Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Rear springs

To give a feedback. Today I drove on undulating country roads. As I said before, the control of the handling, the much better handling in the curves speaks for the removal of the lowering blocks. But the last posts made me think. Maybe I need flatter bump stop rubber. So...sorry for possible confusion...more a question, is it like this: When the suspension is compressed the axle moves away from the rubber because the frame goes downwards? But when rebounding there might not be enough space because I had the LBs removed. Is that correct? So rebound is under circumstances stopped too early by the rubbers? So I would have to use flatter rubbers?
My rear shock absorbers are Rutherford AVO TB1260. These are also designed for the Roadster. So they should be long enough to allow more rebound?

Here are two photos from today, the car on its wheels after a long ride, pic taken without passengers. Left and right side. Maybe the car is not standing completely level, maybe the springs are a little different.

Heinz my preference is around a 10mm minimum gap between the axle and rebound rubber to ensure there is enough extension travel for optimum handling and comfort. There is a simple suspension check that might be worth doing particularly if you have or are intending to reduce the rebound rubber’s thickness.

Jack the rear of car supporting it on the frame and let the axle dangle. Now check the axle is nicely sat on the rebound rubbers both sides. You should see some decent compression in the rubbers but defiantly no gap. Two things to look out for. Firstly the u-bolt nuts are not contacting the chassis and the other is that the axle is not being lifted/restrained by the dampers. This is only a crude damper extension check. Remove the top fixing and check the stroke if you want to be certain.

Roger, thanks for your very helpful advice. You say „Firstly the u-bolt nuts are not contacting the chassis“. You mean when the rear of the car is jacked? That is so in my case. You say at least 10 mm minimum gap when the car is standing on her wheels re the rubber. Is there also a maximum of gap recommendation so to keep any protection function against to much extended shocks?
Your advice re the shocks (remove the upper mount) I will check as well.

BTW I have learned that the rubber of the 4/4 is made of two layers where one of them can be removed. Is this a DIY job? Perhaps just screw it off? My son has a lift so that is not an issue.

Yes when the car is jacked on the frame and the axle is allowed to sit on the rubbers, the nuts ideally should be clear of the chassis. Regarding protecting the dampers I’m not aware of any min/max dimensions.

The rubbers are not that difficult to remove. I’ve built them up with layers of 3mm rubber before.

it sounds like Heinz & I are facing very similar situations. And looking at similar solutions.

Could anyone help by telling me the compressed & extended lengths (between the centres of the eyes) of an AVO 1260 damper? AVO 1183 are 210/280mm (too short even with thick rebound bump stops) and AVO 1181 are 240/325mm (but the compressed length does not give enough travel)

With a little luck I find time on Saturday and I can go to my son's hobby workshop. There is a lifting platform. Since the rebound limiting rubbers of the 4/4 are simply double layered, I can remove one of the two layers to try it out after doing a measure how it is now. I will follow Roger's advice to see if the damper limits the rebound or if it is long enough.
But...if the TB1260 shock is designed for the Roadster, then it should be long enough? The Roadster doesn't have a lowering block either? And the frame is about the same, I think? And the compression works fine, it is even less stressed now than with the LBs.
At least my sagged springs compensate a bit for the probably slightly heavier weight of the Roadster at the rear.

It really looks to me the the axle is too close to the bumpstops. I removed one layer of the rubber to maximise the rebound travel but I have a different setup If the axle is hitting the bumpstop hard on rebound it can give the effect of crashing over the bumps that seems very similar to when the shock bottom out.

As pointed out the U bolts (and/or the nuts) should never touch the chassis on maximum rebound. If they do not only will it give a violent jolt in maximum rebound but it will do damage in time. I see from your first photos that the excess thread on the U bolts has already been shortened as much as possible.

I would feel inclined to check it with two people) or equivalent weight) sitting in the car as well. Peter Ballard once told me tha ideally leaf springs should be flat when under normal load, but I'm not sure if that condition can be achieved with a Morgan.

Just a thought but you may be getting less body roll with this setup because the spring on the inside of a curve is at the maximum of its possible extension in corners with the axle resting on the bumpstop. .

