Rambler American front suspension 1958 through 1963

Nash Rambler front suspension 1950 through 1956 (likely)

26 may 2020

new 16 apr 2020

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This document covers the basic stock suspension, including non-factory modifications to re-use failed parts. There is a separate document for high performance modifications.

Introduction

The early Rambler American front suspension, 1958 through 1963, was derived from, and may be actually identical to, the 1950 through 1955 Nash Rambler suspension. Of course it's components work together as a system, but this page looks at it more closely as a set of sub-assemblies, how those sub-assemblies work and critically, how to work on them.

Supporting each wheel is a double-wishbone coupled by a steering knuckle to which the wheel and brake assembly attaches, with a road spring directly over the knuckle. The control arms and knuckle are coupled with trunnions, not ball joints. The knuckle is steered with conventional ball and socket tie-rods. The steering linkage ("drag link") couples the two sides to an idler arm and steering gear in the usual way.

The devil is in the details. The components and techniques used in this system are just plain weird to folks with only "modern car" experience. A large number of design-peculiar components are used and assembly and adjustment is very labor-intensive with specific procedures that do not exist in modern ball-joint type suspensions. Then there are a number of components that are just poorly done, and some common parts, like shock absorbers, are completely non-standard and cannot simply be bought at a parts store.

All of my cars are daily-drivers, always long-distance ready. The more advancd work on this suspension started on my 1963 American, and advanced on the roadster, where I have achieved throttle-neutral steering (using a home-built rear suspension). This page should be useful for restoration sine there is a lot of technical detail and procedural stuff, but it's mainly aimed at making this car reliable and on the road without resorting to what are now extremely scarce and expensive NOS parts that will in turn wear out with modern use patterns.

Double-wishbone assembly (one each side)

(This page derives from the 2007 write up for suspension work I did on my 1963 Rambler American. This page supercedes that page, incorporates my experience since then on both "stock" cars and some substantial high-performance mods on my Rambler Roadster.)

The front suspension in the 1958 through 1963 Americans is a very old Nash design, and appears to be the same as the 1950 through 1955 Nash Ramblers, according to Frank Swygert (2007 note) and my recent examination of a 1952 Nash Rambler in a junkyard.

The main problem with this suspension is that it is decidedly non-modern. It is unlike any American car suspension designed in the 1950's or later, is very labor intensive and contains a very un-modern amount of fussy assembly procedure, and none of it appears to have been written down.

Design overview

This is a do`uble wishbone and trunnion system, with the road spring directly over the steering knuckle, in line with the virtual kingpin. This design has wonderful control over understeer in turns, and a anti-roll bar is unneeded (and not available). The spring carries load directly, not multiplied by moment (distance from fulcrum) so the spring is softer and lighter. Spring-over-knuckle also eliminates decreasing roll resistance in turns, a characteristic of most American suspensions through the 1980's, often compensated for by anti-roll bars. The downside of the spring-over-knuckle system is that it is very tall -- this really limited AMC's styling choices until the adoption of the new system in 1970. The spring is 20 inches long uncompressed, and 5 inches diameter; I think of it as a weapons-grade ball point pen spring.

The pivot on both upper and lower arms are done with a trunnion (a U-joint is a form of trunnion). Each has it's own set of problems and they are most of the difficulties with this suspension.


Lower control arm

The lower control arm is composed of two identical stamped arm halfs joined into a wishbone (triangle) by the trunnion that hold the steering knuckle, attaches to the chassis with the pivot bar, and is stiffened by a fat spacer towards the outer end that is also the shock absorber lower mount.

Disassembly is easy: remove the nut and washer from each end of the pivot bar, remove the bolt through the shock lower end (not shown below) and the spacer/stiffener (high torque and probably rusted on), then unscrew each trunnion cap. Do not attempt to take off the trunnion caps until at least the stiffener is out, the arm will be damaged.

Bent arms

26 may 2020: All of the arms that I've collected in the last decade are bent, it turns out. After cleaning I methodically measured them, which I neglected to do when I put the last two cars together. Only five arm-halfs were what I thought were usable.

