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Powerflex polyurethane bushings

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  • Powerflex polyurethane bushings

    Has anyone replaced the metalastic bushings with Powerflexs polyurethane bushings? I'm looking for information. Blatchat and the Powerflex US distributor don't have much useful info. Specifically, will these bushings affect the preload/compliance of the suspension. The stock bushings create a lot of preload (resistance) which I would like to remove. And if so, that means new springs, maybe dampers as well?. Any intel on the effects of these bushings beyond "now my car is awesomer" (per blatchat) would be greatly appreciated.

  • #2
    A reasonable thread on BC here. And a follow-on thread here would indicate a pre-load of some 24Kg from the stockers.

    I need to change mine too as I'm on the originals.:-O. As mentioned in the thread, the "change" w/ Polyflex that people notice may be down to the fact that they have new bushings.

    I'm not sure which way to go - wallet says one thing, upgradeitis (if in fact that's what Poly bushings are) says another. It's آ£92.00 for a complete set from CC (if available) vs. آ£240 for a complete set of Powerflex poly bushings. Part of the pitch w/ the Polyflex is longevity. At that price differential the stock ones could be replaced 2 1/2 times or so for a money wash, labor and PITA factor notwithstanding.

    The, or rather a, hot bone item for me is this, also available in Deutschland. I'd love to know if there's an equivalent (I have no idea what the specs are) available Over Here for less. 5 bills is a bunch.

    edit: I'm hoping that Santa will bring new shocks...er... dampers and springs this Xmas. So I'll be investigating all of the interrelationships between all of the suspension elements in the coming months. Simon at Meteormotorsports is well thought of it seems. I know Sean has spoken well of him.
    Last edited by moosetestbestanden; September 3, 2014, 07:46 AM.
    Chris
    ------------
    A day you don't go a hundred is a day wasted

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    • #3
      PM sent.

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      • #4
        As it was my thread on blatchat I will chime in here. I replaced all the front suspension bushings on my Caterham CSR this year as 2 of the original metalastic ones had worn out. I had a spare set of the originals in the garage but could not use them as replacements as I had the rude shock of discovering that certain of the CSR metalastic bushes are installed before the side skin is installed on the chassis meaning replacing the old metalastic bushes with new is not possible. So I went the powerflex option as they are much easier to install.

        So far the car has performed well. Noticeably firmer than before which is not a negative as the CSR is quite soft as standard - so quite happy there. Car handling is if anything better. It is mostly a track car now so I am yet to try it on road. I am expecting that I may only get 1-2 years driving out of the bushes before they need to be replaced - they do not have a good reputation for long life. I am lubing them monthly to try and get max life out of them. At the point of next replacement I am thinking of going to a 2 part custom delrin bush solution (using the metalastic bushes as a template) as I think that will last longer and have no adverse suspension/handling effects.
        Mike
        Caterham Seven CSR Cosworth Superlight

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        • #5
          As an add on, I bought shocks for my road Caterham from Simon at Meteor Motorsport. Top guy - very helpful, responsive and knowledgeable. We had importing issues during the shipping and he was excellent at helping to resolve. I would recommend him to anyone. As soon as my broken foot mends I am looking forward to trying out the new shocks on road.
          Mike
          Caterham Seven CSR Cosworth Superlight

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          • #6
            Originally posted by moosetestbestanden View Post
            The, or rather a, hot bone item for me is this, also available in Deutschland. I'd love to know if there's an equivalent (I have no idea what the specs are) available Over Here for less. 5 bills is a bunch.
            Chris

            If you do use the heim joints / rod ends / rosejoints a good idea is to also use a safety washer. Similar to HERE

            It is possible for the ball of the joint to push out and go over the end of the bolt with nasty results. The safety washer will at least keep your upright closer to vertical.

