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MG Midget and Sprite Technical - Rear end sagging....

Hi to all. One of the few items not replaced during my reshell was the rear leaf springs. Now back on the road the car was definitely low on the drivers side. So, new ones were bought from Moss, and I fitted them yesterday. Whilst the ride height is SLIGHTLY increased, it is lower than the passenger side- and when I'm in it, the wheel arch lip is only just above the wheel rim!
On a previous midget, I had very similar problems, and in the end fitted an extra leaf from the old set to the drivers side - problem solved. But, I had sorted the symptom- and not the cause. Before I go down this way once more, I would appreciate any advice please.
And before I get the comments- I only weigh 12 stone!! John.
J M Hutton

What state are the front springs in? Slight variation at the front has a significant effect on the diagonally opposite rear side. You could also try swapping the rears over, although when l tried that a few years ago it made no difference at all!
GuyW

I was thinking the same, perhaps front effecting rear.

Plenty of info in the Archives too.

At 12 stone you may need to treat yourself to a good meal before starting any work on the car.
Nigel Atkins

Thanks GuyW and Nigel. Understand your comments re front springs. Will have a large meal, and consult the archives. John.
J M Hutton

It always helps to have the springs re-arched and to have an extra leaf added. If the car sits a bit higher in the rear, it will settle down after a few months of driving. Proper ride height is critical to handling.
Glenn Mallory

When I re-shelled my Midget I had exactly the same problem. Measuring the body showed height discrepancies in the boot area. (Remember the shells were assembled with original worn tooling). I opted to put suitably thick metal plates between the floor and spring. Same end product as you had by adding an extra spring.
Geoff Mears

Thanks for that Glenn.
Geoff - interested in your comment as have noticed body discrepancies when fitting new interior panels in the rear inner wing area. Did you pack the brackets at both ends of the spring? John.
J.M. Hutton

I had the same issue,
Tried swapping the rear springs over, no change.
Tried different sized lowering spacers on the front,this made it look better but after checking the weight distribution was just screwing things up.

Ended up making some spacers/packers out of some 5mm thick steel and putting them between the front drivers side spring carrier and the body, bought some longer screws to compensate.

This fixed it.
Andy Phillips (frankenfrog)

Thanks for that Andy.
J.M. Hutton

John
It's easy to check which end is giving you problems

Place something small-like a 1" socket or similar on its end- on the middle of your trolly jack and then - on a level surface , jack the car up under the dead centre of the rear axle housing (measure from spring to spring) till both wheels just leave the ground
Then, if your car is still leaning down on the rh side there is a problem in the front suspension not the rear and this will also show up by the lh rear coming off the ground more than the driver's side
But if you jack it like this and the car levels up with the rears off the ground the front is ok and the problem is in the rear springs which will show up with the drivers side rear being further off the ground than the left side-
See how you go with that, it'll be interesting to see what you find
William Revit

John,
Yes, I put metal blocks at both ends.I should point out that there is now variance at the front nearside, but nowhere near as bad as it was at the back. I do get a fair bit of tyre scuffing at the front, no doubt self inflicted as I have lowered springs and lowering blocks at the back. I just think it looks nicer.
Geoff Mears

Thanks Willy - will get onto that and advise further. During the rebuild I did measure the front springs and they were of equal length though, so assumed they would be ok. Obviously, the nsf wheel arch has a good 1" more clearance above the tyre than the osf, and I appreciate as GuyW says how this would affect the rear.
Geoff, thanks for your further info. Thinking time required!
J.M. Hutton

Willy - have now done as suggested. By lifting the rear, and with the tyres equally off the ground - the car maintains its pre lift attitude. Looking from the drivers side the top of the wheel arch covers a much greater area of the tyre than the passenger side. Therefore with the driver installed the position is obviously exacerbated somewhat further!
So, does this confirm a front end problem, or should I go with Geoff Mears suggestion and pack the rear springs? Still confused, John.
J.M. Hutton

John
I'm a bit confused too--
So you are saying that with the rear wheels off the ground the car itself is still leaning over to the right or are you saying the rh rear is further up in the guard than the left with both wheels still being equal off the ground

I'm thinking that while the rears are off the ground like this(jacked in the centre) you now need to measure from somewhere like the centre of the axle up to the wheelarch on both sides and both ends to find where the problem lies
It sounds a bit like you might have a problem on both ends from what you have said

willy
William Revit

Also
What is the history of your front springs
William Revit

Willy, yes I am saying that with the rear wheels an 1" or so off the ground (equal) that the rh rear is further up the guard. The front springs could well be original, but when measured were equal in length when off the car.
need to jack up and take some measurements. John.
J.M. Hutton

Hmm. Is the axle central in the car?
Greybeard

Hi Greybeard. Using 4' spirit level, vertical against the wheel arch, and measured from centre of hubcap, the lhs measures 1/2" less.😱John.
J.M. Hutton

With the car raised and the axle level relative to the ground, if the height to the front wheel arches is the same, but to the rear arches it is different,then either a) there is a twist in the body or b) there is a difference (fault) with the rear springs.

