Polyurethane strut rod bushings - ok or dangerous?

Flatback72

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Got some slightly worn strut rod rubbers which are starting to make a bit of noise, so I recently bought some polyurethane bushings the same as these from ebay:- Prothane Strut rod bushings

Since buying them I looked on the net and found lots of people saying they are dangerous because they put too much shock strain on the strut rods and can cause them to break, and only rubber bushings should be used. I've also seen quite a few mentions that there is nothing wrong with using them, and the worst that will happen is you might feel the bumps in the road a bit more. Does anybody here have any actual bad experiences with poly strut rod bushings? I get the feeling that 90 percent of the people on the net that are against them are only repeating what other people have said, and I have a hard time believing that when the company selling them says "Replace worn suspension components for better than new performance" that they are leaving out the bit that says "our parts will cause your strut rods to break and cause you to crash and die a fiery death"......

Also, I had a wheel alignment done not too long back and obviously after replacing the strut bushings I should get another alignment done. What I was wondering though is if I take an accurate measurement from the lower control arms to a fixed part of the car body before I take the strut rods out, shouldn't it mean that after the new bushings are installed that if I adjust the strut rods to duplicate the previous measurement then my alignment will stay the same so I won't need to take it to a shop for a new alignment??

 
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Qcode351mach

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Got some slightly worn strut rod rubbers which are starting to make a bit of noise, so I recently bought some polyurethane bushings the same as these from ebay:- Prothane Strut rod bushings

Since buying them I looked on the net and found lots of people saying they are dangerous because they put too much shock strain on the strut rods and can cause them to break, and only rubber bushings should be used. I've also seen quite a few mentions that there is nothing wrong with using them, and the worst that will happen is you might feel the bumps in the road a bit more. Does anybody here have any actual bad experiences with poly strut rod bushings? I get the feeling that 90 percent of the people on the net that are against them are only repeating what other people have said, and I have a hard time believing that when the company selling them says "Replace worn suspension components for better than new performance" that they are leaving out the bit that says "our parts will cause your strut rods to break and cause you to crash and die a fiery death"......

Also, I had a wheel alignment done not too long back and obviously after replacing the strut bushings I should get another alignment done. What I was wondering though is if I take an accurate measurement from the lower control arms to a fixed part of the car body before I take the strut rods out, shouldn't it mean that after the new bushings are installed that if I adjust the strut rods to duplicate the previous measurement then my alignment will stay the same so I won't need to take it to a shop for a new alignment??
I have used poly bushings on almost all my cars throughout the years..Never had a problem with anything bending or ripping out..What you may notice (if you don't lubricate with poly bushing specific lube) is creaking or squeaking over time..Here's what I put in my 72 No bushing at all http://www.streetortrack.com/Street-or-Track-Adjustable-Strut-Rods-pr-16135.html

I also installed the lower control arm camber kit..Very worthwhile investment if you want to maintain alignment settings http://www.streetortrack.com/Lower-Control-Arm-Camber-Kit-for-67-73-Mustangs-pr-24484.html You can try & take measurements to replicate your prior alignment but it's best to just have it done after you install new parts.

 

72HCODE

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i had an issue with the poly bushings on the strut rods, i had them crack and then the strut rod pulled out of the frame when i stopped suddenly then completely fell out of the strut rod cross member. I changed over to OEM rubber and never had a problem again.

the poly bushings gave the car a tighter feel but i settled for the smoother softer feel of the rubber bushings. i think a little softness in that area made my car handle more comfortably.

photo of my poly bushing failure

100_1548.jpg


100_1549.jpg


 

droptop73

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I have heard that the poly is too rigid and can cause the strut rods to fatigue and fail. I have never personally seen a set fail like that but it does seem in Mythbusters terms to be plausible. I just ordered a set of the Midolyne bushings from CJ's as the "high quality" rubber bushings from a major national 4 letter parts retailer are seriously failing.

 
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Flatback72

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Thanks for the informative replies guys.

