Talk Morgan

Roadster 5 link rear suspension re-visited

Posted By: Richard Wood

Roadster 5 link rear suspension re-visited - 06/07/19 03:50 AM

Whilst visiting Cain yesterday (Wolf Performance) to collect completed valance, the discussion ventured over to the choppy ride I get with my Roadster on anything less than smooth roads. We discussed front spring options to compliment the AVO adjustable shocks I already had. Cain then asked for a ride in my car as he had not been in a 5 link Roadster before. I went one step further and let him drive whilst we sought out rough country roads (not difficult). Within half a mile he pronounced the issue was with the over stiff rear suspension despite two up and near full tank. For my part I had a mind set the issue was with the front given that's the first wheel to travel over any indifferent road allied to the unique nowadays, pillar suspension. He went on to explain that it was a reaction from the back kicking the front hence need for good front damping. After a few spirited blasts up to 6000 rpm in second and third he further pronounced the rear "well planted" but in need of some alternate coil spring damper units.

Fast forward a couple of hours to a visit to Krazy Horse to buy a new mirror. Spoke to Dan Whiting about the 5 link rear and he immediately volunteered that having now got a 5 link Roadster demonstrator they finally had the opportunity to check it out and had come to the exact same conclusion. As they had a pair of modern three wheeler springs lying around they had swapped out original coils for these. Now I can confirm the standard three wheeler rear is quite soft with plenty of articulation. Quite bizarre then they found their Roadster a tad more comfortable but far from under sprung, although now needing softer damping. The ride is so similar they are leaving the three wheeler springs on whilst they investigate properly engineered coil spring damper units. Brilliant minds etc.

I think we can expect little from the factory now given the Roadsters days are numbered but am now convinced this is the route to a more compliant car.

Would be interested to hear comments from other 5 link Roadster owners re above, now that version has been out for over a year.
Posted By: HKNYMOG

Re: Roadster 5 link rear suspension re-visited - 06/07/19 03:06 PM

The ultimate question is how much you can do with an inherently loose chassis. I suspect that if you have a planted and stiff rear end is that something has to give in the other direction. Some part of the suspension has to react to the forces running through it which are amplified by a lack of stiffness in the overall platform. If the rear is inherently stiff, the front end, which is more reactive, reacts in a more pronounced manner. I would think if you stiffen the front end further, you would make the chassis more reactive. If you decrease stiffness in the rear, you would distribute the acting forces more evenly, but at what cost to rear end grip?

With only 2,000 miles on my Roadster, I suspect that you are correct that there is a more “dialed in” solution. My car has the front end bob even on smooth roads. It would be nice to experiment with various damper and spring settling to see if you could capture that elusive balance. That said, it will always be a compromise as you are not working with a very stable platform. When setting up a race car, you only need to think so much about chassis compliance as it is not a major concern. Here, you need to put it front and centre which is complicated.

Aside from the never calm front end, my major complaint is the lack of steering feel and the general numbness of the suspension, particularly at the limit. You have an odd combination of both under and oversteer which could be fun, but you have only the tires to listen to in terms of judging when grip is going to give way. My solution for the time being is to take this as a given and enjoy the ride.
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 06/07/19 05:17 PM

AVO adjustable shocks on setting 6 cure the front end bob on mine. It does little to cure what I now realise is an excessively stiff over dampened rear though which gives the harsh uncompliant ride on anything less than a smooth surface.

Driving over those thin supermarket car park speed bumps highlights this. Even on setting 6 at the front I get just over one bounce, at the rear hardly one full bounce. The axle is well supported with the five links almost irrespective of springs and dampers. As you suggest a dialled in solution would hopefully allow a satisfactory compromise without excessive roll.

