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MG Midget and Sprite Technical - Creaking ¼ elliptics

I have had Frogeye Sprites since 1971, and have lost track of how many rear springs I have replaced. But there is something different about the last set. About three or four years ago they started creaking loudly. I ended up taking them off, separating all the leaves, cleaning them up and reassembling. But this only lasted about 18 months. I couldn't believe it was the springs again after all that work, and the noise was slightly different - a clicking sound. I removed the dampers and the Panhard rod, drove it around and the noise was still there.

A couple of weeks ago I had to replace a rear brake cylinder and fit a Speedi Sleeve to the axle. Needless to say the sleeve took nearly a week to arrive so the car was up on stands with the pressure off the springs. I took the opportunity to spray them with penetrant. I had a couple of cans of generic penetrating oil and some WD40, both of which I used up. There has been some effect in that the nearside spring has largely stopped making any noise. But the offside one, while much better initially was worse again after about 100 miles. I find it hard to face taking them off again, knowing that whatever I do will not last. What baffles me is why this is only happening with this most recent pair of springs, after decades of silence from all the others. I have to wonder what is going on.

I haven't tried removing the trailing arms. That is extremely difficult, and of course I couldn't drive the car without them. They are rubber bushed so I can't imagine they are responsible for the noise. The first time I investigated it I got a friend to listen carefully and he said it was definitely the spring. Because the springs are so damned hard, it's very difficult to provoke the noise by bouncing the rear of the car up and down. Only a road test really tells me anything.

So if penetrating lubricant has any effect, which it may have done this time, is there a product that is going to be more effective? I do remember reading many years ago that it might not be a good idea to lubricate ¼ elliptics because they rely on friction to resist cornering forces. But I probably should not worry about that as I have the Panhard rod.

Les Rose

Didn't leaf springs in the good old days have rubber inserts between the leaves?
I remember seeing an ad for a wrap which was ahem, wrapped around the springs to protect them for water and dirt ingress.
Found it Denso tape
https://www.vintagecarparts.co.uk/products/ca970-drevo-denso-tape
Jeremy MkIII

Les,

How many leaves do your springs have? IIRC the originals had 15 but later replacements had fewer and were stiffer. I've seen that original spec ones are or were available again at a hefty price.

Jeremy,

Denso tape is what I intend to use on mine when I get it back together as I'll apply grease between the leaves and want to keep it clean.
David Billington

Well remembered Jeremy. Denso tape was what I was trying to drag up to the surface of my mind.
Horrible stuff to work with (wear vinyl/latex gloves, or Mrs Les's Marigolds if you're brave enough) but it works quite well.
Used miles of the stuff at sea to protect things like hydraulic connectors and cable glands, but if moisture does ever get in, it's equally effective keeping it in as out.
Greybeard

The last set of new such springs we fitted to a car here was as David describes - fewer but thicker leaves. The result is the springs are way too stiff. Although the overall thickness of the spring is the same, the problem is that stiffness increase is not linear with thickness, whereas the reduction in leaf number is.

We solved the rate question by reconfiguring the springs - reducing the number of leaves and adjusting the lengths to suit - and adding a panhard rod to compensate for the reduced lateral stability that arose from the reduction in overall depth. Result was great, but the effort wouldn't have been necessary if the springs were made right in the first place.

We had a similar issue with the car we bought for our K midget project years ago - it came with (semi ecliptic) leaves that were each 1/4" thick, so sat very high and was very stiff. We knew it would overseer until sorted and it didn't disappoint, swapped ends at a sniff of provocation on the track in the one outing it had like that :).

Les, I'd be worried that the clicking could be a body crack around the mounts due to the higher impact loadings that harder springs give.
Paul Walbran

I successfully use Tectyl, the thin brown variety
Flip Brühl

My springs have 10 leaves. It seems that the choice is between 10 leaves at about £160 the pair and 15 leaves at £600. There is also the issue of material quality, and from what I have read the cheap ones are pretty crappy. This no doubt explains why the original ones lasted for decades.

I don't think chassis cracking is very likely. I have had the springs out so many times and never found the slightest thing wrong with the mountings. I might pluck up courage and get the springs apart again, and use the grease and Denso tape treatment.
Les Rose

I had the same problem,temporarily cured by WD40. I ended up making leather gaitors to fit around the spring to keep Castrol Multipurpose Grease in. If you Google Wefco spring gaitors you'll see old adverts showing them on quarter elliptics.
f pollock

I have had one spring apart and applied the grease and Denso tape method. It is now silent. It was extremely difficult to get the U bolt back on. For the other spring I'll make sure the tape only goes up to the U bolt. It can then be used after assembly to seal up the gap around the spring. Much better than the factory part for this, which seems to comprise a flimsy bit of tin and what looks like a piece of old inner tub.
Les Rose

Glad you've got it sorted Les.
I've got a Peugeot Boxer whose rear leaf springs creaked. Like Fergal's experience, WD40 cured it but not permanently.
It wasn't new but came with a warranty and the dealer disappointingly chose to effect a temporary fix by slacking off the U bolt nuts a fraction (a known bodge) - however not sure how that would work with 1/4 elliptics.
Jeremy MkIII

The other spring is now done. Oh bliss oh joy, a silent rear end. One 10m roll of Denso tape is just right, with enough left to seal up the spring mounting boxes.
Les Rose

Jeremy and Greybeard, thanks for the reminder about Denso Tape: https://denso-tape.co.uk/products/denso-tape?srsltid=AfmBOorWQyKx9tvMmzw9bIIb5RZfkw7O3Woznda-5i1bG9yaSgvnsxNM

Cheers
Mike
M Wood

Mike, that looks a little cheaper than the last time I bought it (about three years ago I think).
I found you can mould it to shape with your hands around whatever it's covering. If you moulded and smoothed it well the tape edges pretty much disappear and it becomes like a single perfectly formed cover. If you see what I mean.
I mentioned earlier that if water does ever get in it will keep it in just as well as out, but in fairness I think the only times I saw it get wet inside was when someone got far too personal with a pressure washer. It would keep carbon steel cable fittings and hydraulic connectors pristine for absolutely ages at sea where everything else rusted around them.
It doesn't like heat though, and I'm not sure how often you might have to reapply to springs for example - I wonder if the movement might dislodge it. But it would be simple to put a pair of vinyl disposables on and remould it back into shape.
I suppose you could also lash the end in place with a couple of turns of wire? Dunno - I never tried it.
Greybeard

This thread was discussed between 09/11/2024 and 21/12/2024

MG Midget and Sprite Technical index

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