Torsion bar adjustment

[1971datsun521]

I removed the passenger side torsion bar and now I'm trying to find out how to adjust it

[Stoffregen Motorsports]

You adjust them in the truck. No need to remove them.

[datzenmike]

The torsion bar is splined at the front into the lower control arm. Re install it in the original position and adjust.

 

Below left side.... Tightening the nut raises the anchor bolt.

 

http://redeye-designs.com/pictures/ratsun/FAQ/torsion_bar.jpg

 

The anchor bolt raises the anchor arm below....

 

http://redeye-designs.com/pictures/ratsun/FAQ/rebuild70.jpg

 

The raising anchor arm twists the torsion bar in a counter clockwise direction. This torque is transferred to the front lower control arm trying to force it downwards against the ground effectively lifting the truck.

[thisismatt]

You only remove it if you want to reindex it when you run out of adjustment

[Beer Snob]

What is the advantage of re-indexing the torsion bars say when lowering? Adjusting up or down only changes ride height, yes??/no?? I was told, (I've been told ALOT of wrong things so that's why the inquiry) that adjusting ride height is just that and the spring rate of a torsion bar doesn't change. The fact that you run out of travel (why we all used to remove or cut bump stops) is what we all associate with the "rides like shit" after adjusting our 620's down. Let's throw out shock stroke and camber issued and just focus on what's happening with the torsion bar itself. Does raising by adjusting "stiffen" and lowering by adjusting "soften" ride characteristics? Based on how increasing torque on the lower control arm raises and vice versa to lower it would seem that I does, however, in my head I can also picture how the "spring rate" of the torsion bar would allow it to absorb bumps in the road the same regardless of ride height. Haha, man I all over the board here I know, just like learning. It's like math class in school, if you understand "how and why" it works its a lot better than just plugging in numbers. 🍻

[banzai510(hainz)]

24 minutes ago, Beer Snob said:

Does raising by adjusting "stiffen" and lowering by adjusting "soften" ride characteristics?

NO  in therey its just spring steel and same if you raise or lower it.  But be honest it seems softer when it was stock height when i first got my 521. But I put KYB gas a just shocks which are harder.

 

only affect if your down on the rubber bump stops

 

if you want more than say 3 inches them people reindex the bar cause you run out of threads on the bolt. Thats why they reindex

 

 

rides like shit to me is more low profile tires. stick with stock taller tire will help keep that softer ride

[Beer Snob]

Thanks Banzai, man I can't imagine lowering that far that way. I've run many 620's down, removed the bump stops completely, I still don't seem to have much suspension travel before hitting the control arm. This is my 79 cranked down with a little more to give before I'd have to re-index. Even with the stops removed little travel. I could only imagine that with a re-index I could set it metal to metal but why? At the point of re-indexing wouldn't it be better to start thinking drop spindle, bags, or full custom??🍻

[datzenmike]

Raising or lowering does not change the spring rate but to ride properly there has to be room for the shock absorber to work. At stock ride height the bump stop is there for extreme suspension travel so the closer you get to the rubber bump stop the more the truck will hit it. You only see it when sitting still but the lower control arm moves a long way. The rubber does nothing toward dampening the energy stored then released by the torsion bar which is simply another form of spring. Once into the bump stop the lower control arm can't move anymore and the truck is compressing the air in the tire and like a rubber ball becomes bouncy. If you are on the bump stop or have to cut it to go lower then you may as well take the shocks off.  

 

Definitely drop spindles are the answer. It will keep the steering and suspension geometry (camber) closer to stock and eliminate unwanted bump steer.  

[Stoffregen Motorsports]

It may seem softer at stock height because the GC and roll center are higher, causing the body to roll more easily.

 

Also, a flatter control arm position will be effectively "longer" than a control arm that's at an angle, so a flatter arm connected to a torsion bar may feel stiffer because of the arc angle to vertical ride height change is minimal. I don't know the right term for that last example, but hopefully this makes sense. I'm sure there's a more elegant way to explain it.

[mainer311]

4 hours ago, Stoffregen Motorsports said:

It may seem softer at stock height because the GC and roll center are higher, causing the body to roll more easily.

 

Also, a flatter control arm position will be effectively "longer" than a control arm that's at an angle, so a flatter arm connected to a torsion bar may feel stiffer because of the arc angle to vertical ride height change is minimal. I don't know the right term for that last example, but hopefully this makes sense. I'm sure there's a more elegant way to explain it.

I think you have it backwards. Your control arm being longer would make the ride softer, since the wheel has more leverage against the spring.

Edited September 29, 2022 by mainer311

[Stoffregen Motorsports]

Right, but it's not really longer. I'm having a hard time putting the visual in my head into words. It's the arm position combined with the arc on which it is rotating.

[thisismatt]

The amount of bump force that is tangential to the rotation of the control arm is highest when the arm is horizontal to its pivot, as opposed to taking the extremes of entirely vertical upward or downward where the force is 100% radial towards the pivot and causes zero suspension travel.

 

Something like that

 

 

[datzenmike]

 

[Beer Snob]

I'm going to memorize your knowledgable smack down that just left my wanting to get in a time machine and go to college!! Thisismatt, I love it, keep it coming my brother!! That put a big ol smile on my face! AND I think I actually can make sense of, lets say, 85% of that😆! I wish being uber smart was cool in the 80's, I would have done things Alot different🍻 

[banzai510(hainz)]

if you worried about hitting the bump stop or frame you can run a KYB Gas a Just  or Mono Max. but it will be stiffer and maybe a harder ride. those blue shocks look like NAPA hydralic which is minimal at best.

just remeber not to cut the tystrap on the shock . Mount it then line it up on the truck then cut the strap and shoot the top of the shock thru the mounting hole. Otherwise its a MOFO to compress that shock to get it in

[Stoffregen Motorsports]

16 hours ago, thisismatt said:

The amount of bump force that is tangential to the rotation of the control arm is highest when the arm is horizontal to its pivot, as opposed to taking the extremes of entirely vertical upward or downward where the force is 100% radial towards the pivot and causes zero suspension travel.

 

Something like that

 

 

Amen

[Beer Snob]

Thanks Banzai, I'll upgrade for sure. That's the next project to get on the road. Appreciate the advice, good eye🍻