Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Roadster rear suspension fail

Oh yes! The one only sided ATB Morgan fit, That's enough to upset the handling of the Mog even if Fangio was driving it ,and he managed to tame the auto union car of his day!

Staying in the history class room a little longer takes us to the release of the TR2 in 1953 where we saw the same axle over chassis setup.



And for comparison here's a trad chassis:



As we can see it's the same setup, both are equally crude and prehistoric in their design, but I strongly suspect the TR chassis is more tortionally rigid than that of the Morgan. Anyone familiar with the TR2, 3, 3A and 4 will know the chassis/suspension had all the same issues suffered by us traditional chassis Morgan owners, so it's nothing new.

Triumph retained the same chassis right up to 1965 when the TR4A appeared, a run of some 12 years. By the late 1950's Triumph already knew they needed something better so in 1965 they released their solution, the coil sprung trailing arm setup that first appeared on the TR4A as shown below.



This arrangement persisted through the six cylinder TR range until 1976 when Triumph discontinued the TR6, the above system actually worked pretty well allowing as much as 150hp to be tamed without issue. Amazingly, Morgan ignored all this and continued with a setup that Triumph deemed outdated and redundant by the early 60's.

Morgan on the other hand decided the leaf spung axle over chassis arrangement was perfectly fine, and in 2012 they even considered it suitable for their near 300hp Roadster model. Clearly, it was a very long way off being up to the job of controlling such power and torque, realising this and instead of copying what Triumph had done some 50 years earlier to solve the exact same issues, they simply fitted a rigid anti-tramp bar without properly considering its true operation, then called that fixed .

Morgan didn’t even fit two of the dreadful things, a choice that can only introduce some interesting twisting forces as one spring is effectively a solid rod, while the other does it's best to do what comes naturally

I asked a retired metallurgist pal about the failed bolt. He said: "The failure of your HT bolt looks suspiciously like fatigue with crack initiation at the thread roots which form a significant stress raiser. A suspension component such as an anti-tramp bar is bound to be subjected to cyclic loads, which in this case will be in predominantly in shear, and a bolt having a hardness/tensile strength at a level where a conventional HSS drill makes little impression on it would not be expected to have much ductility. Was the bolt zinc-plated for corrosion resistance? If it was, then hydrogen embrittlement could well be a contributory factor".

Not condoning MMC fitting a single torque reaction arm on the earlier Roadsters, but at least they had the nous to fit it to the offside spring. This because without, the spring wind up would be worse that side due to diff torque reaction. Some US cars in the past used a stronger offside (r/h) leaf spring to counteract same.

The free travel of the suspension is related to lowering blocks. You shorten the spring travel by the thickness of the lowering block. My springs sagged a little. Instead of buying new springs, I had the lowering blocks removed. Now, for 5 years, the spring travel has remained constant and there is much more suspension travel. The other advantage is that the axle is now directly on the spring. This gives much more control when cornering. In my experience, it's better than a Panhard rod plus lowering blocks. When I removed the lowering blocks, I had to remove one of the two layers of rubber bump stops on the upper side of the axle so that the axle could swing out properly after compression.
I would agree with everything Montgue says about the ATBs. You did an excellent write up!

Here is the original report with a few pictures on more of the following pages.

https://www.talkmorgan.com/ubbthreads.php/topics/670243/re-rear-springs#Post670243

I've decided to remove Mogan's super crude rubber rebound blocks, on Monty the rubber they're made from is a very hard compound so offer next to no compliance, they're also too thick in my opinion.

I'll be replacing them with axle mounted bump stops that will give more rebound travel, they also have a shaped strike face and are hollow. With the more advanced polyurethane compound contributing, this all adds up to give an initially softer action that becomes progressively firmer when compressed.



More rebound travel and a way softer more progressive action than Morgan's comically basic hard rubber blocks, in theory these axle mounted polly bump stops should be a win, win, win

I'll let everyone know how they perform

Ok so that's my rear suspension sorted, I've finally regained the rear damper travel lost when I fitted lowering blocks, BCC anti-tramp rear leaf springs and a Bilstein rear dampers.

The spring and dampers are quality components, however, Morgan's damper orientation choice is clearly all wrong, and their hard rubber rebound pads aren't much better either. The key issue was the guy who supplied the Bilsteins really should have explained I needed to raise my top mounts when he sold me the dampers. The end result of withholding this critical information was for some time Monty has been running on his bump stops, obviously this is far from ideal and it eventually resulted in the rear hoop clean tearing itself out of its lower mounts!

With the hoop welded back up I again contacted the Morgan suspension specialist and supplier of my dampers in an attempt to understand why his Bilstiens were forcing Monty to ride on his bump stops ?????

To my surprise he responded by saying he runs the same Bilstein dampers himself, he then went on to admit he'd also ran into the exact same issue. Unbelievably and with no apology offered, he even sent me a photo of his rear upper damper mounts that he'd been forced to raise to reclaim the lost travel, if he'd only told me to do the same when he sold me the dampers a lot of hassle and expense could have been avoided

Anyway, moving on from my disappointment in others, I took ownership and turned on the problem myself. However, rather than weld in new raised upper mounts, I started by studying the natural total stroke of the dampers, I then subtracted the length of the big bump stops that came with them, this give me the Bilstein's true working stroke.

What I discovered was these Bilsteins only have a stroke of 30mm, or no stroke at all on a lowered Morgan if you don't do something about it

To fix it, my solution was simply to reduce the thickness of both the compression and rebound bump stops to regain the correct operating stroke of 30mm, and without the need to weld in raised upper damper mounts, the rest is explained in another one of my really stimulating and award winning videos



Dave.