Rear Coil-over Shock

[Paul]

Hi,

Can anyone advise on a coil-over shock absorber that I could fit to the rear suspension of my three wheeler. The shock is intended to supplement of even replace the existing Citroen single suspension unit, which cannot achieve the correct ride height.

I'm looking for a long travel shock, or as long as I can get, as the car will be used on classic trials. I've experimented with some motorcycle shocks from a Kawasaki trail bike, but even with both shocks installed, I can only get the ride height to about 240 mm; the springs are just too low a rating. Most bikes now use a monoshock, which, though having a beefy spring, only have a short travel because they work through a linkage. Other twin-shocks like my unsatisfactory Kawasaki shocks will, I suspect, also not have a sufficient spring rating.

I figure there might be something for a car that I could pick up from a breakers. Even if the travel is not as long as I would like, if the spring rating were high enough, I could lay the shock further away from the vertical and gain some travel at the wheel.

Has anyone else gone down this road with success. I've considered linking the other Citroen unit to the rear wheel, but time and budget rule that option out.

Regards

Paul

[Geoff Ryall-Harvey]

Sounds like you need something intended for one of the off road buggy things like the Blitz;

http://www.blitzworld.co.uk/coilover-da ... 2-i28.html

A cheap alternative might be to adapt a MacPherson strut.

[hutchii]

Paul, Sorry I'm a little puzzled.
Is one standard spring too weak and/or does it give too little travel for your needs?
I would think the ride height is almost infinitely adjustable, at least until the spring to knife edge eye pull rod fouls on the chassis mounting for the suspension spring can. Using a front knife edge "eye" (which I think is shorter) would give greater height, if that's not enough, shorten the pull rod and cut the thread (M11 x 1mm) on the rod longer.

[Paul]

Hi Geoff,

Thanks for the link, but that Blitz shock is way out of my budget. I've considered modding a McPherson strut as you've suggested; I've got a dufunct Triumph shock that I can cut the bottom eye off and weld onto a strut (once the I've pressed out the rubber bush). But it's a lot less hassle if there's something off the shelf that only requires some bracketry.

Hutchii; as regards the standard spring, yes, it appears too weak to support the all the weight at the rear. I've wound the pull rod into the eye to almost the end of the thread and the difference to the ride height is minimal; all I'm doing is compressing the spring. That appears a logical outcome to me because whereas there were two springs supporting the rear of the car, there is now only one, albeit the rear weight is less than with the standard body.

Paul

[Duncan Grimmond]

Hutchi said

if that's not enough, shorten the pull rod and cut the thread (M11 x 1mm) on the rod longer.

You can cut 12-15mm off the tie rod allowing it to go further into the eye. M11 * 1 is a difficult and expensive die to find. You could also fit some 6mm thick washers under the spring (easier on a Pembleton) from your local agricultural engineers supply which will pre-load the spring.

[Tom Rae]

I seem to remember the front and rear rods are different lengths, perhaps you have the wrong one fitted?

Tom

[whitelomax]

There are two possible solutions here. The ideal would be to link in the other suspension cannister so that the back of the car is once again supported by two springs. This can be via a Falcon-style rear supension set-up, or a torsion bar or tube put inside the hollow rear axle tube and linking both sides together. The answer to your original question is a Reliant three wheeler front coil-over shock fitted to the back. Shouldn't be too expensive from a breaker (if you can find one at a breaker these days !) and the spring should be about the right rating, being intended to hold the front of a car up on its' own !

[Silly CVs]

I have a Falcon rear axle assy should you wish to go that route, re coilover application, how do you plan to mount it, some Lomii had coilover rear end but needed subframes to mount it,

[Mike]

Hi Paul, the original springs were designed to carry the weight of the car + 4 adults + luggage. so theoretically as you'v halfed the cars weight, limited the adults to 2 and rejuced the luggage space the one spring on your 3 wheeler should be adequate as it is on most 223 conversions.
Maybe you should check the spring is the correct one.
Regards
Mike

[Paul]

I eventually installed a rear coilover shock from a Rover 200. The bottom of the shock fits into a bracket on the extension of the rear suspension arm as close to the backplate as possible and the top of the shock attaches to a 'saw-horse' type arrangement. This 'saw-horse' type arrangement is bolted to the remains of the rear longtitudinals of the chassis.

The ride height is currently about 300 mm, and can be adjusted by altering the position of the knife edge eye on the standard Citroen suspension.

The arrangement worked well on the trial sections, which had some deep ruts and rocky steps.