adjustable strut rods

Posted by: krautrock

adjustable strut rods - 09/17/17 05:14 PM

can anyone tell me how much shorter I can go with something like a Hotchkis adjustable strut rod? there is plenty of adjustability I presume?

the strut mount on my k-member is a little caved in looking on the pass side, other sides looks ok. just went through all of my suspension and I am using an alignment gauge on the spindle and I can't get good numbers on the pass side.

Measuring from common holes in the frame rails to the grease fitting on teh LBJ, the pass side is 1/2" pushed back.

can I be confident the adjustable strut rods will get me that 1/2" back?

the k-member mount looks like it's only pushed in 1/8" at most, which is the reason I decided to put it back together and see what it looked like...
Posted by: GoodysGotaCuda

Re: adjustable strut rods - 09/17/17 07:28 PM

Time for a new K.

You can adjust things pretty far with the Hotchkis parts, but it sounds like a bandaid solution. What will happen to the lower control arm pivot when you do that? It sounds like you'll eat LCA bushings very fast.
Posted by: krautrock

Re: adjustable strut rods - 09/17/17 07:47 PM

I plan to replace the K member when I pull the motor. OK with a bandaid solution for a while.
Posted by: geo.

Re: adjustable strut rods - 09/17/17 11:42 PM

I don't think there's any reason you couldn't attempt to straighten, and then reinforce your K.
Take plenty of measurements, you should be able the press the caved in spot back where it belongs.
Posted by: krautrock

Re: adjustable strut rods - 09/18/17 10:18 AM

To give you an idea what I'm looking at, this pic shows it. Those are the Moog improved design strut rod bushings.

Posted by: Mopar Mitch

Re: adjustable strut rods - 09/18/17 03:10 PM

I often wonder about the wear of the LCA bushing -- as it passes through the LCA - and the angular effect of moving the LCA forward with adjustable strut rods (to gain positive caster). With rubber LCA bushings (factory stock design), the rubber material can allow some angular flex of the LCA. However, with less forgiving material, such as POLY or Nylon/Delrin, or so far as steel) that angular motion (in other words, no longer a ~90 degree perpendicular attachment), would be causing excess and premature wear on that non-rubber LCA bushing.

I'm currently installing Firm Feel's Nylon/Delrin LCA bushings... and hope they won't prematurely wear out.

I also wonder about POLY strut bushings (from FF) -- if they will prematurely wear out, say, vs the "forgiving" rubber factory design.

Then... there is the heim-joint designs of struts... would they be "pulling" the strut forward/backward within the range of motion (up/down) of the LCA?... and ultimately wearing out the LCA bushings, especially if they are POLY or nor non-rubber?

(I think these concerns could be adjoined within the original poster's inquiry.)
Posted by: krautrock

Re: adjustable strut rods - 09/18/17 04:42 PM

I talked to Dick at Firm Feel, he said heat, a BFH and a really stout bar to hammer it out.

I think I'm going to use some 1/4" plate I have hanging around here and see if I can weld up a form that will go on the front side of the K-Member mount area and use a 5/8" bolt/washers/breaker bar to pull that area back into shape. Atleast get it close, then use some adjustable strut rods to get everything equal. Sucks to pull it apart again but it should go quick now, everything is clean.

How thick is the K-member at the strut rod mount? It's from 1967.
Is it two pieces of 3/32" metal sandwiched together??

Mopar Mitch, I was thinking about the arc that the strut rod makes the LCA follow. It can't be much change at all. How long is a strut rod, like 19" or something?
the arc of a 19" radius is pretty flat. Then think about the length of the LCA, the effect on the bushing probably isn't too extreme.
Posted by: Supercuda

Re: adjustable strut rods - 09/18/17 09:03 PM

Originally Posted By Mopar Mitch


Then... there is the heim-joint designs of struts... would they be "pulling" the strut forward/backward within the range of motion (up/down) of the LCA?... and ultimately wearing out the LCA bushings, especially if they are POLY or nor non-rubber?



Heim jointed strut rods that I have seen move the pivot location adding a bind to the setup.

Yet another aftermaket pos design that many fall for.
Posted by: krautrock

Re: adjustable strut rods - 09/18/17 09:51 PM

Originally Posted By Supercuda
Originally Posted By Mopar Mitch


Then... there is the heim-joint designs of struts... would they be "pulling" the strut forward/backward within the range of motion (up/down) of the LCA?... and ultimately wearing out the LCA bushings, especially if they are POLY or nor non-rubber?



Heim jointed strut rods that I have seen move the pivot location adding a bind to the setup.

Yet another aftermaket pos design that many fall for.





how much shorter is the radius from the closer pivot point and how much tighter does it make the arc?
Posted by: Supercuda

Re: adjustable strut rods - 09/18/17 09:57 PM

Who knows, I'm not about to start buying poorly thought out items to measure and satisfy someone elses curiosity.

Why induce a problem, however small, into your front suspension when you do not have to.
Posted by: 68rrunner

Re: adjustable strut rods - 09/22/17 09:14 AM

Originally Posted By Supercuda
Who knows, I'm not about to start buying poorly thought out items to measure and satisfy someone elses curiosity.

Why induce a problem, however small, into your front suspension when you do not have to.


What math or real world data do you have to back that up?
Generally speaking, the cars that are set up with an adjustable strut rod have tighter suspension with stiffer springs and shocks, using less suspension travel; and requiring less of an ark. Moving the origin point of the arc rearward 1-2 inches over that amount of run probably doesn't make as big of a difference in handling as a properly located lower ball joint, which directly effects KPA and handling while cornering.
Posted by: Supercuda

Re: adjustable strut rods - 09/22/17 09:24 AM

It's called geometry and an understanding of how the suspension is supposed to work.

