Replaced failed strutrod poly-bushing today - Took video of working suspension

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BigBlockMopar

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Just some driving around near my garage.
Mostly flat roads with a few speedbumps halfway the clip.
At 17:22 (videotime) I do some firm braketests. See strutrod in action at the right of the screen where the bushing gets compressed.
I didn't think it would be compressed that much but was wrong. Thinking of making larger bushings.

 
Is that the kind of strut rod bushing with the metal sleeve between them? Or not? The metal bushing makes a difference on how stiff they are

If you want stiffer bushings just get poly ones. They're cheap enough. Search for Energy Suspension 57109G and check those out, they're poly with a metal sleeve.

**as a related side note I've always wondering how good those QA1 adjustable strut rods are.
 
The failed bushing was a polyurethane bushing. 2-part with metal sleeve inside.
Since I needed to find out was what causing the "pulling when braking" on my car, first thing I checked was the strutrod bushing.
The front bushing was missing and only a tiny ring was left.
I had to get my car on the road again so I took a pair of polyurethane front leafspring bushings and made new strutrod bushing out of them on my lathe.
 
Totally failed pass.side bushing on the right,
bushing on the left is driver.side and starting to fail / tearing from the center.

IMG_5765.jpg



More pics on my site:
1973 Dodge Dart – Strutrod bushing repair
 
I've done a couple of poly front ends.
All poly except for that one.
I was kind of worried about it not compressing like rubber does.
 
Why would you be worried it wouldn't compress?
It actually shouldn't compress (much).
They prevent the lower control arm from moving/angling rearward during braking and mess up the wheel alignment.
 
How many miles on the failed bushings?

I think you know that your custom bushings aren't a long term solution. The flexing you see with suspension travel is necessary with the solid strut rod, the LCA end has to move in an arc. The fore/aft movement with braking seems excessive, but really there is a decent amount of flex in the stock rubber bushings.

I think the big deal is why the other poly bushings failed. LCA pins are tight and torqued properly? What LCA bushings are in there? Was there any binding in the range of motion of the LCA with that strut rod length? How compressed were the original poly bushings with the strut rod nut tightened?

This is why I use adjustable strut rods. No guessing if the strut rod is the right length or if there's any binding in the LCA's range of motion, set it so there's no binding and it's taken care of. The adjustable strut rods are solid mounted, so, no fore/aft movement of the LCA because of strut rod bushing compression, just articulation.
 
That's wild that a poly bushing with metal sleeve failed like that, and that badly

What brand was it? Where did you purchase them?
 
These bushings have been on the car for about 6 years.
Daily driven.

I didn't mount them myself, they where on the car when I bought it.
But the car had not been driven since they where installed. All suspension bushings where new at the time.
LCA's have polybushings too. They appear in good shape what I can see, no play in LCA either.

Didn't measure compression distance but I did look at that to decide if maybe the sleeve was too short perhaps, putting too much force on the bushings.
I made the new pair of front strut bushings because I needed the car on the road again that day.

If you look at the left bushing in the pic, you can just make out it's starting to tear near the center.
I tend to think the strut rod was pulling the center out from these bushings, tearing off the rest of it.
Perhaps the edge of the strut-hole on the K-member was too sharp (?) causing it to cut into the bushing?
But I would think more of these failures would show up.
The K-member has been powder coated also 6 years ago.

The 'new' bushings have the same contact patch as the previous bushings had.
Only thing I did different now is I mounted the large washers as a 'cup' to the bushing (like the factory ones), and not as a 'dish'.

Had I known upfront the strutrod still managed to compress the bushing that much during hard braking, I would turned larger discs on the lathe from a piece of round polyurethane I've got.

IMG_5772-e1503269718957.jpg
 
Some lubrication would help, don't be afraid to slather the contact areas with grease. Poly bushings are way stiffer than rubber and need to slide a little instead of squishing, grease will keep them moving smoothly.
 
These bushings have been on the car for about 6 years.
Daily driven.

I didn't mount them myself, they where on the car when I bought it.
But the car had not been driven since they where installed. All suspension bushings where new at the time.
LCA's have polybushings too. They appear in good shape what I can see, no play in LCA either.

Didn't measure compression distance but I did look at that to decide if maybe the sleeve was too short perhaps, putting too much force on the bushings.
I made the new pair of front strut bushings because I needed the car on the road again that day.

If you look at the left bushing in the pic, you can just make out it's starting to tear near the center.
I tend to think the strut rod was pulling the center out from these bushings, tearing off the rest of it.
Perhaps the edge of the strut-hole on the K-member was too sharp (?) causing it to cut into the bushing?
But I would think more of these failures would show up.
The K-member has been powder coated also 6 years ago.

