Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Knackered AVOs

My Roadster came with AVO's in 2008. I was very happy with them.The rears leaked after a few thousand miles so I renewed all four. I fitted AVOs to my 2012. When I got my 2016 P4, what did surprise me was how good the standard non adjustable Spax were. They were vice free. I replaced them with AVO's which are still fitted and there was only a marginal "improvement" in feel, which basically boils down to being a bit harder.

In the meantime, I had driven from Canterbury to Yorkshire fully loaded, with a rear damper bracket broken, and you could not tell. Much later I drove from Ullapool to Yorkshire fully loaded with one front top mounting disconnected and it was the same. There were no indications of zero damping. Since then I fitted Spax Gaz adjustables to my Roadster, but quite honestly the difference between having a damper or not is hardly detectable.

So I applaud those who innovate and experiment with fancier dampers, but I remain unconvined that changes make much difference. For that reason I haven't done theSSL front or five link rear.

The changes which did make a noticeable difference are Rog's bump assists, changing the six leaves for four on my Roadster, adding Mulfab steering bearings to my Roadster, and adding a Panhard rod, again to my Roadster. All were very worthwhile improvements.

montegue,

Yes I was going to ask you about the top hoop mount, it doesn't look standard and is much beefed up! That can't hurt, the crappy spot welded original mounting tube is useless were real force applied.!
But it does look a little lower than the original and perhaps wider ie further out from the tube. Can't clearly see it in the pic's. Have you lost some length to it being more vertical, Can't be much though. Have you checked the closed length of the shock without the bump stop fitted. If you can get another 20=30mm or so you could get a smaller bump stop which will still protect the damper from bottoming out. If you look at the current bump stop and the lowering plates there must be 30mm+ there to get. The 4 seater has a massive bump stop despite the massive springs and seems to be driving on those when 4 up. Rog's assisters are fully adjustable and really smooth those crashing thumps you can get from awful road surfaces and on my car I would say that it's 90% better and when I do get a bad thump it still feels as though the suspension hasn't bottomed out and the evidence marks on the springs show (I believe) that the assister cones still have plenty of range left in them that as yet I haven't needed. Because you have in effect lifted the axle and not the springs Rog's assisters should still fit within their normal fitting perameters.

+1

Rog's bump stops were the simplest and best mods ever for my more recent trads. Really worth doing to any trad with the rear hoop.
Nick

I'll definitely fit a set Nick, but not until I've raised my top damper mounts by 35mm to regain my lost damper compression travel.

For a long time now it's been clear to me the 20mm lowering blocks I fitted lost me 20mm of super valuable, and in very short supply compression travel. I also believe the BCC anti-tramp springs lost me a further 10mm of compression travel, this is born out in the measurement comparisons Roger and I have been running through together over a series of emails .

Thanks Rog

When we study the distance from the leaf spring to the centre of the top damper bolt we get 205mm on Roger's Plus 4, a Trad built in the same period as Monty. However, when I take the same measurement on Monty I get 175mm, a difference of 30mm. I've also taken some other measurements such as clearance between the axle tube and my inner wheel arches, and while everything tells us the top mounts only need to be raised by 30mm, I believe I can actually squeeze this to 35mm and still clear everything.

Five millimetres more doesn't sound like a lot, but with rear suspension compression travel in such short supply on our Trads I figure if I'm going to raise the top mounts, I may as well do so by as much as I possibly can, so 35mm it is.

But no more than 35mm

Once I've done this I can fit Roger's spring assisters, adjusting them with what I've calculatedto be a 30mm clearance (elastomers to leaf spring faces), and then finally a safe deletion of the Bilstein damper's 30mm bump stops, like this I should end up with 50mm of damper safe compression travel.

