Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Front shock absorbers

Further to the above, I sent an email to Peter B, Director of SSL and received a timely response. He is not permitted to post on TM for commercial reasons, but has given me permission to share his response. I am happy and relieved to say that he affirms that the installation instructions are correct and has given reasons why. This all makes good engineering sense to me and is the way I have always fitted mine. I cannot see why any type of shock absorber would warrant a different approach as the forces and stresses would be similar as the suspension moves. Being over tight on the top cannot do the damper plate any good either.
Anyway, here is his reply: (hoping I am not breaking any TM rules by posting!)

Douglas, thanks for the email, the SSL RS instructions are correct.

The bottom nut indeed tightens against a step so should be tight against that.

The top nut must be just tight enough so one is able to just turn the top washer or rubber bush.
There are reasons for this:
#1 As the steering turns the damper axis moves in a conical path and so pivots on the top damper plate. If the rubbers are too tight then the damper rod twists the damper plate so potentially reducing the life of the damper plate that are not that robust anyway.

#2 If the top rubbers are tight then turning the steering puts bending into the damper thus increasing the wear rate in the rod bearing/seal and the piston/bore thus potentially causing leaks and loss of damping sooner than expected. SSL follows advice from SPAX.

#3 Leaving the rubber bush under the top plate uncompressed means that it is able to deform a little to reduce road induced harshness coming through the damper to the chassis.

NB We have used an axial self lubricating bearing instead of the lower rubber bush on the damper rod on some of the race cars, also on my Morgan. As image attached.

PS Despite being a Morgan owner I am not allowed to post on TalkMorgan as I am commercial. I have asked to be allowed to post again, but no longer get replies.

Hope this helps, if you wish to post this or summarise then that is fine by me, thanks.

Having recently adjusted my SSL to reset the correct compression (zero) on the rebound spring, I found you can nip the top nut up on the Spax shocker pretty tight and still get the correct friction on the rubbers to allow them to 'just' turn, this year I smeared a little red rubber grease on during assembly as I think they sort of bond to the top bracket with age

Thanks for info from PB Doug and yourself Jon. I take onboard the useful info about the damper axis moving through a conical plane as steering turns. What this also reveals to me though, given the damper rod movement and essence of this thread, is it's even more important to clamp against top spacers (commensurate with not compressing rubbers) to ensure the nut doesn't loosen although it is a fine 10mm thread. Clearly the bottom mount nut being at right angles to the top is not affected by this movement otherwise mine would have loosened long ago.

My steering has always been very light but given Jon's findings I'm hoping the application of rubber grease will allow the rubbers above and below shock mount plate to turn whilst clamped down onto their spacers. If not I will cut and fit some slightly longer spacers from suitable tubing.

Having accepted that there is a conical movement by the damper rod, If the top of the damper is clamped hard down to the damper plate, nothing there can move and it suggests to me that the rubbers will have absolutely no effect at all. The whole conical movement forces will be transmitted directly to the damper plate; there is no give. Consequently, something will have to give or deform, such as the damper rod itself, as PB has said.
As for some nuts undoing, think they are nylocks and as such should always be renewed after removal. Even a spot of loctite may help but for me, I am firmly sticking with what I have always done.
Looks like we have to agree to differ on this one.

Sorry Doug but that's not the case although I appreciate your persistence as it's given me the opportunity to look deeper when I took the mount apart last night to prove and hopefully re-engineer. The reaction from dampers onto top mount is still exclusively via the rubber bushes the nut simply clamping upper washer and metal bush to spindle. They are unconstrained therefore within their elasticity to forces in the vertical plane and with help from grease I will use to movement against the 12mm o/d metal bush. Their position laterally is held to some degree by the inward facing lips of rubber bushes that match the considerably larger approx 17mm hole in top plate allowing elastic articulation when full lock approached. Leaving the metal bush loose it would be free to wear away the lower threads on shock spindle, movement of thick upper washer might also contribute, although wear here might be considered unimportant. Speaking of that large diameter washer it would unfortunately be in a very good position to unscrew nut with steering movement once it was loose as unlikely the opposite movement would retighten!

Brief measurements suggest the metal bush would be correct length to tighten against if it wasn't for the conical movement. I've ordered some stainless 12mm o/d x 1mm wall tubing and will experiment with bushes initially 1mm longer which should allow the rubbers to be turned. Note though there is a significant difference between wheels in straight ahead position when bushes are tolerably square to plate, and full lock which on close inspection shows considerable compression on one side of each bush. PB was unclear the position in which bush movement should be checked but I'm guessing straight ahead wheel position. Will get hold of some fresh top nuts as well, they are locking fine thread M10 and as best as I can measure 1mm pitch.

Let's face it the whole exercise is a bodge to correct a badly engineered design starting with the cantilever top mount plate that Peter Morgan introduced when he felt pressurised into introducing dampers in the first place. I was alarmed when I first set eyes on this arrangement and nothing has changed

Yep, as Richard says, and I too have said in a previous thread the whole shock mount design is a total weekend bodge so that Peter Morgan could install shocks in order to pacify the masses who just couldn't get the fact that at that time the sliding pillar suspension was designed to counteract and damp bounce and didn't in fact require them. A rudimentary change to the top mount was quickly made and a lower mount drilled and mounted into the hub assembly to carry a shock absorber. Now we have all sorts of theories around setting up adjustable shock absorbers which have evolved from a racing scenario, fine tuning cars which have extremely advanced suspension systems! The Morgan classic doesn't! It's range of travel is probably under 37mm and if the main spring rating is correct what the hell are you damping? I can only think of one use for a damper here and that is to help the wheel from accelerating into a pot hole but when you see how little resistance the shocks have fitted on a classic, it wouldn't/couldn't even do that.
It is purely a shockingly awful add-on design that is the causal fault of distortion and damage to either the top mount or shock absorber itself.

Much like the classic rear modification when the hoop and telescopic shocks were installed. This too doesn't allow for the rotational forces which occur at the top mount point on the hoop. stuffing the rubber mounting bushes at best and even destroying the mounting sites at either hub or hoop. Probably there was a cost saving over the lever arm system and or ease of procurement. I really can't see any design or use regulations having been applied here!

A rubber mount such as in a shock absorber has a shoulder or sleeve fitted in order for it to allow the fixings to be secured correctly and the rubber bushes allow for movement within the range required. No wonder nuts are coming undone! perhaps we aren't using the correct torque settings for rubber!

Thanks Richard. It’s been a while since I have had mine apart and couldn't recall the precise washer & nut arrangement but if they only clamp to the spindle and not the plate, then it’s not as bad as I thought.
Like you, I assume the bush movement is checked in the straight ahead position.
Good luck with your experiment.

I understand PB's warning on fitting the SSL RS kit with Spax gas assisted shocks, particularly as I've had both shock upper mount plates break! However I disagree that the top mount nut should be left other than bolted up tight against the metal spacer as intended, particularly given experience of the OP of this thread.

To this end I disassembled upper mounts and made some measurements. The spacers are 12mm o/d x 10mm i/d and 32.2mm long. I obtained some matching stainless tubing (from here) and cut fresh ones 1mm longer. This I determined would leave minimal pre-load on the two upper mount rubbers that sandwich the mount plate, and so match PB's instructions. I re-assembled with red rubber grease (thanks Cooperman) using fresh stainless nylock nuts. Note the latter are fine thread M10 x 1mm pitch and available here. The rubbers can now just be turned by hand when steering in straight ahead position but will always tighten up on full lock due to the conical twisting that PB mentions.