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MG Midget and Sprite Technical - Frogeye rear springs

Big milestone today when I bolted the first bits onto the Sprite! But also time to ask for advice from those who have done this before.

These springs have 15 leaves. There are two "adjustments" that I am aware some choose.

1. Should I consider removing any leaves from the springs.
2. I believe that spring wedges are available. Are they a good idea?

Anyone spot the error!

GuyW

My frog has replacement 9 (or perhaps 10) leaf springs. When I fitted them the car sat very high at the back, it looked like something out of hot-rod magazine. I didn't bother with wedges, I simply fitted spacers between the spring and spring box where the U-bolts pass through.

Not sure why you'd need spacers (wedges) with original springs. If the springs are in good condition and you've welded the car up correctly the rear should sit at the right height, but you won't know this for sure until you have loaded it all up with engine, gearbox and all the other stuff. If the springs are weak or have sagged over the years you may have the opposite problem with the car sitting too low at the rear.

I don't know whether any cars left the factory with wedged rear springs.
Simon Wood

As simon says the standard 15 leave springs should be fine. The replacement springs are stiffer and affect the ride height. The wedges were a tuning mod to lower the rear of the car in conjunction with a lowered front end. You will be surprised how they springs move when loaded with all the weight.
Bob Beaumont

Have you switched to Speedwell Blue, Guy?

This is very exciting.
Nick and Cherry Scoop

Yes, and no, Nick. I have switched from the Leaf Green which was what the car left the factory in, but to Iris Blue, not Speedwell. Still a flower colour though!

Having struggled with finding a supplier for the leaf Green I realised that the real problem behind my procrastination was that I wasn't that keen on the colour so I changed to blue which I have always liked. Seeing as the whole bodyshell has been rebuilt anyway and it hadn't been in its factory colour for at least 40 years it seems like a fair decision.

Regarding the spring, I think the best thing is to carry on with assembly as standard. I can always adjust things later with wedges if it turns out to be whoo-ee, riding high.


GuyW

Hi Guy

Regarding error - should you have fitted the spring u-bolt before fitting the tie rod bracket?

Have you painted the springs? Which paint? Should they be oiled? Asking as I am about to replace the springs on my Mk2 Sprite with some good second hand ones.

Les
Les Robinson

Hi Les,
No, I don't think that's the error. At least I hope not! The spring U bolts had been cut off by the PO. I hadn't spotted that so new ones are on order along with some other bits and bobs. I didn't dismantle this car and everything was just packed into boxes willy-nilly so its hard to know what might be missing as opposed to just in another box somewhere.

The error is pretty obscure, but I think the springs are supposed to be handed. The small U clamps have a countersunk headed screw which I am thinking should be on the visible face, rather than on the inside.

The springs were dismantled and painted with Frost's extreme Chassis paint. It is very thin and hard though I expect it will wear where the leaves are in contact and moving against each other. I then oiled each blade with STP as I reassembled them.
GuyW

If you are not running wide tires I do not think those bolts will be in the way.
Trevor Jessie

Should the little screw heads have nuts on? None of mine do. The screws are threaded into the U clamp, so a nut on the end would serve as a lock nut only.
GuyW

Mine do not have nuts on.

Les
Les Robinson

No nuts here.
Nick and Cherry Scoop

OK, I too will go nutless
GuyW

First spineless and now nutless...
I you don't watch it there wouldnt be much of you left Guy. ;)
A de Best

I've never been called spineless, Arie. Gormless, yes. but not spineless.
How's your Gorm these days?
GuyW

Lawrence called a few people spineless, but never Guy, I think.

Nick and Cherry Scoop

Of the last 3 sets of springs I have purchased, two were of the earlier 15 leaf style with flat head screws threaded into the u bolt. They were threaded the whole length but the factory parts book shows them only threaded about 1/2". Old sets of springs were also threaded all the way. I will be reproducing both styles of screws this fall. Why? because I can. The 10 leaf set which is the type available now came with a hex head bolt and a nut on the other end. I haven't checked to see if the u bolt has a countersink, but I will guess not. I had a 10 leaf on an auto x car in the '70's and had to wedge them because it made the car look like a '60's hotrod. Apparently the spring material of the correct size isn't made anymore? Was there some company in the UK making the correct spring at a very high cost?
J Bubela

Yes. £650 if I remember right, but can't remember who made them.

I'm very glad about the colour change, Guy.
Nick and Cherry Scoop

I now have a set of very good condition 15 leaf springs that I am cleaning up to fit.
Two questions:-
the rear u-bolt, were should it be located? As in this picture - I think this is correct as there are wear marks on the spring indicating it has been here previously.


Les Robinson

Or should u-bolt be here, as on my existing springs.



Les Robinson

My second question is regarding the tubes that are clamped between the fixed u-bolts.
Should they be a close fit to the springs or clear?
The countersunk screw bolts, the one's Guy was referring to earlier, have been drilled out and are a rather loose fitting bolt used. I will rectify these to be a better fit.

Thanks

Les



Les Robinson

Rear fixed u-bolt tube.



Les Robinson

Hi Les,
Q1 : on mine the outer spring leaf around the rear eye has a recess bent into it for that rear clamp. (not wear!) Its close to the curve of the eye, similar to your second photo.

Q2 : the clearance on the fixed clamps is dictated by the length of the tube. On mine this gives a close fit to the springs, but without actually clamping the sides of them.