That is 35mm gained by raising my top mounts, plus 30mm from deleting the damper bump stops, gives me 65mm of compression travel. However, I will then deduct 15mm to keep the damper safe to finally give me the 50mm of safe usable compression travel. I believe the conical rubber elastomers used by Rog give a true maximum working compression of 20mm, so Ill set the spring to elastomer clearance at 30mm.

This will give 30mm of spring travel before the rising rate elastomers come into play, at the full elastomer compression of 20mm plus the 30mm, I will end up with rear suspension that has 50mm of damper safe compression travel in total with the last 20mm of this travel being a rising rate system that ensures progressive compression, thus eliminating the violent bottoming out behaviour that thankfully is actually quite rare on Monty.

Well, thats the plan

Dave

Dave, if you raise the hoop height, which I think “was” your plan. Remember the H/Brake cable length to the drums etc.

It's a good point, and for this reason it's probably a good job we didn't achieve much hoop lift when it was re-welded.

One thing I can definitely confirm that may be on interest to others, is a softer font end definitely equates to a less unsettled rear end. The Mulfab front wishbone conversion is excellent, it works way better than the unequal length wishbone and Bilstein coil over setup on my TVR ever did, it delivers a lot less dive and roll.

Well done Peter Mulberry

What was letting it down were my adjustable AVOs, they were completely knackered, I'd wound them right up but in truth they really had nothing more to give, they were leaking badly so had zero damping and all their cheesium bushes were completely shot too!

Enter the Protechs, the first thing I noticed was the adjustment actually works, way better than my adjustable Gaz Gold Pros I ran for a while on my TVR, those things were quite crude and seemed either floppy as a man needing a blue diamond shaped pill, or hard as hell with nothing in between. I could never get them right, the Protechs on the other hand give genuine click by click adjustment you can actually feel, I started on 8 clicks and am now on a far softer setting of 5.

And what I discovered was the softer I went on the front the less unsettled the rear became, and noticeably so too. I honestly think the stiffer front setting sent loads down the chassis the rather basic live axle and leaf sprung rear setup wasn't able to cope with very well at all, this discovery got me thinking, perhaps an original sliding pillar front suspension is quite hard, so maybe its not helping the rear end situation?

Don't get me wrong, with the far softer front end the wibble wobble Morgan chassis still twists and flexes, but it seems to do so in a more controlled way, I'm out now and have just stopped after another epic Monty blast, one of the roads I specifically chose for its multiple unsettling camber changes and its frequent suspension confusing dips and bumps, its a proper roller coaster. However, I was able to rip down this challenging road at 80 leptons with absolutely no brown trouser moments at all, how very un Morgan like!

Monty took it all in his stride, letting the wheel stay light in my hands I could feel everything working in harmony, the softer but super well damped front end now being very well matched to the Bilstein damped rear, and the flexible chassis between them playing its part in the whole suspension system.

I appreciate anyone other than Morgan owner would probably read the above with utter horror, but for me it's all about what the Japanese refer to as Wabi-sabi, this being the theory that perfection is sometimes only found within imperfection. What I can confirm is, Monty rides and handles better than he ever has, but he's certainly no Lotus.

However, if giving driving joy is the true measurement of success, Monty's Wabi-sabi approach to handling is definitely now delivering in spades

I absolutely love this. If ever a Morgan was summed up in one phrase, this is it.

And, of course, the perfect state of imperfection will vary with the owner - just as it should.

Handbrake cable routing can be accommodated into a higher hoop by welding in lower carrier bracketing/frame to in effect keep the handbrake cable standard. I believe the hoop for the four seat version is in fact higher and might be a good starting point to re-mod for monty. I also think that if you gain that amount of travel for the suspension/shock's you would still be able to fit bump stop protection to the shock of a size that would probably never come into play but it would be nice to know its there just for that once a year fright!

