ADJUSTABLE STRUT RODS - different designs

There are two basic types of adjustable strut rods:

1. With heim-joint ends (example: Hotchkis, PST)
2. Without heim-joint ends (example: Firm Feel).. using poly bushings.

Advantages, dis-advantages, of each design? Both designs assist in keeping the LCA pulled forward properly, as well as to gain more positive camber.

Longevity of both designs?

Car (my Challenger) is driven minimally on the street/hwy for wknd events (cruises), but also a high concentration in pylon AX and road course HSAX/HPDE.

Would the heim-joint design eventually fail?

What type of bushings are in the heim-joint design? They appear to be flat metal plates (no bushings?).

Would the poly bushings (using Firm Feel strut rods) eventually fail (instead of using rubber bushings)? I've used the stock factory setup (non-adjustable) with rubber bushings forever and have had no problems... after ~30 years, they still look a-ok.

Winter project in-progress.

T/Anks ahead!

Mitch,

You are entering the no free lunch zone.

You have potentially 3 choices going with adjustable strut rods:
1) adjustable struts w/ rubber bushings
2) adjustable struts w/ poly bushings
3) adjustable struts w/ no bushing & using a heim joint.

1) the rubber will flex and negate some of the effects of the adjustable strut. As such, you'll adjust more to compensate for the flex. Part of the reason your rubber bushings have lasted so long (besides the limited use) is the fact that they were working with the factory strut rod. Using an adjustable will introduce preload into the bushing and make it flex more than it used to. That will undoubtedly increase bushing wear, but without empirical evidence, this is still just theory in my head.
2) the poly flexes less and in my experiences poly has a shorter life compared to rubber in the same environments, but it does firm up stuff some.
3) This style actually keeps the most consistent suspension geometry as everything is a hard point with a pivot. Heim joints will actually free up the bushing bind as the LCA travels in its arc. Uncovered heim joints require inspection. They are like a ball joint. Precision fit, but a small amount of dirt can make them crap in short order. The position of the forward heim really won't get much dirt kick up like an UCA with a heim. Put a boot on it and treat it like a sealed ball joint. Just give it a good dose of dry lubricant before you put the boot on. This style of strut rod will put the tension load on the K-frame. A reinforced k-frame won't care. Non-reinforced its not much of an issue, either. HOWEVER an accident with an impact to the front wheel may incur more damage as the load path from the strike won't terminate in a bushing (that's why factory style tie rods are cheap and hollow, they are the first sacrificial part in that scenario).

My personal choice is #3. I'm just trying to keep the car pointed the right way now.

(sorry for the long post)

This is good to know as I was wondering how long the heim joints will last on a Hotchkis setup

Won't using the strut rod to add caster put a side load on the LCA bushing causing it to wear faster?

As said, no free lunch but I wouldn't use the strut rod to get more caster.

I have the Reilly Motorsports adjustable strut rods. I am pleased. The 'bushings' are aluminum with a locating ring (sandwiches K mounting point like factory).

I've got 7500 miles or so on them with a number of track days and a number of removals. No play in the heims.

I also now have delron bushings in the LCA's. Zero binding issues.

Yes, and I believe that is part of the reason for a moog LCA bushing failure on my car. I have now swapped to Delron, and trimmed the bushing slightly to 'fix' the binding that existed.

You covered a lot pertinent ground, but you have not mentioned that a rigid pivot strut rod, induces a small arc in the LCA as it moves up and down. The OEM allows for this by using rubber I suspect. Almost all other LCA bushings, I suspect even the delrin bushing will allow that small motion. If that arc was resisted, you would have bind. Granted the induced arc is minor, but then those who are making this upgrade "think" they are reducing unwanted movement in the first place. I suspect the LCA might even flex in this new arc induced by a rigid strut rod mounting, since the LCA main strength is vertical by its greater height cross section. Of course those that add the lower rein forcing plate would reduce this flex, and therefore drift closer to bind, not a wanted outcome. All this means to me going full circle, not sure why bother with the upgrade if the installed rubber bushings are in good shape and tight, for anything short of Nascar
use.

