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MG Midget and Sprite Technical - Frogeye front springs

Well this is embarrassing. After owning the car for 40 years I have realised that the front springs are not a matching pair. One is 9.25", the other is 9.6". The longer one has the last coil wound round a bit more, so overall there is slightly more metal in it. I think the shorter one is correct for the car. Is the other one from a later car, and if so which one? Did some reprobate before my time replace one spring with the wrong type? Physics tells me that the longer one with slightly more coils should be softer, but under lockdown I can't take it anywhere to test it. For the time being I will put them back on the car, but I'm not sure which way round. As the car is mainly driven one-up I would probably want to compensate for the asymmetric loading. So shorter or longer one on the driver's side?

Alternatively, these springs may be within production tolerances, which were not up to much in 1959 by all accounts!

Les
L B Rose

According to my Haynes manual, early models were 9.4" and late models were 9.85", although it doesn't define 'early' or 'late'.
Dave O'Neill 2

Following on from Willy's suggestion on the other thread, I've tested my old race springs with bathroom scales and my 10-ton press.

They came in at 560lb/in





Dave O'Neill 2

It's fairly common for there to be a small amount of twisting in the structure of these cars resulting in one corner being lower than the other. often shows up more at the back than the front but It's usually the front that needs the correction.

It's more aesthetic than a real problem but I wonder if some previous owner has attempted to correct this by using a longer spring on one side.
GuyW

I'm more disturbed that a bathroom scale can read up to 560lb!
Nice press Dave.
Greybeard

Grey

Yes, that would be alarming. The scales only go up to 23st, so I measured half an inch at 20st.
Dave O'Neill 2

I wouldn't rely on Haynes, my 1982 and IIRC 1974 Haynes show the wrong spring length for my 1973 car.

According to Terry Horler's book, page 37 Frogeye springs were 1/2" diameter spring steel with 7 working coils, 271 lb/in, free length 9.4".

I should know the other spring lengths but I forget, there's at least another two IIRC, loads will be in the Archives (all 271 lb/in IIRC).



Nigel Atkins

Looking at Terry's book further later spring free lengths were 9.59", 9.85" and 10.2".

The 9.85" were fitted to the later 1275s and to the earlier 1500s.

Original Sprite & midget The Restorer’s Guide by Terry Horler. –
http://www.amazon.co.uk/gp/product/1906133336
Nigel Atkins

Les you are right; tolerances where not so tight in 1960. If you drive the car alone the quarter eliptic on the right side will be softer as well after 40 years. I used to measure the weight of every wheel on a place where they weight lorries by placing one wheel on the scale and measure the height as well. If you do not know such a scale near you, you can place a jack under the banjo and measure the distance from the frame to the ground, left and right. The same at the front. Place the jack in the middle of the ARB. In fact this is more easy.

I change the quarter ecliptics every now and then. It makes a lot of difference in behavior! The front coil springs do not alter so much.
Flip Brühl

I had a 1985 Range Rover that leaned down from the driver's side. It turned out that the springs for each side came from the factory with different heights, assuming correctly that the Range would be mostly a driver-only vehicle.

I recently replaced the coil springs on my 1970 MGB using later model rubber bumper model springs. The car was drooping in the front, catching parking barriers and speed bumps. The ride height is now ideal and the car handles beautifully and no longer scrapes the road. The headlights really reach down the road again.

1975 coil springs on a Frog Eye? I don't know, that may be a bit much.
Glenn Mallory

Unless they'd compressed the 9.6" would be 1960s spring length, I forgot to look for change points on those. IIRC 1975 would be 9.85" free length new.

Nigel Atkins

Nigel, although factory specifications were clearly for different sizes and different applications at production it seems unlikely to me that measurement after 60 years of use can be related back to the fairly small steps in some of the sizes you are quoting. With incremental variations down to 2 10ths of an inch and the possibility of aftermarket supplied springs as well there seems little point in relying on length measurement to identify the fitted spring. A measure of spring rate as Willy and Dave have done makes much more sense.I

Better to refer to the correct factory specification for the year/ model and buy a matched pair from a reliable supplier.
GuyW

From the BL parts book:-

Sprites up to HAN8-58380 (North America) and HAN8-60259 (Rest of World) and Midgets up to GAN3-46041 (NA) 47526 (RoW) used part no. 2A4214.

Sprites from the above numbers to end of production and Midget up to GAN6-171477 used CHA129.

GAN6-171478 onwards used CHA570.

It doesn't quote any lengths, unfortunately.

Moss, on the other hand, give the same numbers, but for individual models - 948/1098, 1275 and 1500.

My BMC workshop manual quotes spring lengths as 9.4" for Sprite 1&2 and Midget Mk1. 9.59" for Sprites 3&4 and Midgets 2&3. It doesn't cover 1500s.
Dave O'Neill 2

Guy,
you are misunderstanding me, I'm not relating the 9.6" to Les's car but to Glenn's 1975 (UK) springs statement.