The critical relationships in the lower arm are bushing, spacer/stiffener, trunnion parallelism. This much is obvious; the lower arm assembly moves (only) up and down. The arm halfs are one part number hence the trunnion is centered in the pivot bar. Rarely are dimensions like this given in manuals; they're derived from good parts or at least identical measurements from collections of parts (if they're all the same, it's probably the correct measurement).

I have no such information here: no two are alike. They are all visibly bent. (This is why I clean and inspect all critical old parts.) I checked parallelism by clamping a Starrett straightedge to the spacer/stiffener area (where the .090" washer is welded) and measured to a consistent place on the flat outside the stamped boss where the bushing/trunnion fit, an area under no stress, using a Starrett dial caliper.

Here are the measurements on arbitrary arm halfs:

dim. A, inches dim. B, inches
3.685 .495
3.832 .427
3.470 .472
2.905 .399
3.80* .56*

Here are visual confirmation of the bent outer, trunnion, end of the lower arms. At this point I made no effort to correlate arms with measurements. The left-most image is an arm without the "washer" on the spacer location of the arm. This was the second-worst bend, which broke the spot welds loose. I manually added .090 to the measurements above, marked with *. They are therefore not accurate, but it doesn't matter. These are now all junk parts.




Lower control arm stiffener

This is the critical lower control arm stiffener, that doubles as lower shock mount. It is a critical part, it cannot be left out, and it cannot be replaced with a thinwall tube, and a conventional shock cannot be mounted here. "Everyone does it" and everyone is flatly wrong. Please refer to the bent-arm discussion above.

Galvin's AMC sells correct replacement kits, you'll need two. For home-builders here are the dimensions of the lower arm spacer. The raised edge (flange) keeps the shock centered. The spacer is in two pieces so that it can be inserted into the shock eye. You could fabricate the spacer as a simple bored-out dowel if you used washers at each end and kept the overall stack height correct. Spacer length dimension is critical. It is determined by the dimensions of the stamped arms, and the particulars of the assembled trunnion threads.

This is a new replacement kit from Galvin's AMC, so that you at least know what it is you are missing:

Overall length (both spacers) 1.510"
Length, each half .753"
Flange width .075" approx
Diameter .878"
Flange diameter 1.00"
Bore .568"
Bolt Grade 8, 3", 9/16-NF
Nut Self-locking (swaged type)



Lower trunnion

The lower trunnion is a precision casting that attaches the two stamped lower arm halves into a unit, and accepts the lower end of the steering knuckle. The trunnion attaches to each arm half via a bizarre (sorry, right word) double-threaded nut. There is a "type 1" and a "type 2" design, they are interchangeable, and type two is to help eliminate what a certain car and rocket designer calls "rapid unscheduled disassembly". (In Rambler/Nash's defense said disassembly requires years of utter and complete neglect, plus some abuse. They are plenty safe with any maintainance at all.)

Even reasonably maintained they wear more quickly than one would like; the moving parts are threaded to each other (vertically and horizontally) providing a lot of opportunity for hardened metal to grind on hardened metal. Lubricated they will last 100,000 miles. Unlubricated, less than half that (guessing, from the disasters I've disassembled.)

The steering knuckle threads into the trunnion, vertically (wear center). The trunnion caps thread onto the trunnion itself, and into the arm halves, simultaneously, and horizontally. I can only assume this was for a (misplaced) idea of increased safety; the suspension will maintain structure if a part fails or a bolt falls out. In practice the threads tend to grind the metal to a paste, as the suspension moves; up and down (steering) and force/aft (bumps). The motion is tiny, and harmless; but it greatly increases wear.

Lower trunnion failure

I have not personally experienced a self-disassembling lower trunnion, I assume those were rare, though would be a reputation hit for a manufacture with a fleet of product on the road. The do wear however, and need replacing. Worse, if not assembled right in the first place, or if lubrication is neglected, the trunnion caps bind on the trunnion casting, the caps rotate in the threaded holes in the arm, and ruin the arms. Usually by then chronic lack of maintenance has induced excess wear within the trunnion.

