Oct 3, 2017 update to the Lotus Elan project car

Restoration Impossible: Rebuilding the Rear Suspension

Here’s what we started with: a rusted, mangled mess. Thankfully we had a parts car and and our trusty Eastwood bead blasting cabinet.
Disassembled, this is what the rear suspension of an Elan looks like. The Roto-flex coupling in the picture is a new one we had purchased. We also had a few extra half shafts in our parts bin to check for cracks and trueness.
We ran all of our rotating components on a lathe and used a dial indicator to make sure none of our components were bent.

The rear suspension on a Lotus Elan is much more complicated than the front suspension.

Lotus’ design for this rear suspension system starts with bespoke aluminum rear hubs and uprights, combined with a strut insert and coil-over spring. Very wide, Lotus designed lower A-arms combine with what is called a Lotocone—upper mount that moves slightly—to absorb suspension deflection.

Roto-flex couplings and rear disc brakes—with a unique and separate disc parking brake—finish things up at the rear.

The Elan uses a clever rear strut with sealed wheel bearings. We replaced these bearings with new ones from R.D. Enterprises. Since our parts car was a later series 4 car and the left strut on our project car was damaged, we used the later style struts from our parts car. This later style strut we’re using features a larger wheel bearing.

While cleaning, media blasting and painting the components was just as straightforward as working on the front end, assembly proved to be a bit more complex.

First, the rear brake calipers are considerably more complicated than the front. But the toughest part of restoring the rear suspension, was figuring out in which order to assemble the Roto-flex couplings, and how to compress the springs enough not to tear these couplings.

We eventually designed our own system. We initially used a spring compressor, and then kept the springs compressed with hose clamps. While we are not sure this is the safest way to accomplish this job, the rear spring rate on a Lotus Elan is quite soft, so we had no difficulty keeping the springs compressed in this manner.

Once the springs were compressed, the Roto-flex couplings and half shafts lined up much more easily and we were able to complete this entire job with no further difficulty.

It must also be noted that the differential should be in place before any rear suspension assembly commences.

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roblamoreaux
roblamoreaux New Reader
10/3/17 3:50 p.m.

I've actually used short tie down straps to compress my rear springs, and I've got stiffer springs and adjustable shock inserts.

The rotoflex go on much easier when the springs are compressed, and I've put them on before and after the strut is connected to the chassis. Before  works better when the body is off, but then almost everything is easier when the body is off.

Also don't fully tighten the inner suspension pivot bolts until the car is all together and the suspension is loaded to road weight. The rubber acts as part of the spring and will fail early if you tighten them at anything but normal ride height.

 

You might add that the diff only goes in from the left side, and even then it is tight.

plrichen
plrichen
10/6/17 11:46 a.m.

A lot of Elan owners have replaced rotoflex couplings with CV Joints due to concerns about the quality of the currently available rotoflex couplings. 

Tim Suddard
Tim Suddard Publisher
10/12/17 6:17 a.m.

In reply to roblamoreaux:

You are right about the diff. What a pain! I had a long talk with Dave Bean, before he passed recently, and he asked me if I was trying to restore the car or not? I sheepishly answered yes. He told me to stop trying to modify it then and return it to stock. He also told me that while the CV joints do have their plusses, they destroy some of the awesome ride quality that the Elan was famous for.

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