The 'new' bushings have the same contact patch as the previous bushings had.
Only thing I did different now is I mounted the large washers as a 'cup' to the bushing (like the factory ones), and not as a 'dish'.

Had I known upfront the strutrod still managed to compress the bushing that much during hard braking, I would turned larger discs on the lathe from a piece of round polyurethane I've got.

View attachment 1715084464

The problem I have with the poly bushings is that they list the same kits for both the 67-72 and the 73-76 strut rods. And the factory used different bushings and different length strut rods for the 73+ cars. So no matter what, the energy suspension and prothane bushings have to be wrong for at least one of those applications, because the strut rods are different lengths. I know guys have needed to cut down the poly bushings to get them to work on the 67-72 strut rods, but that doesn't mean they're the right size for thr 73+ cars either. I honestly think most people either use the OE style rubber bushings or use adjustable strut rods.

Polyurethane is definitely tougher for compression, but it will cut against a sharp edge, so there might be something to that too. To me the bushings you made don't look compressed enough at rest, the bushings should be under compression with the washers and that would reduce the fore/aft movement. Of course it could also make the strut rod functionally too short and cause the LCA's to bind. But you don't have much choice there, they have to be tight enough to compress the bushings fairly substantially and the length is just what you get.
 
i have never been a fan of those hard plastic pieces..they just can't give the torsional movement required.
...many of them just crack and come apart.
 
i have never been a fan of those hard plastic pieces..they just can't give the torsional movement required.
...many of them just crack and come apart.

First set I've seen fail. I don't like the original strut rods period, all the rubber strut rod bushings I've seen have been totally shot too. And neither actually allows you to set the strut rod length your car actually needs.

The poly and delrin bushings work great at the other bushing locations, better than rubber does. You just have to recognize it's a different material and make the appropriate adjustments.
 
original rubber bushings do not move and are designed to provide some torsional resistance.Aren't some of the poly bushings lubricated so they move freely? That would allow the moving ones to last longer.
I have seen the little anti sway bar bushings cracked after a couple years though.
 
original rubber bushings do not move and are designed to provide some torsional resistance.Aren't some of the poly bushings lubricated so they move freely? That would allow the moving ones to last longer.
I have seen the little anti sway bar bushings cracked after a couple years though.

Well since the strut rod bushings don't carry any torsional loads I'm assuming you're talking about the LCA bushings now?

In which case, I really don't understand why you think any of that is an advantage. Torsional resistance at the LCA bushing means the suspension isn't moving freely. But that's a marginal claim anyway, since you know that you can ruin the stock bushings just by tightening the LCA pins with the suspension extended and then sitting the car down to ride height. Think about that. The only "torsional resistance" the stock bushings offer is the shear strength of the rubber, which is slightly more than nothing. It just happens to be less than the surface friction that holds the rubber in the inner and outer bushing shells so the bushings tear before the shells spin in the bushing. It's not an advantage. Yes, most of the poly LCA bushings don't have an inner shell, so the bushing rides on the pin and you lubricate the pin and bushing so the LCA can move freely. That's a better set up for the suspension, you just have to more tightly control the length of the strut rod so the LCA doesn't move fore/aft on the pin. But that doesn't mean the rubber bushings didn't allow that, they just had a bunch of rubber at the LCA bushing and at the strut rod so that the length of the strut rod was less important, the suspension just moved around and the rubber squished about and allowed it. The poly bushings resist compression more, so the tolerances have to be more accurate to put everything in the right place.

If your sway bar bushings are cracking after a few years, buy better bushings. Or maybe lubricate them better and don't over tighten the mounts and compress them so much. I haven't had that issue with any of the poly bushings I've been running. The poly LCA bushings I just pulled out of my Duster after close to 12k miles look brand new, I just swapped them for Delrin.
 
Would this condition cause a noticeable ''clunk'' when going over a speed bump or small pot hole?
If so, my car does that and i suspect that the rubber bushings that i have in my strut rods are for an older '72 and down instead of a '73 and up.
What's the best way to check this?
BTW, my car is a '74 Dart Sport with the correct '73 and up front suspension and k-member. All of the suspension is rebuilt with new parts and factory style rubber bushings throughout. The only thing suspect are if the strut rod bushings are the correct ones.
I know that the strut rod bushings are tight when sitting on the tires with the weight on them. The car has about 1500 miles on it now since the rebuild, and the condition doesn't seem to be getting worse.
Other than that, the car drives fine and i may add, that i didn't order the parts or put that part of the front suspension together myself, so i don't know if the bushings are for the proper year and application.
I don't intend to hijack the thread, it's just a point of discussion that many might find interesting and relevant to their cars............
BTW, nice video footage!
 
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If the bushing is completely gone then the metal strutrod can knock/vibrate against the K-member. But the noise would be more constant during driving.
But a one should also inspect the ball joint in the UCA. This is a usually less loaded part that gets worked and possible play becomes noticable with larger suspension movements.