For discussion sake, is there consensus the strut's biggest and most important loading is when under braking?

I like the "repeatable" aspect of eliminating any possible slop from the strut rod. I have RMS heim/adjustables and they work well. The nice thing about them is being able to "set" the lower control arc to move as freely as possible while also keeping the lca seated on its bushing properly. Using them to gain caster will bind up the lca bushing.

I have wondered the same thing. Basic bonehead logic says the LCA bushing would be distorted and fail sooner.
Heim joints for the street? Smart guys like Rick Ehrenberg is against them due to rapid wear due to them being UNprotected. I don't agree with everything the guy says, but I see his point on this one.

I will put it to the test!
I daily drive my Hotchkis setup to work about 11 miles one way.
I have the rubber boots on the heim joints and will see if I have any major problems in the future

I use the adjustable rod basically to deal with tolerances. Poly LCA bushings don't hold the LCA in position. Poly strut rod bushings may install thicker vs rubber. I run poly in both locations. Plus there are tolerances on the K itself.

On the drivers side, I had ~1/8" play/gap at the LCA bushing with the OE strut rod. I couldn't get the alignment dialed in and it moved in use... not nice. The adjustable rods got the slop out. It took some fiddling to get it right and not bind up the LCA.

Cranking on the strut rods to gain caster beyond getting the slop out is likely to bind it up and shorten bushing life. Better to use the offset UCA bushings and/or aftermarket UCA's to get caster and camber set for handling and the adjustable rod to get everything positioned correctly

please clarify my thinking. is the lower control arm [only] responsible for the wheel base setting while the upper arm is used for caster/camber adjustments only ? or is the caster adjustment an insignificant aspect of wheelbase measurement ?

That is my understanding. The LCA handles braking loads and positions the spindle... the UCA works with it to handle the alignment.

With the bushing type rod installed and T bars out and everything greased there is some resistance to up and down movement. The strut rod + bushing effectively has some very slight spring rate. I guess the Heim joint type would not. Also the "pivot point" on the bushing type would be in the middle of the bushing pack while the Heim joint pivot is behind the bushings. The Heim is effectively shorter and the LCA would have a shorter arc. Its not clear to me what the benefit of the Heim type is.

Only benefit to a heim, as I understand it, is less compliance at the pivot point. A rubber, and to lesser extent poly, strut rod bushing will compress and relax in addition to twist as the strut rod goes thru up/down and braking/unlaoding forces. A heim doesn't compress/relax, at least it doesn't till it wears.

I've got ~9,000 miles on mine. Mostly street miles.

I need to replace the uppers and tie rod ends.

I think the strut rods are ok. When I unloaded the suspension to check bumpsteer I did my best to look at them really close and carefully feel them while someone else tugged and pushed on them. The tie rods and uppers are obviously loose.

The heims make for smooth repeatable suspension movement. We used to have to run bushings in our circle track car. They were very temperamental on binding/snagging/resistance when we digital scaled the car. If you over tightened them sometimes you wouldn't get the same static frame (ride) heights. And that completely screws up chassis setup on scale when you setting weight balances to the nearest half percent or smaller increment.

The poly and rubber stut rod bushing makes the strut rod into a diving spring board.

I use a Teflon lined joint that usually lasts many years of the typical part time usage our cars see. For me, combined with my delrin lower control arm bushing I am looking for the most precise movement possible. True, the arc is changed from the stock arc, but its not something one would notice.

don't forget to put some anti-seize on the heim that the bolt goes through, I've had one rust and seize on a bolt in my race car and it was a f***ing nightmare getting it out

I've had the RMS ones for about 4 years and they are fabulous. Still perfectly tight and they certainly improved the tracking of the car significantly.

Struts rods always produce a conflicting arc with the lower control the further the control arm moves. No mounting method eliminates that. The best part of an adjustable rod is to put the lower arm into its best arc position while minimizing the conflicting arc. If you onl;y use it to dial in additional caster, you will increase the conflict of that arc.

