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MG Midget and Sprite Technical - How to guide - rear spings 1275

Going to replace both rear springs and bushes/hangers etc. Haynes offers its usual very brief paragraph, and there are snippets dotted within this BBS and the web's voluminious skirts, but does anyone know of the wherebouts of a more detailed step by step guide?

Many thanks

Mark
Mark O

I have got close to that when replacing my rear axle and I took the opportunity to renew the bushes at the back end of the springs. Nothing difficult about it except that you are working under the car with quite heavy bits of kit.

You should be able to support the whole axle assembly on axle stands and leave in position, just undoing the U shaped clamps.

It's worth replacing the old bushes although getting new ones in, lined up and the bolt pushed through is a bit of a b**g*r.

THe main warning I recall is do not tighten any of the spring pivots (through the bushes) at either end until the weight is back on the wheels (or presumably onto the springs via stands) and "settled". This makes sure they are locked in their running position. If you don't do this the back end will appear higher than it should be and the bushes will be in a strained position for normal running.
Graeme Williams

<<appear higher than it should be and the bushes will be in a strained position for normal running>>

What happens is that as you lower the body onto the wheels (or axle) the rear end of the spring has an urge to tuck up in front of the rear mounting point, with the rear shackle pointing forwards and jammed. This is because new springs will initially have a more pronounced curve than they eventually settle down to. The trick is to use a lever and as the body is slowly lowered, simultaneously lever the rear shackle round so that it points to the rear and the spring occupies its proper position. Once compressed (flattened) for the first time it will happily remain in it the correct location. Then you tighten up the shackle bolts.

The only guide you need is to undo bolts, and then do them up all again with the new components fitted. The rest is down to your sense of adventure and your enquiring mind. There may be something in the handbook about it - I haven't looked.
Guy W

Guy - How very daring of you not to look in the handbook. I await chastisement from a certain member. Good tips, many thanks. Would removing the mounting plates at each end faciliate matters - to insert new bushes etc on the bench rather than under the car?

Additional Q - Are springs from the usual suspects etc now OK after the bad batches previously?
Mark O

Mark: that sounds a good approach (bench assembly, not handbook!). I found, as happens with the rubber (or plastic) bushes that they take a bit of encouraging to squeeze into location.

I had to drop the back ends of my springs because the po had put the pivot bolts in from the tank side, so the presence of the tank prevented them from being removed. Actually, thinking about it, with bench assembly there is a risk you could do the same thing! The nut needs to be on the inside face.
Graeme Williams

Graeme, good point about those shackle bushes! As far as I could tell, that "bolted through the wrong way round" was a factory original arrangement! Crazy! They must have assembled the suspension before adding the tank and never considered future dismantling.
Guy W

Mark - I've got most of the bits you would need for this job, unused from an abandoned project last year.
Get in touch if you're interested.

Malcolm
M J Chapman

Mark,
a Handbook for learning and getting used to your new car with full regular servicing schedule and details wouldn't cover this - changing your rear springs isn't part of regular servicing, the manufacture would hope you'd bought another new car from them before this

the Haynes is for repairs (Handbook is for prevention) but as you've found the Haynes can be lacking in detail

consider yourself chastised !

I'm disappointed in Guy too, :shakeshead:, giving written instruction for Mark to 'book' learn from rather than leaving it to Mark to intuitively learn

does no one stick to their principles here(?) is it just Prop and I that do(?)

like Prop, I now retire to a darkened room with all hope for humanity depleted








only the sight of a good book could possibly revive me and give me strength to go on
Nigel Atkins

Nigel,
I was, as you well know, adding a reference there just for your personal satisfaction. And don't misquote me. I never instructed Mark to use your favourite book. I merely said that I had not looked at it. I suggested that he use his sense of adventure, this being to me what working on these cars is all about. ;-)
Guy W

Guy: but it looks much neater with the bolt heads to the outside!
I looked in the manual and there are no pictures, However I note that the instructions to remove the springs tells you to drop the rear ends by removing the attachment to the boot floor rather than knocking the pin out, so it wouldn't matter that way round.

I wonder whether replacing like that would prevent the issue of the end of the spring kicking the shackle the wrong way round?
Graeme Williams

Mark-
Once you get the spring off, examine the hanger brackets and the areas around them. It is not at all unusual to find rust there, especially in the area around the front bracket. Also, take a moment to examine the rear brake hoses. Be aware that they can collapse internally while showing no outward signs. Fragments from their interior lining can break free and cause clogs. If any of them are bulged, swollen, or, even worse, cracked, you should replace them as a matched set. This would also be an excellent occasion to flush the hydraulic system with denatured alcohol. If you do, you will be amazed at the crud that will come flushing out of the system. Denatured alcohol can be obtained at any paint store. Since the wheels have been removed in order to grant easy access to everything, pull the brake drums off and look to see if the brake slave cylinders or axle seals exhibit any signs of leakage.

