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MG Midget and Sprite Technical - update on my spring saga

As you may recall, I got the Moss 2 inch lowered springs with the eyes at the end curved in the reverse direction (partly how they made it lower). I also used a 1 1/4 inch lowering block.

Anyway, I installed that one and now the height of my left side is pretty close to where I want it. The right side is closer but still 3/4 inch higher than the left (but the difference is much less - the car is a lot closer to being level).

It appears that the worst of this difference was due to the difference between the previous two springs that I installed.

It appears that what remains is a slight twisting in the body of the car. I am guessing that many old midgets are far from perfect given the cheap light weight uni-body construction.

That being said, I am really bothered by this.

Does anyone think that I can fix it by using a 3/4 thicker lowering block on the right rear to make up for this?

It is possible that I would have to do something with the left front but I don't think so.

Would this be a bad idea? I am inclined to try it unless someone gives me a good reason why I should not.

By the way, I am getting really fast at changing shocks and springs. I did the right rear spring today in 1 hour and I can do a shock in under 20 minutes now. ;)

thanks,
Rebecca
R Harvey

Forgot to post a few pics:
http://www.pangalacticconsortium.com/cars/MG_Midget//index020.html

Rebecca
R Harvey

Re the twist: Are you sure it's in the body? Easy to check by setting axle stands under the body and measuring down to the floor at a number of points. If it is a twist it could give grief in numerous places. Using a thicker lower block might have the effect of trying to lift the wheel rather than pull down the body. Not good for traction.
Wherever the twist is, I suspect it could easily be pulled true without adversely affecting anything else. You might need to talk to "panel shop man with car aligner".
My previous car used to hold up its front left a little. Showed up when I'd put stands under the ant-roll bar mounts. When I corner weighted it I had to make adjustments to compensate. Never noticed anything amiss on the track though.
Incidentally, if you can swap out those splined wheels/hubs/axles etc for bolt-ons, the car will lose about 10kg. A not inconsiderable amount for a small car.
Who needs Santa when we have toys like this in our toyboxes?
Mike Allen

Hi Rebecca, Have you checked the front springs? A difference on the front will reflect at the rearYours, Dave
DM Gibson

Hi Beck Mick

The car looks great at that height - well done
It could be that because your car has been sitting crooked for so long that the front springs have settled into that position.
To check what is going on -
1- Undo your front swaybar off the body so that it eliminates it from being the causal part
2- Measure exactly half way between the back springs and mark this on the diff housing. Now get a piece of round bar or a socket or something and place it on your jack and line it up with your centre mark and jack the car up till both rear wheels are off the ground
Then measure from the centre of each wheel to the wheelarch and this will tell you if the problem is in the front or rear springs
Hope this helps Willy

Have a nice Christmas

Also if it is the front it might settle back after a day or two
William Revit

Hi Rebecca,
Happy Christmas!

I think you will find that an awful lot of Spridgets have at least a small amount of lean, one way or the other. In fact I suspect that if checked, very few would sit dead level.
At one stage mine was uneven at the back. I thought swapping the rear springs over, left to right might correct it. It didn't! I did even it up by a very slight lowering adjustment at the opposite front corner that lifted the low rear corner up. I don't think it affects handling and is more of a cosmetic concern really. The best thing is to learn to accept it.
Guy Oneandahalf Sprites

Mine always had a lean towards the drivers side at the rear. Tried swapping the springs round, no diffrence. It did affect the handling a bit when changing direction quickly eg. a tight chicane. I tried using a 3/4" lowering block on the opposite side for a while. It levelled it up but for some strange reason caused axle tramp where it had never had any before. I then got some new Moss 1 1/2 lower springs and modified the front spring mount on the high side by in effect raising the point of the pivot bolt by 1 1/2". It needs to be double the ammount you want to lower.

I put it down to the car having been rebuilt slightly out when the front spring mounts/floors etc were replaced a few years ago. It seems fine now. I would try the different size blocks first as it is easier then if you don't like it try the front mount mod. Hope you get it sorted.
John Payne

Rebecca - saw in one of your other pictures the new front springs, may I ask where you sourced them and a part number?

