TR4/4A TR4A rear tub repairs (likely accident damage in front of rear wheels)

[Popeye]

Hi all,

I just (on Sunday) got my TR4A tub and chassis back from the shop. The shop is in Pittsburgh, and I towed the car to my home outside Boston on a Penske car carrier (i.e. conventional trailer, with all four wheels off the ground).

During the journey and the inevitable bouncing through potholes, two cracks appeared in the tub, see pictures.

These cracks were there previously, and were (or should have been) repaired by the body shop - obviously the repair was not sufficient.

I'm thinking to reinforce the area by welding a piece of sheet metal on top. Basically, grind away the paint, apply weld-through primer, weld on a reinforcing piece, apply etching primer, and topcoat with paint from touch-up direct. See red outline in one attached photo; pardon my drawing skills!

Neither side of the affected area is very visible; one side in the wheel well, the other covered by the interior. As such, my intent is long-term endurance, and aesthetics more dictated by function.

Thoughts? (Obviously another question is why id the paint shop use bondo in the wheelwell... Also, as the paint shop is 500 miles away, I'd rather do the repair locally.)

 

[charleyf]

My experience restoring 2 TR4's and 2 TR3's is that the area you show is subject to corrosion and not likely to be accident damage. If there is bondo in that area, I would be suspicious of heavy rusting and loss of metal. The panel you show is not a structural area. If you have good clean metal there just welding up the crack should be sufficient without need for more reinforcing.
But if the metal is thin from rusting then you need to determine the actual condition of the surrounding area. You may try using a weak magnet to determine if you have metal or bondo. In worst case you may need to replace thin /heavily rusted metal. Or just treat the rust and live with it.
Charley

 

[Sarastro]

Those are really common places for fatigue cracks. Putting a patch on top is OK, as long as you don't create new stress areas. Also, simply welding them is OK (that's what I did with mine), but they might open up again in another 50 years.

Yes the body shop should have seen and fixed them. And, why did they use bondo in the wheel wells? Because bondo is what body and paint shops do.

(Apologies for the cynicism, but it's not without a basis.)

 

[Rut]

I’m going to suggest an alternative repair and that is to make a patch or 2 out of sheet metal, epoxy prime all bare spots and use panel adhesive. I’ve used it on a current project Scout and it’s amazing how well it sticks..
Rut

 

[Popeye]

I’m going to suggest an alternative repair and that is to make a patch or 2 out of sheet metal, epoxy prime all bare spots and use panel adhesive. I’ve used it on a current project Scout and it’s amazing how well it sticks..
Rut

That has the advantage of no heat. The paint on the other side won’t get “baked” from hot welding. Thanks!

 

[DrEntropy]

I've used panel bonding material after testing it with some steel and aluminum pieces. In both cases the bonds held well past the point of metal fatigue. Just be sure to get all paint and contaminants off the area to be bonded. And plan the clamping carefully. If aesthetics are a secondary concern, use pop-rivets to "squeeze" the repair down and grind/flatten 'em off after the cure and mud over 'em!

Those epoxies are what hold Corvettes and helicopters together.

 

[malbaby]

That is not accident damage. The cracks are common and seen on most IRS cars, caused by the rear chassis flexing and twisting continuously.
Remedy.....fix the chassis flex problem...and/or cut an "L" shaped section of steel plate for the outside of the inner wing and either plug weld [is what I did on an unpainted car] or bond it on with high grade adhesive.