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

Interesting David, as we visited PJB yesterday to review the Suplex system and I must say I was impressed with the performance. It was particularly interesting watching the suspension work, when following the PJB/Suplex equipped Morgan closely on the road.

Have you had the rear suspension altered as there was no nodding dog syndrome remaining on PJB's car and the handling of the car was transformed in our inexpert opinion.

Certainly if I was contemplating a Trad Morgan this would be an essential bit of kit to be fitted to it, though I would want changes to the rear suspension as well so that the ride and handling were balanced.

Cheers
Brian

Dave

I would suggest checking the adjustment of the springs. It may be that there is too much pressure on the lower spring and that could explain the why nodding dog syndrome still happening. I am sure that the mechanic would have adjusted mine as best he could in the workshop but after about 80 km I checked and found that one side was out quite a bit, about 4 mm. It is also possible that he did not fully understand the instructions. It is worth while reading the fitting instructions before checking.

To check them you need an absolutely level surface as any uneven surface will put more load on one wheel than the other. You then bounce the front of the car up and down and swing the steering wheel from side to side. When you are convinced that the front has completely settled check to make sure that the lower springs can be just turned by hand and that the measurement of the distance from the triangular plate to the underside of the stub axle (top of the lower spring) is 66mm or 86mm if the spacer is at the bottom (tolerance +2mm -0mm). This distance is the most important part of the adjustment of the system and once everything is settled in it should not require further adjustment for a long time.

It is possible to adjust the top rings with the car on the ground by turning the wheel fully to one side and working lying on the ground behind the wheel. There is not much room but it can be done. You need to wedge something in one of the slots at the top of the adjuster sleeve or it turns. I used the handle end of one of the C spanners provided and braced it against the support for the top of the kingpin. After you have adjusted it check the lower springs again, after bouncing the front end and swinging the wheel from side to side, to be sure they are correct.

Hello Peter
Thank you for your suggestions.
I checked both sides and found 84mm each side. To adjust the job I removed both wheels, first winding back each by one turn. Then a short test drive, and measured 85mm ish, allowing for paralax. Then off with the wheels and backed off a further turn, at 1.5mm pitch that should be 3mm total adjustment. Short test drive and measured 85mm. Noted also rebound spring now had free travel on drivers side of about 2mm, then however after turning the steering column full left to full right and to centre this disappeared and I found the rebound spring once again under compression although I am still able to turn the spring.
I noted that the technician who installed the system has put the spacer below the rebound spring instead of above as the instructions show. I cannot think of any reason why this should detriment the way it works, however if anyone could enlighten me, I would be greatfull.
Tomorrow I am out for a 150 mile run , so I should be able to see if I have made any change.
Thank you for your support.
Kind Regards
Dave

Hi Brian
My rears are AVO and set to a fairly soft setting and I have spray greased the leaf springs .
Maybe I could soften a little more. What do you think?
Kind Regards
Dave

Dave H, the location of the spacer sets the ride height, as per the instructions. Later/current cars have a lower ride height at the front than the earlier cars such as yours at 1982.

Early 1980's cars like yours would have had the original Morgan rebound spring compressed by about 3/4 inch (= about 20mm) at static ride height resulting in a rebound spring installed length of 86mm - 20 mm = 66 mm. So in that instance the supplied 20mm spacer should go at the top above the little 'rate riser' spring leaving the SUPLEX 66mm rebound spring on its own at the bottom. Thus you will have the same ride height as you started with.

Later cars sat lower as Morgan fitted shorter main springs to try to get the rebound spring free. They nearly managed it but often still got the rebound spring a little compressed so still got a hard ride. In these instances the 20mm supplied spacer goes at the bottom to match the original ride height of those later cars.

So what is the difference in characteristic with the two different ride heights? Well the initial ride will be the same for both ride heights. The rate increase as the upper 'rate riser' spring comes in during cornering or big bumps will be the same BUT due to the reduction in bump travel with the lower ride height of the later cars the damper bump stop will come into play sooner in bump. That is the penalty of a lower ride height and less bump travel.

NB there is also a small potential risk that is difficult to quantify, but if one sets the ride hight lower than standard it is remotely possible that there will be tyre to wing contact in extreme cornering with bump. Just something to be aware of.

You also have an issue at 58mph I read. Puzzled that you think the nose is nodding but then you mention the effect of the steering? I do not really understand your wording, sorry.
Do you still have the original friction dampers or have you converted to the ball thrust races? If you have the ball thrust races and have not fitted a hydraulic steering damper there will be steering shimmy at between 55 mph and 60 mph that may be causing your concern/observation as that may set up a nodding effect too. If you still have the original friction dampers then check their adjustment.

Damper top rubbers. SUPLEX suggest setting these only just nipped up. If you are getting nodding still, then screw down the M12 nuts on the top damper stud by another two turns to more firmly compress the rubbers and try that, as that will stiffen the small displacement response of the damper and help damp out any nodding.

What tyre pressures? Try 22 psi at the front 24 psi at the rear.

Tracking will change with ride height so make sure yours is still in spec.

I hope this helps, best regards PJB.

PJB is the true expert on this and has covered your questions much better than I could. The instructions cover both ride heights and I can only assume that the mechanic matched your existing ride height and therefore put the spacer at the bottom. If, after your run you find it is still 85mm you may wish to ease it just a little more, say 3/4 to one turn to get it to 86mm.

Thanks PJB for the tip about the top damper mount. I must check mine.

Just a thought - if you are finding that your adjustment is changing as you turn the steering, is it possible that the two adjusting rings aren't locking together properly? You need to tighten them together pretty firmly to keep them locked. Alternatively if you find they still move then you may want to try a dab of loctite on the threads?

Turning the steering left and right a few times allows the suspension to settle. It is mentioned in the instructions.

I don't have the damper blades or ball race on the front suspension on the 2006 4/4 and don't seem to get any steering shimmy . When did they delete the damper blades?

I am not sure the exact date, but my 2003 4/4 has damper blades.
I am sure someone on TM will be able to give a more accurate date.
Bud
__________
2003 - 4/4