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

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My own understanding is that rebound springs were historically shortened as a bodge (as per CBY post) to reduce static pre-load on rebound springs which in turn resulted in the fact based massively high spring rate of having both springs in play. This in turn causing uncomfortably hard suspension but then sagging into corners due to inside main spring compression taking rebound spring out of play and effective spring rate reducing to that of main spring alone. Several owners and at least one magazine test of Plus 8 brought this fact to light many decades ago. Peter Ballard explained it and mentioned that ironically as main springs weakened with age the issue could dissapear. Suggesting the rebound pre-load test is rubbish for an entirely different and less important reason is not a fair comment. Its as relative today for trads as ever.

Exactly correct, a pre-loaded main spring due to a compressed rebound spring gives a massively high initial rate followed by a sudden drop in rate as the rebound spring unloads.

All documented and explained years ago by Peter Ballard, I remember the huge consternation it caused among people who didn't understand the physics behind springs in parallel vs. in series. It was hugely entertaining at the time to read all the eMog posts telling Peter he didn't understand how suspension systems worked!

https://www.lambdapi.co.uk/morganatica/Front_Suspension_Spring_Characteristics_-_Trad_Models

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?

TY CBY, I got you. You are saying an unengaged (!) rebound coil spring has an "increased" effect on the stub axle and its lower contact area. Personally, I have never seen that happen. In any event, my vote is for progressive neoprene or microcellular polyurethane stops Happily, this thread had me do enough research that I see they can be found everywhere. These would certainly not be as fiddly as metal springs, last forever and cover the rebound area of the kingpin so many people try to cover with rubber covers or homemade stockings. (I tried them 30 years ago at Cuthbert's suggestion, and then removed them as they interfered with quick cleaning with a high pressure hose.


I like that very much. You put your finger on it. A trad..or at least until the MMC were forced to use engine fuelling technology that cannot be fully interacted with by an owner, preserved the characteristics of a Golden Age of Automobiling. Up until 1990, trads can be FILLY interacted with..which made my immense mileage possible. It was the reason I bought one, despite it then being the only one in area the size of western Europe. I was in my 40s and the nearest dealer was 400 miles. I had no choice but to learn. If admire you. You had options and embraced the full Morgan hobby nonetheless. IT IS GREAT FUN!

And YES. RichardV6's is a fine post. TY Richard I believe I was confusing front springs and leaf springs. This is why I feel safer posting with a collegiate debate format. I should have followed my comments on GoMoG.But being wrong is the only time one learns anything!

You also touch upon a basic I forgot. IMHO, the front end suspension primary task is to keep the steering wheel neutral. Of course it has other effects. Unsorted that part of driving become no fun. Aside from that deadly discomfort, the comfort inn the cabin (aka your life partner) is at the rear springs. Google it. Leaf spring spring rates do not age....they sag though. (wish I could currently find something in trad leaf springs to recommend!) And I chose Cain's dampers 2-3 years ago, when they just came out. I installed them then. but haven't tried or adjusted them yet as my last remain Plus 8 is up on stands in Canada since. .I began what I thought would be a 3 weeks job changing the dash loom and fusebox..but expanded that to replace the chassis loom and rear loom, (The Rover EFI loom is very high quality. 2-3 days left to do. I don't live in Quebec any more..only visit on occasion.

Sewin, did you know that Peter Morgan only added front shock absorbers because owners complained as they couldn't fathom a car without them! But shock absorbers change oscillations to something more pleasant to humans. Springs do the major work. Shocks change their harmonics https://www.gomog.com/allmorgan/shocks.html


I presume you mean RichardIII? Yes. His is a noteworthy post as well. If the shock bushes are worn (there was a short period when the beloved Rutherford AVOs did but Tim covered us all). James Phillips of ThamesMog pointed that out to me that if the bushes holding dampers are worn or rotten (which can happen prematurely) the absorbers have too much wriggle room and that has a sad effect. Merely changing the those bushes cures it. Amazing how much shock angst and money that one has saved over 30 years. [i]There was a run of faulty bushes not so long ago[i] Thank you for reminding us of this area. Page 1 of this thread. I agree it should have a "service protocol". I shall add that to GoMoG.

Lorne

In essence the rebound spring assists dampers in controlling rebound (no surprise) after a bump or undulation in the road has been absorbed (to a degree ) by main spring compression. It also serves to provide anti-roll characteristics in that the inner wheel unloading in a turn is resisted by combined spring rate so tending to keep body in a flatter plane and consequently more rubber on the tarmac.

For this reason as well as ensuring there is no static compression on rebound spring, as mentioned above, its also important there is no static gap existing between rebound spring and bottom of stub axle, such that both rebound and anti-roll properties come into play soonest. This is why the "just able to turn rebound spring" static test is performed as an aiming point.