Thanks,
Bud
Bud K

As John found out, using lowering blocks can and often does cause axle tramp to be much worse. In effect you are lengthing the leverage of the axle to the spring making it easier to bend the spring with the same amount of torque. If you use lowering blocks to level out the car be ready to install some type of anti tramp device. It's difficult to tell if a low left rear is caused by a weak spring at the rear or a strong spring on the right front. Getting the car on a set of race scales would help so that you can see the loading on each corner. A weak spring won't increase the load on that corner, a strong spring on the opposite corner will increase the loading.
B Young

Have to defend the construction of the Sprite/Midget frame - the metal is far from lightweight, and the structure is immensely strong and cleverly designed. The metal on my car is of a thickness where I found I could arc-weld with an inverter. I think it extremely unlikely that the car is twisted unless it's been in a massive accident.
D le Versha

Which new springs are you talking about, the 1 inch lowered 340 spring rate ones that I installed last summer or the new black ones (not installed yet) that are in a recent picture standing next to my old ones. Those are the 500 spring rate lowered springs from Spridget.com. I did not install them yet.

Rebecca
R Harvey

I think that I would disagree about the midget unibody being strong (at least compared to my other cars it is very fragile - but of course, it is a lightweight car).

Regarding my particular case which is still under investigation. I am planning on installing an adjustable rear antisway bar AND a panharbar or track bars (something like the two race cars that I have been studying).

Regarding my 3/4 inch raised right rear. It was suggested that something could be wrong in the left front. This is a good possibility. The left front is about 1/2 inch lower than the right front. There is left front damage history on this car. When I bought this project, the former owner showed me pictures from before the body shop did the repairs.

I am replacing the lower control arms (and pretty much building a new front suspension assembly). It is possible that a minor problem will be discovered.

Perhaps if I raise the right front 1/2 inch then I would only need to lower the right rear 1/2 inch (basically play around with both). I am not sure now I would raise the front. Would I do this by modifying the left front spring perch? I have seen adjustable spring perches. But I thought that was mostly for lowering them.
R Harvey

I mean to say "raise the left front" instead of right front (typo above).
R Harvey

now that I have two good matched springs in the rear, I can at least say that they are much closer than they were with the last set of springs. It just occurred to me, is it possible that since I have not driven the car since I installed the springs, could they height settle a little more after I flex them a bit or would that account for very little difference? perhaps I should loosen the nuts again and really push down on both springs a bunch of times (can't drive the car, too much snow).

Rebecca
R Harvey

Rebecca

The golden rule

One step at a time

First you have to jack it up under the centre of the diff till the wheels are off the ground and measure to see if there is a problem with your new back springs
Measure from the centre of your knockon wheelnut up to the wheelarch on both sides and compare. They should be the same or at least within 1/4"
Don't even think about different thickness lowering blocks it would just multiply the problems you already have.
While you have the back jacked up like this also measure up to your front wheelarches to see if the front is causing any drama
The main thing is to not jump around all over the car changing things everywhere
Get one thing right, then move onto the next
Cheers Willy
William Revit

Thanks for the tip. I thought that I was changing one thing at a time. This time, just the rear springs (rather than doing everything on my list). I have been doing one thing at a time all along (and then driving it to test the result). However, this time I can't test it(.

I will try the tests that you mention and report back.
thanks,

Rebecca
R Harvey

Yep
You're going good, It's just that your doors look to fit too well to have a twisted tub
Just trying to help Willy
William Revit

>>>>>>>Regarding my 3/4 inch raised right rear. It was suggested that something could be wrong in the left front. This is a good possibility. The left front is about 1/2 inch lower than the right front. There is left front damage history on this car. When I bought this project, the former owner showed me pictures from before the body shop did the repairs.
<<<<<<<<<<

To me that speaks volumes.... But as willy says... look at those basics 1st

my guess its the front frame section that has a small amount of upward lift may have gotten flattened out... alot of people see this up lift off set of the 2 front frame rails and try to bend it back down into a level position (WRONG)... no doulbt I can see a body shop making this same mistake