Maybe it's because I'm getting old oldgit but after nearly 7000 miles covered I'm becoming less willing to put up with the jarring from the poor roads in our county.
Posted By: IcePack

Re: Roadster 5 link rear suspension re-visited - 06/07/19 06:01 PM

One thing to bear in mind re nodding front is the main spring hub rebound spring set up. My 4/4 does not suffer any nodding with the hub just kissing the rebound spring. (At one person up load)But big but, the front often ( all the time) crashes over most pot holes speed bumps etc. This is because with only 90lb main springs & only 21/2” inches of movement the suspension “bottoms out” & I guess hits the stops within the avos or goes coil lock. I am told the factory just went for weaker springs to try & soften the ride. Unfortunately as in the posts above suspension is much more complex art. Hopefully at some point fitting firmer main springs will help the front as my rear suspension is fully sorted thanks to Roger’s progressive bump stops.
Posted By: HKNYMOG

Re: Roadster 5 link rear suspension re-visited - 07/07/19 01:01 AM

Richard/Ice- thx for the replies. Will try both on the front end. Feel my rear is more sorted, except when I bottom out. The bob is a bummer as is the cowl shake.
Posted By: Heinz

Re: Roadster 5 link rear suspension re-visited - 07/07/19 08:11 AM

I don't have a 5-link rear axle. But I have to say that with my two Morgan where the shock absorbers were adjustable it was always a better ride when it was softer in the back than in the front. This is probably the same with 5-link as with conventional suspension. I also believe that it is basically due to the structure of the flexible ladder frame. And one shouldn't force this ladder frame into something that isn't its nature by choosing a too hard rear setting regardless of the axle type.
Posted By: Lowflyer

Re: Roadster 5 link rear suspension re-visited - 07/07/19 10:59 AM

I have the suplex set up on the front lf my plus 4 and sourced matching bilstein shockers for the rear so i have bilstein all round. The standard rear leaf spring set up on the back much improved the ride quality after i gave the rear springs a severe lubricating. It took a while and a few hundred miles to achieve the improvement. Lubricating the rear springs was something that i overlooked, the cars clearly leave the factory un-lubricated. I can actually feel the increase in compliance when i did a before and after press on the rear end to check the bouncability. I think ive gone as far as i am prepared to in order to improve things in this department apart increasing the tyre profile when new rubber is due.
Posted By: Button

Re: Roadster 5 link rear suspension re-visited - 07/07/19 03:27 PM

Originally Posted by Lowflyer
I have the suplex set up on the front lf my plus 4 and sourced matching bilstein shockers for the rear so i have bilstein all round. The standard rear leaf spring set up on the back much improved the ride quality after i gave the rear springs a severe lubricating. It took a while and a few hundred miles to achieve the improvement. Lubricating the rear springs was something that i overlooked, the cars clearly leave the factory un-lubricated. I can actually feel the increase in compliance when i did a before and after press on the rear end to check the bouncability. I think ive gone as far as i am prepared to in order to improve things in this department apart increasing the tyre profile when new rubber is due.


I agree. In a conversation with Peter Mulberry about 10 years ago, Peter told Me that cleaning and lubricating the rear springs is the single most important item to address for a more compliant ride in a Morgan. I did this and I feel I have about as compliant ride as obtainable in a Morgan. I now spray chain oil on the top of the spring and it works itself in between the leafs. Last year I took the spring apart to insure it was getting lubrication properly. It was!

On My 650 mile trip to Sun Valley and back to Seattle I took separate routes with many different road beds. It was easy for Me to determine that it was the quality of road that is causing the uncomfortable ride. As was stated there is just so much one can do with Morgan suspension..
Posted By: CooperMan

Re: Roadster 5 link rear suspension re-visited - 07/07/19 03:38 PM

Originally Posted by HKNYMOG
Richard/Ice- thx for the replies. Will try both on the front end. Feel my rear is more sorted, except when I bottom out. The bob is a bummer as is the cowl shake.