As you are putting it all back together, be sure to use antisieze compound on all of the threads, and especially on the steel bushing sleeve that goes on the front mounting bolt. Whatever you do, do not reuse any of the old mounting bolts, nuts, or U-bolts as their threads are almost certainly corroded beyond redemption. Remount the rear end of the spring first (Yeah, I know that the manual says to do the front first, but let us do this the easy way, shall we?). Swivel the shackle links as far forward (toward the front of the car) as they will go and use the hydraulic jack under the axle in order to compress the spring so that it will extend forward into the front spring bracket until things align. As the spring extends you will need to tap the block of wood under the hydraulic jack with a heavy hammer in order to move the mounts of the axle into proper alignment with its locating holes in the leaf spring. An alternative method is to place a hydraulic jack under the spring with the axle unattached and tap the wooden block and jack forward as the spring extends. From the front side of the bracket, slide the tip of a tire iron above the eye of the spring so that you will be able to use it as a wedge lever in order to align the height of the eye of the spring inside of the bracket. When the eye of the spring is longitudinally even with the mounting hole of the bracket, work the tire iron slowly to lower the eye of the spring into alignment with the mounting hole of the bracket.

When replacing the mounting bolt of the shackle, note that the Original Equipment specification mounting bolt is pressed into a splined hole in the shackle plate and that the mounting bolt has a double shoulder at the threaded end, the smaller of which fits inside of the hole in the closing plate. This not only serves to protect the threads by keeping them away from the edge of the hole, but more importantly makes the tightened shackle into a rigid parallelogram that aids spring location, and hence in turn, axle location. Should you lose one of these special-purpose mounting bolts, do not attempt to use a plain machine bolt instead. Plain machine bolts will permit the rectangle of the closed shackle to be distorted into a rhomboid during cornering, which will give more lateral movement of the spring and hence of the axle. Over time, this will wear the holes in the plates into ovals as well as wearing grooves into the machine bolts, thus weakening them. There is also the issue of tightening the shackles. Even when the original shackle is tightened to 30 Ft-lbs, the bushings are only lightly nipped and clearance remains for the spring eye to pivot on them. However, without some form of spacer tube, a plain machine bolt is going to tighten the shackles onto both the bushings and the spring eye, thus restricting movement and damaging the bushings in a short time, as well as causing wear of the shackles.

Test the alignment by pushing in the mounting bolt. If it will not go through, do not attempt to pound it in with a hammer or you will damage the threads. Instead, patiently peer in there with a flashlight and adjust the alignment by compressing or decompressing the spring with the bottle jack (horizontal alignment), or by moving the tire iron (vertical alignment). Sometimes it helps to hold the flashlight against the outside of the bracket on the opposite side so that the necessary concentricity can be confirmed. When it is aligned, install the mounting bolt using hand pressure, and then spin on the nut. Be sure to use antisieze compound in order to protect the threads. Use the floor jack (trolley jack) to maneuver the axle so that the U-bolts can be installed into the spring plates and the damper arm plate. Also, check to be sure that the pads have their cutouts aligned properly. Misalignment of these can result in all sorts of strange handling effects. Once all of the U-bolts are in place on both ends of the axle, be aware that a static tension in the leaves is present whenever the leaves and the spring mounting plates are not longitudinally or laterally parallel. Any static tension will cause an increase in Spring Rate. If necessary, reposition the U-bolts on the axle tube in order to eliminate any twist. Bolt up the new springs loosely, push the axle over to center, and then lower the car onto the ground. Never tighten the front or rear spring mounting bolts until the car is back on the ground and the rear has been bounced up and down a few times in order to settle the suspension! Finally, torque the nuts on the U-bolts to 25-30 Ft-lbs. The axle should be about mid-way between hitting the bump-rubber stop and taking up all the slack in the limiting strap, with a bit more distance to the bump rubber than the limiting strap. The shackle should be pointing down and back slightly.
Stephen Strange

Gents

Many thanks again for the info - Stephen especially for his trouble.

Well done Nigel...you rose to the fly again! I would challenge the assertion that Haynes is for repairs. Sometimes it is utterly woeful in lack of detail - which is odd, as in many areas it is pretty thorough.

Malcolm C - yes please, sent an e-mail....