The reference to the four different spring lengths was in relation to DaveO's Haynes manual that only gives two lengths "early" and " late" and to my 1974 Haynes that only gives one size when by then there were three and my 1982 Haynes which gives three when there were four. Sorry to say you can't trust all books.

I know I'm not the very sharpest knife in the drawer but I do know road springs sag with age, use and abuse, you've insulted me and I feel hurt.

I'm going giddy, I think I've done my boot laces far too tight ... feel faint . . .




thud!
Nigel Atkins

Where am I ... wots going on, oh.

Dave,
once again you must have posted whilst I was still typing my last post (then it all went black).

Moss claim to sell 2A4214 and CHA129 for the 1275 and CHA570 for the 1500, I can't remember the lengths they sell the last two as but it'll be in the Archives.

My 1982 Haynes has 9.4" and 9.59" for Sprites 1-4 and Midgets 1-3 with 9.85" for the 1500s.

My 1974 Haynes, despite the chapter 13 supplement to cover later 1275s, which is why I bought it, only has the 9.4" shown.

My paper reprint of the 1976 factory Parts Catalogue only shows three springs, 2A 4214, CHA 129 and CHA 570.

Whereas Terry's book has from August 1972 increase of free length to 9.85" at GAN5-123837 and remained on the Midget 1500 until January 1976 when the increase to 10.2" came in at GAN6-1714788.

As the electronic files I have are so clunky I can't be bothered at the moment to check them.

Now I don't rally know if the 9.85" ever existed but they are mentioned in two books, perhaps both books are incorrect but I did make my sources of information clear in my earlier posts.

Not that it really matters because unless you're having new springs custom made you'll get what the suppliers have and I've no idea how accurate and accurately matched these are and the same for the original or spare parts factory springs.
Nigel Atkins

Don't have a manual for frogeye but this from 1972 BL manual for Midget I, SpriteII


W Dunsmore

And this for Midget II and Sprite III (also presumably early Midget III, Sprite IV)


W Dunsmore

Finally this for later Midget III


W Dunsmore

A supposedly matched pair of springs for a 1970 1275cc Sprite purchased from well known Derbyshire supplier coming in at around 10", compared with the old spring I removed at just under 10"





I L Cooke

Bill,
the 9.85" is for the later 1275 and early 1500 MkIII Midgets.

Anorak firmely on - the 1500 was also the Midget MkIII.

From January 1976, at GAN6-1714788 springs increased to 10.2" .
Nigel Atkins

Ian,
do yourself a big favour and hand those back to whoever the well-known Derbyshire supplier is (who I can't think of or don't know) or just sell them on or give them away and go to Kim Dear at Magic Midget (a great chap to deal with) and get yourself some "9.5" freelength 360lb rate. Retains standard ride height to overcome sleeping policemen, rough surface autotests/auto-solo's etc, whilst reducing body roll/ brake dive. £27.50 each".

http://www.magicmidget.co.uk/suspension.htm

Remember the cars when factory new sat a bit higher than we're used to seeing now with Spridgets with worn and sloppy springs, and Spridgets and modern cars lowered so the "wheels fill the arches" as is the fashion. I'll put a brochure photo up later.
Nigel Atkins

There you go Ian, how they used to look when new, back in der day.

The road springs ride height I mean.




Nigel Atkins

I don't think she is a midget, she's just sitting down.
GuyW

She's looking for a Midget that's why she's sitting down.

"It's behind you!"

She looks entirely different in the photos of the Bs, nowhere near as raunchy.

Nigel Atkins

My last Midget sat at a similar height and was still on its original springs after nearly 40 years and 43000 miles.


Dave O'Neill 2

Looks really great too.

An average of 1,000 miles a year isn't pushing or wearing on the springs too much though.
Nigel Atkins

Ian,
FYI, I've been looking in the Archives, the last two CHA129 springs I got a few years back were it seems both just about 9¾” (248 mm).

One poster suggested 10mm variance in front springs was usual.
Nigel Atkins

Well that got you all going.

Flip, I have never known a quarter elliptic to last 20 years let alone 40. I am on my third pair.

Anyway I have put the slightly longer front one on the right. BTW I did an accidental controlled trial of powder coating. 8 years ago I had all the front suspension blasted and powder coated, but for some reason only did one of the springs. The other one I derusted and painted with stone chip. The powder coated one was rampant with rust, while the painted one had only a few patches. So I have derusted them again, this time with 80 grit and Kurust, then stone chip. Even on the rigid parts the powder coating was crap.

Les
L B Rose

Avengers and Sunbeams had a longer front spring on the drivers' side as standard to compensate for the camber of the road. I seem to think leaf sprung Landies did too.
Clive Berry

This thread was discussed between 30/04/2020 and 04/05/2020

MG Midget and Sprite Technical index

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