At only 2000 miles your kingpins will still be tight, so give them some grease perhaps every 2-300 miles (mine were quite dry from the factory) whilst they bed in

Also are your tyre pressures too high this can induce nodding too
Posted By: CooperMan

Re: Roadster 5 link rear suspension re-visited - 07/07/19 03:53 PM

Originally Posted by Richard Wood
Whilst visiting Cain yesterday (Wolf Performance) to collect completed valance, the discussion ventured over to the choppy ride I get with my Roadster on anything less than smooth roads. We discussed front spring options to compliment the AVO adjustable shocks I already had. Cain then asked for a ride in my car as he had not been in a 5 link Roadster before. I went one step further and let him drive whilst we sought out rough country roads (not difficult). Within half a mile he pronounced the issue was with the over stiff rear suspension despite two up and near full tank. For my part I had a mind set the issue was with the front given that's the first wheel to travel over any indifferent road allied to the unique nowadays, pillar suspension. He went on to explain that it was a reaction from the back kicking the front hence need for good front damping. After a few spirited blasts up to 6000 rpm in second and third he further pronounced the rear "well planted" but in need of some alternate coil spring damper units.

Fast forward a couple of hours to a visit to Krazy Horse to buy a new mirror. Spoke to Dan Whiting about the 5 link rear and he immediately volunteered that having now got a 5 link Roadster demonstrator they finally had the opportunity to check it out and had come to the exact same conclusion. As they had a pair of modern three wheeler springs lying around they had swapped out original coils for these. Now I can confirm the standard three wheeler rear is quite soft with plenty of articulation. Quite bizarre then they found their Roadster a tad more comfortable but far from under sprung, although now needing softer damping. The ride is so similar they are leaving the three wheeler springs on whilst they investigate properly engineered coil spring damper units. Brilliant minds etc.

I think we can expect little from the factory now given the Roadsters days are numbered but am now convinced this is the route to a more compliant car.

Would be interested to hear comments from other 5 link Roadster owners re above, now that version has been out for over a year.


Richard, I came to the same conclusion last year after only driving the new Roadster for a few weeks and comparing it to my previous very well sorted S1, so I forked out for a SSL front kit, as I felt the standard front set-up was fighting a very stiff rear

It definitely improved balance & nodding but I still suspect the rear has way too stiff springs, of course the MMC 5link is derived from track handling tests whereas the SSL rear links the diff in a completely different way and was set-up for road style driving / comfort. Dan at SSL knows my feelings & agrees so perhaps he may develop a tweak kit
Posted By: MOG 615

Re: Roadster 5 link rear suspension re-visited - 08/07/19 08:57 AM

I fitted the SSL front kit many moons ago, and have been very pleased with the results. The only real issue for me is the need to keep adjusting the ride hide to get the optimum setting at regular intervals, say each service.

Last year I fitted the 5L rear and although the ride improvement was not as dramatic as I had hoped , it was an improvement. However the big bonus was a really drastic improvement in the handling. It has sharpened the turn-in, and taken completely tamed the rear end waywardness that is inherent using leaf springs and a powerful engine.

I think the balance between front and rear is really good, and the whole car feels so much better. I am now happy to let my wife drive fast in the wet and I will nod off in passengers seat (on longer journeys!)
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 09/07/19 07:46 AM

Just to add I wasn't referring to the SSL kit but MMC's own version and spec of such. On a mixed road 240 mile trip on Sunday the ride was considerably improved by having a heavily laden suitcase on the rear carrier although only myself and small dog as passenger. As expected not a hint of bottoming out due to high spring rate and dampening but definately favourable articulation, maybe requiring a click more on the front AVO's as well, highlighting how the rear affects the front as Cain had previously suggested.

To cast the net further as I believe the ARP4 had similar 5 link rear (and have been around longer), I wonder what spring and damper rates were used on those.
Posted By: MOG 615

Re: Roadster 5 link rear suspension re-visited - 09/07/19 02:03 PM

Originally Posted by Richard Wood
Just to add I wasn't referring to the SSL kit but MMC's own version and spec of such. .


I had assumed that, Richard.

