TheSamba.com :: View topic - 29-1/2" Torsion Bars

Sun Mar 31, 2013 8:01 pm

I see sway away has 29-1/2" length torsion bars. I assume they're for widened torsion housings, but I was wondering if anyone's tried lengthening the collar on the spring plate 3" to fit them. I'm really interested in trying this.
At the same time, I'd use longer torsion leaf sets in my 6" wider beam, bringing the adjusters/set screws back to the center of the beam. I want to get max suspension travel with torsion suspension.

Mon Apr 01, 2013 2:28 am

Advantage to lengthening the collar on the spring plate?...nope.

However, widening the torsion housing so that the trailing arms are farther apart can be advantageous for stability.

Mon Apr 01, 2013 8:34 am

I was thinking more like advantage from longer torsion bars for a better long-travel spring rate and most importantly max twist angle. I don't want to switch to coilovers, there's something bandlandish about the torsion suspension that I like. And my rail with 3x3s is not getting any wider, i won't fit through my trails anymore. I thought I even saw wide spring plates for the 29-1/2 bars, maybe I'm mistaken. I'm using 26-9/16 bars right now.

Mon Apr 01, 2013 8:42 am

The 26 9/16" long torsions work well with the later style spring plates. They sag much less than the short torsions and are much better to use off roading. They seem to be about 7 to 10% softer for a given diameter.
I suppose the even longer ones have similar advantages, but would be pretty expensive to retrofit in for not much advantage unless you were building a wider car. Of course if you were building that fresh car with KingKong adjusters and all of that, why not go all the way?
Dennis

Mon Apr 01, 2013 4:58 pm

To be honest i don't think it would be that hard. I could just lengthen the collar on each spring plate to accommodate the 29-1/2" bars. The advantage of longer torsion bars is proven, vw lengthened the bars twice over the years. As i've learned, if you twist a torsion bar past its limit it will sag prematurely. And the added twist I gain from longer bars allows me to put more preload on the bars (using a smaller diameter/softer bar). Proper suspension travel has almost 50% droop and nobody is getting that with current long-travel torsion bar setups. Everybody uses a thicker bar (which gives you less wheel travel), and they jack the bars up, which leaves you very little droop before your CV's start to bind. The problem is if your droop is 4" of travel and your compression is 11" of travel, with 28mm torsion bars you will never be using all your compression. And even if you were driving hard enough to push 28mm bars through 11" of travel, you would then be seriously lacking droop for those conditions. Not to mention the stress stiffer bars add to all the suspension components. I have no desire for more ground clearance, just wheel travel.

Mon Apr 01, 2013 9:44 pm

What diameter bars do you have now? how much wheel travel are trying to get and type of shocks do you have?

Tue Apr 02, 2013 11:40 am

Look at McKenzies catalog they show various lengths of the ends that weld to the springplate. Perhaps an easier way is to use a bolt on extension to your torsion housing, 3 inches per side, and then use your regular torsion end caps. McKenzies catalog also shows these extensions but they are something something you could make.

Tue Apr 02, 2013 6:40 pm

im using stock 22mm bars right now, my 28mm bars we're waay too stiff. my buggy is really light. i had bilstein 5125 but the valving is too stiff for 22mm bars, my 14" bilstein 7100's will be here tomorrow. i like the spring rate of the stock bars right now, but i've already beaten a set of stock bars to death when i first switched to 3x3 arms, this is my second set. i read some people saying the torsion bars dont really break from twisting too far, you can add preload without worrying, but sway-away states max angles for each bar diameter. this is really why i'm considering longer bars, greater max twist angle. using a thin bar (maybe 23 or 24mm race bar), i'll add more preload, hopefully making a very responsive torsion setup and not just raising the ride height.

Tue Apr 02, 2013 8:54 pm

if your car is between 1550 and 1700 lbs. you could use a 24mm long bar(26 9/6) 300m and at least 2 shocks per side, this bar on a light car is good for 16-17 in. of travel. How much travel you getin?

Tue Apr 02, 2013 10:58 pm

Here is the catch...longer bars will need to be larger in diameter for a given spring rate. There really is no advantage to the longer torsion bars as far as maximum angle of rotation. Sure it's longer, but it will have to be thicker, so in reality, you don't gain anything worth while.

Wed Apr 03, 2013 6:19 am

sorry vanapplebomb, but I dont think you understand what i'm trying to accomplish. a longer bar would need to be thicker ONLY if i were trying to match the spring rate of the shorter bar. im doing the opposite, trying to achieve less spring rate (softer suspension) which is what you need when increasing suspension travel (unless you were already bottoming out, lets assume each setup was engineered properly)
Jcr. Kat, i think you see what i'm saying. I'm measuring my rear travel later today, and ill post the numbers. my woods buggy is likely under 1500lbs. I was planning on using one shock per wheel for now, but i know your probably right about 2 shocks per wheel. 16" of rear travel is what I was aiming for.
I think the problem here is that most people seriously trying to achieve suspension travel go straight to coilovers. I need to talk to a baja racer, but i live in canada :roll: most people around here have never even seen a dunebuggy. Jcr Kat, you understand why I would use a thinner, longer bar and add alot of preload to it, right? its the only way i can see to achieve proper droop with torsion bars. instead of a stiffer bar, a softer bar (capable of twisting as far as i please) with additional preload, should be just as stiff but the preload allows for more droop. this all started when i read about the German Panther tank which needed torsion bars longer than the width of the tank, so Prof. Ernst Lehr effectively folded the bars in half, using a lever system to tie the two half bars into each arm.
I've also read about making secondary torsion bars in a buggy for progressive rate suspension, but those setups look sketchy to me.

Wed Apr 03, 2013 10:37 am

Yes i understand what your trying to do i set up cars like this before. My last race set up is #2100lb. bajabug 1" longer microstub arms, 26mm long bars 300m, fox 14" lg. -3" dia. 3 bipass tubes and 1 fox 12"- 2.0 shock per side, 930 race cv max out at 29 degrees for 15 3/4 travel.

Wed Apr 03, 2013 7:52 pm

What torsion bars are you running right now that are too stiff?

Before doing a bunch of modifications to use the longer torsion bar, why don't you just keep everything else the same and use a smaller in diameter torsion bar? Sounds like a much simpler solution to me.