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July 5, 2004
2.5 hours

Frame Straightening

Happy Independence Day! Hope you had a fun and safe holiday.

Despite it being a holiday weekend, I wanted to get something done on the car this weekend. Unfortunately, the weather has made it difficult to be outside. Between rain and incredible heat and humidity, it's been unpleasant to be in the back yard working on the frame. Julia's also power-washing the deck, so I can't really work in the driveway without getting soaked. So we worked around each other. No problem.

The first thing I did was hook up a tow strap with a ratcheing mechanism to the rear crossmember and pull it straight. It was surprisingly difficult, putting a real strain on my 3000 lb. straps. I also noticed that it tended to pull harder on the side with the ratchet, so the crossmember tended to became trapezoidal in cross section. No problem; a second pull from underneath got everything square again.

Frame Straight 432.jpg (95202 bytes)
Rear crossmember is now straight. Compare it to this picture and see
how far it had to come back into shape.

Of course, any time you bend metal, it stretches, and my frame was no exception. Where it had bowed out in the middle had partially collapsed (the metal had to go somewhere to accomodate the longer crossmember) the top and bottom rails. With the frame straight again, that metal was now bowed up. In addition, the ends where the body mounts are located had also bowed up when I straightened the crossmember (you can sort-of see the bends in the photo above). I tried hammering them flat using a hammer and dolly to no effect. This is, after all, 1/8" thick heat-treated steel. The hammer just bounced off of it like a spring. I had to try something else.

I needed some sort of press. Unfortunately, the frame won't fit in my hydraulic press, which would have been ideal. Instead, I grabbed two scrap pieces of 1/2" thick steel and sandwiched the frame between them, clamping them together with a large C-clamp. I torqued the clamp and it actually started flattening the stretched frame metal. I kept a steady spray of WD-40 on the clamp's screw, and cranked on it with a pipe extension. Eventually, the clamp screw started to bend and I backed it off. I repositioned and tried again, but the screw, having bent once, now bent again far earlier. And the frame still needed a lot of straightening.

So I went to Home Depot and bought a cheap vise for $20. The extra rigidity and surface area of the vise made all the difference. I was able to flatten the steel completely using the vise and a long section of pipe to really tighten it down (you can see how the vise handle is slightly bent from my efforts). A few pulls and everything was straight again.

Clamp press 4325.jpg (68434 bytes)
Cheap vise with two pieces of steel worked surprisingly well.

I moved down the crossmember and fixed both the upper and lower channels where the metal was distorted. The passenger's side body mount hole was the worst of the bunch, but I was able to get it right with just a few pulls.

Passenger Frame 6543.jpg (85357 bytes)

Passenger Frame Straight.jpg (87226 bytes)
Before and after. The red arrow points to the original contour of the
crossmember, which I was able to preserve. The black arrow points to
another bend that I believe is factory since it is virtually identical on both
sides of the frame. I think it is for clearance to tighten the body mount bolt.

Now that I have it straight again, I measured the frame as described in the manual to make sure it is square before I send it off to the powdercoater. In all critical dimensions (diagonals in two locations, width in three locations, etc.) it is well within spec. Definitely good news!

Frame Diagram 6543.jpg (97969 bytes)
Factory dimension diagram. Note that opposite diagonals cannot vary more than 3/16". Those on
my frame were less than 1/8". Nice.

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Last modified on 02/06/2005

Thanks, Fidget!