Recommended material for chassis rail repairs

[sword]

Hi All,

Unfortunately on the weekend I discovered that my 1988 E30 BMW project car has a rusted chassis rail. Fortunately the rust has not penetrated the whole way through, though some of the pits come close. The rust is almost not worth worrying about, I could just remove it and repaint. However this is for a race car and I want the extra rigidity.

I was thinking I could just weld a long patch panel over the affected areas to tie the unrusted parts together. Does this sound OK? What material would you recommend?

Many thanks!

 

[troppo]

I`d go like for like with the thickness, as for a patch i`d go 100 mm past the end of the pitting each end and make the ends round or triangular, square ends tend to crack under a lot of stress

 

[sword]

Thanks troppo.

Any advice on whether hot or cold rolled is better?

Cheers,

Greg.

 

[troppo]

I`ve never really bothered with the difference and as it is only a car the thickness`es you`ll be working with wont make any real change

 

[droopsnoot]

I think you'd be better cutting out the rusty bit and putting the plate over the hole, not welding a plate over rusty metal.

The trouble is, the old bit will carry on rusting behind the new patch, and you won't know how bad it's getting because you won't be able to see it. Then at some point the rust will reach the section you've welded to, and the patch will come off in your hand. OK, like they say in the adverts, "sequences shortened", but that's the gist of it.

 

[sword]

Thanks droopsnoot,

As far as I can tell, the rail is rusting from the outside in and has almost, but not fully penetrated the rail. Can't I just remove the rust with a sandblaster and put a patch over the top with 100mm of overlap as troppo said? I would fully seam weld the patch to prevent moisture from finding its way in. Sound OK?

 

[Lawnmowerboy]

If it's that bad I'd replace the whole length of the bit of metal

 

[hotrodder]

Hi All,

Unfortunately on the weekend I discovered that my 1988 E30 BMW project car has a rusted chassis rail. Fortunately the rust has not penetrated the whole way through, though some of the pits come close. The rust is almost not worth worrying about, I could just remove it and repaint. However this is for a race car and I want the extra rigidity.

I was thinking I could just weld a long patch panel over the affected areas to tie the unrusted parts together. Does this sound OK? What material would you recommend?

Many thanks!

Plating over the rust is gonna add weight without contributing anything useful stiffness wise

Personally i'd remove the rusty bits back to clean metal and let in fresh metal. I'd use cold reduced simply because i wouldn't buy hot rolled in this sort of thickness- there's nothing in it price wise and cold reduced is nice and clean