MGB Rear Spring Mount Repairs

The rear spring rear mounting brackets are exposed to water and dirt being thrown up by the wheel and over a period of time can suffer from rust. The mounting bracket is part of the rear chassis rail and repairs are best done when the lower half of the rear wing has been removed to allow access. The repair panel comes in two parts, the main chassis member and a closing panel. The boot side closing panel should also be replaced because this has to be removed when making this repair.

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Remove the rear spring shackles from both springs and lower the axle to allow access the mounting. Take suitable triangulation measurements from the centre of the spring shackle mounting eye so that you can locate the new shackle eye in exactly the same place as the old eye. The new chassis member extends from the rear valance to the rear of the wheel arch but it is not always necessary to use its full length and it can be trimmed as appropriate. To assess the extent of the repair remove the outer closing panel. Before doing this it is necessary to remove the boot side closing panel by drilling out the spot-welded around the wheel arch and along the chassis rail.

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Cut out the rusted parts of the chassis leg using an angle grinder to leave sound metal. The boot floor is spot-welded to the chassis member and the relevant spot-welds should be drilled out. Trim the new chassis member repair section to fit and clamp it into place. Using the measurements taken previously ensure that the spring shackle eye is in precisely the same position as the old eye. Also raise the axle and bolt the spring back into place and re-check the measurements. This will ensure that the shackle eye is aligned squarely with the spring. As the new section is part of the main chassis member strength is important when welding. In addition to seam welding the new chassis member to the remains of the old chassis member, gussets should also be welded over joints inside the chassis member for additional strength. At this point the inside of the main chassis member can be painted to preserve it for the future. The inside surface of the closing panel would also benefit from a coat of paint before it is welded into place. Take care not to paint over surfaces that are to be welded. The closing panel will not be trimmed and should be welded into place to close the full length between rear valance and wheel arch. The panel should also be welded around the spring shackle bolt hole and the two bumper dumb iron mounting bolt holes. Following welding the welds can be dressed with an angle grinder. The boot side-closing panel still remains to be fitted but this will be attached during the rear wing has been repair. Although the main chassis member has been painted inside, it should also be injected with rust proofing wax to preserve the areas where welding has burnt the paint. Painting/preserving the outer surfaces will be done after the remaining repairs to the wing.

Kingpin