I too have realised that playing around with the front suspension definitely affects the rear. In my case I have been trying to get the optimum setting for the front ride height (on the Suplex/SSL platforms) so the rebound springs are taken out of the initial loading on bump. This has had a big effect on the bump absorption at the front AND appears to have softened the rear as well (although I made no changes there)

To me the balance front/rear now feels pretty good running solo. I will be interested to see whether it changes when touring 2 up and laden.
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 16/07/19 11:33 AM

Just had a chat with Dan White at SSL. Apparently they are already working on alternative coil spring/damper units. Thoughts are that MMC went for excessively stiff units to limit roll. SSL's own 5 link offering has top links angled inwards to limit roll, so allowing softer springs. For the factory system which has parallel links top and bottom, they are hoping to provide progressive springing using two end to end to give a more immediate effect on roll control. Conversion when available in six to eight weeks, will be adjustable for both spring pre-load and damping.
Posted By: CooperMan

Re: Roadster 5 link rear suspension re-visited - 16/07/19 02:02 PM

Richard, having discussed this with Dan a few times over the last 12 months, he knows the issues with mine (1st production 5link) problem is the spring length available on the MMC setup is difficult to get 2 coil springs in and not coil bind in compression, but fingers crossed he develops a solution
Posted By: Gambalunga

Re: Roadster 5 link rear suspension re-visited - 16/07/19 05:22 PM

Originally Posted by MOG 615
I too have realised that playing around with the front suspension definitely affects the rear. In my case I have been trying to get the optimum setting for the front ride height (on the Suplex/SSL platforms) so the rebound springs are taken out of the initial loading on bump. This has had a big effect on the bump absorption at the front AND appears to have softened the rear as well (although I made no changes there)

To me the balance front/rear now feels pretty good running solo. I will be interested to see whether it changes when touring 2 up and laden.

I have increased the size of the tyres to 195/65 R15 so this lifted the front end by 10mm. I then used 10X1mm shims (from the race kit courtesy of Peter Ballard) under and 10 over to lower the ride height to maintain the same front ride height of the car. On the rear, because we often tour with heavy luggage ( swmbo ) I have fitted slightly higher rated springs on the rear. I still need to play aroundd with the damping a little at the rear though. I still occasionally get bottoming out on bad bumps. It would be less of a problem if our roads were less of a problem swear
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 17/07/19 07:39 AM

Originally Posted by CooperMan
Richard, having discussed this with Dan a few times over the last 12 months, he knows the issues with mine (1st production 5link) problem is the spring length available on the MMC setup is difficult to get 2 coil springs in and not coil bind in compression, but fingers crossed he develops a solution


Yes I mentioned to him the possibility of concentric springs to achieve desired progression but don't know if that's practical. His follow up suggested not. Apparently a single progressive spring wouldn't give the necessary roll resistance so final solution will be something of a balancing act.
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 02/09/19 09:47 PM

First complete assembled Spax coil spring/damper unit from SSL to address the over firm, over damped units on the factory 5 link rear. As promised adjustable spring pre-load and damping for these dual spring rate units.

[Linked Image]

Provisionally arranged to have a pair of these fitted next week at SSL allowing an immediate opportunity to evaluate drive


Posted By: CooperMan

Re: Roadster 5 link rear suspension re-visited - 03/09/19 01:27 PM

Well despite discussing with Dan over 14 months ago, us impecunious northerners are last in the queue

Many thanks for posting Richard, update patiently awaited, I'm so close to SSL you can call in for a cuppa
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 10/09/19 08:24 PM

Long day travelling first to SSL and then return to Norfolk. Met the hospitable Dan White, a director of SSL, to have a pair of his prototype dual rate coilspring/damper units fitted. His able assistant Andy had them on in no time after jacking up the chassis just enough to remove weight on wheels and allow easy removal of mount bolts.

Meanwhile Dan explained just how they were going to work. The short higher rate spring at the bottom dilutes the rate of the longer softer spring giving an even lower overall spring rate initially as per the reciprocity formula of springs in series. After a calculated 25mm of suspension movement above static, the shorter spring becomes coil bound leaving the longer spring alone in play with consequent immediate increase in spring rate to limit roll.

As the new units were the same free length as OE, the swap over was very quick and easy.

[Linked Image]

[Linked Image]

Andy noticed the axle was not quite central to the chassis so that was tweaked as well via the panhard rod. Unfortunately this then left the wheels not centralised to the body, although only by a few mm, so a compromise was found. Dan and I then went for a 5 mile test drive on his favourite set of local roads.