Your'e totally right about the softer front end improving the whole ride but on the standard sliding pillar set up it will never be possible to achieve Monty's wishbone positivity or travel. Did you buy Monty for that set up or were you pleasantly surprised that it was fitted. I so wish it had been made into a parts kit which was readily available but I seem to remember there being a lot of poo-pooing of it at the time as it couldn't possibly a trad Morgan if that was fitted! It could have been a real move forward for the classic in its last ten/fifteen years of production as the cars in performance had moved from a B road Sunday driver to a bit of a sporty number and the limitations of the 1936 4/4 front end became very apparent. Morgan have now gone where Land Rover did with the new Defender and there is a massive gulf between what existed four years ago in A Morgan car and the current configuration. Apart from these two examples in the car world only the Bugatti had done this although it was more a badge re-birth than a transitional car.

UPDATE!

Yesterday, and as an experiment, I lowered Monty's Mulfab front wishbone conversion front end by 23mm on the new Protech coil overs.

I brought the front end down to more or less where it was with the AVOs largely to test if the improvements I've experienced with the Protechs are only coming from their superior damping, or as I suspect, roll axis is also at play?

In theory the effects of lowering the front will be:

A 23mm reduction in ground clearance over the initial higher setting I’ve been running for the first few days with the Protechs

Pretty obvious really, however the car isn’t sitting much lower now than it was on the knackered AVOs, the Protech have much better damping & control, so I do not see that this one causing any issues


An increase in forward bias rake

Typically should improve high speed stability, this worked really well on my TVR


A reduction in the preload on the springs

The effect will be nominal as the 275 lb spring rate remains the same


A decrease in compression travel

Only an issue if I find the bump stops, the Protechs have far greater travel than the AVOs so I do not anticipate any issues here


An increase the rebound travel

Again, the Protechs have far greater travel than the AVOs so I doubt I need the additional articulation at full droop


A lowering of the centre of gravity (front end only)

Should improve turn in and cornering speeds


A decrease in the front roll centre

Should improve turn in, but may increase roll


A change the relationship between the front and rear roll centres (roll axis)

This is the big one, while a lower roll centre is better for handling, what's more important is the relationship between the front and rear roll centres, i.e. the roll axis


On a live axle the roll centre is the nose of the diff, this gives vehicles with this ancient arrangement a very high roll centre, typically a live axle is slung under the chassis but Morgan fitted it above the chassis, this was a trick used in the 1930's to make a car look lower and more sporty but it actually makes the roll centre even higher which is never a good thing for handling. Unlike Monty's adjustable wishbone front end, the roll centre at the rear its largely fixed. Excluding the lowing blocks, changing the roll centre front to rear (roll axis) can only really be achieved with the Protechs on the front, but I can definitely use them to change how Monty handles during cornering, his overall weight distribution and rake.

Changing the roll centre will transfer weight front to rear, more weight on the flawed rear suspension will make it work even harder, while more weight at the front will improve front-end grip and by taking some load of the rear may also improve overall ride quality. It all needs testing, for example lowering the front may have a negative impact on Monty's front end ride quality because as his tires move up and down relative to the body, the height of the roll centre causes a side-to-side motion of the tire contact patch which is clearly undesirable for smooth suspension articulation.

For many reasons the 23mm front end drop I dialled in yesterday has the potential to have a negative impact on Monty's handling and ride quality. However, changing the relationship between the front and rear roll centres is a real science and the results could easily go either way, ultimately the only way to find out is test it, so I'll report back here with my findings. Essentially what I'm looking to study and understand with this experiment is how the front end effects the rear, I've already proven a more compliant and well damped front end noticeably improves the behaviour of the rear suspension.

What I now need to study are the effects of altering the roll axis, i.e. the line drawn from the rear roll centre to the front roll centre?



Every car is different, to achieve better handling and go faster one must properly understand what the car likes and doesn’t like, and the best way to achieve this is to experiment with different setups until the Goldilocks settings are found.

After that, it’s back to accepting the limitations of the system, managing one’s expectations of what it can ultimately achieve, and of course being guided our old friend and mentor Wabi-sabi