MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - shocking shockers

Well I did have an interesting weekend with so called "reconditioned and up-rated", lever arm dampers.
The first problem to manifest itself was one of a recently installed pair discharging it's fluid out of the back plate. When I removed it for a close look the reason was obvious, the plate was "hanging off". To my horror it had been secured, not with it's 8 machine screws, but with various sizes of self tappers, on two cork gaskets!! Only two of the tapped holes were stripped, so some re-conditioner, rather than re-tapping these two M5, just wacked in self tappers in ALL the holes. Needless to say I returned it and got a, outwardly at least, properly assembled one.
Now the next "fun" part. I decided to check the damping resistance of both. I devised a system of loading the arms and timing their rate of travel. But the two I had were incredibly different. So I decided to teach myself to adjust them at least to match, after all unless you have a datum, who knows what 30% is anyway? Is it 30% of the way from zero to rock solid or 30% up on "normal". I guess the latter but finding an accurate damper to use as a base line............I give in!!
It's like driving a different car, no more corkscrewing and drifting left under braking...........result!!
So the lesson, if you're not up to the tedious, but quite simple task, of adjusting lever arms; when it comes to replacement, ask for a matched pair (optomistic request I know), test them yourself and keep returning till you find two which are vaguely similar, buy new............if you can, or go for a telescopic conversion.
Allan Reeling

"Matched pair" ho ho! I had enough trouble getting a matched pair of coil springs where all you had to do was stand them side by side on the counter. "It won't make any difference" the salesman said, and it didn't as on car there is a difference where there wasn't before. Oh, and the free height was quite a bit more than the spec free height anyway. With dampers unless you carry a test rig long with you about all you can do is wiggle the arm up and down at the central point and check there isn't an undamped section (BT, DT) and see if they feel about the same. You *may* be able to attach the arms together, pull on both bodies and see if both arms go from one end to the other in the same time i.e. comparatively correct if nothing else. There were several different specs originally, but as most are probably done by the same rebuilder they probably use the same components in all of them.

Telescopic? No thanks! Most are as hard as a brick even when on their softest setting, and very expensive. My V8 came with them and I had to replace both when one started leaking. Then they started getting softer and softer (but only in one direction), and the adjuster had seized. So I converted back to lever-arms:

"The parallel-piston lever-arm damper was functionally very good, and the fact it has been superseded by the hydraulic telescopic, and the strut in particular at the front, is mainly due to the final assembly advantages of these, rather than any functional gain in the areas of ride and handling."
PaulH Solihull

Probably prohibitively expensive for folks in England and Europe, but here is a premiere shock rebuilding business with an iron clad warranty http://www.nosimport.com/ Cheers - Dave
David DuBois

The owner of this company rebuilds the shocks to a higher level of quality than they had when they left the factory new. He installs seals on the shafts, after machining the housings, to accept them. The factory never used seals and this led to many units failing over the years. Peter does the rebuilding for Moss, in the U.S., but I don't know if he is their supplier for the U.K. It would be worth a call to Moss to find out. RAY
rjm RAY

I fitted my V8 roadster with a Ron Hopkinson front conversion.................(Bilstein dampers), which I have to say is very good. Initially I fitted Spax to the rear and they were awful! I also have a GT to which I then fitted the discarded Spax. I wanted to see how they were with more weight over them AND they are much better on the GT, if quite noisy. I even have then on 4 clicks!!! The main problem I noticed, when I returned to cars with oil filled lever arms, was their decline in performance when they warmed up. Gas filled are far less prone to this.
Lucky Yanks, sounds like someone is doing it properly!
As I said, adjusting two Armstrongs for balance, is not that difficult, but whether you finish up with the CORRECT damping rate is another thing. Testing on the vehicle is the only way I can think of. Rebound damping is easy to see by "leaning" on a corner, compression is best determined by driving the thing.
The bottom line is, I doubt whether most re-conditioners do any more than lever the arms of clamped down units and compare the relative muscle power needed. A high protein breakfast after a good night's sleep.............result, rock solid, filling rattling. Feeling miserable with flu onset, end of a long day..........result, suet pudding ride!!!! When you think that the dampers affect ride, handling, braking, steering and tyre wear, it's a disgrace.
I'm with Paul on the sring question, have we anyone who can set and temper springs to original spec? I got fed up with uneven, sinking coils and semi elliptics. In the end I put my old ones back on the front with spacers and stuck with the old rears, at least they were the same!!
Allan Reeling

