> > Matthew Gnagy wrote:
> >
> > I believe you have it backwards. Nylatron, I believe, is harder than
> > polyurethane.
> Aron Travis replied:
>
> Could be! Both very hard none the less. Nylatron being more brittle
> seems to indicate more hardness too....
> When I run across a reference I'll post the correct answer.
Could be either!! A couple of years ago, Mark Sayer, who owns Performance
Engineering (formerly a Brit Car race shop, but now mostly Nisson Z cars and
510s) wrote an article for Grassroots Motorsports Magazine about suspension
bushings. Despite all the nasty things people have said about Mark's business
acumen, he is a very knowledgeable engineering type. All of the following
(other
than my snips and parenthetical insertions, for clarity) is quoted from his
article:
Polyurethanes . . . are available in a (wide) range of hardnesses . . . (some)
so hard they can shatter under sharp impact . . . poly is impervious to most
automotive chemicals as well as UV radiation, so it does not deteriorate as
rubber will.
In most automotive bushing applications, poly is used in compounds which are so
hard they must be considered a hard plastic rather than an elastomeric (like
rubber). This means that poly bushings compensate for control arm movement by
means of a rotational sliding action, rather than rotational shear.
Consequently . . . (they) must be lubricated, and require a close tolerance
fit. If poly is not regularly lubricated, it will first start to squeak and
will eventually rip itself apart.Polyurethane will usually offer a much longer
service life than rubber, however.
There are several hard plastics which are currently being used to make
automotive suspension bushings . . . and depend on rotational sliding action.
They all require a close tolerance fit, and . . . offer excellent control and
superior handling.
Nylon . . . is dimensionally unstable, since it is able to absorb water and
will swell as it does so (and) shrink (as it dries out). Nylatron . . . is the
. . .brand name for (a) blend of Nylon with a molydisulfide additive to provide
for some self lubrication.
(Marc goes on to recommend Carsan, a plastic, like Nylon/Nylatron and Delrin,
but self-lubricating, chemically stable, and non-absorbant. It is softer than
the other plastics, so has better sound and vibration dampening, along with
high abrasion resistance and an extremely long service life. The down side is
that it has to be machined to size rather than molded, and is MUCH more
expensive. In 1991 Marc rebuilt the front suspension on my GT using offset
Carsan bushings, so it is completely adjustable for caster, camber, and toe,
and powder coated the metal parts (including the coil springs) for about
US$800. He also supplied extended shackles, Carsan bushings, and interleaving
strips for my de-arched rear springs (couldn't find the receipt for all that).
I am still completely pleased with the results).
When last I checked, the Performance Engineering Web page was at:
http://www.efn.org/~msayer/welcome.html
Regards,
Jerry Causey - 1967 MGB GT
Whidbey Island, Washington, embraced by the Puget Sound
(fairly close to Seattle, and the rest of the USA)
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