Thoughts On Replacing Frame Rails with Heavy Gauge Steel

[The Red Scourge]

I came across this YouTube video today.  He cuts down 2-3/4" x 2-3/4" square steel to custom make frame rails.  I imagine it'd make the chassis stiffer.  It seems like overkill to me, but never thought of this and haven't seen it done before.  Any potential drawbacks to doing this?

 

 

 

[Mark Maras]

It's an improvement in my book. No drawbacks other than it's not an original frame piece.

[dutchzcarguy]

15 hours ago, The Red Scourge said:

It seems like overkill to me, but never thought of this and haven't seen it done before.  Any potential drawbacks to doing this?

I think it's overkill.. 1,0 to 1,4 mm steel is more than enough, i had to remove a floor that was made of much to thick steel.. when i took it out some 25 kg of steel fell to the floor.. i replaced it with 1mm steel and the car got a bit faster!  Also... never weld steel over some old steel it will always create a mountain of rust!!  Always weld head to head..

so:

1 not necassary..

2 much to heavy (= slower car.)

3 covering is asking for rust.. (Weld some steel IN it not OVER it!)

4 If done on the front, you take out the crumple zone.. you create a even more dangerous car to drive.. 

I once seen a car that had those fat beams in the front (over the front wheels), It's dangerous to do because if you have an accident the crumple zone is... the place were you are sitting... not a nice thought!

Edited December 5, 2022 by dutchzcarguy

[The Red Scourge]

Thanks for the response.  That definitely makes sense.  I'll probably just order prefabbed frame rails then.

[rturbo 930]

What dutchzcarguy said. The strength comes from the shape of the piece, not the thickness. I don't know what thickness the guy in the video is using but I've seen people use really thick box tube, like 1/8", and in that case you're just adding weight. If you want to improve chassis stiffness, make or buy a piece that connects the front subframe to the rear. Even if you make the floor rails super strong, there's still a bunch of other places the car flexes in anyway.

I just browsed the video, he didn't even connect the floor rails to the rear subframe, so there isn't even any added stiffness lol. He cut the bottom off the old rails so I don't think he's created any kind of water/rust trap as he might've if he just put them straight over top of the old ones. I'm guessing he just wanted a cheap replacement. If he's going to all that effort, I don't know why he didn't just have some steel in the correct thickness bent up, and then do the rest of his fab work.

Edited December 5, 2022 by rturbo 930

[Patcon]

I am not sure this is a good repair. I'm not worried about crumple zones in a Z car. Let's face it the driver is the crumple zone!

John at Bad Dog rails makes a replacement piece for this exact area and is very insistent that they not be welded in continuously. Evidently that extra rigidity in the floor causes problems or cracking in other areas of the car. I believe it was in Atlanta he and I were talking to Matsuo San (?) about the lead joints at the A pillars and quarter panels and he expressed that it was so the car could "breathe" ie flex. So those areas are very important to the over all structure of the car. Overly reinforcing one area forces the flexing to a different area with unpredictable consequences. Caveat Emptor...

[dutchzcarguy]

@Bart Hoedemaker read the above before welding in a new floor Bart, so only spotwelds not long closed welds on the beams.

[The Red Scourge]

13 hours ago, Patcon said:

John at Bad Dog rails makes a replacement piece for this exact area and is very insistent that they not be welded in continuously. Evidently that extra rigidity in the floor causes problems or cracking in other areas of the car. I believe it was in Atlanta he and I were talking to Matsuo San (?) about the lead joints at the A pillars and quarter panels and he expressed that it was so the car could "breathe" ie flex. So those areas are very important to the over all structure of the car. Overly reinforcing one area forces the flexing to a different area with unpredictable consequences. Caveat Emptor...

Wow!  I've never heard that before.  I wonder how many people know this.  I'm very new to Z bodywork, but have only ever seen people welding them continuously in videos.

[Patcon]

Probably not many and in all reality it problem only causes problems on cars that are pushed pretty hard or have lots of horsepower

[The Red Scourge]

On 12/8/2022 at 10:35 AM, Patcon said:

Probably not many and in all reality it problem only causes problems on cars that are pushed pretty hard or have lots of horsepower

Gotcha.  That's definitely good to know though.

[Racer X]

The guy needs a proper hammer. He must be a carpenter.

I have a number of hammers in my toolbox, and none of them have a claw.  I keep my framing hammer with my carpentry tools.

Edited December 9, 2022 by Racer X