Oh dear! what a lot of bad luck some of you fellas are having. I converted to gaz telescpics for fun! ie the lever arms were serviceable but the project I thought would be 'character building",? Don't your readers do this? Anyway, all is well the shocks appear to work , yes a little hard, but then I have uprated and shorter springs, and it is on a GT, oh, and I don't think I am at the lowest setting. Sure, I still have my lever arms ready to put back at any time.I just like fiddling, one learns so much. Mike
J.M. Doust

Allan, I wish I had your email address so I could contact you without "advertising" on this BBS. We are doing some different sorts of things with these shocks, such as external adjustability for front and rear.

Contact me, and I'll send some pics.

Peter
Peter Caldwell

Peter's work is amazing and worth looking into. RAY
rjm RAY

Mike,
I was under the impression that every one of us only ran "old" cars BECAUSE we were inveterate fiddlers!! The GT is my daily driver and the V8 "the special one! If there was nothing to fiddle with I would have to create something!!!!
Peter, will send you an e-mail I love learning!!!!!
Al
Allan Reeling

Hi Allan,
with regard to your lever arm problem, can you tell me how you actually matched up the damping effect, as I seem to be experiencing the same problem. It all started when I noticed a pronounced lean on the offside rear, a difference of 1" from the nearside rear. Taking off the new, as yet unused dampers I could detect the offside damper seemed softer at the bottom of its travel than the nearside. I was told by Moss that the Armstrongs needed to be driven after installing to prime the oil/air content that settles when stored, any thoughts on that? if, as I was told the leaf springs do not affect the ride height and the dampers only smooth out the ride what actually affects the ride height? or is it only the case that a 41 yr old car sufferss this with wear and tear?? any advice would be gratefully received, I need to solve this before taking the car to the paint shop. Peter
P Mayo

Ride height IS spring related, damper has no effect. B's usually settle on that side because that's where we sit and the petrol tank is over that way. I can explain the balancing technique if you want but it won't affect ride height. Often people just swap the springs over and let the other one settle a bit with the extra load.
Al
Allan Reeling

Sorry, meant to add that a soggy damper will accelerate the decline of a spring by subjecting it to increased movement, so getting properly functioning dampers will help the longevity of springs as well as making the B more comfortable!!
Have to go out now, but if you want to balance you will need both of them off the car.
Allan Reeling

Thought I'd add my experience FWIW.

I converted from tired (very) lever arm to telescopics around a decade ago. I did so initially because of the price advantage over replacing lever arms with a rebuilt pair - that was a local market characteristic - rebuilds were of the order of $250 a side at that time. Telescopics, with the conversion kit, were around $200.

I'm very happy with the way the telescopics perform. Of course, as others have often mentioned, I would probably feel the same had I reinstalled a decent pair of lever arms.

My key point is that my telescopics are not of the oft-mentioned adjustable type. They are Gabriel 'Classic' shocks, catalogue part # 82001. Made essentially for Volkswagen - Beetle '54-'65, Fastback and Squareback '66-'73, some Super Beetles '73-'74 as well as some of the Dodge Colts of '90. Retailed I can only suppose because of similarities in vehicle weights.

These 82001 shocks have extended length of 15.89", compressed length of 10.28", hence a stroke of 5.61". I have never felt these parameters reached in local day driver traffic as required, mixed with spirited touring driving. I do not do any sporting events.

Of course in any conversion it is the shock compression and extension lengths that must be workable in terms of bump stop to axle strap arresting point dimension requirements. The design of the mounting bracket fixing point is critical in matching individual shock parameters to the dimensions demanded by the suspension so the 82001s may not 'match' all conversion kits. Some simple measurement and calculation with brackets in place will tell whether they will work in individual cases.