If you still have discrepinsys with the alianment after a though measurement and check then ID take the car to a professional frame shop,,,someone with a frame machine called a "Kansas Jack" (((definatly a must)))


What a kansas jack does is it bolts the car into a platform system and automaticly finds any discrepencys and can make instant pulls and shoves to correct any out of spec bends...its a remarkable system... expensive YES but really cheap when you consider how fast and easy it is to diagnoise an issue, find the problem, then fix it

here is there website for kansas jack and what all the system does.., Id call the company and ask for a recommendation of a shop in your area that has there best system of the kansas jack

http://www.kansasjack.com/

Prop
Prop

If initial tests indicate there may be a faulty spring, the best way to confirm if it is causing the lean is to swap the springs from side to side and see if the lean follows. It's time consuming but definitive.

Either a front spring or a rear spring could caouse a lean, and it isn't always obvious which. When swapping the springs, do only one end at a time.

There was a batch of dodgy spring steel a few years ago which gave such results. Also there was variability in the manufacturing, with differences in the amount of arch being common. All this has now been sorted but there may be a few still left in the system so it could be down to the new springs being wrong spec.
Paul Walbran

I did not get to my hangar today to make some measurements. Only hand time to shovel the snow at home.

Paul, I did want to comment that I would be surprised if this tiny but annoying problem were the springs because the car has been listing a little to the left with three different spring sets. However, it is much more level now than it was with the previous two sets.

As soon as I can get to my hangar (40 minute drive) I will make more measurements and report back. possibly can't get there until the weekend.

Rebecca
R Harvey

Rebecca
A quick basic check to see if your tub has a twist would be to put a jack under the low side and jack it up till both rear heights measured the same and then measure the front heights while it is in this position and they should be equal as well - or close to equal,they probably never came perfect.
I take it the floor you are working off is flat/level
Willy
William Revit

I verified lack of twist (while on the rotisserie) by using water levels. First levelled the car using the water level between the front shock mount points, then moved to the rear shock mounts. I was comforted to see them "spot on" according to the levels.
TS Smith

rear jacked up on rear end drain plug (only touch one point). Measurements in inches (sorry) from center of wheel nut to top of wheel arch:

#1) rear jacked up
LR = 12 3/8
RR = 13 inches
LF 11 5/8
RF 12 7/8
RR is 5/8 inch higher
RF is 1 2/8 inch higher (the greater problem in front)
I saw very little difference in front when the entire car is down (but there was 3/4 inch higher in RR)

#2) try to level body (not sure what this proves)
car start down on floor.
jack body under left rear spring forward spring mount point until all dimensions are as even as possible.
I was able to raise the left rear (but of course I was changing the springs).
LF 12 5/8
RF 12 5/8
LR 13 5/16
RR 13 8/16 (all even except RR still 3/16 higher)
To do this I had to raise the left rear 3/4 inches.

My current thinking is that I should shim the left front up a very small amount and that I should put a slightly inch thicker lowering block on the right rear.

I don't think that I have a serious problem but I do think that I have two small problems in the body (left front is a very tiny bit low and the right rear is a little high and these two problems have added together). Fixing them both a little will almost completely solve it (rather than trying to fix the entire problem by just lowering the right rear).

It would be a good idea for me to consult a professional if I can find one who knows about this car.

Rebecca
R Harvey

Rebecca

Hi
From your first set of figures, with the back jacked up it shows that your problem is in the front.

From your second set it shows there is only 3/16" of difference in the body - but don't panic about this as all wheels are on the ground doing your second set of figures and if the floor isn't 100% accurate your figures will be affected. It's very rare to have a perfect floor or a perfect car. Just for peace of mind you could turn the car around 1/4 of a turn from where it is and repeat the no.2 measurements and I'm sure you will get different figures-

To progress on the next move is to undo the front swaybar and recheck your measurements with the jack under the centre of the diff as it could be a badly bent swaybar causing the drama.
If the measurements reamain the same or close to your 1st set of measurements with the bar off then the problem is going to be either a sagged left front spring or bent bottom suspension arm.