The (1960's) aftermarket came up with a solution: "trunnion repair kits" replaced the lower trunnion with a far more robust, greasable part. It however retained the caps, out of necessity. I have a set of these in my Roadster. They were expensive and sourced from two foreign countries.

Lower control arm bushings

The inner bushings on the lower control arm are a press fit into the stamped arm. These can be pressed out, and new ones in, with 1/2" drive sockets and a big bench vise, or a threaded rod washers and nuts.

Bushings are Raybestos 565-1017 or equivalent, and may or may not be available. I have been fabricating my own (upper and lower) bushings, refer to the performance suspension page for details.

The bushing is pressed into the arm until the step-up shoulder of the bushing shell contacts the arm, this determines proper depth. (Note also that lower control arm bushings can be used in the upper arm position if you control insertion depth.)

Assembly procedure

26 may 2020: No wonder I had such trouble assembling the lower arm (text below from 2010). At that time I did not think to check for bent arms. They're probably all bad on the car. The loss of accuracy in locating that lower trunnion in the chassis will "adjust out" when the alignment is done, but that is not a good thing.

Assembling the trunnion into the lower arm is simply difficult, there's no way around it. My description below will probably not help much. I assume that I am simply ignorant of the correct procedure, but in my defense, no one else has ever told me there is one. The 1963 and up "big car" upper trunnion system, for instance, has a similar order-of-assembly problem; but on that system once puzzled out, the assembly process is easy to get right, first time every time. The 1950-1963 Nash system, still no idea what the trick is.

I pressed in the bushings and fitted the trunnion nuts into the arms. To the lower trunnion I added the new O-rings, greased the threaded journals, and assembled the trunnion and lower arms, adjusting it so that the shock absorber mount/spacer just fit. This sets the spacing at the trunnion end of the arm.

Then I clamped one arm of this sub-assembly in the vise so that the inner pivot will be vertical. Of course you can't put the pivot bar in; so now take the trunnion nut (1-1/8") out of the top (unclamped) arm, put the inner cup washers and pivot bar in place, then the arm, and inserted the shock spacers with the bolt very loose.

Now comes the tricky part -- getting that last trunnion nut on. As assembled in the vise, the threaded end of the trunnion is protruding from the arm. This part is all feel and judgement and danger. The trunnion nut threads onto the trunnion, but at some point it contacts the arm. The nut's external threads are really broad and shallow an thread into the arm. Cross-thread this, and you ruin the arm. But you have to thread two different-pitch threads at once! And in doing so maintain the exact spacing between the arms for the shock spacer.

Basically I pull up and pushed down on the arm (slight flex) to feel the start of the external thread. Once caught, it goes OK. Caught wrong, it wants to cross-thread.

I got it right but it pretty much defies explanation. I neglected to take pictures of the lower arm assembly, sorry.




Upper control arm

The upper trunnion assembly on the arm consists of all of the parts inline with the green lines on the drawing below. The trunnion is free to pivot in one plane, riding on the trunnion bolt. Note that as side effect, as the wheel moves up and down, causing the trunnion casting to pivot/rotate on the bolt, the trunnion casting moves fore and aft (the green line is parallel to a line drawn between the front and rear wheels on one side). The bolt also cuts threads into the arm, making them non-interchangable once installed (therefore in 2020 all used arms are leading or trailing -- not interchangable when used with the bolt).

The upper trunnion bolt is hollow, with a zerk fitting on it's head. I do not have one to photograph because I have never successfully removed one in one piece, and they are too expensive to buy without reason. A cross-drilled hole is intended to disperse grease into the threads; this does not happen, even with the reduced OD (John Elle's insight to check). Coupled to the common 1960's attitude to economy-car maintenance ("buy a new car soon") upper trunnions were rarely successfully greased.

Here's a photo if the relationship between the assembled stamped arm halfs and the trunnion, on the bench, with a threaded rod substituting for the hardened bolt. Note the large gap to either side of the casting; this space is filled with rubber grease seal(s), on the car. There is a zerk grease fitting installed on this casting, described elsewhere.

(The steering knuckle would install up from below in the photo above.)

