Steel for frame rail rust repairs?

JamesDF

Hi All,

I have an 1985 Mazda RX7 which I am attempting to restore. There is a fair bit of pitted rust on the front part of both frame rails (Chassis legs) and the wheel arches and sills are pretty bad in spots as well.

I am wondering what grade of steel is normally used for these repairs, specifically for the frame rail repairs? By grade I mean what standards does they steel confirm too.

Thanks for reading,

James.

JamesDF

Hi All,

I got my hands on a Mazda bodyshop manual for the rx7 and it states that the tensile strength of the steel used in the chassis is 35-45Kg/mm^2 (295-440MPa). After a bit of research I found a steel called EN10139 DC01 C340 which has a tensile strength of 340-490MPa. This would be idle, but I haven't yet found a place to buy it. I did find a UK site that sells steel called EN10130 DC01 (BS CR4), but its tensile strength is 270-400MPa.

Another option I am looking into is trying to source replacement chassis legs!

The joys of amature car restoration!!

Zebrano

Hi.

To be honest 99% of places wont go into that level of caring about a repair.

They will just use whats ever available of a similar thickness and to be honest the welding will just change the structural make up of it anyway.

For me the quality of the weld would be more important.

Zebrano

JamesDF

Hi Zebrano,

Thanks for your reply.

That gives me some confidence! I have some 1.2mm cold reduced steel that i got a while back that's the same thickness as the material used in the chassis leg, so I guess that'll do!

I had been thinking of getting some 1.4mm stuff just to be extra safe but that's probably a bit overkill!!

Since my last post I found that the left side chassis leg is still available to buy, but the right one isn't. To makes things more interesting they only seem to be available in the USA, and those suppliers won't ship internationally! So, I think making patch panels would be the easiest option...

JamesDF

Probably should have had these in my opening post, but, here are some pictures of the fun that awaits!

thereitisgone

How did you get on with this

JamesDF

Hi thereitisgone,

The battle is still on-going!

Replacement chassis legs can't be got (Tried a few sites and a Mazda dealer, but they no longer stock them). I think I wouldn't fair out much better looking for donor chassis legs either, so I'll not bother going down that route.

I was planning to patch the chassis legs, but I can't source steel with the tensile strength I require; 295-440MPa.

So the only option I see is to fabricate new chassis legs! I have started to create a CAD model of the chassis legs, and I hope to find a fabricator that will fabricate them for me.

As the Iarnród Éireann advert used to say one time "we're not there yet, but we're getting there!!"