72HCODE, those pictures you posted were enough evidence for me - I'm going to get some rubber ones instead!!

 

c9zx

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There is a middle ground choice From Global west. http://www.globalwest.net/srb-5.html

There are a higher durometer rubber. I've used them on at least 6 car with no problem and improved handling. Eaton Detroit Spring may make them as well. Both companies make great products that are exactly what the advertise.

Chuck

 

luxstang

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For what it's worth: I read on a European Mustang Forum that someone almost got himself killed when the strut rod broke due to fatigue making the car go out of control while driving quite fast on a country road. He had poly bushings and many people chimed in that it was a natural thing to happen and that the strut rods need that little flex and twist provided by the rubber bushings to dampen the blows.

Of course this is all hearsay, but I begin to see a pattern here......

As long as you don't wanna seriously race you Mustang, I'd say use rubber bushings just so you're on the safe side, even if the poly bashing might not turn out to be true.

(I edited that last sentence as originally I had written: "Use rubber on the rod to be on the safe side" but I thought I'd spare me the kinky replies!) rofl

 
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72HCODE

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i can see that happening.

here is my experience:

1 month before the above pictures, was the first test drive of my car after i completed mechanical work.

I took it on short drives to try and get the really bad issues fixed.

the above happened on the first long test drive, it was 1 week before a major ford show in my area, that would require me to drive the car 130+ miles round trip.

I started my test drive everything was fine. about 30 minutes in i started to notice my steering wheel was no longer centered when i drove, it was centered when i started. After that i noticed when slowing down i was correcting for right side pull with the wheel.

at first i thought i had Air in the brake lines and turned for home. got home jacked up the car and saw nothing was wrong under the car i couldn't figure it out, but i re-bleed the brakes again. 4 hours later went for a drive in the neighborhood again the the steering wheel was not centered and the car was pulling to one side when light braking.

then an A55HOLE blew a stop sign in front of me, and i slammed the brakes. once back on the gas i heard a Nasty 'CLANG' sound from the front end. I pushed the brakes again 'CLANG'

went back home... jacked up the car and Again i couldn't understand where the sound was coming from.

then it occurred to me to check the strut rods, that is when i discovered the driver's side strut brushing was totally gone and the strut was dangling and the passenger side was shown in the photo above.

at that point between the squeaking issue with poly and what i saw with the strut bushing failure. i switched to rubber.

zero problems after.

I can totally see how somebody can loose control of the car after a failure of the strut rod it allows the front suspension arm to float back and forth changing the caster at will. you can have a wheel make contact with frame when braking or lock up in a turn or worse cause a lower arm failure.

now After i replaced the strut bushings I did have a lower Cam bolt failure and suddenly had -10 degs of camber on one front tire i think this was more due to defective hardware but its possible the strut failure contributed to it.

personally if i drive the car on the track fine i'll take the risk with poly or switch over to a completely different suspension system, with a coil over and solid strut mount, on the road no way i'm taking the chance with poly again.

The thing with poly is its like an egg shell with a yoke inside, the outer case is a more solid plastic and the inner core is like rubber.

if the outer shell becomes cracked for what ever reason it basically spills its guts out and fails.

that is what happened to mine. the case cracked(better that then my strut rods) and the entire thing completely failed.

its impossible to see in the photos but the inner poly bushing was also cracked it just was not deformed from coming through the frame like the front one did.

i did make the ford show after all this just barely. longest drive i ever took in it to date. managed almost 15mpg :)

 

Flatback72

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Thanks for the write-up 72HCODE, certainly is an interesting (and frightening) read!

I've found a Mustang parts dealer here in Australia who is going to sell me a set of OEM rubber bushings for AU$45, and the poly ones I bought are going in the bin.