Obliged as ever

Mark
Mark O

Guy,
don't misquote me
the 'book' learning I meant was from your written instructions rather than the good book or any other actual book (note 'book')
how can he use his sense of adventure if you've given written instructions to 'book' learn from, breaking your principles, I'm very disappointed in you

;-)

a pretty full answer from Stephen :)
Nigel Atkins

Stephen's fullsome answer is a cut and paste from his MGB article. I find it much easier on the Spridget to attach the front mounting plate of the spring first. There is less jiggling about aligning the simple push-in shackle bushes at the rear than trying to get the 4 bolt holes aligned at each of the front plates whilst working against the tension in the spring.
Guy W

Guy

Duly noted and thanks - if you have done it before on a Spridget and found an easier method then fine...I like easy....

Cheers

Mark
Mark O

mark, 6 times, 4 different cars.

If you are just replacing the springs then no need to disconnect anything from the axle - it stays attached to the car, just support it on a jack. The biggest problem I found in each case was the front spring mounting plate bolts being seized. I would start by checking that each of those bolts will undo - especially if the car is a daily driver as you can work on those bolts to ease them one at a time without it immobilising the car. Once you know they will undo, or have replaced them with new bolts well coppereased, you can then set to on the main removal and swapping of springs which should be straightforward.
Guy W

I honestly do not understand why Haynes gets so much stick. I cut my teeth on haynes manuals for a number of cars and motorbikes. When the likes of the Spridget versions were written, the writers of haynes assumed a bit of mental effort on the part of the reader. But being frank, especially with the removal and replacement of the rear springs, I don't see how they could have made it much clearer. There's a very clear description about jacking up the car and supporting under the axle. It details the removal of the various fixings and replacing the bushes. And if you can't read, there are 5 excellent pictures, that make it bleeding obvious when you look at the car. I think a lot of it has to do with lack of confidence.

I also think the difference today, is that people expect instructions that essentially "spoon feed" them. Whereas, previous publications relied on the readers willingness to use their cognition.

As for the rear shackles not being in the right way around. I don't know if there was a specific reason for them being installed that way, but I've never had any trouble removing the shackle plate. Remove the nuts, remove the outer rubber bushes, and as you pull the plate towards the tank, push the inner bushes through, at the same time as angling the shackle plate. There's plenty of room.

I've actually just done this on the midget(removed the drivers side rear spring), to give me better access to weld the lower rear section inner rear wing and a few other bits in that area.
Lawrence Slater

Lawrence: it's not removing the plates that's the issue. If the bolt has been inserted from the tank side then with the tank in position you can't get the bolt out. THat was my experience anyway.
Graeme Williams

Lawrence

I agree Haynes is very good at telling you what to do, just not so good at telling you just how to do it. For me it is more a question of preparation and knowing what to expect before I dive in there - not having done the job before.

PPPPPP....



Mark O

Graeme, it's not a bolt but a shackle plate; Lawrence's instruction is just how I would have written it, the potential pitfall is not freeing off the inner bushes and pushing them though with the shackle.
David Smith

Well each to their own with Haynes, but I think it's about the best workshop manual out there for Spridgets. You learn by using it. Try it.

Rear shackle. I took a few pics to demonstrate. Like so.




Lawrence Slater

Works like that OK, but not so simple if the rubber bush remains attached to the spring eye, in which case one cannot tilt the shackle over until it is further out and the tank does then get in the way. It's no big problem, but easier for the future just to push them back in from the other side.
Guy W

..but then there's no room to get a ratchet and socket on the nut to do it up !
David Smith

strong fingers and spanner(?), ratchet ringspanner(?)
Nigel Atkins

Guy, you just use a flat blade to prise the bush free, or a rod to push it through from the other side. I took those pics specifically to show how to manouvre the shackle plate at an angle. They were not the original bushes in there. The bushes originally in there were "stuck" in there, and I got them out easily as described above. It took less than 30 seconds, which is far less time than droping the mounting plate.

As for fitting the shackle plate from the other side, I've never needed to try. But as Dave says, if it restricts access to the nut, I'd rather leave it as the factory built it. Since as demonstrated, it's not really a problem in need of a solution. :).
Lawrence Slater

I've never thought about it before, but if so many people have difficulty with this (-- I've never heard of it until now --), in all the years of production, I wonder why BMC didn't change it. After all, even if they were first factory installed without the tank in situ, as has been suggested, they were later serviced at BMC garages with the tank in situ. So why didn't the BMC garages reverse the installation to make it easier?