I drove first and immediately noticed the expected softer ride. I could say it was like a magic carpet but that might be overcooking it wink It was a substantial improvement though with no more crashing over bumps as before. We tried a few speed bumps and it took those in its stride as well. What I wasn't expecting was an improvement to the cornering though. Sitting close to the back axle the improvement is felt literally through the seat of your pants. The sudden increase in spring rate limits roll even better than before increasing grip of tyre on outside of turn. This translates to even better tuck into corners although it was good before. Dan then had a very spirited drive and pronounced the settings as good as you could get in a single days testing. As mentioned before these units are adjustable for both spring pre-load (via locked base collar) and damping to compensate for driving style, touring etc.

Job done we retired to the pub for a late lunch followed by comfy drive home A very enjoyable and informative day.

I understand these units are now available for other 5 link Roadster owners.
Posted By: MDS61

Re: Roadster 5 link rear suspension re-visited - 10/09/19 08:41 PM

That is a super update Richard.....I would like that for Seve'

Thanks Mark
Posted By: CooperMan

Re: Roadster 5 link rear suspension re-visited - 11/09/19 07:49 AM

Richard, many thanks for the photos and update thumbs
Posted By: OZ 4/4

Re: Roadster 5 link rear suspension re-visited - 11/09/19 07:54 AM

Fantastic post.....
Posted By: MOG 615

Re: Roadster 5 link rear suspension re-visited - 11/09/19 07:56 AM

Richard

I am pleased that you have a good result from the SSL work.

I am also of the opinion that although the ride comfort is improved , the most noticeable difference is the vastly improved turn-in with the SSL 5L on my +8.

It really does makes driving twisty roads so much more pleasurable, and that slight "twitch" that you get with the rear weight transfer on cornering hard (especially in low friction conditions) is eradicated.

OK the conversion is not cheap, but in my opinion well worth while.
Posted By: Gambalunga

Re: Roadster 5 link rear suspension re-visited - 11/09/19 08:21 AM

One of the interesting things is the way in which this type of suspension keeps more weight on the inside wheel which tends to stop it losing traction in hard cornering.
Posted By: PaulJ

Re: Roadster 5 link rear suspension re-visited - 11/09/19 09:31 AM

I have had this setup on my ARP4 for 3 years or so now, after contacting Peter Ballard who I believe may have thought up this design. I initially found the ride choppy although do not remember it bottoming out. Peter sourced the short springs and some shorter main springs which I then fitted.

The ride immediately improved, as per Richards report, however I was having problems with bottoming out when fully laden with passenger and luggage. Having screwed the spring seats to the top of their travel and set the damping slightly harder when touring laden, this has largely been eliminated except on the worst of bumps. I think a slightly longer spring would really be called for, which would lift the rear of the car a little more, this is probably what is now being used, however I cannot be bothered to spend money and time for what would be a small and occasional improvement and am pretty happy with the setup as it now is.
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 11/09/19 10:04 AM

Originally Posted by Gambalunga
One of the interesting things is the way in which this type of suspension keeps more weight on the inside wheel which tends to stop it losing traction in hard cornering.


Thanks Peter, omitted to mention that although very relevant. TBH I was expecting just an improvemet in the ride with a compromise on OE roll resistance. What I got was an improvement in both thanks to Dan's magic thumbs

In retrospect it has highlighted the front end stiffness now. Dan has just emailed me suggesting I fit the SSL kit, which I may now do if it's compatible with the AVO's I already have.
Posted By: Gambalunga

Re: Roadster 5 link rear suspension re-visited - 11/09/19 10:13 AM

Originally Posted by PaulJ
I have had this setup on my ARP4 for 3 years or so now, after contacting Peter Ballard who I believe may have thought up this design. I initially found the ride choppy although do not remember it bottoming out. Peter sourced the short springs and some shorter main springs which I then fitted.

