crossmember cracks

[treed2 at wsu.edu (T. Reed)]

So there has been some talk about crossmember cracks.. here is what I
have to say on the topic:

My crossmember started cracking about 15 months ago. There are five or six
cracks in all. I designed and built my own bolt-on bar, and installed
it exactly 12 months ago. (I had planned to sell copies of the bar to
interested parties but unfortunately that fell through.)

Since then, no new cracks have appeared and the pre-existing cracks have
not lengthened, according to my measurements and photographs. I haven't
toned down my driving style at all (quite the opposite ;) so I feel like
the bar might be helping things (perhaps not, wtf do I know)

When I get together enough dough for a nice MIG I will weld up the cracks,
brush off the slag and douse 'em with a little paint and primer. After
that it's game over as far as I'm concerned, other than the occasional
checkup.

Welds, when done properly, are stronger than the surrounding metal and I
am confident that crossmember damage, if caught in time, can be adequately
repaired with welding alone. Although it is definitely advisable to add
some sort of reinforcement.

I have never welded on a car chassis before (i know, i know.. disconnect
the battery), so I don't know just how big the heat-affected zone is. A
chassis is a pretty big heat sink, but I'm sure the paint surrounding the
weld would be burned off or at least discolored by all that heat.

I've seen several more complicated repairs:

- cutting a crossmember out of a donor and welding it up. probably not as
  easy as it sounds as the crossmember is spot welded and if you seam weld
  it there are a lot of seams.

- drilling out the spot welds on the bad crossmember, and using small
  nuts+bolts to install a donor crossmember. attractive because no welding
  is involved, but removing the spot welds would be a big pain, as well as
  installing the bolts. you'd have to be sure the bolts aren't going to
  depart one by one until you engine hits the pavement.

- cutting apart and welding two donor crossmembers together in to a
  "double thick" crossmember. cool, but not very practical, and there's
  the added weight.

- simply welding a plate where the front motor mount attaches. a bad idea
  imho because it does nothing to strengthen the rest of the crossmember;
  I have cracks rather evenly distributed along the whole length

- welding a bar or tube across the whole front end. worthy of
  consideration but guaranteed to get in the way when you want to drop a
  motor or something like that. personally, i prefer a more removable
  solution.

Anyway, my recommendation is to weld up the cracks and add a removable
bar. But it depends on what you use the car for, really.

My 2 cents..

-Toby