I've coated the fresh poly-bushings with ARP grey molycote grease. The shiny line between bushing and K-member is the grease.

I took notice when torquing the lock nuts if the LCA got pulled forward or not. Couldn't notice a difference so I suspect the bushings where the correct thickness.
I did make the fresh bushings 1mm thicker than the 'old', intact one that I removed.
Also decided to mount the large washers with the 'cup' side to the bushing now, thinking it would keep/grab/hold/ the bushing together a bit more. I know the washers are ment to be installed with the convex curve to the bushings to prevent the swivel-movements and cause bending/breakage of the strutrod-threads.
 
i didn't say which performed better only that i have seen the hard plastic ones deformed or cracked and that they cannot provide any torsional resistance,or compression.Which performs better i can't say because i have never used the plastic ones but i think o.e. rubber are more durable.
The strut and sway bar bushings allow movement by compressing the rubber and the control arm bushings add some torsional resistance because they are vulcanized and fixed, that's the way the factory designed them.Tightening them on jack stands will indeed cause them to be permanently deformed when the suspension is loaded.
 
Would this condition cause a noticeable ''clunk'' when going over a speed bump or small pot hole?
If so, my car does that and i suspect that the rubber bushings that i have in my strut rods are for an older '72 and down instead of a '73 and up.
What's the best way to check this?
BTW, my car is a '74 Dart Sport with the correct '73 and up front suspension and k-member. All of the suspension is rebuilt with new parts and factory style rubber bushings throughout. The only thing suspect are if the strut rod bushings are the correct ones.
I know that the strut rod bushings are tight when sitting on the tires with the weight on them. The car has about 1500 miles on it now since the rebuild, and the condition doesn't seem to be getting worse.
Other than that, the car drives fine and i may add, that i didn't order the parts or put that part of the front suspension together myself, so i don't know if the bushings are for the proper year and application.
I don't intend to hijack the thread, it's just a point of discussion that many might find interesting and relevant to their cars............
BTW, nice video footage!

It could be, if the rubber is worn out or too thin it could be allowing the strut rod washers to contact the K-frame under certain conditions. But a clunk in those situations could also be almost anything in the suspension or even parts of the steering. You'd definitely have to investigate further.

If the bushing is completely gone then the metal strutrod can knock/vibrate against the K-member. But the noise would be more constant during driving.
But a one should also inspect the ball joint in the UCA. This is a usually less loaded part that gets worked and possible play becomes noticable with larger suspension movements.

I've coated the fresh poly-bushings with ARP grey molycote grease. The shiny line between bushing and K-member is the grease.

I took notice when torquing the lock nuts if the LCA got pulled forward or not. Couldn't notice a difference so I suspect the bushings where the correct thickness.
I did make the fresh bushings 1mm thicker than the 'old', intact one that I removed.
Also decided to mount the large washers with the 'cup' side to the bushing now, thinking it would keep/grab/hold/ the bushing together a bit more. I know the washers are ment to be installed with the convex curve to the bushings to prevent the swivel-movements and cause bending/breakage of the strutrod-threads.

Ideally you'd want the LCA to be perpendicular to the frame and the LCA bushing all the way up against the shoulder on the LCA pin. You can pull a little tension on the LCA without causing binding, just enough to keep the LCA and bushings tight against the shoulder of the pin. Without angling the LCA or putting the bushing in a bind of course. With a non-adjustable strut rod though you pretty much just get what you get. The washer has to be tight to the bushing and the bushing to the K frame, you can pull a little more length out of the strut rod by tightening the strut rod nut further to compress the bushings, but obviously you don't want to overdo that.

i didn't say which performed better only that i have seen the hard plastic ones deformed or cracked and that they cannot provide any torsional resistance,or compression.Which performs better i can't say because i have never used the plastic ones but i think o.e. rubber are more durable.
The strut and sway bar bushings allow movement by compressing the rubber and the control arm bushings add some torsional resistance because they are vulcanized and fixed, that's the way the factory designed them.Tightening them on jack stands will indeed cause them to be permanently deformed when the suspension is loaded.

Ugh. First, none of the bushings are "plastic". None of them. There are polyurethane bushings, polygraphite bushings, Delrin bushings, and of course the OE rubber bushings that I'm aware of. None of those are "plastic", and they all have different properties in regard to compressibility, durability, and elasticity. If you can't tell the difference between polyurethane and "plastic", you're probably not too well versed on their different properties either.

