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MG Midget and Sprite Technical - On a Promise

Banging from the rear.

A brief history - my car was rebuilt onto a new shell around 2001 ish, its had all the front and rear Frontline suspension mods including AVO adjustables alround (AVO's could be 10 years old now!).

I bought the car in 2008 and pretty much ever since, the rear has been banging around (on kerb side) when loaded.

I did resort to asking my local MG mechanic to 'have a look' last spring. The only problem he found was saggy springs that were duly replaced with multi leaves. For a short time, the problem appeared to have subsided (for a couple of weeks before returning).
The car now sits 1.5" higher at the rear with the new springs (prior to this, the square arches were just above rim level).

We went to Le Mans last summer, so well loaded up with case on the boot. To reduce the banging I wound the adjustables right up to hard which did seem to help just a little bit!

From my driving position, the noise sounds like heavy metal on metal and comes from the rear kerb side of the car (when driving through potholes and or dips in the road).

Do these AVO's stop working properly after time? Should these be replaced or what else do you think I need to check or do next.

I have promised my darling wife that I will cure this unnerving 'crunch' prior to this years activities and would like you guys to give me some clues where to start.


Chris



Chris Guards Red Midget

Chris

When I first installed my FL rear dampers (10 years ago?) they would bottom under certain conditions, esp hitting a dip at speed with uneven surface.

The mechanical crash of a damper bottoming is almost too painful to describe.

I had a friend weld a damping mounting lug at the other end of the original damper mount (these being swapped to other side and inverted). This provided another 1" of damper 'bottom' clearance and was fine. (Actually tested by driving from Castleton, past the dams, turn left to pass Strines in... some major road dips/bumps along road to Langsett on way to DC nr Halifax; probably the worst conditions I will ever drive it... fully loaded too, with 4 wheels/tyres/trolley jack/tools/etc for 2-days at Harewood Hillclimb).

Bew rear springs lifted car away from the 'damper bottoming'... but as they settle, you approach this possibility again.

So if this is your problem... you need to weld new lugs so you can mount the bottom of damper slightly lower.

A
Anthony Cutler

Is it the shock botoming out or is it side ways inside the wheelarch?
You do not mention what tyre size, rims or panhard rod you have
Onno Könemann

Anthony - The noise of the 'crash' is certainly one that I have to prepare for, you can see it coming through the road surface. Your description seems very familiar.

Onno, I have 13" Minilite's with 155/80 Yoko's, quite a common size I think.
Chris Guards Red Midget

Frontline do a later bracket that avoids this situation which I designed for them to address that specific problem.
Daniel Thirteen-Twelve

I was going to say the later Frontline (ooh, horrible taste in my mouth) bracket has two positions

but you can still fit the kit wrong and be hitting the bump stops and boy will you know when that happens

although the later bracket has a second lower hole and obviously stick down forther to the ground my dampers are fitted to the higher orignal hole ('73 RWA)
Nigel Atkins

I'm in the bottom hole as i won't fit in the usual one, but i still manage to bottom out on large humps.
Is that rude?
Brad 1380

I think it could be something in the instructions that come with the kit, they seemed a little ambiguous to me but I'm no engineer or linguist to say the least
Nigel Atkins

Chris
I was just saying that it does not have to be shocks botoming out.
The axle moving around and tyre's hiting the inner wheel arches can make dreadfull noises.
Onno Könemann

Plenty of people driving Spridgets quickly with lever arm dampers, just don't buy cheap rebuilt ones.
Jeremy Cogman

I will have a closer look this weekend and make enquiries with FL before doing anything else.

Onno, thanks for the advice. I used to have a 2.8i Capri that had the tyre/wheel arch problem and agree the noise is rather awful.

Cheers all.
Chris Guards Red Midget

Chris,

I had the same problem of banging about when I put on telescopics on the rear. I think they became damaged as they acted as dampers and bump and rebound stops so damaging the internals. I recently changed back to lever arm and now have no noise, and you get greater axle travel.

Mike
M J Pearson

Definetly the shockers, i have an RTL (no slop in the mechanism & the rose joints are all good, plus the noise was there before i fitted that), good inner wing clearance & solid ali axle mounts so the axle doesn't move sideways much at all now adays.
Maybe i have broken the shockers as Mike says they also act as bump & rebound stops.

Brad 1380

Shock's not catching the exhaust is it?
On mine I have telescopics mounted in place of the rubber axle straps, not the FL kit. Although there appeared to be reasonable clearance, under cornering plus a sudden dip in the road I got a noisy contact. Realigning the exhaust a little solved it.
Guy

Mike

Your thoughts seem to make sense in my case. I have previously had the wheels off to try and see visual signs of surface to surface contact without success. Would I really get a crunching noise (metal/metal) through a rubber bump stop? The sound of a shock running out of travel sounds feasible to me, but if I change this for a new unit will I not simply have the same problem?

Thanks for all the thoughts guys....
Chris Guards Red Midget

Had a look at it this evening, the lower shock mount was touching the Daniel designed lower spring hanger, so i have spaced it off with large washers, i'll find out tommorow if that was any good or not.
The exhaust seems to be in the correct position, i have even modified the hanger under the passengers seat so that the exhaust is more inboard to give greater clearance.
Brad 1380

Just had another look this afternoon and attached the following pictures.
I was assuming that I had an FL rear kit but no doubt some one can correct me if I am wrong.