Is it possible that apart from nut access, there's actually a reason for the plate being inserted from the tank side? I can't think of one. Maybe it's as graeme says, it just doesn't look right. I'll install mine reversed and take a look.
Lawrence Slater

I don't think I ever described this as a significant problem. Just easier to slide them in from the other side. And I have always favoured open ended or ring spanners over a socket for firm tightening so the point about access to the nut doesn't really apply (to me). Just old fashioned, I guess, and prefer to not put a lot of strain onto ratchets - which is what I use my sockets with mostly.

But, did they change the fuel tank dimensions? On my '71 car the side of the tank is closer to the shackle than in your photos, Lawrence.

As I am sorting rear brakes the car is up on stands at the moment so I checked. The edge of the tank mounting flange reaches over to the edge of the bracket, so there is about 5/8" clearance between the side of the shackle and the tank. There is even a short length where the tank flange is narrower alongside the bracket. That is why it is awkward. I do know that when I first did this job I had to unbolt the mounting bracket from the floor of the car to get it out. Since then, the shackle has been inserted from the other side so there is no problem at all.

Thinking now, my tank is a replacement one. The original was rusted out. I remember buying the replacement at a car show in around 1992, I think it was from the MGOC club stand.
Guy W

That's interesting Guy. The pics are from my '73 Midget. I haven't checked the Sprite('66), I'll check it tommorow, but I've never had a problem removing that one either.

If you're right though, and a lot of cars did have the tank that close, it makes me wonder even more, why BMC fitted the shackle the way they did. Why didn't they fit from the outside in, as you do now, and why didn't BMC garages pick up on it and change it? Maybe it's just that everybody assumes that "factory fit" is best? Even if it's not.
Lawrence Slater

Well, original springs last a long time, so there probably wasn't that much of a need to remove springs on original cars for many years. Its possible that there wasn't that much of a problem during the manufacturing period if the earlier cars all had enough clearance (as yours do) for the shackle to be removed from that side. Perhaps mine is a 1500 tank, or an aftermarket one at least.

As to why was it fitted that way round? I suspect during assembly the running gear was fitted to the shells at an early stage, and the fuel tank added later so it wouldn't have been a problem in assembly.
Guy W

Sorry, it's coming back to me now. I mistakenly recalled it was a bolt but now I can remember. Even so, it was difficult to pull out towards the tank so I dropped the assembly from the boot floor attachments. Not major and saved struggling, but I did put it back what I saw as the "correct" way round.
Graeme Williams

How can the fuel tank be a different w/l dimension? I think they started out as 5 gallons, and changed to 6 gallons, and then ?7? for the 1500, but wasn't that that achieved by increasing the depth of the tank, not by increasing the width or length?

Moss only list one tank for all models, as does my old Sprite and Midget parts cat' from the early '80's. If the same tank fits all models, I'm guessing the tank mounting studs under the boot floor must be in the same place on all cars. So how is the shackle closer to the tank on some cars and not on others? Was the rear shackle mounting plate moved closer on some models? Were there differences on some chassis?
Lawrence Slater

Lots of question marks there Lawrence! I don't know.

I do know that the tank capacity increased and wondered if this was achieved partly by a slight increase in width as well as the depth increase. I doubt if the spring mount is moved inboard as that would mean the whole spring moved over, and the front spring mount would also be moved inboard. Most unlikely I would say.

Just to check that it isn't an optical illusion though, the clearance between the tank side and face of the shackle plate on mine measures exactly 7/8". I think that the flange on my tank is wider than in your photo, although as I mentioned, it is cut back slightly narrower just where the tank flange runs alongside the spring mounting bracket.
Guy W

the fuel tank increased to 7 gal from 6 gal on the later 1275s, that's one reason I bought my Midget






only to find at the first fill up that the tank on mine had been replaced with a 6 gal

I've got a feeling the tanks got deeper and wider if IIRC what I was told only today
Nigel Atkins

I did a quick measure yesterday Guy, and my gap on both the 66 Sprite and the 73 midget, is circa 40 mmm, tank face to shackle face. That's almost double what yours is. 7/8"=22mm. So it does seem that you have longer tank.

The depth of my tanks is 6". I've always assumed that they hold 6 gals. So maybe your right, the extra gallon to make 7, comes in part from from having a longer tank?

Does anyone have the exact dimensions of the 7 gallon(imp)tank?
Lawrence Slater

Hi Mark,

The thing about leaf springs is - you need to have something to attach them to!! Had a slight problem when taking the car for MOT


SM Gater

3 months later, I've ended up fitting most of the passenger side panels, just put the door back on and guess what - it fits. Bad news is, the other side seems as bad. Still, to be expected after 40 years eh! Don't think it will hit the road this year.

Regards

Steve


SM Gater

This thread was discussed between 23/09/2013 and 28/09/2013

MG Midget and Sprite Technical index

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