through the coil.


.

 

I would have answered "yes." But...

...I see exactly what you're saying here. And now I don't know. My inclination is to say there is no torsion, because the spring material doesn't twist. If you paint a reference mark on the end of the coil spring wire and then compress the spring, the mark won't twist around the axis of the wire. Likewise, with a flat spring wound into a coil that starts with the spring stock oriented horizontally (again, like a Slinky), the material remains horizontal as the spring is compressed, all the way from one end of the spring to the other. If the material isn't twisting, it can't be in torsion. That's what I think, but I wouldn't bet my life on it! I'm going to have to ponder this, dammit.

 

Sorry.

 

Here is a little reading. Check out post 8 and especially POST 10

A little more reading HERE.

 

Sir, Thank you so much for the explain. You have saved me a lot of time and effort and helped me understand suspensions a lot more. Have a great day

 

So...I finally got around to reading these links. Okay, I relent: a coil spring is primarily a torsion spring. You learn something new every day! The funny thing is that Post #10 in your first link is a friend of mine, Neil Roberts. He is a hard-core motorsports engineer, having worked at Swift and now at Honda Performance Division, where he led the design of the current DPi Acura used in IMSA. He knows his shizzle.

 

Thanks for the post....and you're right on about learning a thing every day. Blew my mind the first time I read that....then I got mad and thought the author was totally FOS.

Crazy that you know that poster...you're right, the guy knows what he's talking about. That would be a good friend to have.