Upper control arm failure

The upper control arm trunnion system fails more often than not. The head of the trunnion pivot bolt is supposed to "jam" on the leading arm (at pink X), and a nut and lock washer jams the bolt to the arm on the other (at pink Y). This simply does not survive ordinary use patterns.

What inevitably happens is that due to lack of lubrication the bolt binds within the casting (lots of surface area) then the bolt begins to apply rotational force to the bolt, which then rotates within the stamped arm's laughable tiny thread volume. Though in no danger of disassembly, but the upper trunnion system rattles and shakes, and ruins both arms. Every time.

Disassembly is easy, in theory -- in practice the trunnion bolt is often frozen into the casting from years of neglect. In my experience the stucked bolt I ever had to extract. See "Severe wear case study" below.

Below is a photo of typical damage to an upper arm half resulting from upper trunnion system failure.

The trunnion casting generally survives, but bolt and arm halfs destroyed. However, even badly-damaged arm halfs are candidates for my suggested repair/improvement, described below. Don't throw them out just yet.

For the historical record, here is what they should look like.

Upper control arm bushings

The upper control arm bushings are a press-fit into the stamped arm, same as the lower arm bushings. They are dimensionally the same except for press-fit-depth limiting ridges on the outer shell. In my experience these upper bushings are "not available" when the lowers are, and sometimes parts catalogs substitute lower bushings, for uppers.

The possibly-more-available lower bushings can be used in the upper arm as long as you carefully measure and control the depth to which you press them into the arm. The TSM states to press them in until the stepped portion is 1/2" from the arm itself. The photo below shows an upper arm half with one of my home-made bushings installed. It was made from a dead lower arm bushing, and pressed in to the desired depth of 1/2".

The bushings look like many common bushings, but the dimensions make them scarce, mainly the bore; the AMC pivot bars are 11/16" diameter.

PartRaybestos 565-1017
ID.785"
OD (smaller)1.255"
Shell1.00"
To step0.725"

Upper control arm failure: Severe wear case study

Next is a look at at the front suspension from my 1963 Rambler American, disassembled for repair in 2007. If I recall correctly the car had 90,000 miles on it.

This was a case of extreme neglect. The lower trunnion was worn, but reusable. The upper trunnion bolt on both sides had frozen into the casting, stripping the threads out of each arm. In both cases the hardened trunnion bolt was removed in pieces. Both bolts had to be ground out, millimeter by millimeter, with carbide drill bits sacrificed for the job. Luckily the trunnion bolts are bored (the aspirational grease hole) providing a centerhole for the grinding bit.

(Before I resorted to this grinding business, I had gone to extraordinary lengths to remove it: heated dull red/plunge-cooled six times, penetrant fluids of all kinds; longitudinal tapping both directions, rotational pressure back and forth. Eventually I torqued the head off -- of a 5/8" shank hardened bolt.)

(I managed to extract one half-inch length of bolt thread, the measurement of which backed up John Elle's suspicion of the reduced OD.)

Homebrew upper trunnion reinforcement

I worked up a scheme that replaces the expensive hardened, tapered, ungreasable upper trunnion bolt with an afforable solution that is greasable, and additionally hugely increases the number of threads available to "jam" the trunnion bolt into the arms. Ruined arm halfs can be reused instead of replaced.

The solution is in two parts:

Upper arm-half thread reinforcement (welded nuts)

Here is the end result: a 5/8-11 nut welded to the outside of each arm, providing sufficient threads for a jam-nut system.

The nuts must be indexed before welding. This is done by assembling the (newly-bushed) arms onto the pivot bar, inserting the bump stop, and snugging the fasteners. This sets the open distance, the gap, betweep the two arm ends where the trunnion will fit.

Consider the path of the bolt/threaded rod: the threads on the left hole must align with those on the right. The easiest way to do this is to assemble as above, pass a section of threaded rod through the holes (stripped/partially stripped or OK), add the nuts to the threaded rod, tightened finger tight (don't bend the arms tightening them) and then weld the nuts to the arms.

After the above the threaded rod is guaranteed to pass through all parts at final assembly.