The ride immediately improved, as per Richards report, however I was having problems with bottoming out when fully laden with passenger and luggage. Having screwed the spring seats to the top of their travel and set the damping slightly harder when touring laden, this has largely been eliminated except on the worst of bumps. I think a slightly longer spring would really be called for, which would lift the rear of the car a little more, this is probably what is now being used, however I cannot be bothered to spend money and time for what would be a small and occasional improvement and am pretty happy with the setup as it now is.

Peter Ballard was the designer of the SSL (previously Suplex) 5 link suspension. It was still in development when Morgan first saw it but for some reason or other they decided to develop their own design. I know that Peter did offer some advice as the system was developed from one version to the next.

A longer spring would allow an increase of the preload but the result would be a higher static ride height and the possibility of the suspension topping out on the rebound. As the spring rate would not change the travel, when hitting a bump, would remain the same. Because we had the same problem when touring I had SSL make me a slightly higher rated spring for our 5L suspension.
Posted By: MOG 615

Re: Roadster 5 link rear suspension re-visited - 11/09/19 10:14 AM

Originally Posted by Richard Wood
Originally Posted by Gambalunga
One of the interesting things is the way in which this type of suspension keeps more weight on the inside wheel which tends to stop it losing traction in hard cornering.


Thanks Peter, omitted to mention that although very relevant. TBH I was expecting just an improvemet in the ride with a compromise on OE roll resistance. What I got was an improvement in both thanks to Dan's magic thumbs

In retrospect it has highlighted the front end stiffness now. Dan has just emailed me suggesting I fit the SSL kit, which I may now do if it's compatible with the AVO's I already have.


Richard

I can certainly recommend the SSL front kit, I suspect you will find it will OK-ish with the AVOs but perhaps better with a set of adjustable Spax specifically developed for this application by Dan and Peter , or the original ( to this kit) non-adjustable Bilsteins (which I have)
Posted By: CooperMan

Re: Roadster 5 link rear suspension re-visited - 11/09/19 11:05 AM

Despite my 3.7 being equipped with the 5 link, after only a couple of months I just had to swop the front to SSL, I had obviously become used to the front end feel of SSL for 5 years on the previous Roadster
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 11/09/19 12:40 PM

Originally Posted by CooperMan
Despite my 3.7 being equipped with the 5 link, after only a couple of months I just had to swop the front to SSL, I had obviously become used to the front end feel of SSL for 5 years on the previous Roadster


Following on from my post above, have just ordered the front RS kit from Dan who already has them in the post to me. He did a deal minus shocks and steering bearings as I have them already.
Posted By: PJB

Re: Roadster 5 link rear suspension re-visited - 14/09/19 05:36 AM

Reminder. The initial harshness of the original front suspension setup is due to the rebound spring and main spring being compressed together at ride height, their stiffnesses add together resulting in a very stiff initial spring rate. That is what causes the nose of the cars to bob up and down, that is the car bouncing on the front tyres at around 3 Hz.
To get rid of that initial stiffness and resulting harshness to thus get the front suspension to actually work the rebound spring must be only just kissing the slider/hub at ride height, you must be able to turn it by hand. This requires a shorter main spring and/or a shorter rebound spring or go for a main spring supported on adjustable spring seats.
Declared interest - Director of SSL, product range includes the SSL 5L rear suspension, SSL RS front suspension and alterative springs and dampers.
Regards Peter J Ballard. http://www.suspensionsupplies.co.uk/
Posted By: PaulJ

Re: Roadster 5 link rear suspension re-visited - 14/09/19 01:34 PM

What Peter says re. the rebound spring compressing the main spring, on the front suspension, makes perfect sense. In fact I can't help but wonder why MMC decided to put the two springs into contention with each other in the first place, or maybe it wasn't an actual design decision, rather something that just happened?
Posted By: Peter J

Re: Roadster 5 link rear suspension re-visited - 14/09/19 01:58 PM

I had an extended ride across Salisbury plain in Peter Ballard car, "Molly", now in the ownership of my pal Ian.
With SSL's front and rear ends the ride was remarkable: no "Morgan nod", no crashing in and out or ruts: just composed.
Ian said that other than a slight tendency to follow longitudinal ruts, such as where a cable tench has been laid and badly repaired, it is remarkably good.

