help me stiffen my suspension

[chromefeet_withbeat]

Hey everyone, got a new guy here that needs some legit suspension advice. I got:

71 el camino, 350, all iron, no a/c, suspension all stock except for moog front springs, stock height, moog rear cargo coils, kyb gasadjust shocks, 265/60r15, 4"+ ground clearance

Problem: suspension is way too bouncy. On typical pitted, garbage SF roads, bumps make it oscillate from front to rear (or vice versa) and it usually takes 3 back and forths to level out, unless I hit another bump. :bsjerk: Minor bumps seem to make the suspension travel its max travel sometimes, and trying to drive on the freeway and hit any high speed can be dangerous.

I love straight line performance, but this car is a daily driver that bends alot of corners as well, and alot of the roads I encounter are in poor condition. My budget is also extremelely limited. Ive pretty much concluded I will get a new sway bar with poly bushings, but I don't think that will solve the problem alone. And since el-cos parts are cross-linked with chevelle parts, that means I have alot of choices which can get overwhelming. What do you guys recommend?

[zbugger]

Start out with better shocks. Maybe your shocks are dead?

[baz67]

The doubt the sway bar has nothing to do with it. I am with Allen here on the need for new shocks.

If you think of the spring as a ball you may understand why we think it is the shocks. If you drop a ball to the ground it continues bouncing untill it loses its energy or some other force acts on it. That is what your springs are doing, bouncing. Another name for the shock is a damper. It is the shocks job to dampen and absorb the energy of the spring.

[chromefeet_withbeat]

The KYB shocks I got in there are brand new but are some rather cheap stuff, do you guys still think thats the best thing to replace first? What about big block springs in the front? If not what kind of shocks would you recommend, and should I go for the front shocks first, or do all four?

Thanks

[sinned]

Spend a few dollars on good shocks. Shocks are the foundation of the chassis, without a good shock anything else is going to be money ill spent. Like I said earlier, Koni and Bilstein are a couple of the best, but a set of Edlebrocks will make a world difference as well.

[Damn True]

The KYB shocks I got in there are brand new but are some rather cheap stuff, do you guys still think thats the best thing to replace first? What about big block springs in the front? If not what kind of shocks would you recommend, and should I go for the front shocks first, or do all four?

Thanks

The amount of damping has to match the rate of the spring. If your shocks are underdamped vs your spring rate (sounds that way) the springs movement will be uncontrolled (bouncing).

[Norm Peterson]

In addition, if the relationship between the front and rear spring rates vs the front to rear weight distribution gets altered much, the pitch motion that you describe can be exaggerated. It's a frequency thing, with consideration for your speed and wheelbase added in to the mix. Probably the case here if it's particularly worse in some speed ranges than in others over the same stretch of road. Relatively "weaker" damping at one end as compared to the other will also let this pitch motion become worse.

There's a couple of spring threads that get into this in the advanced tech forum here, one of which contains a link to some pitch plots on another automotive site. (Fair warning: this other site has a certain reputation for, ummm, politically incorrect impatience with most displays of "newbie-ness").

Norm

[chromefeet_withbeat]

Thanks for all the replies. So the consensus is building towards me getting some new shocks? If I get some, say edelbrock IAS shocks, which I would hope damp better than the KYBs I got, only in the front, keep everything else I got now, is there a good chance this will fix or greatly reduce the over oscillation? Being that every bump I hit goes over the front wheels first, I think maybe if it gets absorbed more in the front, the body wont be pitching as much to allow the rear cargo coils to oscillate so badly. Or am I completley wrong?

Norm: You bring up a good point about speed, which I didn't mention. My shocks/springs do seem to work fine at low speeds, lets say 20mph and below, (it would probably be good for off-road )but that's not my preferred speed range. I hate having to slow down so much when I see bumps on the road, with an el-camino I think you should be able to take minor bumps at 30mph and not have your head hit the roof.

As for the spring thread, I think I'll just read it without commenting, cuz I'm definately noobish when it comes to these things.

[Norm Peterson]

If you're going to work on it piecemeal, start with the end that's moving more (as seen from outside the vehicle). It's not clear whether both ends are underdamped or just one, so a little observation from a separate car may help. Obviously, if only one end is moving all over the place following a bump, that's where you'll want to focus your attention. If it's both ends about equally and you fix only one end, things might get worse before they get better (with the job completed).

I don't know what your test road looks like, nor am I in any way recommending driving illegally, but I'm more wondering about pitch effects at 50-ish vs 30. The first quarter cycle of front suspension oscillation is a bust anyway, as there is nothing happening out back during that time to either add to or reduce pitch motion. How bad is the pitch at 70-ish on the interstates (assuming you can find a few 'heaves' in the road to get things moving)?

If you can provide some Moog part numbers (and a range of rate for the rear cargo coils if at all possible) as well as a few other pieces of information, it's possible to construct similar ride plots for your car.

Norm

[chromefeet_withbeat]

Thanks for following up, Norm. I'm not sure which end is bouncier or likes to oscillate more. A little while ago I just pushed down on either corner of the vehicle and it will easily bounce, but its hard to say which end is bouncier that way.

At 70+mph on the freeway, the pitch can be VERY bad when a minor irregularity in the road comes up. So bad, that on a very bouncy non-level part of the 280 freeway, at about 60-70mph, my front tires got air and smashed my crossmember/sway bar mount!

Unfortunatley, a local shop ordered the moog springs for me, and I doubt they still have the records, so I'm not sure what p/n I have in there right now. I'm assuming they put SB front coils since they saw the 350.

[Norm Peterson]

If it really is that bad, I'd start checking for one or more shocks that are not connected at both ends or are otherwise broken. Even cheapie replacement shocks should be better than that, at least out of the box.

Norm