Regards

Roger
Roger T

Thanks for the input Allan, as the dampers are both off at the moment I would like to try your levelling up technique.I think would it be more beneficial to replace both leaf springs, after all 41yrs service is quite some time and with your levelling trick Im hoping that puts it back to normal. regards Peter
P Mayo

Peter,
Clamp the two units down to a bench etc., with the arms overhanging. Checking the rebound load is easy, hang a weight on the arm and time a full stroke from top to bottom. The compression involves a pulley and a length of rope, to time a full stroke from bottom to top of movement. You will need a heavy weight, if you don't want to wait an absolute age!! I used an MGB fly wheel.
Adjustment of rebound is easy, take the valve out. There may be small shim washers between the valve body and the larger spring, don't lose them. On the valve body there is a small spring held in place by a small nut, usually soldered in place. This nut is the adjustment, but only move it in 1/4 turn increments. One turn will harden the rebound significantly, you will have to judge the adjustment. Compression is adjusted via the pre-load shim washers, one or two of which already in place. If you need more resistance you will have to add shims. The ones i've removed have been in the order of 15 or 20 thou. I you need some extra you might have to modify washers.
Then it's re-assemble, top up and try the load test again. It is tedious I know. Identical isn't obsolutely necessary, within 5 seconds or so, is pretty good. Oh and if you want to replace the oil with something which is stable when hot, try Silkolene synthetic, 30w.
The main problem after you have had the valve out is getting rid of the air. You will think the thing has locked up, but persist with a few minutes of "working" the lever and full movement will be restored. Oh, and best of luck finding decent leaf springs, I gave up after 2 "failures" and put the old ones back.
Allan Reeling

Hi Allan,
thanks for the info,sounds quite intimidating, although not sure now if I really need to go all thro that as when I put the one that appears to be a little weaker into the bench vice and operated the lever a few times it seemed the resistance increased quite considerably. As I put in my earlier thread Moss did say that when the cars rolled off the line a guy drove them to the parking area over a stretch of prepared rough road to settle the Armstrong's suspension. As far as the leaf springs are concerned, in what way did the ones you tried fail? and how did you work out that they had,was it the ride height? I would have thought that the old ones you put back would have already had their life, It makes me wonder at what point do they actually wear out. Sorry this is a bit long winded but I find it very difficult to actually come up with the answer to this problem and I have had completely different opinions. It seems an awful lot of work to put on the new springs and then possibly have to take them all off again and put the old ones back,and we say that owning a classic is FUN!are we all mad? Best Regards Peter.
P Mayo

Peter, Fun, as they say, is in the eye, or the knuckles, of ther beholder.
In answer, the old ones didn't quite hit the chassis rail. The new ones, made by a "supposed" local spring specialist, hit the chassis rail within 2 miles!! Their second attempt to get it right ended the same!! My V8 roadster has RV8 parabolics, they are very good. Wish I could find another pair!
Allan Reeling

I might also add that it's worth putting some decent, modern damper oil in, while they are off the car., Redline and Silkolene both do synthetic damper oil. Critically these oils are stable up to 600degC. Hence little drop off when the damper and oil warm up.They also resist foaming. Don't use cheap stuff or Jack oil.
Allan Reeling

Interesting. One of my front dampers has started leaking. But with it on the car I haven't worked out where from. There is no one about here who can rebuild them but I do have a spare set sitting on an old crossmember I might swap over for the ones on the car. I'll need to re-oil them and swap the valves over for the uprated ones I am using. When I re-oiled the ones on the car I used Silkolene from a motorcycle shop and it works well.

Simon
Simon Jansen

If you're lucky it will be the back cover leaking. An easy fix but use a new gasket. The usual ones are not that good, i make mine out of decent gasket material.
Whenyou put the replacements on the bench, this is a good chance to play with the settings. If the ones you are using are uprated you have a base line to set up the replacements. Be a devil!!
Allan Reeling

This thread was discussed between 17/05/2011 and 23/05/2011

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now