(The visible gap between arms and casting is where the grease seals go. Instead of the expensive and old Rambler part, simply substitute two fat O-rings. These work as well or better than the originals, which never did much anyways because it was impossible for grease to exit the casting in the first place!)

The above paragraph is preface to what looks silly below. With new bushings pressed into the upper arm halves, and assembled on the bench as above (pivot bar, bump stop/spacer)run a length of threaded rod through the (probably stripped) holes in the arms. Then thread new 5/8"-11 NC nuts onto the rod until they are finger-snug to the arm metal. Then weld the nuts to the arm.

This partial-assembly business only needs to be done once when welding the nuts in place. This assures that later final assembly will put not unwanted torque on the threads through the arms.

Trunnion-bolt replacement

The trunnion bolt is replaced with a section of threaded rod modified as described below. Fabrication can be done with a vise, hacksaw, drill press and hand files. I used a small mill-drill.

I bought a three-foot length of 5/8"-11 chrome-moly threaded rod from MSCDirect.com, chopped two pieces long enough to pass through the casting, both arms, the newly welded nuts, then another inch of rod for a second (jam) nut.

A 1/8" hole is cross-drilled in the rod. This is grease passage from the zerk added to the casting, above, to the back side of the casting and threads.

The rod is flatted (threads removed) within the section of the rod that passes through the casting. I removed metal past the thread roots; 10 years later I realized I could have simply reduced them to half-height. This could be done with a file, precision is not required.

Somehow mark at least one end of the rod so that you know where the flat is located. An easy way is to simply file a few threads at the end flat also, enough to visually locate.

Assemble such that the hole drilled in the threaded rod aligns with the new hole and zerk fitting in the casting. The flats on each side of the rod provide the inner path for grease to flow, in an "H" pattern; along the flat in front, through the hole, along the flats in the rear. It works.

Note on the trunnion bolt and stamped arm halfs -- Assembly with the correct and original parts, trunnion bolt, each arm half, requirs more care than my assembly above. The trunnion bolt isn't a simple bolt -- the threaded portion closest to the head has a larger diameter than the other end, meaning that one arm has a larger hole than the other, and the bolt can only go in one way. This means there is a leading half (towards front of car) and a trailing half (towards the rear) and you cannot swap them. In my replacement scenario, it is assumed that you are using worn, even "bad", parts, and that these very threaded holes are ruined beyond stock use.

Note on longevity -- Upon removal from service 10 years later, there is noticable wear on the threads of the rod, that ride within the casting. There was no safety issue, and this did not affect alignment or performance. The reason is that there is so much thread contact area, the parts can't move much, relative to each other, and upper-pivot slop has less effect on alignment anyway.

Trunnion casting modification

A hole is drilled in the outward flat face of the trunnion casting, directly over the center of the bored, threaded trunnion bolt hole. The hole drilled will depend on the type of zerk fitting used; follow directions on the package. Mine were press fit but I would have preferred tapped. YMMV.

When assembled, this hole will line up with the hole in the replacement trunnion bolt, below. Here's the hole and flat alignments relative to the trunnion casting.

On assembly the rod is threaded in such that the hole in the rod aligns with the new hole and zerk fitting in the casting. The flats on each side of the rod provide the inner path for grease to flow. It works.




Steering knuckle

There's not a lot to go wrong here, just a nice casting, though see the section on the lower arm and lower trunnion for wear issues with the type 1 trunnion. The upper knuckle pivot has needle roller bearings inside the upper trunnion casting, and a thrust bearing assembly between knuckle and casting, that bears the dead weight of the car, and pivot and pot-hold impulse loads.

knuckle vertical needle roller bearing

Even the ruined parts I had had reusable needles. They are under very little load, and greased from the factory a half century ago seems to be enough. There is a zerk fitting on the back of the casting to grease them. The factory lubricating interval is adequate for these bearings. I wash mine in a solvent+oil mix, hand pack with grease for assembly.

