Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Steering bearings

Well CBY is totally correct in his analysis of cutting springs down, take the boy racer with his cut down micro hatch back. It's not an MOT fail for no reason!
To a great extent the rebound spring is just a damper. When in a turn enough to effect G forces which load the outside suspension the spring compression rate of the main spring has no detrimental effect from its ability to compress at the design rate regardless of whether or not the rebound spring remains at full unloaded length or is subjected to a degree of compression itself. Its main functions are to keep the hub carrier in a balanced contact position on the pin whilst allowing the small movements as the hub responds via the wheel to the movement from the road surface. This prevents hub carriers hanging up on the pin as during these smaller movement it has a push pull effect to the carrier.

When/if the suspension is subjected to a sudden and harsh suspension requirement the compression rate applied to the main spring can be large and the distance up the pin the carrier can travel is substantial within the design profile. During this event the carrier will lose all contact with the rebound spring and when returned to its normal position by the return force of the main spring the rebound spring will absorb the shock as the carrier reaches the bottom of it's travel and damp the shock that would otherwise become a metal to metal crash. were it to be a bump stop instead, the return action would be too great for the repeated and constant contact it would receive, and indeed to harsh.

Now here is why they wished to unload the static compression to the rebound spring. and remember these cars originally had no shock absorbers. You can do this in two ways. firstly cut the spring down which increases its compression strength or fit a spring with a greater load rating. What you then want to see is next to no compression or decompression to the rebound spring from either static load position or unloaded and to a great extent this was achieved by spring length, spring load rating and the extended load rating of the main spring. so, if the car now hits a negative obstiacle ie a pot hole most modern cars accelerate the suspension down into the hole only for the wheel to hit the other side and possibly disrupt the stability of the car. This is only offset by the shock absorber fitted as it slows the downward suspension acceleration into the negative obstacle. The sliding pillar system tends to hold its wheel clear without the aid of a shock absorber.

It is actually a genius system, not invented by H.F.S. as other manufacturers were using very similar set-ups. however we are only talking about an item between to opposing springs allowing it to move and return to it's rest position. The SSL does offer two things over standard, not that it can improve the basic function of the set-up. It has a variable load rate spring, This allows the small suspension movements from relatively good surfaces so the oscillation between the rebound spring and main spring allow slightly more travel movement and is softer enabling these movements of the suspension to have less effect to the car body and people traveling in it. After this compression level any greater forces are absorbed progressively by the stonger section of the main spring so that higher driving forces are accommodated. That is really returning to normal Morgan suspension function however, what it does give here as an extra is that you have an adjustable load setting which does give an option to set the stiffness which suits you best for both comfort and driving style.
Some people love this set up others loath it although I can't see why. I personally haven't found when I have driven cars so fitted that I found it a marvellous thing but I hadn't set it for my driving preference so who knows? But I find my cars standard set up which is correct and serviced suits me fine. Perhaps I would consider variable rate springs as that could only help, I find the standard car firm enough for me but would I then start chasing the Kings new clothes?