I had a long chat with Peter about the suspension on my Plus 8, which he and Dan drove extensively, in early 2014 and have some very good pointers as to the best way to refine the ride, without harming the roadholding. It seems my car had Koni/Erbach suspension later cars have non adjustable SPAX coil-over units. As the suspension is now 41000 miles run and upgrade is due, Peter agreed to recommend SPAX adjustable units, probably with progressive springs.

The service this November will be costly as the front upright road joints also need replacing.....

Still cheaper than a new Plus Six! exting
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 14/09/19 05:00 PM

Originally Posted by PaulJ
What Peter says re. the rebound spring compressing the main spring, on the front suspension, makes perfect sense. In fact I can't help but wonder why MMC decided to put the two springs into contention with each other in the first place, or maybe it wasn't an actual design decision, rather something that just happened?


Ironic that in preparation to fitting my SSL RS kit I measured the length of rebound springs yesterday as best I could static with Wolf gaiters on. I then realised I could turn the nearside one just. When I checked the offside not only could I turn it easily, but found 2-3mm of vertical movement. This despite have Wolf lower steering bearings which take up an extra 3mm! I guess the main springs have settled although only 8000 miles covered. Maybe as I drive mainly solo it explains the difference as well.

This discovery threw out the window the premise that compressed rebound springs accounted for harsh front ride. Nevertheless expect a comfort improvement when kit is fitted.
Posted By: PJB

Re: Roadster 5 link rear suspension re-visited - 15/09/19 08:35 AM

Thanks to you all adding your observations for us all to share.
Additional tech. for those new to the Traditional Morgan front suspension...….

1. If one has "zero droop" on a suspension, rather than allowing droop as well as bump from static ride height, the roll stiffness is doubled. But zero droop causes the occasional knock as the suspension tries to droop after a compression. Thus some compliance in droop softens that, hence a rebound spring.

2. By controlling droop the front instantaneous roll centre moves from below ground to ground level. That lifting of the roll centre, reduces the 'roll moment' and thus increases roll stiffness.

3. If you have a gap between the slider/hub and the rebound spring you loose that initial high roll stiffness. If you have the rebound spring compressed you not only get harsh initial ride but the roll centre moves as you enter a corner so the balance of the car changes, not nice. Read http://www.britishv8.org/Articles/Morgan-Plus-8-Road-Test.htm "...……..and by the front-end suddenly going softish.." That is the slider/hub coming off the rebound spring! You need a main spring that can be preloaded to balance the corner weight and set the rebound spring contact.

4. MMC do know the effect of the rebound spring and do try to get the main springs the right length but there are so many weight variants they prefer the compressed rebound spring option, rather than a gap - playing on the safe side. But of course Morgan supply the RS as an option on new builds anyway.

5. Morgan have relied for decades on that high initial spring rate to get the car to turn in quickly by loading the outside front. However also for decades all other cars (saloon & sports) have softened the front suspension springs to get better ride comfort but then have increased the low velocity bump force provided by the damper to get turn in. Many Morgan dampers on production cars have very little bump damping so still rely on the high initial spring rate with compressed rebound spring, but then having to accept consequential the poor ride. However when one goes for a softer initial spring rate one must add low velocity bump force in the damper. So not any old damper off the shelf but a damper valved to give that specific required low velocity force to get the car to turn in but then the valves must open to give good ride - at the same time! This is what damper tuning is so much about. Fit a damper designed for a different spring rate and car weight and it will not be optimum degrading both ride and handling.

6. Many other makes of cars are now using dampers with internal rebound springs to give increased roll stiffness and better ride BUT with much smaller anti roll bars. The current Merc E Class is the best example. The first dozen or so M3W (& the demo cars) is another example with the SUPLEX coil overs, that is before production went to SPAX without any internal rebound springs and hence more roll. The early 5 door 'Mini's (also the BMW X3 etc) are among the worst; come off a full width speed bump and the suspension feels quite soft, drive along a country lane with undulations on the near side and your head is continuously nodded side to side, uncomfortable - ARB 'too' big! BMW are too going to internal damper rebound springs - Morgan were first!

