Talk Morgan Forums Community The Malvern Arms Rear Suspension . 2006 +4

BCC's website still shows a four leaf spring for four seaters. See BCC 4 seater, 4 leaf rear springs

Glad that you got it sorted. I have owned 2 2008 +4’s, the first a 4 seat, the rear springs sagged within weeks of collection and after 8 months back and forward to the dealer (and 3 sets of springs from MMC) ............clip.........
BR
Colin

Hi Peter B. Like many others, it seems, I have the same problem.
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What i see from the above is a major failure in the design/production of these cars and i wonder why it has been left to a few concerned owners and a clever supplier to resolve, all at their own expense?
Peter, can you please advise what the cost is to correct my sagging Plus 4?

As far as I know Peter Ballard does not come on the forum all that often these days. He can be contacted at http://www.suspensionsupplies.co.uk/ and I am sure he would be happy to discuss options with you.

OK lots going on here, sorry if this is a bit long, but it is a big subject.

Morgan leaf springs and related matters:-

Some of the Morgan models have a weight bias to one side, eg due to steering, exhaust, battery all on right side, then plus driver. As std the left and right front springs and left and right rear springs are the same rate (stiffness in Imperial units typically lbf/inch) and camber (leaf spring) or length (coil spring). Most other production cars will have different rates or lengths left to right to level the car, Morgans do not.

The current four leaf springs fitted to all models and sold as replacement by Morgan are I believe made in the Indian subcontinent, that is not to say they are necessarily cheap and nasty, but there are lots of warranty returns and are half the price of leaf springs made in Sheffield.

The four seater leaf springs have more camber than the two seater springs. Camber is how much they are curved BUT they are the same rate or stiffness so ride quality will be the same. They are the same spring just formed into more of a camber. So the four seater springs will sit the car higher. OK for a four seater as they are heavier at the rear and they often/should have thinner (1/4" instead of 1") rebound rubbers under the axle to give greater ride height and importantly for the four seaters also have a closed cell foam elastomeric 'spring aid' like a long soft bump stop but with little hysteric damping on the special rear dampers. These are absolutely vital on a four seater to carry the load of the rear passengers.

Leaf springs are designed to be flat at laden ride height or thereabouts. This applies to the two seater and maybe to the four seater with four occupants. A flat leaf spring has maximum lateral stiffness, that is important for enthusiastic cornering, thus reducing the need for a Panhard rod. A Panhard rod prevents the axle moving sidewards in a hard corner and does not affect ride.

If the car sits too high, such as with new Morgan's own springs many are fitted with lowering blocks (that can also incorporate different pin positions - see later) but then the spring no longer sits flat even if the car is at the right ride height, then the springs twist sideways under later loads in cornering, so people then add a Panhard rod to correct the use of lowering blocks. Not clever.

The factory anti-tramp bars (and others) fight the path the axle wants to take in bump. That is to say the axle wants to move up and rearwards in bump but the axle end of the anti-tramp bar forces it to move in an arc about the front leaf spring eye. The anti-tramp bar wins and the fight is taken up in the rubber bushes of the anti-tramp bars. The anti-tramp bar can add over 50% to the leaf spring rate! So if you only fit one then the spring rate on that side will be more than on the other side, not for a performance sports car please! Best is to make sure the anti-tramp bar is not loaded at laden ride height by adjusting its length. Maybe consider fitting two anti-tramp bars or asymmetric leaf springs or a five link if really keen!

Leaf springs made from the wrong material spec' or wrong heat treatment will sag with use. They loose ride height but they do not loose stiffness. So they do not go 'soft' they just sag. The springs off my 1980's 4/4 were made in Sheffield and in 30 years and 60,000 miles had not sagged! Before I went five link and coil overs of course.

Check for sag of leaf springs and left to right sag. Jack up under the exact middle of the front lower cross tube, ie the lower tube of the front frame. Get the front wheels just off the ground by say 1". Remove parcel shelf. Reach in without resting on the car and feel the gap between the axle and the rebound rubber below it that is screwed to the chassis curved cutout. Both sides should be about the same, but as we know some models are lopsided in weight distribution anyway. Gap should be about 10mm, so your first finger should slip in there, two or three fingers and the springs have sagged. If one or other spring has sagged then you can swap sides but the springs will keep sagging and you will have to do the job again of course.

