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MG Midget and Sprite Technical - 1500 chassis rail query

Hi all,

I'm in the 'serious metalwork' stage of a full restoration, and need a little help with the chassis rail 'extensions' which have been badly bent, and poorly reshaped, in the past and now need replacement.

The plan is to cut the extensions back to the line of the suspension crossmember, sacrificing the forward wishbone brackets in the process. New full length rails will be purchased and - with careful measurement - cut back to give the replacement pieces. There are, I believe, repair sections out there, but I'm not sure how much of the rail is included, and the prices seem to be comparable to the full rail.

Unfortunatly, there's a shortage of Heritage 1500 rails at the moment, so the question is: are the mountings for the front end, roll bar and towing eyes/bumpers the same on the 1500 rails as the 1275's? I know there are differences further back to allow for the 1500 engine and gearbox, but I'll not be using those sections.

Thanks,

Sean
S W

Sean,
I'm not certain of the answer so can't reply but I do remember a thread from this year or last where the same or something similar was done so try searching the Archives
Nigel Atkins

Yes the chassis extensions are the same as regards the ARB mounts and towing brackets / bumper mounts.
The short repair sections go as far back as the front face of the main cross rail and the ones l have seen are accurately made to this length. So if damage is confined to forward off this point there is not much point in buying the full lengths and then cutting them down.

The important bit is to align properly, maintaining the 3 degree upward slant of the front of the chassis rails, and ensuring that the two extensions are also parallel and not twisted. The easiest thing is to temporarily brace them into position and do some check measurements before starting to weld.
Guy W

IIRC the wishbone mounting brackets are different, to allow for different ride height and geometry.
Dave O'Neill2

Hi both,

Thanks for the replies - I had a run through the archive and couldn't easily find a note definitivly saying the mount points are the same. I couldn't think of a reason why those mountings would be different between 1275 and 1500, good to get confirmation though.

Given the damage, I'll get the full rails, if nothing else it'll be a solid reference for what they should be like.

Thanks for the alignment tips, there's very little sign of the original alignment left! I did see a note of 'about an inch from horizontal', which will also help.

The work is being done by a specialist and highly qualified bodyshop, with jig and pulling equipment if needed, so the repair should come out pretty well.

At some point, I'll also be asking for measurements for positioning the radiator brackets, but a quick sketch showing what's needed would be a good thing, I think.

Cheers!

Sean
S W

Was writing another reply - yes, the 1500 wishbone brackets are shallower, for a lower pivot position.

Not sure if the reinforcements (angle pieces from the top of the brackets to the spring turret) are original, they're not supplied with replacement brackets, but I have seen them on photos of a heritage shell.

(apologies for lousy photo!)

Séan

S W

Sorry. I thought you were just asking if the mounting points on the front extensions were the same. But if you are replacing the full chassis rail then yes, there are differences in the wishbone mount positions. And these definitely need jigging to keep the suspension geometry right. It's a good reason to only replace those front sections, and leave the wishbone brackets undisturbed unless you really have to.
Guy W

Guy, yes I am only replacing the front extensions, but the forward wishbone mountings will probably have to come off first to get to solid metal.

If it was so bad as to replace the entire rail, I'd either go for the complete frame assembly from crossmember forwards, or a full reshell!

Cheers,

Sean
S W

This thread was discussed on 13/11/2012

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