A lot of ride and handling is indeed subjective, but there is a book full of 'rules of thumb' that gets one quite close to the required ride and handling characteristics before the detailed spring and damper tuning to suit the character of the car and the customers.

If you are still awake, thanks for your attention. Regards Peter.
Declared interest Director SSL.
Current SSL suspension projects include; Porsche 356C & 911S, Jensen CV8, FIA ACCobras, FIA MGB, off road rapid response 4x4 truck etc. as well as Morgans of course for road and track.
Posted By: Button

Re: Roadster 5 link rear suspension re-visited - 15/09/19 04:46 PM

So for us that think We understand Morgan Suspension, do I source Front Shocks with adjustments for both Bump and ????? - Both Up and Down?
Posted By: PJB

Re: Roadster 5 link rear suspension re-visited - 15/09/19 07:27 PM

You can source dampers with one two or three (or more) adjustments.
1. Low speed bump up to around 2" per second that controls turn in, control over hard braking, long undulations etc.
2. High speed bump above 2" per second that is the ability to absorb road surface irregularities such as a very coarser surface.
3. Rebound.
OR set them in ratios.
Typically the ratio of low speed bump to rebound is around 1:3 for a road car to minimise bump forces but control oscillations, or 1:2 for a sports car to create more ability to turn in, or 1:1 for a race car where turn in rules over comfort.
The high velocity bump should be as close to flat as possible (so force not increasing much with velocity), some trick dampers can actually reduce force over say 2" per second.
The 2" per second is typical for a road car, maybe up to 3" or 4" per second for a race car as you hit bumps faster so the damper velocity is higher.

For critical damping so any oscillation dies in one cycle the Force:Velocity slope is 2xsqrt(mass x spring rate). For a road car use 30% critical, a sports car 70% and for a race car around 100%.

Make the suspension adjustable and they will adjust it wrong -- look what they can do to a Weber carburetor in just a few moments of stupidity with a screwdriver.
Posted By: PJB

Re: Roadster 5 link rear suspension re-visited - 15/09/19 07:35 PM

Sorry I hit send too early...……...
Then you need to consider damper types: twin tubes gas pressurised or atmospheric, monotubes gas pressurised or atmospheric & specials where the damping is also dependent on stroke etc. They all have different responses with respect to rate of change of velocity, ie how fast they give force for a velocity input. For a road car you want them to respond relatively slowly to give good ride over rough surfaces but for a race car respond quickly as you are going faster. Difficulty is to make a responsive damper like a gas pressurised monotube Bilstein give good ride but then work well when driven hard - it is done!
Any of the above damper types can give the same force;vel curves, but it is the transients and change in characteristic with heat that are the differences. Pays your money, takes your choice and do the road testing for the spring rate and car weight in mind. Hours of fun and many hundreds/thousands of miles of testing.

Cheers Peter.
SSL Director.
Posted By: Richard Wood

Re: Roadster 5 link rear suspension re-visited - 18/09/19 08:35 PM

Originally Posted by Richard Wood

Following on from my post above, have just ordered the front RS kit from Dan who already has them in the post to me. He did a deal minus shocks and steering bearings as I have them already.


Following Peter's convincing arguments ended up ordering the matching Spax adjustables. Finished the fit late this afternoon with just enough time for a short test drive. Still need to tune them to the worst of Norfolk roads but gratifying to find in the short run that front now matches the back in ironing out most bumps. Car seems more chuckable as well with super sensitive steering.

Needless to say the second side was stripped and rebuilt in half the time of first although I did release spring tension with a jack. Would suggest it's ideally a two man job to replace using same method though. Bizarre that I did find a kingpin bump stop on second (offside). Left it out of rebuild for symmetry as definately not present on other side. Bump stop's on dampers with RS kit anyway.

Anyone want a pair of front adjustable AVO's, only 6000 miles from new innocent
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