That said, l am not convinced by Willie's theory of jacking the car centrally under the axle. If jacked up with a level axle, the rear is still sitting on its 2 leaf springs so it doesn't eliminate anything from the way the body of the car sits on the springs.
GuyW

Guy, the nsf is 1/4" higher than the osf. Surely that would not transfer to the much greater rear difference, or would it?
J.M. Hutton

John, don't take me as an expert on this. But l think of it in terms of the height from the top of the wheel arch to the ground at each corner. I assume your tyre pressures are correct, or at least match side to side and the tyres themselves are in axle matched pairs.

Then l found that it works in diagonals, so a NSF that is high will dip the diagonally opposite corner and the OSR will be low. And yes it does seem to accentuate the difference at the rear so 1/4" up at the front NS could well drop the rear OS by 1/2". It did on mine.

This saga has come up several times before. The common view is that "they all do that, sir" to a degree at least. It's also not an exact science. Bouncing the car on the corners may well result in different readings.

And of course, once sitting in the car and driving you will no longer be aware of it, and your silly grin will not be lessened in any way at all!
GuyW

I think before it's been expressed that 1/2"-3/4" variance in any measurements to do with the body and/or suspension is within acceptable tolerances.

1/4" up one side and 1/4" down the other and you have 1/2" difference on whatever.

Perhaps even body panel shape, and their fixing, contributing.

Have a passenger of around 18 stone and see if that evens things out. :)

Or swap around front springs as they're easier to do (2 long bolt method).
Nigel Atkins

Guy - hear where you are coming from on this. Tyres are new, and pressures correct (per axle). Yes, I know 'they all do that' also. I was just trying for some sort of optical perfection! Silly grin ever present in a Spridget. Those not in the know just don't understand the phenomena.
Nigel- again hear what you are saying. The wife is used to sitting with the Cocker on her lap in the car. Actually, I believe the dog prefers the whole seat!
Will look again at the front springs (2 stud method).
Thanks all for you input.


J.M. Hutton

John
If you have got the rear off the ground by jacking centraly on the centre of the axle housing and at this stage have a difference in front ride heights, you need to fix this first
If it has a front sway bar, disconnect one end just incase the bar has a twist then measure again like this
If it is still crooked(leaning to the right) like it was then there must be a problem in the springs and you could try swapping side to side for a try

If it sits up a tiddle on the drivers side after this ,that won't matter quite as much
Don't forget to go for a little drive after swapping the springs before you measure again just to settleit in

Once you have the front sorted then you will be able to see more clearly what is happening aft.

willy

William Revit

Thanks Willy. Will report back. Apologies for 'silly Sprite grins' - it was parky here last week, 7degrees.......John.
J.M. Hutton

I am sorry Willy, but I still don't see how jacking centrally on the rear axle eliminates any discrepancy that might be caused by the rear springs. The car body is still supported on those rear springs when lifted by the axle, and if, as an example, one had a broken leaf then it would sag on that side and the diagonally opposite front corner would lift, just to confuse.
(this is just as an example; I am not suggesting that John's car has a broken leaf as that would cause more rear end droop than he appears to have)

I do agree that the front needs to be checked and sorted first though. What would achieve what you describe would be to lift the body at a single central point at the rear. This could be achieved by using a rigid spreader beam across the width of the car under the rear spring front mounting plates. Something like a 3" X 4" would do it. Measure and mark the centre of this and then jack at that point using your trolley jack and 1" socket. This will then lift the body at the rear without involving the rear springs. Any subsequent lean would be down to variation in the front suspension.
GuyW

Another way would be to jack at the centre of the axle, but put blocks of wood of equal dimensions between the axle and bump stops at either side so that the body lifts with the axle but the rear springs don't compress and take the load.
GuyW

John,
great to see your driving your Midget with the roof down when it's a bit parky, you'd be warm enough in your sensible clothing though.
Nigel Atkins

My interpretation of what willy is saying makes sense. The rear axle is jacked in the centre, allowing it to hang at whatever angle it wants too. But allowing the front to be unaffected by the rear. Then you can check to see how the front is sitting. If it's all even, the problem is at the back. I guess you could then do the same for the rear, jack the front from a central location on a small point.
Karl Bielby

