Polyurethane or Rubber

Suspension, Steering and Chassis

  1. George Lawicki

    George Lawicki Well-Known Member

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    Hi guys,
    I am doing a complete rebuild of the front suspension on my 74 Dart. Iam having a tough time deciding on polyurethane or rubber. I know what characteristics each has and the pros and cons So I was wondering if anyone is running either of these and what they thought. On a side note, I live in Cleveland POT HOLEs rough roads. Not doing any racing yet or anything just looking for what will work best for riding around town.
     
  2. 72Dart6pack

    72Dart6pack Harder Better Faster Stronger.

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    What does your budget dictate? All stock parts in my photo.

    20170704_220653.jpg
     
  3. George Lawicki

    George Lawicki Well-Known Member

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    I can afford either or. I am keeping the suspension stock except the bushings either rubber or polyurethane
     
  4. KosmicKuda

    KosmicKuda FABO Gold Member FABO Gold Member

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    Hmmm. I think I went to H.S. with Bruce. Im also familiar with the green T-bucket. If you go to Laurel Square then you've seen my junk.

    Everybody will have their own opinion but I have 2 driveable a-bodies, a 64 and a 68. I completely rebuilt the 68 suspension and used no poly in the front end except sway bar bushings and links. My theory on front ends is if the ball joints are good I see no reason to replace them. I use the Moog offset bushings in the UCAs to get 2* positive caster. Dont forget to replace the LCA byshings and its also good to upsize the T-bars. I use poly in the rear spring shackles as it helps on that end.

    I have new parts and disc brakes to do the 64 front end soon but the 68 drives very well and tracks like a freight train. My cars are drivers and on the streets several times a week during the summer but both cars are temporarily off the road for up grades or I'd give you a ride.
     
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    • CudaKid16

      CudaKid16 Member

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      you have poly on the 68??
       
    • yellow rose

      yellow rose Overnight Sensation FABO Gold Member

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      If you are talking about using Poly on the LCA bushings there are several good threads about that here.

      IMO, if you go that way, spend the money on adjustable struts rods. When I first rebuilt my front end I went Poly and OE strut rods. When I updated the front end I used Poly again, but I used adjustable strut rods.

      At this point I think I’d use adjustable strut rods no matter what bushing materiel I was using.

      Several others on here can explain much better why the ASR’s are better.
       
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      • autoxcuda

        autoxcuda Well-Known Member

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        For cruiser with nice ride, less rattles, stock springs...

        rubber bushings:
        • LCA
        • UCA offset K7103 installed for max positive caster
        • strut rod problem solver style
        • Leaf spring eye & shackle
        poly
        • sway bar end links
        • Frame bushings

        Consider:
        • 1 1/8” dia sway bar
        • Bilstein RCD shock
        • 2nd choice shocks HD Monroe
        • Rear sway bar

        that’s what I have in my 68 Dart Conv. Convertible’s always rattle, twist, translate noise, etc more than their sedan/hardtop versions.
         
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        • RAT ROD AL

          RAT ROD AL I know just enough to be dangerous FABO Gold Member

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          I have an un used rear sway bar that came with poly bushings still in the box. May have been 3 -4 years old. Bushings all just crumbled into pieces in the box. I wouldn't put them on anything I own.
           
        • QuickDart360

          QuickDart360 Well-Known Member

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          I went poly all the way. No complaints. Headers and Flowmaster make more noise/sound than any squeaks from suspension. Quite frankly not much noise comes from front end! I think most people that complain about squeaks need to just give up muscle cars and drive a Lexus or other luxury car to have an all quiet ride. (Boring in my humble opinion!)
           
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          • autoxcuda

            autoxcuda Well-Known Member

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            I have rear poly bushings in my Barracuda since 1993. Strut rods since ‘95. LCA since ‘97

            mine were Energy Suspension brand

            When we put hotchkis kit on we reused the poly LCA’s... still good. So was the other stuff.

            when I just changed the poly leaf bushings and no other changes... there was slight but noticeable increased resonance from trunk area.
             
