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Absolutely agree with Michael here, from past experience I would
completely avoid urethane for any car to replace original rubber bushes.
Its a pity that the correct rubber bushes are not made, but I would
still use the reproductions rather than urethane. From an engineering
standpoint urethane has a totally different way of operating to what the
car was originally designed for, stretching rubber fixed against steel
surfaces is not the same as rotating urethane on a pin. Has anyone ever
asked any of the urethane bush manufacturers if their products are
approved by current auto manufacturers, or if they will accept liability
for any damage they will cause? I would prefer to stay with a product
that is as close as possible to the original specification. In closing,
enlighten me, do any current auto manufacturers use urethane as their
standard suspension bush?
Cheers
Larry Varley
On 22/10/2015 7:08 AM, Michael Salter wrote:
> Bob,
> I suspect that I'm not telling you anything that you don't already
> know here BUT:
> I think the critical point is that the original suspension bushes work
> in the same way that rubber engine mounts are designed to work. The
> steel mounting plates (or in the case of mounts steel tubes) are
> rigidly attached to parts that move relative to each other and that
> movement is accommodated by the flexing of the rubber medium bonded to
> each plate.
> The plastic bushes work more like bearings in that the rotational
> movement is accommodated by rotation of the bolt (shaft) within the
> bush (bearing). All very well while you are flying straight and level.
> The problem, as I see it, is that when angular displacement is
> required, as in body roll, the plastic bushes must distort and as the
> plastic is by necessity relatively rigid, when compared to the
> original rubber, the loads imparted to the mounting points will be
> substantially higher than that for which they were designed.
> Maybe you will get away with it, maybe you won't., I just don't want
> to be passing you in the opposite direction if you don't!!!!
> Michael S
> BN1 #174 (All rubber bushes :-))
>
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Absolutely agree with Michael here, from past experience I would
completely avoid urethane for any car to replace original rubber
bushes. Its a pity that the correct rubber bushes are not made, but
I would still use the reproductions rather than urethane. From an
engineering standpoint urethane has a totally different way of
operating to what the car was originally designed for, stretching
rubber fixed against steel surfaces is not the same as rotating
urethane on a pin. Has anyone ever asked any of the urethane bush
manufacturers if their products are approved by current auto
manufacturers, or if they will accept liability for any damage they
will cause? I would prefer to stay with a product that is as close
as possible to the original specification. In closing, enlighten me,
do any current auto manufacturers use urethane as their standard
suspension bush?<br>
Cheers<br>
Larry Varley <br>
<br>
<div class="moz-cite-prefix">On 22/10/2015 7:08 AM, Michael Salter
wrote:<br>
</div>
<blockquote
cite="mid:CAB3i7LJq-3GSU5VDcXcP03aKzzZ6vxXcu6Xv0U9-h7an6rxB1g@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_default" style="font-family:comic sans
ms,sans-serif;font-size:small">Bob, <br>
I suspect that I'm not telling you anything that you don't
already know here BUT:<br>
I think the critical point is that the original suspension
bushes work in the same way that rubber engine mounts are
designed to work. The steel mounting plates (or in the case of
mounts steel tubes) are rigidly attached to parts that move
relative to each other and that movement is accommodated by
the flexing of the rubber medium bonded to each plate.<br>
</div>
<div class="gmail_default" style="font-family:comic sans
ms,sans-serif;font-size:small">The plastic bushes work more
like bearings in that the rotational movement is accommodated
by rotation of the bolt (shaft) within the bush (bearing). All
very well while you are flying straight and level.<br>
</div>
<div class="gmail_default" style="font-family:comic sans
ms,sans-serif;font-size:small">The problem, as I see it, is
that when angular displacement is required, as in body roll,
the plastic bushes must distort and as the plastic is by
necessity relatively rigid, when compared to the original
rubber, the loads imparted to the mounting points will be
substantially higher than that for which they were designed. <br>
</div>
<div class="gmail_default" style="font-family:comic sans
ms,sans-serif;font-size:small">Maybe you will get away with
it, maybe you won't., I just don't want to be passing you in
the opposite direction if you don't!!!!<br>
</div>
<div class="gmail_default" style="font-family:comic sans
ms,sans-serif;font-size:small">Michael S<br>
</div>
<div class="gmail_default" style="font-family:comic sans
ms,sans-serif;font-size:small">BN1 #174 (All rubber bushes
:-))<br>
</div>
</div>
<div class="gmail_extra"><br>
</div>
</blockquote>
<br>
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