(Once again) (for what it's worth with my lack of knowledge) I'm with Guy, the rear axle is connected to the springs, the springs to the floor, that six points of connection and possible variance already. Then there's the floor and body panels and the front connections. I can see that Willy's method might give a general indication of where the problem might be but it might also mislead. Our cars and components weren't made to the most exactly measurements and standards so the discrepancies can compound and/or compensate.
Nigel Atkins

Crikey
I can see this is going to get big
Karl - You've got it covered
Guy - It's like this--
If you jack dead centre of the rear axle housing by any method that will let the housing self level, either by using a small lifting point like a socket on the jack or your piece of wood, and a socket --it doesn't matter which as long as the axle is free to tilt when lifted--
As soon as both rear wheels leave the ground the rear springs will not effect the leaning of the car as it is free to move anywhere on it's axis (the socket)
The lean of the body (if there is one) at this stage is under the influence of the front suspension only
This can be measured at the front wheel arches as sugested or if you want to double check the measurement from the front of the sill to the ground could also be used-----------
From what John has said is happening to his car, and I'm hoping he has it jacked dead centre--
He has lh front 1/4" higher than the rh side which could be the gaurds and a measurement off the sill would check that and as mentioned it could be a sway bar problem as well- BUT also what concerns ma a bit is his comment that the rh rear wheel was further up in the body than the lh when the car is jacked like this which would mean he also has a problem with the rear springs--
I'm thinking we'll wait and see what his next set of results are-
I've been using this triangle method of measuring for years as a preliminary on 911 Porsches and it works great-- If you scale one up after using this method
they weigh up beautifully and hardly need touching
If you get one of these out 1/4" there would be major brake locking issues-- And even if you only used scales on one you could have a car scaled up weight wise perfect but still leaning to one side - that's why the triangle method is so good for suspension work
I'm not trying to be a dictator here,and everyone's opinion is respected, it's just something I've done a lot of in the past ---
willy
William Revit

Willy, l absolutely and fully understand the principle of the 3 point system and the importance of checking and getting the front set up done correctly first. That's why l said to check the front levels in the very first response to John's original message.

I have also used the same method as you, with the only difference being l raise the car at the rear on a mid point of the body, rather than on the rear banjo. The idea is to take the rear suspension completely out of the equation at this stage so that there is no possibility of it skewing the lift. Then, when the front is correct, one can then turn attention to the rear.
What is difficult to determine accurately is any twisting in the body. They are not as rigid as one would like to believe!
GuyW

Actually 1/4" difference at the front isn't that much. Because of the weight distribution and the position of the CofG that could translate into 1/2" down at the rear o/s, if it's an accurate measurement.

I would remove the ARB, check tyre pressures and take several measurements, bouncing the car to settle it. With bolt on front wings one cannot even be certain of accuracy in measuring to the wheel arch top on both sides!
GuyW

Thanks guys, will report back. All this assistance very much appreciated. John.
J.M. Hutton

Guy
I reckon we're thinking the same -
Cheers
willy

William Revit

Yes, l think we are. I guess that with the rear axle clear of the ground and free to tilt, the body probably self levels between the springs. It's just l can't get my brain cell to understand that possibly unequal springs, dampers or resistance in the shackle bushes won't have some unexpected influence. It's easier for me to just leave them out of the process. ;-)
GuyW

Yeah, would it be better to measure from a better datum than the arch? Jacking point maybe?
Karl Bielby

Karl
Spot on
Usually when I do this sort of thing i get the car on a flat surface and jack the low side of the car up till all is level, then go measuring at different points like
wheel arches etc, sills, and I've found headlights and the bottom edge of tailights are also good reference points----If there is something out, like a wheelarch a reference point with a marker pen fixes that issue-

To be honest it's difficult advising online like this as really there needs to be about three pages of possibilities and methods etc put up prior to cover all the questions etc
You start off responding to a question and then there will always be hidden extras not on purpouse but it's just a fact that you can't write everything down at once
But it is what it is
John appears to have an understanding of what needs to be done-maybe we can help hopefully to reassure,guide and support him.
I suspect his car has a small issue in the front being multiplied by a bigger issue in his rear springs
Swapping the back springs over would probbably make it sit square to the eye but all the weight will be accross left front to right rear and it wouldn't feel very nice on the road--------The front needs to be sorted first IF it's out much
Cheers
willy

William Revit

Thanks again guys for your continued support. There will be a slight delay this end due to a spinal injection yesterday - but will be in contact in a few days when things have settled down. John.
J.M. Hutton

There's sort of a consensus to start at the front, whilst looking at and possibly swapping front springs all the other related stuff at the front can be checked, adjusted or rectified as required, then a few test drives to see if things are better and to enjoy driving the car rather than just working on it.