Second, I don't think you have a good idea of what torsional or compression forces are as they relate to the suspension. Because you don't want torsional resistance in any of your suspension bushings, it's a bad thing. Torsional resistance in the LCA bushings slows your suspensions response and keeps your suspension from moving freely. Same for the sway bars. And since polyurethane has higher a compression resistance than rubber by a long shot, I don't really understand at all what you're trying to say. The best case scenario at the sway bar bushings and the LCA bushings is the respective suspension parts moving without having the bushings resist or slow their movement. Now, harder bushings will transmit more suspension forces to the chassis and can add some harshness to the ride quality, but if your shocks and torsion bars are well matched that shouldn't be an issue. The softer the bushings are the more sluggish and vague the suspension response will be. And the rubber bushings are not more durable. They're more elastic, but they're softer, less resistance to cuts and tearing than the poly bushings are (just try and cut up a set of poly bushings!) That doesn't mean the poly bushings can't be damaged, but rubber bushings of the same shape would be damaged even faster. The strut rod bushings though are not the same shape, and you do have to consider the different properties of the different materials in those situations. Which I don't think is always done by the manufacturers, and why you get generic parts. Which is why I especially don't like the poly strut rod bushings that are out there, because they're generic for the whole A-body year range, which makes them the wrong size for at least half of the year range, if not everything.

And finally, no, the rubber bushings to not add any appreciable torsional resistance. When they work within their elastic range (which is what they're doing if installed properly) they have very little resistance at all. When they exceed their elastic range, they tear almost immediately. And since their elastic range is fairly small, you have to tighten everything with the bushing and suspension in the center of the available suspension travel, otherwise they'll tear. Not deform, tear. Ruining the bushing entirely. I added that they need to be centered in their range of travel because if you have a significantly lowered car and torsion bars that are too small, you could still ruin the OE bushings even if you tighten them at ride height, because ride height is at one end of the range of travel. And this wasn't something that the factory designed into the bushing. It's a side effect of the materials used, not an intended result. They did take advantage of the soft rubber bushings though, because all that movement at the bushings allowed the suspension tolerances to be fairly loose. So you could get away with things like fixed length strut rods to begin with. And the materials were just what was available and cost effective at the time, not necessarily what was best for performance.
 
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you are correct..when removing these cracked or torn used bushings i don't know what they but they are hard and usually red or black and not very old.
Also i have taken apart many old front suspensions and found some of the original rubber bushings cracked but still doing their job after maybe 40 or 50 years.
 
Also i have taken apart many old front suspensions and found some of the original rubber bushings cracked but still doing their job after maybe 40 or 50 years.

While I don't doubt that it's possible, that's never been my experience personally. I've actually had the LCA's fall off the pins on a couple of my cars because the LCA bushings were just totally gone. I mean, I only have a handful of mopars. And I've only pulled suspension parts off a handful more at the local wrecking yards, plus some more I didn't mess with because they were C-bodies or I already had enough parts. So probably a bit less than a couple dozen cars all totaled up. But so far I've yet to find a car where the LCA bushings were in good enough shape to run without replacing, and that's on cars with as little as 80k original miles. They've ranged from worn out to almost completely missing. My EL5 GT, with only 81k original miles, had wiped out one of the bushings so badly that the pin was riding on the inner shell of the bushing. When I took that one apart the LCA just fell off the pin when I pulled the torsion bar. But I don't know the histories of any of those cars really, and you can ruin a set of brand new rubber bushings pretty easily just by tightening the suspension parts incorrectly.

When I pulled the poly bushings on my Duster last week to replace them with my new tubular LCA's and Delrin bushings the poly LCA bushings looked brand new with 12k miles on them, like I'd installed them yesterday. But I know they can be ruined by improper installation too (like anything), it just takes a little more work.
 
Regarding K-member strength...

Reviewing the video-clip; at 3:40 in the clip (17h20m50s videotime), I'm doing a few quick left/right/left/right steering movements.
Besides the light up&down play in the swaybar bushing, I also noticed some K-member flexing where the swaybar bushings are mounted to the K-member.

During the entire clip I do see some occassional overal movements but I think most are due to the vibrations and the refresh rate of the camera when it encounters some vibrations through its mounting. The camera was mounted to the fender strut.
(This K-member has not been reinforced, except for the steering box mounting pad.)
 
I think I see what you're talking about. The sway bar mounts are just bolted to the outer flanges of the K member, if you haven't seam welded the K there will be some flex there. Even with a seam welded k I would expect some flex there, I suppose you could further gusset those mounting points.

What sway bar/bracket is that?
 
The K-member is not reinforced at all unfortunatly.
It was nicely powder coated when I bought the car.
I just beefed up the steering mount pad which gave a slight noticable improvement.

I might be looking into welding some gussets to the flanges in the area of the swaybar mounts.

It's a Hellwig swaybar.
Here it is some 5 years ago when it was brand new and just installed;

20120311-73Dart-Swaybar-IMG_1828.jpg
 
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