Both the LCA inner pivot and the strut rod pivot points need to be in a line, said line defined by the LCA pin. When you use a heim jointed (get it right) strut rod you relocate that pivot by several inches. Which moves it out of line and induces a bind.

How much bind is irrelevant, it is there. how much the LCA may move is irrelevant, the bind is there.

Why would you put a part in your suspension that will induce a bind?

If you really wanted a strut rod without the bushing compliance some dislike then fab up one with a ball joint and center that joint in the line we talked about earlier. Then you get a solid, no bind connection. Probably cost less than the heim joint junk too.


Once again, I am talking about a strut rod that uses a heim joint as the front pivot point. It may or may not be adjustable, but that is irrelevant.
Posted by: 68rrunner

Re: adjustable strut rods - 09/22/17 09:46 AM

Again, where is your data? The factory racers in the day with Upper ball joints mounted on the front of the strut rod and the current setups with heims use the devices for the same reason, to drag the LCA forward and get a desired KPA that is advantageous to a properly handling car. We've prototyped a couple variations of a properly designed LCA that would eliminate the bind in the LCA pin bushing while providing a better LBJ position; but it was determined that the market wouldn't support the cost.
Posted by: jcc

Re: adjustable strut rods - 09/22/17 10:06 AM

You are asking for numbers/data to back up the conflicting Arcs/bind issue. Tell us what numbers would make you have a different outlook. The reasoning shared here, IMO is correct. whether it matters to anyone, is personal choice. We repeatedly for example discuss 9/16" vs 11/16" TR stiffness differences, and for over a decade, no one has shared any supporting data to make their case. Why start now? work
Posted by: Supercuda

Re: adjustable strut rods - 09/22/17 10:12 AM

Where's my DATA? Go read what you posted. Your words right here:

We've prototyped a couple variations of a properly designed LCA that would eliminate the bind in the LCA pin bushing while providing a better LBJ position

You've stated the exact same thing I did. THE EXACT SAME THING.

Using your strut rod to get a "desired KPA" is the assbackwards way of doing it. Relocate the UBJ.


Posted by: 68rrunner

Re: adjustable strut rods - 09/22/17 11:38 PM

I am personally willing to accept the insignificant bind that I put the LCA bushing under because I understand the fact that performing that adjustment makes a better handling car.
However, if I can design a component to make the best of both situations; I will, and I did.
Unfortunately for this community, there are a lot of bench racers and folks working on theory and not real world data. We've been racing these cars for a lot of years and we've got quite a few trophies on our walls to prove we know what we are doing.
Posted by: jcc

Re: adjustable strut rods - 09/23/17 12:41 AM

And you should. The conflicting arcs/bind issue is I guess resolvable be re-configuring the LCA original constraints (1 degree of freedom), but only by making, I suppose the strut a non compliant member. That is quickly approaching and exceeding the scope of most of the suspension mods here in this forum.
So what is your LCA pivot solution?
Posted by: 68rrunner

Re: adjustable strut rods - 09/23/17 02:06 PM

I don't think there is a problem with the pivot. A Heim with an adjustable shaft is the best solution to make a car handle confidently.
Posted by: krautrock

Re: adjustable strut rods - 10/06/17 10:57 AM

Well, I have the Hotchkis strut rods now. Was in France for a while so didn't have a chance to mess with it.

Noticed something else, I boxed the lower control arms so they are nice and stiff.
Well, with the front K-member strut mount hole being a little deformed, and the stiff (metal reinforced) "improved design" moog strut rod bushings, there is not much give.
The lower control arm pin actually pulled out of the bushing a slight amount as I tightened everything up.

Going to pull both arms off and replace the bushings.
Going to weld up a stiff plate/bolt/washer type press and see if that will flatten out the strut mount area in the K-member.
Then the Hotchkis strut rods should allow me to get arms in so that the are in their natural position, and from there I should be able to get some decent alignment specs on both sides. I'm not planning on trying to pull the arms forward to try to get huge caster specs...
Posted by: krautrock

Re: adjustable strut rods - 10/07/17 06:24 PM

was able to get some time to pull this crap apart again.

this is how much the lower pin pulled out.




a simple little plate and bolt with some washers on the other side.




not perfect, but should be good enough. the hotchkis strut rods have a nice amount of movement in the heim joint so if it is a little cocked to one side it should be fine. as long as i can get good alignment numbers on this side now i'm happy to move on to the next thing to fix on the car. but zero caster and .25* pos camber wasn't going to cut it.

Posted by: krautrock

Re: adjustable strut rods - 10/18/17 11:16 AM

Back together. My alignment numbers on the pass side still seemed weak after fixing this. Dropped marks on the ground from the rear of each torsion bar socket, made a line across that. Dropped marks at the face of each LCA real close to the lower ball joint and also dropped marks from the front ball joint bolt in the spindle. Both sides were less than 1/8" difference.

Alignment numbers for DS I was able to get -.50* camber/+4* caster.
PS I was only able to get 0* camber/+1.5 caster.
Got kinda frustrated, started thinking about camber spacers and all that.

Decided to see how much my weight in the drivers seat changed stuff around. My wife plus a puppy in the car and PS came around to -.3* camber and +2.75* caster.
DS numbers changed to -.15* camber/+3.5 caster. slight adjustments to the DS and it's also at -.3* camber/+2.75* caster.

I think I'm losing a full degree of caster from the rear of the car being higher than the front so I'm happy with 2.75* caster.
Posted by: Frankenduster

Re: adjustable strut rods - 10/19/17 01:18 AM

If my EX wife were to sit in the drivers seat of my car, I'd need a block of wood under the frame rail to limit the compression of even my 1.15 torsion bars!