The needle rollers are in a cage. Drive it out from the top with a 3/8" drive extention and socket. The cavity will be packed with ancient grease, you will probably have to dig it all out to discern cage from casting. Make sure the socket contacts the edge of the cage, not the rollers, and not the casting. Drive them back in the opposite way with the same socket. Don't deform it reseating it; its position inside the casting is not critical, just make sure it is slightly below flush with the face of the casting, where the thrust bearing rides.

knuckle thrust bearing

These are lubricated once at assembly, only. They wear, but seem to be durable. Replacements are often spotty, but I was able to find an inexpensive pair on Amazon in 2020. Spend the 20 minutes it takes to pack thoroughly.

PartNICE 608V
ID.878"
OD1.985" (not critical)
Height0.595" (not critical)

Grease seals

I recommend using O-rings and not bother with "correct" seals, which will be expensive anyway, and old rubber is bad rubber. The O-rings below will deform under pressure from the grease gun then return to shape, effectively sealing the moving joint. That's their only purpose, and the O-rings below were in good enough shape to reuse after disassembly. Use whatever works though.

Assembly procedure

Assembling this new design is straightforward. Bushings must be installed in each arm half first, and the nuts already welded. Loosely assemble the two arm halfs onto the pivot bar and spring bump stop/spacer, fasteners tightened. This leaves a gap at the outer end, where the trunnion casting fits.

The gap is wider than the trunnion casting. My method is to thread the new trunnion bolt (the flatted rod) into one arm half so that approximately 1/4" sticks out, inside the gap. Add two O-rings to that, hold the trunnion casting into the gap.

Stop here and measure the distance from one end of the new bolt, to the cross-drilled grease hole in the bolt. Note this distance. (This photo was taken on mockup parts, the nut not welded to the arm, because I forgot to take the photo on the installed parts!)

Center the casting in the gap by hand, then thread the new bolt into the casting. It should be within 1/16" of centered, and definitely not touching either arm half.

Run the new bolt through, add two O-rings, and catch the threads in the other arm half. (This will be easy if you indexed the nuts before welding.)

Using the measurement taken in the third step above, run the new bolt in until that measurement (the location of the cross-drilled grease hole) aligns with the zerk on the casting. Additionally, rotate the bolt so that the flats are vertical, eg. the hole is concentric with the zerk. (This photo was taken on mockup parts, the nut not welded to the arm, because I forgot to take the photo on the installed parts!)

Holding the bolt in rotational position, add a jam nut to each end of the new trunnion bolt. It is not attractive, I admit. The additional width does not interfere with tires or fit.

Here is the completed assembly installed on the car.

spacer in shock eye.jpg spacer kit from Galvins.jpg spacer kit parts.jpg spacer shock view.jpg


Shock absorber and lower-arm stiffener spacer

The front shocks on this suspension are unique to Nash and these early Ramblers. The shock has conventional stud type upper mount, but the lower mounting is of the eye type, but an unusual diameter, as far as I can tell unique to this suspension.

The lower shock mount appears to be a simple spacer that runs through the shock eye, but it is a critical component. This spacer is what prevents the lower trunnions from being turn out when you hit the brakes, a pothole, or bump a curb.

There is no "parts store" shock absorber available for this car. Replacements are available, as of this writing, from dedicated AMC suppliers. I need to emphasize, driving this car without this spacer installed correctly most definitely will ruin hard-to-find and expensive suspension components.

The two arm halfs form the traiangular lower wishbone, but it is not exactly a triangle -- it's a trapezoid, and the two "arms" of the trunnion, with their caps threaded into the outer ends of the stamped arm halfs, will skew when fore/aft pressure is applied, eg. braking. The spacer in the lower arm is the only thing stiffening the outer end of the critical lower arm. It is this lower control arm that bears all fore/aft forces of driving!

There is not a straighforward way to substitute a shock absorber on the front of this car. The problem is that the lower shock mount is a critical component . It is this bushing that stiffens the lower arm, and keeps twisting forces off the lower trunnion nuts. Leave this bushing out at your own peril -- bumping a curb, for example, will apply shearing force to the trunnion as the two arm halfs will rotate the trunnion -- the front arm will arc back pushing the front trunnion cap inward, the rear arm will push outward. These forces will elongate the threaded holes in the arms -- already thin -- and loosen the caps.