Measure corner weight at a dealer. NB Salter Scales still sell bathroom scales that read up to 250kg !!!!!!!!!!!!!!!!! Cost less than £20 on Amazon etc. Good for corner weighting!

In our experience the std Morgan four leaf springs do not actually meet their own drawing (SSL has copies), they sit too high as new thus maybe inadvertently allow for future sagging or settling. Leaf springs may settle if they have not been scragged at manufacture, scragging is taking the spring past yield to align the steel micro structure. Settling takes place after a few miles, but then should stop. Sagging is a longer term loss of camber. The Sheffield made four leaf springs supplied by BCC meet the Morgan drawing as new and have been scragged. SSL have their own calibrated leaf spring test rig that we use to test leaf springs to check rate for Morgans and other road and race cars as part of our ride and handling development projects.

Morgan front springs have an important influence. As we know the initial high spring rate of the std front end is the addition of the main spring rate plus the rebound spring rate, hence the very harsh ride. So around 140 lbf/inch + 300 lbf/inch = 440 lbf/inch. BUT the four leaf rear springs are around 150 lbf/inch. The front springs are also widely spaced, ie closer to the front wheels than the rear springs that are inside the chassis. Hence the roll stiffness of the front end is very much more than the rear (hence the understeer tendancy) so what happens if one rear spring has sagged, well the chassis twists a little. BUT what it also means is that if you are trying to correct the offset weight of the car with different rear spring cambers (more camber on the heavy side) then you also have to overcome the very high roll stiffness at the front. So basically overdo the extra one sided camber. We (SSL/BCC/Owens/Williams) did this on one customer's car where the weight was offset and the driver was solidly built. We added about 2" extra camber to the right side that did correct the offset weight, coped with the solidly built driver and overcame the front roll stiffness. Car drove away level, happy customer BUT the extra camber made fitting so very very difficult, thanks Tom!

So yes it is possible to obtain a pair of Sheffield made springs with different cambers left and right, or get one recambered at around £75 each. SSL will work with the dealer/customer and BCC (the wholesaler) and Owen Springs (the manufacturer). SSL provide advice as to how much camber difference left to right is needed in these situations, but SSL no longer sell the springs and thus no longer add their 'markup' between BCC and customer, as it all got a bit silly!

BCC also supply asymmetric four leaf springs that were designed by the other SSL director (Dan) before SSL existed. These are close to the same rate as the std springs, but have the leaves biased towards the front. This stiffer front half gets towards a flexible trailing arm with the compliance in the rear half.

Morgan springs do not have the pin for the axle in the middle so can only be fitted one way round. The pins have moved about 3/4" forwards and then back over the years. As I understand it, early cars had the rear wheels central in the wheel arch, then when the Salisbury axle was fitted with the 'harpoon' of the hand brake mechanism behind the axle close to the fuel tank the axle was moved forward, then later with the BTR and Dana (made in Thailand) axles with the cables going direct to the hubs the axle was moved back central again. So beware when ordering springs!

Ideally the customer should also consider adjustable spring seats up front and a rebound spring that is not quite in contact with the slider/hub to reduce front roll stiffness. Thus some of the offset weight can be compensated for by preloading the heavy side at the front. SSL main springs are around 110 lbf/inch, so you can see if an extra 1" of preload is applied to one front side then that side carries an extra 110 lbf, a long way to compensating.

Springs that BCC (British Classic Car spares) supply are made in Sheffield by Owen Springs. SSL work closely with BCC and OwenSprings on these issues. SSL also use Owens for the leaf springs we supply to many race cars including Morgans, so lower and stiffer in the case of the 20+ race Morgans so fitted.

Suggest:
Check the springs left to right for sagging.
Consider new British springs from BCC.
Consider extra camber on one side at around £75.
Fit adjustable spring seats up front with the SSL RS front kit to help compensate off set weight and of course will improve ride and handling.

I hope that this has helped.

SSL are always keen to help Morgan owners and their dealers and suppliers, we love Morgans, as well as other really special cars.
SSL are always available to chat to owners/dealers about springs and dampers, that is what we do, details as you know on our website.

Hear's wishing you all a safe and comfortable 2020.

Peter J Ballard.
Director of Suspension Supplies Ltd - SSL.