Thanks for the link Tim, had been trying to find Peters explanation for my post above. Have now bookmarked it

Hopefully my shorter (orginal) explanation of trad suspension roll resistance isn't too far at odds with Peter's.

Yes Lorne, I remember how Peter bodged on some front shocks to placate the masses, evidently he got tired of explaining to customers. That might explain why we still have shock mounts failing at the front end as frankly they were only just about tidied up from the bodge! Peter's favourite was to allow a customer to drive his car that had no shock absorbers fitted, just the lever arm Armstrongs at the back! Like the morris minor has! What am I talking about you'd have to be 55 at least to know that. But as we all now know he relented in the end! As a nipper I can remember asking my dad to get new front shocks when he set me to cleaning up the front end (That bloody oiler!)for my pocket money. You could push them in and out like a.... well let's not go there! "Nothing wrong with them" he said and relayed the Peter story to me! Do you know what..... they are still as weak and as they ever were and as you said, all they can possibly do is damp harmonics. It's the springs folks that do all the work! never mind fancy front end make overs! If it could have been improved I'm sure that in the last 75 years it would have been. So let's all take the time to service and understand sliding pillar suspension.

Actually, It was very nearly improved upon and Montegue has the evidence.... double wishbones, am I jealous, of course I am. Think there were only 5 cars that ever had it fitted, I believe by mulberry fabrications but don't quote me! Such a shame that Morgan didn't pick up on it and finish the trad's time using that system.
I think we are in danger of entering the rabbit hole again... or perhaps we are still stuck down there! There are those who are looking for the grail and spend endless sums trying to find it and others who really only need to return to the H.S.F. philosophy of fix and service it on the drive. If you don't you soon won't be able to find anyone who can do it for you...... watch a new mechanic trying to find the OBD2 port, yes he' stuffed unless the computer says do this! And as 1986 was ancient history to him he doesn't believe this shiny bright car doesn't have one.

Hi Lorne,
"You are saying an unengaged (!) rebound coil spring ..."

Why "unengaged"?

If you cut a spring you increase its rate. When the rebound and main springs are both compressed, the stiffness is greater as previous with this non cutted spring.

I guess you use "progressive neoprene or microcellular polyurethane stops" (silent blocks?) instead of rebound springs. Could you provide the dimensions and photos. It is very interessing.

Ah CBY, i've seen the rabbit! You are of course quite right in that a cut spring does indeed carry a greater load yet in standard linear spring ratings each inch compressed carries the same load but an engaged or under compression spring is carrying load and thus pressure whereas one that is just approximating its fitting space at rest or static load, this has no force pressing upwards against the main spring so although the springs appear to be in series they are in fact in parallel. as each spring has a separate load effect. if the rebound spring in this case of which we speak under static load were applying force against the upper main spring the force of the two springs would provide the total spring rating of the suspension. so by using this adjustment of a shorter rebound spring giving a static/driving suspension rating much closer to the value of the main spring. This then releives the locking up pressures on the hub when steering. Now if you fitted a full length rebound spring and it was under load at static rest or straight ahead, when driving all is fairly well, but then you go into a hard corner and the force on the outside suspension equalises the loading of the two springs together now being pushed in the same direction and this has a softening effect on that unit so some chassis stiffness is lost because first the rebound spring being much smaller is quickly overcome and so the total springs rating is provided by the main spring. This then is how a resolution moved to higher rate main springs. Let's stop here other than to say all these modifications will sort one aspect of the suspension you are trying to fix yet introduce another that you might not want.

Incidentally, not all Morgan trad's left the factory with the same rebound spring requirements, I'm not going to go searching at the moment but can tell you that my 2010 plus 4 has RB's which are under load against the main spring whereas others have little to no loading at static rest, fairly sure the Roadster is one! This is to suit the driving characteristics Morgan intended for that mark. So care needs to be taken when changes are being made especially if you want to improve what you have and not make it a detrimental move because someone told you to cut the springs down. The SSL aims to cover this as you are able to adjust main spring loading and therefore take advantage of the progressive rate springs. But again for me personally I haven't felt enough advancement over a properly serviced standard set up to warrant the cost. Again though, I feel mine is as good as it could be and the cars I have driven with the SSL, I had no knowledge of their set-up. I will say again that the two mod's that I really felt improved handling and ride quality on my car were Brake reaction bars and Rog's suspension assisters. When pushing things along a bit the BRB's really take some of the skittishness out of the front end and that's a driving thing and the rear assisters really soften and damp the ride throughout the cabin, that's a comfort thing.