In fact after summering like a spinal injection if you can go out for a fun drive or two before worrying about starting all these checks.
Nigel Atkins

In a Sprite the rear axle is seldom in the middle. Especially in the quarter elliptic ones. It is less in the half elliptic suspension. A quarter elliptic sprung Spridget, without Panhard rod, remembers the last corner. So I am with William.

Flip
Flip Brühl

Flip, lateral movement on the rear axle is all the more reason to jack at a central point on the body rather than rely on the axle being accurately positioned. At least when checking the front for level.
GuyW

Really it doesn't matter where--
Say- if one rear spring (exagerated) is 2" lower than the other- and we jack dead centre on the axle housing exactly half way between the springs--
Assuming the front is perfect, when we jack the rear up the body will stay square to the ground being held square by our perfect front suspension and the axle rear axle will tilt as the wheels clear the ground, leaving the car sitting there square but with one rear wheel 2" further off the ground than the other proving the faulty rear spring as the cause
I agree with Guy that the centre line of the body can be used equally for this purpouse but personally I like to use the axle as it leaves exactly the same weight on the suspension as when the car is grounded--and both ends can be measured at this time but if jacking off the body you would then have to go through the whole process again at the front to check the rear springs
I'm just lazy, that's all
Cheers
willy

How's it going there John
I don't like big needles much anymore
Hope all is going to plan
Cheers - I'll have a beer for you-
William Revit

Willy, Thinking about this, l now suspect that if the body isn't symetrical (i.e. the axle is offset to one side) then jacking as you do would be better at eliminating this anyway. Also, there is more than one way to skin a cat - or a kangeroo! And l can certainly agree life is too short to argue the toss on this!

May the sun shine on you.
Oops, that is supposed to be a blessing, but maybe you are you getting too much sun these days in Taz?
GuyW

Still getting a bit of sun but winter is coming
As soon as Easter leaves, we change back from daylight saving time to normal and the warmer weather usually goes as well
We have to be really careful here during Summer with Uv exposure- Tassy residents are aware of it but visitors from mainland Aust. or elsewhere get caught out (sunburnt) really easily--- Our air is fairly cool and fresh and tricks the unsuspecting into thinking they won't get burnt, but 30 minuites in the middle of the day unprotected is enough to get burnt
Fairly high rate of Melanoma here so you really need to be aware even on overcast days--

thread drift over
willy
William Revit

Sincere apologies for the delay - I'm back! But, have to admit taking Nigel's advice, and using the car over the Easter break (400 miles on engine now).
Well have read all the advice several times, and can see where Willy and Guy are coming from. If you look at the image below, it gives ALL dimensions from the ground, and obviously the car leans from left to right. However, when the rear is lifted, and at this point I have to admit to using Willy's suggestion (can't get meself down under the car at moment - sorry Guy!), the front end levels out equally, as does the rear.
The tyres were equally off the ground BUT the top of the rhs rear tyre is less in view than the left. Dropping the car down, and placing a jack on the front mounting of the rhs leaf spring, and lifting the car 1" levels everything out - and for the first time the car sits level both front (side to side) and rear (the same).
Not entirely sure what this means - advice please! John.
J.M. Hutton

Image.


J.M. Hutton

John, This is my interpretation of it so far:
1. With the car lifted on a jack at the centre rear (note I am quite happy you use Willy's method here!) the front sits exactly level, side to side. A - This confirms that the front, on its own is correct.
2. With the car lifted like this, the rear is also level, side to side. B - this confirms that the body is not twisted

Therefore by the process of elimination, this test now also suggests that your lop-sidedness is down to something in your rear suspension,

Possibles faults, for starters. Tired springs; broken leaf in one of them; worn rear shackle rubbers; worn metalastic bush at front of spring; tired/worn spring pad; buckled or distorted floor panel where rear spring front mount bolts on.

That may sound alarming, but I still think the lean on your car is pretty minimal, and within the sort of variation that is pretty common. There may well not be any fault. So if you cannot identify one you could probably correct it with some judicial fitting of spacer shims as others have suggested
GuyW

Guy, as you may recall the shell is new, but could be distorted where the front of the rear spring attaches of course. The rear springs, fore and aft bushes, drop links, spring plate rubbers and 'u' bolts are all new,
Thinking of using some 5mm plate in between the spring hangers as shims as you suggest. I may need to double this up and space by 10mm (and use longer bolts). Many thanks for your assistance- really appreciated. John.
J.M. Hutton

Just a (not well though out) thought - what about if you turned the driver's side rear spring around in case it's asymmetric because of, er because it is, or one or both eyes is/are slightly wrong (or am I imagining things (again)).