Do not drive this car without the lower arm stiffener installed

I'm not being alarmist when I say that this is a critical part. I worked on a friend's car, a recent purchase, where the previous owner had left out both the upper arm and lower arm stiffeners, and the lower arm trunnions cranked in tight to close the gap around the eye of a conventional shock. This is an invitation for the lower arm to bend backwards and invoke 'unscheduled rapid disassembly'.

He visited another AMCer with a large stock of cars and parts, turned up many suspensions, but all of them missing the spacer, with a conventional shock installed, necessitating buying new and expensive replacements from an AMC supplier. I suspect what happens is, a mechanic goes in to do a rebuild/repair, gets the car apart, assuming parts are available, finds out they are not. Without the inside knowledge of our AMC parts suppliers, find themselves stuck and make the ill-fated substitutions.

All is not lost, see below for a method to retain this critical part and still substitute a "normal" shock.

Correct shock availability

The correct shock absorber is being reproduced (as of this writing) and is available at Galvin's AMC Rambler Parts or Kanter Auto Parts. Check with the various AMC vendors.

Substituting a modern shock absorber

The fix described below has been in use on my cars for more than a decade.

The lower control arm has a pair of disused holes that provide a great opportunity to affix a standard stud type shock.

I fabricated a lower mount from 2" x 3/16" hot-rolled steel, because of the triangular shape I fitted the pieces one at a time, the bolt-tabs first, and tack welding in place, then removed for final welding. It's easy to make, and an obvious candidate for productizing. [April 2020 note: in the 13 years the 3/16" steel shows some signs of deforming, probably 1/4" would be better for the horizontal portion. Keep in mind this is in my roadster, driven hard at speed on mountain roads.)

This shifts the lower end of the shock in a couple inches, which reduces the shock's effect on spring damping slightly due the difference of moment arm and angle. I can't imagine you'd ever tell the difference, and no matter, we're not installing the original shock anyway. Here are two photos showing the new location for the shock.

Lower control arm stiffener

Correction on 09 may 2020: In 2010 I fabricated the spacer shown here (1.5" diameter, 1.475" length, the factory 9/16"-NF bolt), the length based upon measurement of the corroded spacers I had. This spacer is shorter than the new replacement from Galvin's. I suspect my measurement was wrong and Galvin's is correct. So there is probably some tolerance in it's overall length. What is certain is that the stiffener is required, and that it's length be such tat it does not cause the trunnion to bind. Previous 2010 text: I took the opportunity to add some stiffness to the lower arm. The original shock lower mount is a 1" diameter spacer; I replaced that with a 1.5" diameter spacer as shown. (Length is 1.475"). This should significantly increase lower arm stiffness.

Shock selection

With the new mounting scheme there is a reasonable choice of shocks. Using the online PDF Gabriel catalog, which in Reference F lists shock extended and collapsed lengths (in part number order, essentially random!) I found some candidate shocks from cars of similar mass. Amusingly these were later AMC products, eg. 1968 Rambler American front(82069). However these rode very harsh in my opinion, so I sought out lighters cars. These are listed in the table below, for rears as well (google may land rear shock searches here). Note that shock mounting (location, angle) determines damping force as much as the shock's characteristics.

Location Part App Extended Compressed
Front AMC 320 220058 to 63 American 14.5 9.25
Front Gabriel 81270 1964 Volvo 122 (2400 lbs), rear 17.7 10.6
Rear Gabriel 81440 1982 Toyota Starlet (1600 lbs), rear 24.6 14.59

One nice thing about these nice modular suspensions is that you can build them entirely on the bench, and install as a unit. Very convenient for doing careful work!




K-brace

The so-called K-brace (the TSM calls it the "pivot bar brace") is a critical part! Do not leave it out! I have seen cars on the road without them. I've found mine self-loosened. The TSM calls for it's bolts to be tightened to 80 ft/lbs. The bolts look like (and could even be) lug bolts; they are hard, have a conical head, and clamp the K-brace to the pivot bar casting with a 3/8" thick hard toothed bar. Not light-duty stuff.

The unibody seems to want to spread here, as many cars end up with an awful lot of shims to pull the pivot bars inward during alignment.



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