I've thought about a tubular strut that screws into a Camaro ball joint on one end, which bolts into the K frame. Ball joint arrangement allows use of a dust cover, ability to grease the joint, and more articulation than a double sheer heim. Also is easily replaced without dis-assembling the lower arm while still providing the semi-solid mounting method that reduces toe changes under braking/acceleration.

If the centerline of the ball joint setup you mention was in line with the plane of the LCA pivot you'd remove the conflict.

If I understand you correctly, I disagree. Rethink that.

The strut will always have an intersecting arc to the LCA in a stock Mopar setup. As such, there will always be a "conflict." Modern suspensions get around this by having 2 mounting points for the LCA. (thus not needing a strut arm)

The purpose is to control the arc's of the strut and LCAs. As such, there will be a defined point during the travel of the LCA. With this defined point you can adjust/modify other items for beneficial alignment settings. If the strut is "floating" in a bushing, then the position of LCA becomes more dependant on acceleration, braking, or during turning as they apply force on the suspension.

Yes, but the last point I was making, of all those forces, I suspect braking loads the "brake" strut the most, and I also suspect by a large factor.

T/Anks to all who've replied... FWIW... my LCA bushings are ~30 years old, as well.. and still appearing a-ok .. RUBBER. (~30 yrs ago poly lca bushings weren't avlbl... so.. I simply replaced the complete lcas which came with new factory lca rubber bushings.)

As to pulling the lcas a bit forward, using the adjustable struts, I can better understand that's probably not desirable as it'll disturb the lca bushings -- poly potentially to where out more quickly... but rubber can withstand and flex, hence longer life.

I'm unfamiliar with the RMS struts... I'll look them up.

I've recently had my kframe welded, and also the lca plates added. Engine bay is being repainted very soon.... been sanding, prepping, etc (show-quality!).

Despite the factory struts w/rubber bshgs, factory lcas and rubber lca bshgs, the car has always been tight and great handling (SCCA competition AX, and recent HSAX/HPDE, and street/hwy)... the overall suspension setup I have works great: 1.24 TBs, 225/5 flexaform mono leafs, 1.25 F, 1.0 r sway bars, Red Koni Ds, balance corner weight.. 52% f, 48%r. SO... with the engine out for a rebuild, the front end is being gone through.

Yes, but if you went the balljoint route you'd be smart to relocate the thing to remove the conflict, hence my comment about the line (shouldn't of said plane) of the LCA pivot point intersecting the center of the ball joint.

Mitch I am excited to hear you're making IMPROVEMENTS and I really think you will be pleased with some heimed/adjustable strut rods. Like I said earlier they are not for more caster, they are to precisely locate your LCA and preload your LCA bushing to YOUR liking, where its happiest. Calling them "Adjustable Strut Rods" is kinda misleading. RMS, Reilly Motorsports, home of the "Alter K" is where I bought mine, and they are exactly what I wanted, no hype they just work and didn't break the bank. Peter makes Delrin LCA bushings, those and greasable LCA pins with some new strut rods would be the only 2 basic "improvements" I think I would add to your car.

I posted this in another thread, but I wonder if this strut ball joint (greaseable, delrin lined) for a ford is the same thread (5/8 or 3/4) as the adjustable strut rod from firm feel, mix and match the two with the greasable delrin lower control arm bushing should make a pretty free and stable setup.

TCP ford front end

Firm Feel strut rod

That is a modded Uniball.

So, I've been playing with this in my head and some scrap paper now.

Provided that the center of the heim/ball joint is in line with the LCA pivot and t-bar there will be no bind. Ever. The strut actually moves in a conical motion, so the arc is the same as the lca. Therefore there is no intersecting arc. It is the same arc. However if that pivot is not in line, there will be a conflicting arc. Obviously the larger the arc, the less influence it has. Much like a longer panhard bar will shift the rear end less than a shorter panhard bar.

I was going to explain the intersecting arcs and in doing the geometry, discovered this for myself. I feel smart and stupid at the same time. If anyone already knew this, kudos to you.

