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Sway bars...front...

Fifty

Well-Known Member
This colorado in stock form has a pretty stiff way bar...well, let me go back. It has street suspension. A shoddy over priced, great idea, poorly implemented shock (that dssv) and really really really stiff springs for what it is. The truck is 4745 lbs and I think about 55% of that is on the front. (all guessing)

The front suspension uses a 14 inch freelength spring, and uses 2 inches of preload. There are two spring rates available: 550 lbs and 687 lbs (gas vs diesel truck). The 687# spring raises the front about 2/3rds an inch, but makes the front skip at speed.
The shock is a 7 inch travel and the tire moves about 8.6 inches (baller I know)

This truck, like most production vehicles, does not articulate very well in the front. So taking off the stock sway bar helps a bit, but it still just doesnt compress that easy without significant chassis movement. Now on the flip side, there is a little more than wanted amount of body roll when driving.

I have front bumps and when they have 80 psi there doesnt seem to be any change in body roll. Up that to 100-115 psi and the trucks body roll is perfect. I have 16mm air gap of oil in the bumps.

So the stock bar is too stiff. The 687 # spring is too stiff, running bumps over 80 psi is out because it makes the truck skip off road and when you G out it almost launches the truck back into the air.

If I fabricate some sort of "nascar" style sway bar, like a blade bar; how do I calculate the what stiffness or weight rating that I design into the new sway bar?

I assume I would be trying to chase down that 80 to 115 psi effective spring rate? That seems pretty light to me. I can get the math done and calculate the thickness of the main torsion bar and the design of the arms. But what magic number I want to be shooting for in "strength" or "spring rate" of the sway bar is the question. I definitely want to get pretty close to what I need and design an adjustable blade to fine tune it. But I'd like to start off close.

(And then I get to rip it all off and sell it next summer when the stock stuff gets replaced)
 

gwizz

Well-Known Member
i honestly feel like you dont need a sway bar unless you have enough travel for the suspension to cam over fully flexed to one side or while turning.

your bump stop issues? are you fully compressing the bump stop?

as far as the bumps? what type? fox does it strictly on CC volume not a gap, and its significantly lesss fluid than one assumes should be in there so it doesnt blow up.

also you dont want a blade style bar. (your talking about the tune-able kind by spinning/twisting it?)they are designed to be ridged al the way to deflect with a minimal amount of travel/flex. off-road stuff typically cycles to much angle at the sway bar arm to really make use of that.
 

Fifty

Well-Known Member
I was just assuming the blade type for ease of tuning vs buying a number of torsion bars to tune.

But I see your point. I’m still trying to put aside 30 years of tarmac knowledge...

As for the bumps, I currently made the mistake of using a small companies bumps that are trash. When it comes time to redo the entire front they will be replaced with king bumps.

When rebuilding the bumps last year, The company had no idea what fill volume or air gap meant let alone what it was. Not to mention all the bumps were different levels when opened up. I took an avg of air gap and used that when putting them back together... (not that they were able to be put back together. Long story don’t ask.)

As for “camming over”, as the truck sits now, 8.6 whopping inches of front travel and 11 in the rear. I do fully compress the front bumps when you sneeze at it.

It just feels so swayee and seems like it could be tighten up a little with out actually stiffening the shock valving or the spring.

I’m trying to maximize what I have until time and money can allow ripping what’s in there out and replacing with new arms, knuckles, shock mounts etc etc etc...
 
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