I had thought that my springs were original, but there are very slight differences to yours. The tubes between those clamps on mine are rolled from flat so there is a split down the length - not welded tube as one might expect They are also quite thin walled.
GuyW

yep mine are the same Guy. I have the rolled from flat spacer tubes.
I bought the springs from a BMC dealer who was closing down years ago (University Motors Epsom) Princely sum of £8 the pair!
Bob Beaumont

Hi Guy and Bob
Thanks for the replies.
My spacers are also made from rolled flat.
What is the clearance between this spacer and the underside of the spring?
Both clamps are to hold leaves laterally but do the spacers need to be a close fit to the underside of the bottom leaf? More so on the rear clamp.
Regarding the rear c-clamp, looking closely it would appear that I had one as pic one and one as pic two!!
Definitely no recess formed in the spring.
Maybe it doesn't matter?
Thanks again
Les
Les Robinson

Les
Looking at mine the tubes have a small clearance from the underside of the lower leaf. The clamps are really there to hold the leaves laterally as you suggest.

Bob

Bob Beaumont

Bob
Thanks
On the bench there is quite a gap.
However have realised that when the spring is compressed the upper leaves straighten which in turn tilts the c-clamps and reduces the gap.
Therefore when the springs are fitted and the car on its wheels then the gap will be reduced.
Les
Les Robinson

Hi Guy,
I rebuilt with 'original' rear springs but many years of abuse ment that they settled once in use, to the point where I ran out of adjustment.
Bought a new pair of a AH specialist for about £65 each, maybe less. Different material etc and very stiff but after a few trial runs I removed the top three leaves and it really transformed the car. Much better.
Slowly

I'm not sure how easy this would be on an assembled car, but please could someone give me dimensions of a spring wedge for a quarter elliptic car? Or at least the thicker end as I can work out the other dimensions.
GuyW

OK, so no advice forethcoming. I suppose I can work out an approximate dimension with a bit of trigonometry.

Currently the gap between the top of the tyre and the crest of the rear wheel arch is 4" which is way too much. Given that this may naturally settle a bit once the car is in use I think I need to reduce that by around 2" to 2 & 1/2". That will give an unladen clearance of between 1 & 1/2 and 2"
GuyW

Guy, As I alluded to earlier in this thread I didn't bother with wedges, I simply fitted a rectangular spacer between the spring and the lower horizontal part of the spring box between the threads of the u-bolt.

For what it's worth, and bear in mind that I have the later 9 (or 10) leaf heavy duty springs, my spacers are approximately 6mm thick.
Simon Wood

Thanks Simon.
My intenion is to make wedges from some well seasoned oak that I have. I did wonder about just a simple spacer but wondered if doing that might set up a stress point in the spring where it would be levering over the edge of the spacer. But it would certainly be a start point for trialling diferent thicknesses.
GuyW

I thought oak and steel was a bad combination? All those rust stains you see around nails and screws in oak doors...

But maybe a good coat of something between the oak and steel would avoid any problems.
Jonathan Severn

Jonathan,

It's not normally rust but rather iron tannate as the result of the iron reacting with the tannic acid in the oak.
David Billington

Ah, thank you.
Jonathan Severn

Jonathan,

It can be a pain as I had forgotten about the problem but ran into it a few years back when making a rack for my metal spinning tools, the oak was damp due to the PVA adhesive and the slight contact with the steel clamps led to that staining which while annoying visually was not really an issue for a functional item.
David Billington

Guy,

I was wondering if when commercial wedges are used if the same angle wedge washers are provided to place under the bolt heads to prevent bending of the bolt shank/head. That sort off thing is available for use with RSJ where the flanges are angled on the inside.

If machining this type of thing might be useful https://www.ebay.co.uk/itm/Amadeal-8-Piece-4-Universal-Angle-Block-Set/273082570857 . For more accuracy and range of angles a sine bar and slip gauges but that might get spendy if not already available.
David Billington

Spherical washers any good for that?

eg http://www.boneham.co.uk/Products/clamping-and-fixing/spherical-seat-washer
Jonathan Severn

Yes Jonathan those look like they would do it very well as they would be self adjusting to match the angle of the wedge - which of course I don't yet know!
GuyW

Hi

Guess you have seen the wedges and spring plate here: https://www.petermayengineering.com/product-category/rear-suspension/

Cheers
Mike
M Wood

I have, Mike. And although I don't begrudge Peter May from making an honest living I am not prepared to pay £50 for two wedges that I can make myself.

The other point is the car, though on its own wheels, hasn't had any chance to settle and l don't yet know what the ride hight is going to end up as. If l make wedges from oak and the car then settled lower, it is easy to plane a bit off for fine adjustment. I could always then use these as a pattern for making a pair in steel or alloy later.
GuyW

Guy

I like the idea of oak shims, although the high level of oxallic acid may prompt a bit of corrosion.

Fancy using any of these: https://www.screwfix.com/c/screws-nails-fixings/packers-shims/cat840018
?

Cheers
Mike
M Wood

Hi Mike, l have used those Screwfix packing shims for fitting out kitchens. They are good for that but the plastic is quite brittle and wouldn't work for this application.

The idea with the oak was really only as a temporary until I had established the preferred dimension and would then replace with steel or aluminium spacers
GuyW

Guy, just pack the U-bolt out with some shims. Drive it around for a bit and let it all settle. You may then want to review the thickness needed. I've been running with spacers for 30 or so years. No disasters yet. Oak sounds good as a temporary solution. Can't believe that it's all going to rot away in the short term as others have suggested!
Simon
Simon Wood

Just make sure you don't use American red oak as it's not durable outdoors. IIRC American white oak is OK, as is English oak and European oak, they being very durable in outdoor conditions.
David Billington

This thread was discussed between 16/07/2017 and 04/11/2018

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