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            • fklskv

              fklskv Well-Known Member

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              I put a set of polys in a BMW I had. Took them right back out. Rubber all the way for me. IMHO.
               
            • PST

              PST Marketing Manager FABO Vendor

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              If your primary use is cruising stick with rubber and a quality set of shocks. It will provide you with a comfortable overall ride quality. If you are looking for a more modern feel that is firm but not harsh go with the polygraphite kits. We offer front end kit in either rubber or polygraphite if you are interested. Also as a member of the forum we offer a discount on orders of $200 or more and free shipping within the US 48 states.

              Thanks
              James From
              PST
               
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              • KosmicKuda

                KosmicKuda FABO Gold Member FABO Gold Member

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                The only poly I used was front sway bar bushings and links. And rear shackle bushings.
                Everything else is new rubber, not rotted or beat out of shape.

                Pretty much what Autoxcuda says in post #7 is what I did roughly based on Tom Condran's book. I too used the Moog problem solver strut rod bushings. Of course this was 10 yrs ago when Moog was good stuff. Now a lot of people say their quality has degraded with the move to cheaper off shore sourcing.

                The Moog rubber LCA bushings are such thin wall there is not much there to distort and change the pivot point. In my opinion, unless you are autocrossing or something similar, the little bit of compression available won't make a noticeable difference. The pivot points at the LCA, UCA and strut rods are what transmit the impact loading to the frame and the rubber adds a little compliance when hitting pot holes.

                I kinda laugh (ha) when The CA, TX and and AZ guys complain about their roads. They don't go through the annual freeze-thaw cycles that crack the pavement allowing water to get in there. When the road freezes again, the trapped water freezes and expands with massive force and bang, pothole obstacle course.
                 
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                • 66fs

                  66fs FABO Gold Member FABO Gold Member

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                  I've had both, since you had to replace the polyurethane in your old stock shells, somewhere in the late 70's. But I also put 230,000 street miles on an ACR Neon. I only use rubber now with polygraphite in sway bar links only.
                   
                • JoePole1

                  JoePole1 A dude in a B body FABO Gold Member

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                  I am running full Poly bushings from PST front and rear except on shocks. They are in a B-Body for the past 10 years. Tubular UCA's, Heavy Hellwig sway bars and frame connectors. Handles awesome. Zero issues. Set up for handling so it is a little stiff but also have low profile 18's all around.

                  Edit: Oh yeah. I am in NY with possibly the crappiest roads in the country.
                   
                  Last edited: Apr 15, 2021
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                  • dibbons

                    dibbons Well-Known Member

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                    It doesn't need to freeze to find potholes. Here in Baja California it has never dropped to freezing temperatures in all the history of weather data. However, when it rains, downtown paved roads are chuck full of potholes the following week.

                    Maybe the fact there are no storm drains here compounds the problem? I don't know much about the science of potholes except they are a pain in the ass. Many of the downtown streets are now being re-paved in concrete, which seems to eliminated the pothole problem, at least for awhile.
                     
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                    • 72bluNblu

                      72bluNblu FABO Gold Member FABO Gold Member

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                      If you don’t want to install adjustable strut rods and greaseable pivot pins you should stick to rubber.

                      Poly is great, but works differently than stock and it works much better if it’s paired with some other parts. Namely, greaseable LCA pivot pins and adjustable strut rods. Especially the greaseable pins.

                      Suspension parts all have to work together. So if you’re keeping everything else stock, keep the stock bushings. If you’re upgrading and using aftermarket suspension parts, poly and Delrin bushings work better. I switched my poly LCA bushings for a set of Delrin LCA bushings from Bergman Autocraft about 15k miles ago. When the poly bushings came out they look exactly like the day I installed them, despite having over 10k miles on them. Do it right and they’ll last for decades.