John, very well done on the 400 miles it'll have done the car a power of good.
Nigel Atkins

Nigel, you can swap them side for side, which might be worth trying, but not reverse them as they are asymmetrical.
GuyW

Hi

Any MG Midget Challenge racers on here, or on their forum, that have got a view and experiences to share on suspension set up and checking a shell on rebuild?

Cheers
Mike
M Wood

Meticulous corner-weighting in race-ready trim (and the driver in place) sorts out both those issues and uneven weight distribution.
davidsmith

Nigel - did us all good!
J.M. Hutton

Pic.


J.M. Hutton

John,
I think I can see part of your problem with that photo.

Guy,
I was thinking if one (or even both) rear springs were malformed, possibly at the eye end(s) and turning the driver's side spring around so the front eye fixing is put to the rear. Of course a thorough visual inspection might pick this up but the spring would need to be off the car anyway to do this.

David,
you'd also need the passenger in place and the dog would spoil it all by moving around unless it's in a 5 (or 7) point harness.
Nigel Atkins

Nigel, put this pic on three times, and every time it appeared inverted (honestly!) Doh!
The springs are asymmetric- can't be used the wrong way.
J.M. Hutton

John,
I meant like your photo orientation the springs could be (made) wrong, perhaps one or both eyes on a spring shaped or bent wrong giving a distortion to normal fitting set up.

Or perhaps the rear springs are different to each other, the leaves, the eyes, the curvature, strength - just a thought.

There was a John Twist video on rear springs I'll see if I can find it later and see if it might be relevant.

Importantly, did you dye that poor dog just to match your outfits, I'm on to the RSPCA now.
Nigel Atkins

John
As Guy mentioned--you have prooved by measuring that the front suspension and body appear good----all happy there
I agree at this stage that the rh rear spring has settled lower than the left---
I'd be tempted to take the rh rear spring to the springworks and get them to re-arch it the 1" higher you have measured
Packing and fitting plates etc to lift it up is only a bandaid really and not really fixing the fault, the only time I would think of doing that would be if the springs were 100% equal which I would suggest they aren't

congrats on your measuring session

willy
William Revit

Hi Nigel - understand what you mean now re spring. When delivered, I placed both together, and they looked fine. Appreciate they may have different compression strengths though. JohnTwist video sounds helpful if you can unearth it please.
Millie adds she had her 'normal' coat on - ours were dyed! She is far more used to sitting in the front seat, paws on dash top, and head over the screen!
Willy - ok, point taken. These are brand new springs though. Will look into re arching.
Thanks again guys, much appreciated. John.
J.M. Hutton

Nigel, When i said he springs cannot be reversed I wasn't meaning just because of the spring eyes. I don't think the spring pad where the axle attaches is at the mid point. Not certain, I may go and measure one of my spares in a minute or two. When I have finished my tea.

Willy - re-tempering or adjusting one spring may be a solution, but before doing so I would try swapping the springs left and right and see what happens. It may swap the fault over in which case it identifies that spring as the culprit, or it may alter the amount of lean which would be useful in assessing which spring to get re-arched.
GuyW

Nigel, tea consumed now, yum yum. And yes it's as I recalled. Measuring from the stud that locates the axle pad, the front "eye" is at 16 3/8" and the rear at 19.5".
I suppose you could reverse the springs and increase the wheelbase, but then the prop shaft would be too short and the wheels wouldn't fit! ;-)
GuyW

Guy,
I never thought of that, as usual assuming has made an ass of me.

Willy covered part of what I was trying to say only a lot better and more concise, still wonder about the eyes (for no good reason though).

I'll see if I can find the JT vid.
Nigel Atkins

Wow, that was easy, never normally that way when I want something from t'web -

http://www.youtube.com/watch?v=qYEx42iYXc8

It's about MGB but might help generally.
Nigel Atkins

Thanks for that Nigel.
J.M. Hutton

John
Sorry, I missed somewhere that these were new springs
Just read your original posting and sure enough, they sure are new
One has probably just settled quicker than the other
i agree with Guy's suggestion --swap them over and run with it for a while -it could well all settle down then
Cheers
willy
William Revit

No probs Willy. Springs coming off again!
J.M. Hutton

This thread was discussed between 04/04/2017 and 20/04/2017

MG Midget and Sprite Technical index

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