Just to double check the body for twist you could jack the left side up again to level the car and then instead of measuring wheel arches measure from the ground up to say the bottom of the headlights and the bottom of the taillights, these are further apart than the wheelarches and if there is a twist at all it should show a greater difference further out

My gut feeling is that the front spring has died or the right hand spring isn't fitted up in the crossmember properly holding the rh side up

If you really wanted to,just to finish off at the rear, because your car is left hand drive and will have a bit more weight on that side, you could swap the rear springs over to get the RH side one which appears to have slightly more (1/4")arch onto the left side which will help hold the car more level with the driver aboard. But having said that I don't think your problem is in the rear at all it would just be a little extra thing to do

Hope this helps Willy

Whatever you do don't fit different size lowering blocks it will just give you more wrong stuff , the back is fine like it is and even better if you swap them springs over the problem is in the front.
Your next move really is to check the swaybar, check that the bottom arm isn't bent and then get the front springs out and check lengths

One little thing did you measure to check that the drainbung of the diff is exactly halfway between the rear springs,I think it is but you have to jack dead centre for good measurments Willy
William Revit

Rebecca,
I think that those measurements don't indicate any serious problem and that many cars would show similar or worse results. But if you want to get closer to level then you need to do some further measuring. The front is most critical, and a small lean here will be transmitted and accentuated at the rear.

You need to do multiple measurements and to take averages, bouncing the car on its springs between times.(Gently whilst the rear is jacked up on the drain plug) As William says, for accuracy you probably need to disconnect the front ARB / sway bar.

But how accurately aligned are your front wings for taking measurements off. As they are bolt-ons they can be set at different heights anyway and would need to be checked for a side to side match if that is what you are measuring the springs against. For your purpose the easiest check would be to set a taught string line along the bottom of the sills, carried forwards past the front wheels and then measure from this to the wheel arch top. If they differ, then you can add or subtract the difference from your other measurement of the spring compression.

If you use shims to either increase or lower the front spring height the shim needs to be slightly less than one half of the required correction height.

Guy
Guy Oneandahalf Sprites

Guy Rebecca
Yeah, I guess my last posting was a bit drawn out but as Guy says there doesn't really appear to be a big problem

By jacking the rear off the ground and having the rear wheelarch measurements become almost equal with the wheels off the ground eliminates the rear springs from being the cause. The back is very close to being spot on and as Guy mentions giving it a bounce or two while jacked up like this will allow the springs to settle into there spot

The fact remains - With the rear wheels off the ground it allows both front and rear suspensions to operate independantly - the results of which were

Front - 1 1/4" difference - This is where the problem is without doubt
Rear - 5/8" difference which has probably been caused by the new springs settling into an uneven position caused by the front suspension holding the car over to the left so much - The rear springs will hopefully settle down even once the front is fixed up.

Your main aim now is to get the front sitting square, and measured/checked while jacked up by the centre of the diff so that the rear suspension is not affecting your result.

I'm sure Guy is after the same result for you, just be carefull if you are going to shim the spring buckets. Have a jack under the bucket when you undo the bolts as the spring is very strong and powerfull and can hurt - bad If you are thinking of lowering the RH front by shiming the bucket downwards from the arm, the bolts arn't very long and will need replacing with bolts that are longer to accept the thickness of the shim (1/4" shim - 1/4" longer bolts. Personally I;d rather see you pull the springs out and measure them or replace them it's too far out to shim-
If you are going racing they need to be a bit stiffer than standard anyway Willy
William Revit

Thanks for all of your comments.

my front anti-sway bar was out for all of these measurements.
I have eliminated differences in the springs from being the cause of the problem because I am on my third set of springs in the rear (I like these ones now) and I am on my second set of springs in the front. The leaning trend was the same in all three cases.

I am planning on changing the front springs one more time. the ones that I installed this summer are the lowered 340 spring rate ones from Moss. I got some 500 spring rate ones from spridget.com which I expect to further lower the front slightly more (up to 1/2 inch I predict).

My first concern is to get the car sitting such that I can weld in roll over cage and not worry about the body being permanently stuck in that position. If the problem is just a matter of tuning the sprung heights (due to minor localized body variation not caused by the major body twist then I can go ahead and proceed with the rollover cage install and finish the tuning of the suspension later). This is what I would prefer because I want to get the rollover cage done as soon as possible (because it is going to be inconvenient).

