Poly Bush or Standard

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Poly Bush or Standard

Postby DavieBow » Wed 05.04.2017, 21:09

Hi guys ,
i'd appreciate your thoughts and experience on this please , currently completely stripping down all the suspension front and rear for a refurb/overhall, should i replace the bushes with poly ones or stick with an original type ??
Just a bit worried the poly bushes may harden the ride up too much , so it would be nice to know who's done what and what your experiences were before i take the plunge .
Cheers
Dave
Elan SE , Mk1 Mx5, Celica GT4, Mk1 Golf Gti Cab,Vw Camper van, Daimler 250 V8, Ferrari 348
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Re: Poly Bush or Standard

Postby Simon_P » Thu 06.04.2017, 00:20

If the Rubber bushes have any life left in them leave them alone! You are looking for the metal becoming unbounded or the rubber splitting. Don't worry about a bit of scuffing on the face of the bush. Also if you have watched the YouTube video ignore the part where he says to grease the stud as it rotates - yes you copper grease the stud but the whole point is that it doesn't and shouldn't rotate. Hence you tighten the suspension at normal ride height.


Poly bushes are a poor substitute - It isn't just about the hardness and resistance to shock, The tube rotates in the plastic whereas it is bonded to the rubber so provides resistance to suspension movement, which also isn't axially alliigned due to anti dive. furthermore they tuned the rubber hardness and interleaved some of the bushes to get the suspension characteristics right you couldn't hope to replicate this with poly.

Poly may be all that is available, but don't use it unless you absolutely have to, and don't mind the extra noise.

Hardness is the least of your worries on the front, the whole point is that rock hard suspension is mounted on compliant rafts.

They could have chosen any material but they chose rubber!
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Re: Poly Bush or Standard

Postby par » Thu 06.04.2017, 00:34

I have rebuilt the rear suspension on my Elan this winter replacing all the bushes with poly type and the previous winter I rebuilt the front the previous winter replacing most of the bushes with poly so I am probably on about 80-85% new poly bushes all round. Car has been back on the road for around a month now and I cant say it feels any harsher than before but the handling is nice and tight with no noticeable knocks or bangs.

I think there is a view that there is a benefit of using the rubber bushes on the front rafts but I will leave that someone with more knowledge.

I wouldnt hesitate to go down the poly route again and dont think you need to worry about ruining the ride quality with them.
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Re: Poly Bush or Standard

Postby lotusflasherman » Thu 06.04.2017, 14:12

Simon_P wrote:If the Rubber bushes have any life left in them leave them alone! You are looking for the metal becoming unbounded or the rubber splitting. Don't worry about a bit of scuffing on the face of the bush. Also if you have watched the YouTube video ignore the part where he says to grease the stud as it rotates - yes you copper grease the stud but the whole point is that it doesn't and shouldn't rotate. Hence you tighten the suspension at normal ride height.

Poly bushes are a poor substitute - It isn't just about the hardness and resistance to shock, The tube rotates in the plastic whereas it is bonded to the rubber so provides resistance to suspension movement, which also isn't axially aligned due to anti dive. furthermore they tuned the rubber hardness and interleaved some of the bushes to get the suspension characteristics right you couldn't hope to replicate this with poly.

Poly may be all that is available, but don't use it unless you absolutely have to, and don't mind the extra noise.

Hardness is the least of your worries on the front, the whole point is that rock hard suspension is mounted on compliant rafts.

They could have chosen any material but they chose rubber!


:agree: Totally agree with everything Simon has said there about bushes, particularly the often overlooked 'tighten at ride height' for rubber bushes .. :clap: Much easier when jacked up but so wrong.

Also ... be warned that castor and camber adjustment is by various shims and plates in the front suspension and these all need to go back in exactly the same place and orientation as you found them (assuming it hasn't been cocked-up by a previous owner!) Section CE in the Service Manual is essential reading.
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