No lower hole options on these brackets!



Chris Guards Red Midget

Any another

Chris Guards Red Midget

And one more

Chris Guards Red Midget

I presume that the FL one uses a bolt-on bracket at the top end - which yours doesn't. So yours is the normal home DIY variant (like mine). But that is no treason why it shouldn't work well.

The solution in your case is to remove those bottom spring plates and invert them, swapping from side to side. This will then give you the 3 alternative lower bolt positions at the bottom end so you would have plenty of choice!

Guy
Guy

Chris,

I don't have the FL kit but the much maligned Spax kit, mine use the original mounting plates, but swapped left for right such that the damper mount is below the spring saddles and hence longer throw.

Not sure if that is your problem - have you spoken to FL abpout it ?

R.
richard boobier

Photos say it all

Chris the brackets should point down and foward, holes going below springs yours are wrong way up

My '73 RWA uses the top hole of the two as fitted above

You'd gain an ich or so of travel

Saw today one of my shocks is leaking luckliy they were bought in July '09 and have a two year warranty and Avo are in my home town BUT I'm not sure if it's a repair only warranty
Nigel Atkins

Guy the dampers use the restraining (rubber) strap top fixing points and act as restraining straps

I night have the terminology wrong but I hope you know what I mean
Nigel Atkins

Yes Nigel,
I saw that. Same as mine, which is why I said I assumed that these were a DIY version, rather than a FL or Spax kit, which I think would have used bolt on brackets.
Guy

Sorry Guy

no not the FL ones, can't remember what was with the Spax as I gave the whole lot to my mate

I thought FL were the designers until I joined here and heard from David and Daniel

My FL kits were bought from and fitted by FL so hopefully they're right (but I can't be 100% sure based on my experience)

Anyway photo below -

Nigel Atkins

Sorted mine out today, a multitude of problems.

1. The upper damper poly bush insert was 1/8"longer than the bush, so the bush wasn't doing anything. Cut the inserts down & took up the slack on the upper mount with a big penny washer.
2. The lower mounts spring bracket holes had elongated, due to the FL special bolt being threaded all the way, so i made up some 1/2" spacers to sleeve the bolt inside the bracket.
3. Lastly the car is now lower than when i bought the FL kit, so the dampers were running out of travel, so moved the lower bolt up on a notch.

Now at last the metal on metal noise has gone, wish i could say the same about the oil leak.
Brad 1380

All

Thanks for your help guys, another job for next weekend.

Chris
Chris Guards Red Midget

Thinking about no.1 again, i did weld some washers onto the body work previously, as the holes were elongated, then did them up pretty tight, so i have probably distorted the poly bushes.

No.2 is just poor engineering design.
Brad 1380

I too have been suffering with this problem with crashing coming from the back end.

I had noticed my rear springs had sagged and was concerned as this were only replace three years ago.

I have the rear axle off and springs off at the moment and will now put the shock plates the right way up err.. down. Anybody know where I can get a set of the spax bushes from at a reaonable price?

Cheers
Shaun

Shaun,
1st thing would be to get some decent springs, not cheap i'm afraid, got mine from Clive Berry c.berry@fsmail.net .
Brad 1380

Cheers mate, I was going to contact frontline and peter may to see what they have.

I'm also looking for a set of anti tramp bars as well now that I will be putting more power through the back end.

Shaun

Shaun,
be sure to align the anti tramp bars arc properly, theres a thread in the archieves about it, think it was on the 16V forum.
Did you ever make my Mumford?
Brad 1380

Chris, Sorry for the thread hijack,

I have a pair of spacers made to Brad's drawing.

I have the MGB Calipers, now I just need the spitfire discs (remembering to get them machined down to 9" or 228.6mm).

I have a block of bar to space off the steering out by 5mm.

Brad, The engine swap has taken precedent over anything else, which has turned into a partial restoration as I had several rust points that need resolving so am throwing some weld and metal at the car.

Shaun
Shaun

Chris disregard my comments, got my threads crossed.

Shaun
Shaun

As I had to take a rear damper off for repair I took some photos after refitting that perhaps show the installation of bracket better than my previous photo and without it being covered in Waxoyl

this photo is taken from the back of the car and shows the O/S spring

the bracket is inboard of the spring with the fixing holes towards the front of the car

the damper is inboard of the bracket in the top hole ('73 RWA car)





Nigel Atkins

this photo is of the same rear bracket and damper fitted to the O/s of the car

it is taken from the front looking back

the bracket is inboard of the spring with the fixing holes towards the front of the car

the damper is inboard of the bracket in the top hole ('73 RWA car)

the damper adjuster dial is facing toward the front of the car

sorry clicked wrong button see next post for photo
Nigel Atkins

third attempt

Nigel Atkins

Thanks Nigel for the pictures.

Will sort mine out when I get a moment. I have a starting problem as well now so this job will have to wait a bit.

Thanks for the info.


Chris
Chris Guards Red Midget

Bracket changes were done this morning. Drove to a guarenteed 'bang' spot and hey, not a sound.

Thank you guys for helping me out on this.


Chris
Chris Guards Red Midget

Well done Chris, you'd certainly know if the car was bottoming out

On to your next problems - must now mention get yourself a Owners Handbook, better than a Haynes for an owner, invaluable at only £8 - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html
Nigel Atkins

This thread was discussed between 10/03/2011 and 20/03/2011

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