Thanks,
Rebecca
R Harvey

I have been thinking about this. I am willing to bet that the part of the body that rest on the right front spring rests is bent higher than it is supposed to be (as a result of over-compensating for damage when it was bent back by the body shop). I am also going to look at the parts diagram to see if there are any pars that are supposed to be welded or bolted on that could be missing. I am guessing that there is a very localized problem in the body that is causing the left front to be lower and the right rear is sticking up in response to this.

I should do a test where I jack up the left front a little and see if the rest of the car becomes even.

Rebecca
R Harvey

meant to say left front.
Rebecca
R Harvey

Rebecca,

I have to agree with you...i really think you dealing with unresolved car wreck damage on that front frame rail..

Did you look into that kansas jack system i mentioned earlyer in this thread

1 Paper

Before you install the new front springs, do you think it would be worth swapping the existing front springs side to side so that you know for sure if it is a spring problem or not?

Charley
C R Huff

I did not call any body shops yet because of the holiday. I will try this next.
Rebecca
R Harvey

Rebecca

When you fit your front springs you have to really make sure they are located up in the body properly, there is a little step up in there that the spring has to sit up in - My guess at the moment is that your RH front spring isn't located properly up the top and that it is holding the RH side of your car up, The step is about 1/2" high and that would give you the inch and a quarter difference at the wheels that you have.
If you have both your new springs sit them together and check they are exactly the same height before you fit them. If one is slightly longer (up to 1/16") fit the long one to the drivers side.
Also compare your left and right bottom spring buckets that bolt up to the bottom arm just to make sure the car hasn't been fitted up with an odd one from somewhere (bodyworks)

You mention jacking the left front up with your jack to see if the car comes even - It will as that is what we got you to do and you proved with your measurement set no.2 earlier. It was out a tiddle (3'16") but not enough to worry about, it could just be an uneven floor throwing measurements out a bit. You have also proved with measurement set no.1 that you rear springs are good so forget about them for now unless you were going to do the right to left swapover thing mentioned earlier.- not important

Have a good look around that RH front spring before you pull it out and try and look up where the top of the spring goes to see if is located up in there centrally, I've got a feeling that it's not up in there properly
Compare it to how your left spring is fitted up

You'll love them 500 pound springs - they are a good choice for your car, it will feel like it is on rails
What size is your front bar. I found 500 springs and a 3/4" bar a magic combo but a lot of people prefer the 11/16" bar just depends on driving style a bit

Cheers Willy
William Revit

Rebecca

Check the springs are equal - and also check one of the front wishbones isn't bent - that can happen sometimes in accidents.

I would have thought 500lb springs are a little on the heavy side for a car used on the road but it depends how good your local roads are I suppose...

Cheers

JB
James B

Willy and JB,

thanks for the suggestions. I don't think that my wishbones are bent but there could be some unseen damage that I had not noticed. I have some new ones that I am going to use eventually. Also I had been wondering if there was some part of the car body that the is resting on the spring (the 1/2 inch perch that you mentioned). This is a good theory (except that it seems pretty unlikely that the same problem would happen to two sets of springs).

Does anyone have a picture of what that looks like? ( I will find out eventually when I remove the spring again)

Willy, my front bar is 3/4 inch.
I am pretty sure that my left front was low with the previous set of springs too.

I am going to be replacing the lower control arms (including the spring perch).

The new front springs that I installed looked exactly the same height sitting on the floor together (and the old ones did too).

I will investigate whether the front springs are not correctly located and whether any damage to the left lower control arm could also cause these differences.

I could go ahead and finish my front end part replacement before worrying about how the body sits but then I will have to wait even longer before having the rollover cage welded in.

