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MG MGB Technical - Rear Springs

I fitted new rear springs to my 1965 B roadster 4 years ago and have covered 8000 miles since then. This is the the third set in 20years. The set up is standard expect for polypro bushes at the rear - got fed up having to change the rubbish rubber ones we get today every two yeards for the MOT.
The springs were brought from a well known supplier of MG bits supplier and are meant to be OE standard with rubber interleaves.

SO why is the car down 3/4 inch on the neardside and has been for a while and it is now more noticable since I rebuilt the front suspension.

Anybody any ideas?
George Wilder

Amazing how many threads there are about rear springs and sag on the B, midget, and A boards. Seems to be the nature of the beast as far as replacement springs go. The only thing that I can add is this, if your springs do not have the plastic or poly separators between the leaves then add them if possible. I added these to a set of replacement springs for my Midget over 4 years ago and have not noticed any signs of sag although I weigh in at around 250 lbs. My theory is that internal friction between the spring leaves keeps the spring from returning to a true neutral positon after having weight applied. I also noticed that the rear springs are more linear in their response to weight transfer during cornering without any sudden changes in height as weight transfers.
Bill Young

It's probably not the springs.

Many many many B's have this, and it basically a 30 (ish) year old car that is now wonky !

Try swapping the springs side to side, and it'll unlikely change.

j w mcglynn

I find it quite unlikely that the car is twisted. This can be verified by looking at the angles of the two front suspension arms relative to the crossmember - you should find that they are at different from side to side. If they are the same whilst the back still leans, then yes it's twisted.

Have you changed your front springs ever?

ttfn,
--
Olly
Oliver Stephenson

£5 says it is ;-)

j w mcglynn

Thanks for the comments so far.
I have changed the front springs 17 years ago and last week. This has not made any difference to the problemat the rear. The problem has only occured in the last year or so - changing the front springs made no difference - I checked the measurements before and after the change.

I will check the angle of the front wishbones tomorrow and report - I don't think the shell is twisted - I have had it forover half it's life now and it has not been damaged in my ownership.
George

George Wilder

George,
Are the springs showing any signs of seperating or leaf sag? I wonder if there was a manufacturing issue with them as I have heard of several sets not matching and being sent back to the supplier. Also you may have one wrong spring for your car ie gt/roadster CB/RB spring?
TJ
T J Nicolson

I've never *had* to replace the rubber bushes in 14 years and 40k on the roadster, and 10 years and 70k on the V8. I did choose to change them when I changed the springs on the roadster a few years ago, then changed those a couple of years later for red poly as an experiment (pointless). The rubbers I took out were perfect. Like everything else, it all depends on the quality of what you buy.

There are a lot of crap springs out there, in the US for longer than the UK. Several years ago one well known supplier tried to sell me some springs that were copies but which had the OE number stencilled on them, which is illegal. I only noticed because they didn't have any interleaving, but that is easy to 'correct' and then one wouldn't know at all.

On a flat and level surface take some drop measurements from the front and rear spring hangers of the rear springs to the floor as well as from the centres of the axles to the bottom of the bright trim strip. If the drop measurements each side are the same that eliminates the wheels, tyres and springs, and leaves the relationship between the hangers and the bottom of the trim strip. At the front if the A-arms are parallel to the ground, or at an equal angle at least, but the axle to trim strip measurements are different, it could be in the body or the springs. Taking another measurement from the base of the damper to the floor will eliminate the springs. But a problem at one corner is almost certain to show itself at the diagonal corner as well.

If you lift the car a bit manually then let it settle gradually and take a measurement to the floor, then push down manually and let it rise gradually and take the same measurement, you can get an idea of how much 'stiction' there is in the springs. Different amounts of stiction could cause varying amounts of lop-sidedness according to the ground surface it last rolled along. I gave mine a liberal daubing with Waxoyl before fitting to protect and lubricate them.
Paul Hunt

My car has leaned for at least 20 years. Worse now than ever after replacing the rear springs. Still can't figure it out. Makes me want to go IRS.
Steve Simmons

There is a little bit of flex in the MGB. You can see this when you go down a bumpy road. If you have had the car a long time and mostly drive it with no passenger, then the basic structure most likely has twisted. The only way to tell for sure is to take the car to a frame shop and have it checked out. Not sure if there is a cure other than flexing the structure when you replace the sills/rockers.
Jim Lema

Bill

Can you provide a source or brand and part number for the "plastic or poly separators between the leaves"? I am about to redo the rear springs on my 69C and want to add these.

Thanks

Larry
69 C in restoration
Larry Hallanger

I wonder if we should be looking into a coil spring conversion?
Steve Simmons

I can't recall who makes it (Phoenix?), but there is an IRS rear suspension setup you can fit to your MGB which uses coil springs. I think it cost about what my car is worth. Not exactly an option for your everyman.
Matt Kulka

There is flex on a 6 foot long 6 inch diameter shaft if a fly lands on the centre of it. The MGB is a very stiff shell which in general terms does not flex.
No way the shell has twisted unless it has at some time sustained accident damage. If it had flexed this would be immediately apparent and the panel gaps would be all over the place. If it was accident damaged and not properly aligned then panel gaps could have been "made to fit" bny the bodyshop who repaired it. It might be worth putting on a jig for peace of mind otherwise it must be in the suspension/springs.