                      If you toss all poly bushings into the stock suspension you’ll just be one of those guys on here that say their poly bushings started squeaking and wore out. Poly shouldn’t squeak, if it does then it needs to be lubricated. Simple as that. Anything else is improper maintenance.


                      I kinda laugh when Midwesterner’s show how ignorant they are about anything outside the Midwest by saying things like there aren’t annual freeze and thaw cycles in California. California gets more snow than Ohio bud, it’s a big place. There are places in California that get 600-700” of snow annually.

                      List of snowiest places in the United States by state - Wikipedia
                       
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                      • Scody21

                        Scody21 Just send it

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                        Yep, should see the roads in Portland, OR. Don’t get much snow here, but get a shit ton of frozen rain and frozen nights. The roads are some of the worst...
                         
                      • 72bluNblu

                        72bluNblu FABO Gold Member FABO Gold Member

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                        Yeah I just think it’s hilarious when guys say stuff like that. Hey, how many ski resorts are there in Ohio? How many of the highest peaks in the lower 48 states are in Ohio? Huh, like none. Weird.

                        I mean, I’m sure the roads in Ohio suck, I don’t doubt it. I’ve been to Detroit, I get it, I’ve seen Midwest roads in the spring. But there are plenty of terrible roads here too, and more miles of them too.
                         
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                        • George Lawicki

                          George Lawicki Well-Known Member

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                          SOOO enough about roads.. I am planning on putting a 360 in the Dart what are good torsion bars to use?
                           
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                          • 72bluNblu

                            72bluNblu FABO Gold Member FABO Gold Member

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                            1.03” bars from PST are a good all around choice
                             
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                            • Scody21

                              Scody21 Just send it

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                              What style of driving are you wanting from your car? Smaller for weight transfer ie drag racing, thicker for auto-x / heavy road driving and as 72blu said 1.03 is a great all around bar...
                               
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                              • Kern Dog

                                Kern Dog FABO Gold Member FABO Gold Member

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                                I have used BOTH in different cars as well as a little of each in different cars.
                                A car with full urethane does transmit more vibration. That is certain. The car may have had better steering response as compared to an all rubber bushing car but you do pay for that in reduced comfort.
                                I have a '70 Charger with rubber LCA bushings, rubber offset UCA bushings but urethane strut rod and sway bar bushings. The torsion bars are huge but the car still rides and drives well. No harshness, no vibrations through the steering wheel.
                                In the late 90s, many companies popped up to offer suspension rebuild kits. FABO sponsor PST is still around but I haven't heard from Energy Suspension or Just suspension. THey all offered rubber or urethane kits.
                                Something else....
                                If your car is worn out, ANY new bushing is going to be an improvement. A full replacement in rubber will tighten up the feel to that of an original car.
                                When the suspension parts suppliers used to promote the urethane option in their ads, I bought into it. I had full urethane but it was too harsh for me. I'm not a tenderfoot either. I've driven some rough cars. I wanted this one to handle well and not buzz and rattle so I took out the urethane LCA and UCA bushings.
                                It is also the same advertising tactic that the coil over suspension companies use...."Better handling, tighter steering, less weight"....Well, your $5500 front end handles better than my 50 year old worn out stuff? Really? Your manual steering rack weighs less than my power steering setup? Really ??
                                 
                                Last edited: Apr 15, 2021
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                                • MopaR&D

                                  MopaR&D Nerd Member

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                                  Definitely a good move going with 1.03" torsion bars... I have 1" bars I bought back when Just Suspension sold them and they were a huge improvement over the stock 318 bars and that was back when I had 15" Rallyes with 60-series tires. Now I'm looking to step up to like a 1.14" from the massive grip of my recent wheel/tire upgrade.

                                  I also agree on keeping most of the front end bushings rubber for your intended purpose. Poly and others are great, I have poly LCA bushings on my car but like others said they kind of need the adjustable strut rods to work the best. The rest of the suspension isn't going to be pushed hard enough either to notice a difference with polyurethane bushings IMO.
                                   
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