I did find a body shop very nearby that has a frame straightening machine. I don't know if they are any good. I will go and check them out.


thanks,
Rebecca
R Harvey

One other little thing - probably not possible but -
check to make sure the bottom of the spring isn't caught on the lip of the bottom arm and sitting on it instead of through the hole onto the bucket - don't know for sure if that can happen but worth a look Willy
William Revit

If you have not yet checked/fixed the lower control arm inner pivots, do so. Wear or slop here will be approximately doubled at the wheel end. It is pretty common that the stepped washers are not correctly located in the frame, especially if it has been apart in the past. In this case there may or may not be obvious looseness, but the error can easily be about what you think you are seeing. It's a PITA to fix too, degree depending on how bad the resulting wear & distortion is. I posted detailed instructions several years ago, might find in archives.

It is quite simple to check for twist with a couple of 5 foot spirit levels, or even one and a good straightedge or two. And, check your floor area with same; mark your permanent reference spots, or you will chase your tail forever. I seem to recall that you have a car lift - possibly you can check and use that as a decent level reference plane.

FRM
FR Millmore

Rebecca

Like most on this thread I felt that the issue was most likely springs, but it is looking as though there may be an issue elsewhere and others have made some good suggestions of things to check.

I agree with comments above that the body tub is quite rigid, but on what you've found so far it may be worth doing some further measurements yourself to check this out before seeing a body shop. There are only a couple of key places to check.

First - are the sills parallel to each other? I check this by setting the car up with one side dead level using a spirit level on the bottom of the sill, then see if the level shows any difference up at the other side.

Next - check the kick-up of the front chassis rails is the same for both sides. This is the weakest aspect of the car and the most vulnerable to accident damage. (It's always been the first bit to be affected when we got too enthusiastic and collected a bank or strainer post in a hillclimb etc!)

Check each rail by running a straight edge or string line along the line of the rear half of the chassis rail where it merge into the floor and extend this line to the front of the car. At the front end of the chassis rail, the bottom of it should be 1" above the this line.

This is also one that repairers seem to struggle with. I have seen a number of cars where the chassis rail has been repaired to be dead straight (no kick-up, which BMC adopted as a simple way of introducing castor to the front suspension) or in whic the kick-up was wrong. 1/4" difference between the heights of the rails could lead to 1/2" at the spring seats and 1" at the wheels.

An alternative way to check the overall car is to set it up so that the front mounts of the rear spring are level (a spitit level blocked down from the plate by enough to clear the bottom of the bulge in the rear of the transmission tunnel) and compare for level with the rear shackle mounts at the back and the spring seats in the chassis at the front.

This latter method is good for confirming the car is overall true or twisted, but does not tell you where if there is out of true between front of rear spring and the front spring mounts. The sill and chassis rail measurements above will give a good steer on this.

Paul Walbran

THANK YOU ....Paul Walbran, New Zealand

You have come to my darkside...you have done well sith of the slide rule and made my above arguement vary well.

"""Paul I am your father"""...pppssshhhh ttaaahhh pppssshhhhh tttaaahhhh HAhahaha

She (rebecca) did say on several occasions that the car did have some serious damage from a bad wreck on the LEFT FRONT...Hello!

Fear the force, Vader loves to be right

Kansasjack.com is rebeccas friend
Prop

Paul thanks for the excellent info. I to agree that the problem is not the springs.
the front end of the chassis rails was definitely replaced I last section that sticks out beyind the cross brace. Welding is ugly but I thought that it looked strong and straight. I will take another look and try and check the things that you mentioned.

thanks to everybody. I will hopefully make some progress soon (but it is freezing and I have no heat).
Rebecca
R Harvey

Scary thought Prop!!
Paul Walbran

Rebecca,
that rail extension in front of the cross member won't have any direct impact on the suspension geometry if badly fitted - other than possibly putting the ARB out of alignment, but you say that has been disconnected for your measurements. But if that bit is poorly repaired, then possibly the chassis rail behind it was damaged and not corrected, or only partially corrected.

But I would still say that the amount by which your car is out, is not at all unusual. Many cars will be like that! It may not be damaged and there may not even be any one point where a specific fault can be identified.

That isn't to say that you cannot improve on it, especially if you are intending on competition. But you might do this more effectively by measuring the weight distribution than by trying to measure off the body tub.
Guy Oneandahalf Sprites

This thread was discussed between 25/12/2010 and 06/01/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.