The other way of course is to jack the car and level the sills, measure the height to the suspension mounting points each side, then drop a point front and rear centre and an additional four points(two each side) at front and rear mountings marking all points with chalk on the road. Move the car away and "ping" the centre line with a chalked string. Now draw all diagonals of other points which should intersect at the centreline
Iain MacKintosh

Full IRS from John Hoyle. And very good it is too.
http://www.hoyle-engineering.co.uk/

Mike
Mike Howlett

My '68 GT leaned when it was new, so the problem is not just with low quality replacement springs.
John Hubbard

You may want to read this information about lean problems. I helped my 74 roadster lean a little by making a longer shackle for the left spring. I also found there is less lean with a full tank of fuel than if the tank is less than half full. FWIW, Clifton
http://www.mgbmga.com/tech/mgb4c.htm
Clifton Gordon

The product I used was called "Polyslide" if I remember correctly. I bought it at the local street rod shop. This used to be a common upgrade for the springs on hot rods although most are using coil over shock units today. The narrow width was still a little wide for the MG springs, but only needed trimming around the axle mounts and the spring clamps.
Bill Young

Thanks for all your comments

Let me resate that I have owned the car for 20 years and though I have changed springs in the past it has been because both springs sagged whereas at the moment only one appears to do so after 8000 miles and four years.

The parts have only ever been purchased through the two major Hertitage Approved suppliers in the South of England.

The current set of springs have the interleaf beween each spring leaf and are stencilled with the OE part number. I believe there is now only one manufacturer of leaf srpings for Bs in the UK called British Spring. I do not know who made the springs on my car only the supplier.

As suggested by Paul and others I have taken some measurements. All in cms
LH RH
Crome strip to Floor 65.9 66.9
Crome Strip to wheel centre 37.1 38.0
Front Hanger to floor 21.5 21.9
Rear Hanger to floor 32.1 32.9
Sring plate to floor 18.8 18.8
SA to floor 42.5 42.9

The front suspension appears very even thoughthe RH measurements are about 0.1 to 0.2 coms greater than the LH

The above figures suggest to me that the LH spring has sagged.

George
George Wilder

One final thought... when replacing springs and bushings, did you let the car settle with all of its weight on the wheels before tightening the bolts that clamp the bushes up? This is critical to making the car sit right and making the bushes last.

Lean to the left is fairly rare on RHD cars - my RHD GT leans to the right and my LHD roadster leans to the left, both having been driven entirely on UK roads since suspension rebuilds. Too many pies, clearly.

fwiw,
--
Olly
Oliver Stephenson

Thanks for all your comments and suggestions

Firstly I don't want to go the IRS route the B is a simple car so lets keep it that way -its part of its charm and fun to experience motoring in a style of 40years ago.

I have had 251 GRW for 20 years now and have changed springs twice before. This time is the first time thay have shown problems so quickly - 4 years and 8000 miles! The springs and rubber bushes have all been brought from either of the two major Hertiage approved suppliers og MG parts in the South of England.
I understand thatt here is only one company in the UK making these springs now called British Springs.

Anyway I have taken some measurements for you all to study and pass verdict

All in cms.
Looking from the rear LH RH

chrome strip to floor 65.7 66.9
chrome strip to wheel centre 37.o 38.0
front hanger to floor 21.5 21.9
rear hanger to floor 32.1 32.9
SA to floor 42.5 42.9
base of spring plate to floor 18.8 18.9

the front seems all eqaul within 0.1cms

Seems to me the spring on the left has dropped more than the on the right.

George

George Wilder

I know when fitting V8 bushes to the inner A-arms one musn't fully tighten until the suspension is at it's normal level, but I'm pretty sure than doesn't apply to the rear. Certainly the rear rubber bushes are not a press-fit into anything like the V8 bushes for the front are. The measurements you give do seem to point to the spring as the culprit. Since I assume you have an RHD then unless you always carry a passenger or load on that side of considerably more than your own weight, it is unusual, it is the drivers side which usually sags. Unless you are prepared to live with it I'd swap them over just to see what happened initially, and over time.
Paul Hunt

I have heard that the jigs used to assemble the bodies were slightly "off" in the rear spring perch areas and that BL selected springs when assembling to get them as level as possible.

Rumor???

If your springs are identical (and especially if swapping left to right doesn't have an effect) then the mounting points MUST not be level.

Mike!
mike!

Mike,you've got to be kidding us. Jigs? I didn't know the factory knew what these were. I've yet to see a Midget with the rear axle centered in the body and most B's are off a bit also. I've heard of Triumphs fresh from the factory that were almost an inch different in wheelbase from one side to the other. I've found internal body braces on my Midget that were at least 1/2" different from left side to right. That these cars might sag a bit isn't that surprising.
Bill Young

This thread was discussed between 17/08/2004 and 26/08/2004

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