MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Crack of doom prevention

The abandoned project returns..............The 73 is already painted and I wish to re-enforce the critical area, without welding. Can this be done? Thanks, T^om
Tom

Hi Tom
In 1995 when I was restoring the car I Araldited a piece of 18g steel on the inside of the new doorskins where the crack normally appears and [touch wood] I've never had any problems.
Ron [in wet and cold Scotland]
R. Algie

You may be able to bond a piece of metal to the back side of the door skin using one of the new age body adhesives, but you won't get he crack of doom if you don't pull the door shut with the wing window!
Jeff Schlemmer

I rather suspect that he crack of doom is caused by the mirrors inertia. Slam the door hard (by pulling the quarter window, like we all do!!) and the mirror vibrates, work hardening the metal just prior to the quarter window. Spread the mirrors attachment point over a wide area (with a nice big backing plate/rod and you won't get that work hardening and embritlement.
Peter

Another cause of the crack is the wing window frame pressing too hard against the rubber weather strip on the side post of the windshield.
John H

Although I welded the crack and reinforced the edge of the window aperture where it had originated (I later found Heritage doors with the same modification) I also put a plate inside the door skin, but just held by the mirror screws and not welded. I made this with a curvature slightly less than that of the door, so when the two were pulled together the force of the mirror was spread over a much larger area. It is also my opinion that the main cause is lack of clearance between the side of the 1/4-light frame and the very thin strip of rubber on the screen seal, without clearance here the small amount of scuttle shake that does occur in an MGB is transmitted to the 1/4-lights and from there to the door skin. Also the front of the 1/4-light frame must only just touch the main part of the screen seal, and not press so hard that it deforms it, as that also causes scuttle shake to waggle the 1/4-light. Full story at http://www.mgb-stuff.org.uk/wn_bodyframe.htm and click on 'Doors'.
Paul Hunt 2

I used JB Weld (a very strong epoxy) and some curved 18 gauge steel pieces about 3 inches tall by 4 inches long. I held them in place using a cut down broom handle until the JB Weld dried. It has been 3 years and no problems yet.
Cris

My nearside door cracked and that did not have a mirror fitted. It's just a design drop off and anything that carries the stress across that weakness will solve it.
Stan Best

OK, I am re-enforcing the front outside corner of the window slot with a piece of sheet metal, held in place with JB Weld. I am also cementing a piece of sheet metal under the mirror mount holes, about 3 X4 inches. Lets see if it holds. Thanks to all, Tom
Thomas McNamara

Does the crack only occur on roadsters, or can it happen to a GT as well? I used my roadster for 12 years without it ever occurring.
Mike Howlett

I've seen it claimed that it can happen on GTs, but as they don't have scuttle shake that must be down to gross misalignment of the 1/4-light. However the aperture is different on GT doors to roadster doors which will almost certainly affect things one way or the other. If the screen and 1/4-light are correctly aligned you shouldn't get it anyway. I fixed mine when I bought it, that was 20 years ago and counting.
Paul Hunt 2

This thread was discussed between 29/03/2008 and 01/04/2008

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now