To sort Monty's handling I knew the dreadful original factory rear leaf springs had to go, shockingly they'd gone soft in just 10,000 miles so they clearly weren't correctly tempered from new!!!
You were lucky you got 10,000 miles. Mine were gone before the car even left the factory, after we got home Borgi replaced them with a set of 5 leaf springs: way too hard!
Where on earth did Morgan source these dreadful leaf springs from anyway, and what steel were they made from?
My guess is India, where there are lots of leaf spring manufacturers who will sell you something that looks like an automotive leaf spring, but is actually made from very poor quality steel. The metallurgy of spring steel is a huge subject, but if my original Morgan factory springs were anything to go by I suspect they were simply made from a really low grade cheap carbon steel that was never tempered correctly, if at all!
A quality automotive leaf spring should be made from modern EN45, or at least old school AISI 5160 chrome alloy steel that should also be oil quenched at 829C, then tempered at 430c – 700c. Where different yield strengths and formability characteristics are required the carbon and manganese content of the steel can be varied to give AISI 1050, 1074, 1075 and 1095 although AISI 1070 is considered a good compromise.
I do wonder how many trads are out still running their Morgan factory springs, I strongly suspect the AVO rear dampers that came with Monty were fitted by the original owner in a misguided attempt to solve his rear suspension complaint, but the truth is the bigger underlying issue that was never addressed was the springs.
The AVO’s on Monty were of course totally overwhelmed by the original leaves and were completely worn out in short order due to the ridiculous amount of work they were forced to do trying to control Morgan’s so called springs, both top bushes on these rear AVOs were also completely destroyed due to the constant and brutal pounding forces they had to endure.
Perhaps Morgan used the same spring supplier for many years as I think it's highly likely the GDI Plus 4 JayEmm drove in this review suffered the same issue.
https://www.youtube.com/watch?v=TaZiWVU1vRwAfter talking for a few minutes about the suspension's lack of composure, around the 7 mins 30 second point in the video he makes a big play of what happens when he encounters a bump in the road. I'd wager the dampers used by Morgan were also rather basic and combined with their awful weak springs conspired to deliver what looks like a harsh bottoming out experience in this review and JayEmm's overall criticism of the Plus 4's ride and handling.
That's a real shame, because with the right springs and dampers all these issues go away, OK it's still a beam axle on leaf springs so the design is never going to deliver Lotus ride quality and handling, but my Plus 4 running BCC antti-tramp springs and the excellent Bilsteins from SSL really does ride and handle very well indeed, if say you compare it with other vehicles that run the same setup like say an MGB or Triumph TR3.
In my limited experience it seems clear a properly tempered pair of springs that are not too stiff paired with and controlled by a quality and well matched damper set are the best investments to improve the trad Morgan experience and its driving dynamics, revealingly the BCC antti-tramp springs were described to me by Techniques morgan as "softer than what we normally fit ourselves" when they fitted them, and I believe this is part of the secret to Monty's excellent ride quality.
I've long been an advocate of the suspension recipe that combines
compliant springs controlled by a
firm damper of quality construction with well matched valving to that compliant spring, the Bilsteins dampers I chose certainly tick this box and come with the added benefit of really
big progressive shaped bump stops made from the correct material made for the job.
When I first took possession of Monty it was clear the rear springs had gone horribly soft, dangerously so in fact, so I knew the first thing the car needed was a decent pair of properly tempered leaves, I then studied the rear suspension design and concluded the following:l
1. To me the first big challenge to overcome is that the dampers have an awful lot of work to do controlling the rise and fall of such a heavy lump of cast iron, the rear axle. To achieve this I concluded investing in the very best damper set I could lay my hands on was top of the priority list and once the awful factory springs had been replaced.
2. The second flaw in the rear suspension design is it's lack of available travel, there really isn't much you can do to solve this issue so I concluded I needed a setup that uses every last mm of available travel without experiencing the harsh bottoming out issues that becomes a risk when you're using every mm available. I can certainly see why with weak Morgan factory springs paired to their very basic dampers offering next to no bump stop system will result in the kind of unresolved handling JayEmm reported and the harsh botting out episode we all witnessed in his YouTube review.
If JayEmm had just driven the same car with a set of the properly tempered and compliant BCC antti-tramp springs paired with the firm and well valved Bilsteins I suspect he would have given a very different opinion of that GDI Plus 4's ride and handling. The car probably still would have bottomed out due to the lack of suspension travel, but with the big progressive bump stops on the Bilsteins he just wouldn't have felt it. You see that's the thing about bump stops, it doesn't matter if it's a set of Roger's design or if the bump stop is incorporated within the damper as with my Bilsteins, if they're designed correctly they should completely eliminate that harsh bottoming out feeling that travels up your spine, don't get me wrong the system is still bottoming out, it's just you don't feel it
The final addition I would strongly recommend is a Panhard rod, on Monty this definitely solved the considerable and quite alarming lateral axle movement for a very reasonable cost, after fitting there was no loss of ride quality at all either so I’d say fitting a well adjusted Panhard rod is a no-brainer upgrade for every trad Morgan owner.