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            • #7
              I have used rod ends on suspension over the years. They have served me well as long as I have kept the following thoughts in mind relative to their installation in place of the standard rubber or aftermarket polyurethane bushings:
              1) Binding & Stiffness, 1. With the standard Lotus style geometries in front and rear (sway bar upper link and solid axle A-frame rear), the suspension is quite stiff. The primary reason for this is not the spring rate. It is due to binding due to the need to distort the bushings during suspension travel. You may say that this is not the case in the rear suspension due to the live axle. And you would be correct in that assessment for a pure vertical disturbance. But most all suspension disturbances are for a single wheel. And in this case wheel travel requires the bushings to distort.
              2) Wear & Tear. Bushing distortion (i.e. fatigue) and aging are the primary causes of the need for their replacement. On a frequently driven car the leading cause is fatigue.
              3) Shock loads, 1. The bushings provide reduced shock input. I.e. they reduce harshness in the disturbance input to the chassis, and hence, into your butt in the seat (then xferred to your teeth!) and hands on the steering wheel.
              4) Shock loads, 2. Spherical rod ends will increase the transmittal of shock through the chassis. This can result in unexpected consequences like fatigue or fasteners coming loose at other locations due to vibration or shock load transfer. Note: I'm not saying that this will happen. Just that it could.
              5) Binding & Stiffness, 2. Sperical rod ends may actually reduce the overall effective spring rate by eliminating binding. However if there is binding it will be hard meta-to-metal contact in the joint(s). So check for binding by moving the suspension over its entire range of travel with the springs removed. Rod ends should be installed at mid-point of angular displacement of nominal suspension travel during no load installation. Allow for 50% suspension over travel in test set up to ensure that you have adequate safety margin in event of mis-adjustment or component failure in actual use. Also note that you may still encounter some binding if you retain bushings in the dampers.
              6) Lubrication. As mentioned previously, rod ends require periodic lubrication. Without it they will wear prematurely and then fail, either by wearing out or catastrophically. Recommend using rod ends with an integral grease fitting for ease of lubrication. This also has the benefit of possibly forcing old and/or dirty lubricant out from between the joint friction surfaces.
              7) Joint retention safety washers. As noted above and mentioned in Doug's previous post, catastrophic failure is what can happen if the suspension link comes adrift from its mounting bolt. Always use a rigid washer that is larger than the bushing or rod end through-hole when the joint is secured in single shear. I.e. when the bolt head is torqued down directly against the ID of the bushing or rod end as opposed to the case where the joint is installed between the walls of a clevis. And by catastrophic failure you might want to remember Jochen Rindt at Monza. I'm not saying that the suspension failure in his crash was a rod end, but rather that he went under a guard rail as the result of a suspension failure. Something that could happen in a Seven. Not a pretty picture.
              8) Sealing. All rod ends shall have sealed covers to keep dirt and debris out as much as possible. As a reference I recommend this: Tony Rudd's Survival Rules, item #8 from 1976.
              EscondidoRon

              '62 Lotus Seven
              '84 Turbo Esprit (x2)
              '14 Evora
              '77 Esprit S1 (RIP) :(

              "A man must keep a little back shop where he can be himself without reserve. In solitude alone can he know true freedom." -Michel De Montaigne 1588

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              • #8
                I replaced the bushings of the rear suspension radius/trailing arms with ball (heim) joints long time ago. I first used self lubricated teflon composite joints but no covers. I lubricated them on and off but after maybe 10 years of use they had a bit of slack, which made it noisy/clunky but still not in danger of losing it. Recently I replaced them with better quality QA1 joints and added the rubber sealing washers. I still don't have other retaining washers because on the rear they are kind of redundant with a live axle. If you use a normal rod end for the front top suspension that is anyway a closed cup so no retaining washer is possible.

                Not sure what the part in Chris' special link does. On my car, the rod end goes into a bushing with right hand thread inside and left hand thread outside which inturn goes into the upper suspension link. That way the camber can be adjusted as precise as I want without removing anything (except loosening the jam nuts).

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                • #9
                  Originally posted by slomove View Post
                  Not sure what the part in Chris' special link does. On my car, the rod end goes into a bushing with right hand thread inside and left hand thread outside which in turn goes into the upper suspension link. That way the camber can be adjusted as precise as I want without removing anything (except loosening the jam nuts).
                  Not sure about / if there's a difference between a Birkin's & a Caterham's top wishbone spherical joint. But here's an ancient PistonHeads thread here and a coincident BC thread here.

                  Note that both involve the infamous EFA, which always meant argument about technical merit, usability etc. They were entertaining, weren't they?
                  Chris
                  ------------
                  A day you don't go a hundred is a day wasted

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                  • #10
                    Originally posted by moosetestbestanden View Post
                    Not sure about / if there's a difference between a Birkin's & a Caterham's top wishbone spherical joint. But here's an ancient PistonHeads thread here and a coincident BC thread here.

                    Note that both involve the infamous EFA, which always meant argument about technical merit, usability etc. They were entertaining, weren't they?
                    Ah, I get the idea...and remember reading about that before.
                    The old style Birkin joint that my car came with is off a FIAT128 and probably similar to the Caterham configuration. That means for camber adjustment you must either split the joint out of the upright or (much easier on my car) disconnect the two inboard suspension bolts and turn the entire upper A-arm.

                    The newer Birkins have the nice infinitely adjustable joint with the left/right-hand thread. I have it now because it came with the widetrack kit. Camber adjustment takes only a minute and 3 wrench sizes.

                    Top Joint.jpg
                    Last edited by slomove; September 8, 2014, 01:37 PM.

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                    • #11
                      I have those rose type heim joints and it sounds like a bucket of bolts going down the road. I think they're for racers who change them out every season. Going to change to some Teflon lined ones

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                      • #12
                        Update: I ordered a set of urethane bushings through the US distributor PowerflexUSA (aka Bimmerworld). Not surprisingly the US distributor is clueless about Sevens. They supplied the wrong parts. I sorted it out with the UK sales guy and have the correct parts on order. The US website has the wrong info. My advice, if you want to go this route, is buy direct from the UK or better yet Simon at Meteor Motorsports.

                        Also, I'm discovering the joys of removing old bushings. Lessons so far: (i) never buy tools from Harbor Freight. (ii) Don't do this if you are in a hurry.

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