I suppose, if necessary, you could always fit thinner lowering blocks.

I guess Kevin the chap who did a nut and bolt rebuild of has been my +8 for the last circa 18 years must have altered the suspension to some degree perhaps with multiple leaf rear springs for even while fully loaded while touring I have no recollection of a jarring experience over undulations..

It was not until I stumbled on this Plus Four road test vid that it seems some folk can experience ride issues in trads that seem worthy of attention..?

If you do not wish to watch the whole vid you can jump in at 7:20 and get ready for the jolt which seems to have come as a bit of a shock to the tester ?

https://www.youtube.com/watch?v=TaZiWVU1vRw&t=530s

So like I said, the car drives very well without LBs in terms of cornering control and general driving feel.
But I had the impression that especially on the highway the suspension does not swing properly. It was somehow very uncomfortable with rough bumps. In the meantime I learned that this happened when bouncing. Travel way to bump is more than sufficient.

Today I did a workshop afternoon with my son. At the beginning we left the full two layer rebound rubbers in place as they were ever. First we removed the old shock absorbers on the lifting platform with the wheels hanging down at their upper fixing point to see if this old dampers still had some reserve in the length. The number according to my Morgan garage four years ago is Rutherford AVO TB 1260. But they have no reserves even with two layer rubber. Without the LBs which I let remove last week they are on the lift at their maximum length. I even suspect that the uncomfortable ride on the road since the LBs are out was partly due to the thick rebound rubbers which came closer to the axle now, but also to the fact that the shock absorbers were at the anchor point in the rebound situation even having kept the thick rebound rubber.

Here a pic of this situation, the old damper without reserve at full length.



I had ordered new shock absorbers from Cain at Wolf Performance. Not because I thought about the length, but because the old shocks were leaking. So it is just a lucky circumstance that Cain's shocks are longer.

old damper at full length 29,5 cm from hole to hole (center of holes).
new one 30,7 cm hole to hole.



old damper fully compressed 22cm hole to hole
new one 23 cm



That means because the LBs are removed the dampers are 1.9 cm less compressed generally. Therefore the difference of 1 cm of the new one more in compressed length is more than on the safe side.

Then we removed the upper thinner layer of the rubber.






I wanted to proceed carefully and perhaps we will reduce even more the hight of the rubber. But even with only 6mm less it is a huge difference to the better. At least I had some kind of small gap even with the full rubber to the axle when standing on her wheels. But I think the dampers had an influence to stop the free rebound as well as said before. Note, with the reduced rubber from 2,6 cm to 2 cm I could not remount the old dampers any longer. They are simply too short on the lift with the wheels hanging down.

The new dampers at full length, mounted at the lower point and here with 6mm reduced rubber on the lift. They make it well.


Enough reserve re the u bolts as well with reduced rubber with wheels in the air on the lift.


enhanced gap between axle and reduced rebound rubber left and right when standing on the wheels, I guess, about 1,3 cm now if you compare the gap with the 2cm hight of the rubber in the pic below. Have not measured it. But good drive.





The dampers of Caine have this name, M6. I have no clue if this is a differentiator, I have to ask Cain. He said the dampers were Mogsport dampers and more for racers, but I must say they are smoother than my Rutherford old ones. Perhaps the Rutherfords were not any longer like new. As I said they leak a bit but they are harder.

[img]https://www.tm-img.com/images/2020/11/14/FBDEC8C9-B28B-4B59-8163-F57767944249.jpg[/img]


The shock absorbers feel very good with my 4 seater 4 leaf springs together. I still have to fine tune the setting. But the first driving impression with the thinner rubbers and the longer new dampers is fantastic! My car never drove like this before.

To Peter's post (Gambalunga). It is an important thought that the disadvantage of the cut off rebound may be an advantage of less body roll. But the cornering is still very good, even if the tail moves a bit more in the curve with rebound possibility. It is a controlled movement. Only on the race track it would be an advantage. But there the laws and conditions are completely different anyway.

A good day’s work Heinz and an interesting report, thanks for posting. I think you will be very pleased with the results

Now that you have sorted the extension travel I guess the next task will be to check out the bump travel especially with those new dampers and their slightly longer compressed lengths