Lotus Elan

Installing poly bushings

PostPost by: ceejay » Mon Dec 31, 2012 10:57 pm

For optimum performance of urethane bushes, one of the most important
components is the stainless crush tube, this tube controls the amount
of pressure or "squeeze" applied to the inserted bushings.

The bushes are easy to insert (A light press fit) when made as top hat
sections IE, two halves inserted from each side, followed by the crush tube,
and yes insert using a good quality grease.

The crush tube is used to fine tune the fit and operation of the bush in
the suspension ferule, IE, the tube is machined so that it is just a few
thou wider then the bush, but the fit is kind of done by feel,
not to loose, not to tight, we use special bench tuning tools
to help to achieve that state.

Our S2 elan has been running urethane bushings through out the
car since 1985, and have only changed two bushes in the front
suspension during that period.

I don't think urethane bushes make the elan any harsher than
normal, if anything, urethane bushes make the handling sharper
and more responsive.

But if you intend to fit urethane or poly bushes as you guys call
them, be prepared to spend the time for correct fitting and fine
tuning, otherwise you might as well not do the conversion.
The shots below show urethane bushes inserted into outer
rear suspension.

The urethane bushes when inserted correctly rotate on the
stainless tube insert during the arc movement of the suspension,
they don't have torsional flex as per the original rubber bonded
metalastic bushes.

There is quite a lot of work involved in changing from the old rubber
bushings to urethane, but in my opinion, it is worth the effort, but
it wont suit everyone.

The bushings are not moulded but machined from solid rod,
and feel this method produces a more exact fit than moulded
bushes, it is an advantage to be able to do all of this work
in house, and not have to farm the work out.

Good luck.
Attachments
rear-susp-mount-point-0011.jpg and
Urethane bush and stainless steel crush tube.
strut-mount-point-010.jpg and
Thrust washers are essential to control sideways forces applied to suspension.
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PostPost by: collins_dan » Tue Jan 01, 2013 11:06 pm

Right side of rear done. The old inner rubber bushings seemed fine, but now that poly is in, I realize the old rubber had swollen a lot and was binding. Fit washers by bolt heads on outer and clearance is OK, barely. I will update the other post about the removal tool I used for the rear. In short, instead of using 1/2" threaded rod and copper coupling, I used 3/8" threaded rod and 1.25" threaded black steel coupling for inner and 1" for outer. Lots of heat! Dan
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PostPost by: miked » Wed Jan 02, 2013 8:58 am

Hi Ceejay, I have only used the moulded ones and they do not protrude to the outer enough to fit an external washer. Only single tophat! The washer has alway been required on the inner part against the alloy to prevent the top hat section from spreading on the small alloy landing area. The top hat flange is quite wide and thick. With fitting the thicknes of the washer and top hat the alloy has to be shaved. This is how I believe Mick Miller saw it. It is a bit of a pain as you have to measure and get the right amount of loading on the poly so it does not sqash the top hat but is not moving fore and aft'. I have never been over impressed with the rear outers, although they work fine when done.
I like the bushes that you show, they appear to have a cotton bobbin section and can have washers both sides. Is this the case? Who's bushes are they, or did you turn them? Any chnace of a side shot showing how the butt up to the alloy. They look a great job!

Mike :D
Last edited by miked on Wed Jan 02, 2013 10:22 am, edited 1 time in total.
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PostPost by: ceejay » Wed Jan 02, 2013 9:35 am

Hi Mike

The outer A arm bushes only have the washers on the outside, all of
the bushes; inner & outer of the A arm are of top hat construction.
The top hat rim is thin, at about 3mm.

The loading on these bushes is controlled via the stainless inner
crush tube, when inserted and set up the bushes should be firm
but not overly tight, you don't want to have any excessive stiffness
in the bushes, the wishbone arms need to be free to move without
binding, if that make sense.

All of the bushes in my elan are machined from round solid
red poly urethane, it is the accepted hardness for auto
suspensions here in Australia, manufacturers in other
parts of the world may think otherwise.

If you have in house machining facilities and some stock
lengths of poly rod, new bushes are not difficult to make,
although there are some tricks to use with the lathe
cutting tools

The entire front suspension inc roll bar bushes,
plus the entire rear suspension, plus diff bushes and
the diff torque rod bushes are all poly urethane, the
conversion was done way back in the 80s, and I rather
like this bushing material, if you convert an all rubber
bushed elan to urethane bushes, you would probably
notice some increase in harshness, but not having driven
a "normal elan" I don't notice any difference, it's a 60s
sports car, they are bare bones motoring.

You can't make strawberry jam from pig s**t, no matter
how much sugar you throw in.

I enjoy the drive behavior of the elan.

We have also carried out some other interesting chassis
tuning mods which I am eager to see how they go... but
more on that in the future.
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PostPost by: stevebroad » Wed Jan 02, 2013 10:59 am

ceejay wrote:You can't make strawberry jam from pig s**t, no matter
how much sugar you throw in.

I enjoy the drive behavior of the elan.

We have also carried out some other interesting chassis
tuning mods which I am eager to see how they go... but
more on that in the future.


But you can at least make make it sweeter :-)

Very interested in your proposed chassis mods, maybe we can compare notes?

Regards

Steve
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