72Swngr.. I'm doing these mods only because the car is apart (engine out)... so, now is the time. Otherwise it has handled superbly even with the rubber lca bushgs and stock/rubber struts (replaced them all new about 30 years ago).

I wonder if the RMS, PST and Hotchkis adjustable strut rods are all identical? Same manufacturer for all? They look identical except for the paint/color/markings. Does anyone know the difference?

I seriously doubt same manufacturer.

Need to look at quality of rod ends. The real high quality stuff is rarely in a kit cause it's just too expensive to be marketable.

If you look at Construction, the PST and Reilly units appear to be the same and most likely someone is doing private label for the other.

PST



RMS

[img]https://www.reillymotorsports.com/store/image.php?type=D&id=143[/img]

However the Hotchkis units are quite different in construction. The most advantageous part of the Hotchkis design in that the Strut rod engages the LCA the same way the factory unit does, by resting on a machined shoulder. The other units bolt in from the rear which means that the engagement is the clamping force of the faster and the face of the rod which could allow movement of the threaded section. I've seen folks who install Heims onto the threaded section of of a fastener and over time and cycles, the threads will "waller" out the hole. No good, especially if that fastener shears or backs out...you have nothing holding your strut rod to the LCA.

In addition to what Dan said:

We also use a billet steel front clevis mount, where as the other brands use a broken piece of plate steel; our front mount is quite a bit stiffer and stronger, while in my opinion being cleaner.

(I only have a good picture of our new Mustang struts, but the same clevis is used)

This also assumes LCA and Strut have same pivot length?

They would have to in order to work in the scenario we are talking about, who knows what the stock setup is. I can't imagine it's too far off or bump steer would be interesting.

Good point! Also look at the forward heim on the Hotchkis. I have to inspect mine to see if they used more than a standard bolt or I suspect that heim may be resting on threads, as well. Only about 200mi on my setup so far so I'm sure no wear.
Dan Weishaar posted about this regarding the Hotchkis UCAs a while back and I made sure I grabbed new Socket Head Cap Screws and modded them for the brackets.
My only complaint about the Hotchkis ones is the washer stack used to locate the forward mount is cumbersome (at least when your car is only 12" in the air and your head is against the concrete) and I would have much preferred a machined step washer like the RMS/PST unit. (something else to make!)

Wonder how the Nichels stock car arrangement would compare.
They welded a sleeve into the k-member, screwed in what looked like a typical Mopar ball joint, and joined it to a shortened two piece strut rod, with a threaded collar. A tie rod type adjustment was used to change the length as needed.

Would work like the Mustang ones that nstgl1970 posted about. In other words, perfectly fine and with more resistance to wear than a spherical rod end.

That's similar to what I proposed, only I'm saying don't bother with the welding and screwing in the ball joint. You'll eventually fatigue the threads and have to replace the sleeve. Instead, use a bolt in ball joint.

I appreciate these comments, opinions and ideas. I don't, unfortunately, have the luxury of comparing any of all these struts side-by-side.

Fastest cars at the Mopar events are all running Hotchkis equipment. Most other manufactures don't even bother to try to keep up. Seems like a no-brainer to me.

I put a quick eye ball on a K frame laying around. The OEM strut pivot point and the LCA point appear to be in line, I'm humbled and apologetic that i might have helped in splitting hairs and chasing our own tails on this whole subject.

Yes! I missed the mustang pic, how 'bout a mustang Mopar hybrid, with a protective boot. Might be best of all.

Yea that would be good too, especially if you can't or don't want to weld anything to your K member. I'd think any ball joint would be more wear resistant than a heim.
Not sure I'd agree on the threads wearing out though, have you seen any worn out upper control arm threads?

You gave me an idea.
http://www.speedwaymotors.com/Steel-Upper-Ball-Joint-Sleeve-K772-Style,2126.html

Yup, and it is occasionally posted here as well when some one can get a ball joint into the control arm but not get it to torque to spec. Solution from way back was to put 3-4 tack welds on the ball joint to hold it in the control arm.

Now that you mention it I've done that myself a looooong time ago, and it worked!