 

Bill73Ragtop

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former owner (25 yrs) of 1973 Convertible, 351c, A/C, RA
Looks like the consensus is to use the rubber. However, for what's it's worth, I installed urethane front bushings on my 73 vert back in 1995 and have driven over 25K (all kinds of roads and conditions) and have had no issues to date. Actually, all my suspension bushings are urethane (with the exception of the upper shock bushing). It was the newest product on the market back then. I used teflon tape and oil to combat he "squeak". Now there seems to be about 15 different types of material to pick from. I began seeing stories of breakage 5 - 6 years later, but I give everything a close inspection each spring and so far have seen nothing to indicate severe stress. Is this a case of passing the 50th floor on the leap off the top and everything so far is okay? I don't know.

Having just said all that I will admit to installing rubber strut bushings in my 69 vert a couple years back when I rebuilt it's suspension. But everything else is poly .

 

72HCODE

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going back 15 years I'm sure the design and material used back then was different from the made in china stuff today. This was my first attempt at using poly, I believe i kept the poly bushings on my Sway bar connection to the suspensions, but i used rubber on everything else.

I think the bigger complaint is the squeaking first and foremost it has to be the biggest complaint people give.

next is bushing failures.

if you want the best bang for the buck, install sub-frame connectors holy cow do they make a difference.

 

droptop73

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So far I have a couple of weeks on the Midolyne bushings... so far, so good.

Here's a photo of my old rubber pieces.

0430111213.jpg

 
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URUGUAYAN_FASTBACK

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going back 15 years I'm sure the design and material used back then was different from the made in china stuff today. This was my first attempt at using poly, I believe i kept the poly bushings on my Sway bar connection to the suspensions, but i used rubber on everything else.

I think the bigger complaint is the squeaking first and foremost it has to be the biggest complaint people give.

next is bushing failures.

if you want the best bang for the buck, install sub-frame connectors holy cow do they make a difference.
Hey Danny, how are you!?? you mention subframe connectors... If i get it right, those supposed to be the tubes that conects the front and rear rails...

What is the improvement of having those installed?? Is a nice option just for over powerful cars?

Thanks :p

 

verona

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I wonder what Performance Suspension Technologies would say about polygraphite.

 

MeZapU

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I broke two strut rods within two years using polyurethane strut rod bushings. Since installing the rubber ones it's been 10 years and still going. I actually prefer the rubber as it offers a smoother ride and none of the negatives.

 

vamach1

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I wonder what Performance Suspension Technologies would say about polygraphite.
I had a strut rod break while driving on the highway about 60 mph. Thankfully the only damage was my soiled underwear and I replaced both rods and the bushings after that scary experience. I think I had poly bushings (replaced a lot of bushings years ago) but I think it was just a case of years of hard driving and metal fatigue. :s

 

M Beauchamp

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Good discussion guys

I was wondering about the prothane bushings as well and couldn't grasp the problem with the strut rods.

After seeing 72Hcode's pics its clear that the durometer of the prothane is too hard and causing the strut rod to bend in moment and of course breaking at the threads.

The original design worked because the rubber was soft enough to flex before over stressing the strut rod.

This same torsional load would happen again at the ends of the sway bar.

Really the only place that the urethane would work and out preform the rubber would be at the joints that only pivot.

Thanks guys you answered my nagging questions

 

kblackav8or

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I recommend getting rid of the poly bushings and running a proper jointed aftermarket strut rod. I have a set on my 71 and they work much much better then the factory setup. A lot safer. This place has a lot of good stuff for 71-73 cars. http://streetortrack.com/. The type of strut rod kits they have are the same as what I have. I can't remember where I got mine but they are the same. I have done a lot of suspension and chassis work on my car and about the only poly parts I would use are things like shock mounts.

 

72mac1

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Thanks for the write-up 72HCODE, certainly is an interesting (and frightening) read!

I've found a Mustang parts dealer here in Australia who is going to sell me a set of OEM rubber bushings for AU$45, and the poly ones I bought are going in the bin.
Hey Bret, I scored some from PEP's Auto's here in Sydney, not sure if

you have PEP's - bit like Repco's. took in the old ones and they had them

on the shelf as they are the same as heaps of other fords from the same era,

from memory they were $3.50ea.

Cheers

Mark

 
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