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MG Midget and Sprite Technical - Spridget chassis legs

A couple of Spridget challenge competitors had a bit of a coming together on Saturday at Brands.

One of the cars was quite badly bent and is in need of a front chassis legs (H frame) transplant.

Does anyone know if the front chassis legs on 1500 cars are the same as on 1275 cars? - to be clear, if the chassis legs/ H frame are cut out of a scrap 1500 chassis, will it require substantial modification to fit them into the damaged 1275 chassis or is it a like for like replacement?

Regards

JB
James Bilsland

Alternatively does anyone have a set of Chassis legs or the front end of a Spridget chassis in reasonable condition that they would be willing to part with for not too much cash?
James Bilsland

Exactly the same as far as I am aware, apart from the cross member to which the steering rack attaches.

On the 1275 this was a horizontal box section all the way across. On the 1500 they had to 'cut' a bit out the middle to clear the crank pulley on the new engine. But this shouldn't cause problems transplanting a 1500 front onto a 1275, just vica versa.

My front is a 1275 front modified for 1500 fitment, but less said about that the better...

Picture to try and clarify (not that clear, don't have my full picture collection at work!)

Malcolm


Malcolm Le Chevalier

James. In the Moss catalogue it has two different part numbers for the H frame for 1275 cars and 1500 cars. From memory I think the main difference is in the engine cross member. The 1500 one has a dip in it to accommodate the 1500 pulley where as the 1275 one is flat. I think the longitudinal legs are the same with the same kick up at the cross member.

Bernie.
b higginson

James - bit confused - but if it's the front end of a 1500 - then contact me if you want - only problem is - it might not be race legal ......... after what I did to it - whoops :)

rachel-macbat hot mail.co. uk
rachmacb

A dip in the crossmember on a race car is a positive boon as we wished we'd had one when the front timing cover was weeping oil. With the dip it would have been an easy swap, without the dip it's engine lifted up.

I'm tempted to cut and cut the cross member in all honesty as I've seen it done on other race midgets and previously wondered why... now I know!
Andrew McGee

But you will lose crucial stiffness between the front suspension mounting areas!

(I am partly joking, it will theoretically make a difference, but if you can tell the difference I would wonder why your last night is not Schumacher!).

Malcolm
Malcolm Le Chevalier

The mounting points for the front suspension are not the same.
Alex G Matla

In what way Alex? You sure you aren't thinking of the MGB?

Malcolm
Malcolm Le Chevalier

Given that the car in question uses MGB front dampers, I'm not sure that the top suspension mounting points will make much difference, However the bottom mounts may be a problem if they are substantially different - I don't think the difference between the 1275 and 1500 crossmembers will be a problem...

Rach - to be clear is it the front end of a 1500 midget chassis that you are selling?
James Bilsland

Mounting points should all be the same.

On the rubberbumper B the crossmember is different to heighten the car.
On the midget they just fitted longer springs.
Onno K

'tis indeed - but - ...... well, if you want it - I'll email you a photo, coz it might be a little outside regs
rachmacb

??? Onno's & Rach's comment.
The front crossmember is different in the Midget too, isn't it?

I thought that Horler said the Midget crossmemeber is taller (to raise the ride height), and I recall someone measuring the difference between the two crossmembers a few months ago and posting about it here.

However, if James can re-use his 1275 crossmember and simply weld in a 1500 H-frame below it, that should work.

Norm
Norm Kerr

As Alex pointed out, the brackets locating the inner wishbone pivots are different.

Simply changing the ride height with springs would also alter the suspension geometry. The brackets were changed to compensate for this.
Dave O'Neill2

This is from Moss parts list...


Dave O'Neill2

Hi again,
OK, I found the reference information that I was looking for about the springs:

The front springs were not lengthened until January '76, so the +1" ride height that was introduced in October '74 must have come from frame changes (the big cross member that controls the damper location and the wishbone inner pivots location).

When the springs were lengthened, almost mid-'76 model year, they were only increased 9.85 -> 10.2", or 0.35".
Also, back in '73 they were first lengthened, from 9.59 -> 9.85, or 0.26".


Norm
Norm Kerr

note: front spring free lengths as per Norm's measurements, ignore the various Haynes, you may remember I had to do a bit of research on this subject

and Terry Horler's book does mention something about different crossmember(?) variances after r/b was introduded and not at the same time (IIRC)
Nigel Atkins

Can't remember exactly what (It was NMP) But when Ben's front end was to be exchanged after a bodged repair, and Thijs had the front end of a 1500 lying around it soon came out that it could not be used because of the differences.
Remember Onno? Otherwise ask Thijs. (If you really want to know) ;^)
Alex G Matla

Bugger my memory is terrible Alex is right!
Onno K

I stand corrected, sorry Alex.

Malcolm
Malcolm Le Chevalier

No problemo guys.
Alex G Matla

Thanks - I'll pass the information on

Regards

JB
James B

If it helps, I had an odd-ball shell with RWA, a 1973 chassis number but a 1500 front frame. I originally had a 2-litre Lancia engine in it but went for an Ital block after the Lancia died. The Ital needed 2 sets of 1275 engine mount towers welded together since the platform for the engine mount on the chassis was a good 3cm+ lower to the ground.
r thomas

This thread was discussed between 09/05/2012 and 11/05/2012

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