Hi Guys, I'm New to Posting on this forum, been a long-time reader: P,
I currently have a '70 1200 Coupe and a '73 Sedan,
The problem being is that on the driver’s side seat rail has snapped close to the bend for the front mount. I've had a look on the Wiki to see what I can do about replacing the seat and rails but I’m still not sure as I’m 6 foot 3 and a bit on the round side of things.

Has anyone got any ideas for what i can try because of the legalities of road legal and such I’m trying to get it right, I did find a place that sold rails for $250 but I’m concerned it could happen again?

i wouldnt be worried unless it happened a second tme,

i would put in another original at minimal cost, and just keep an eye on it. i think you have been unlucky to have one snap on you. could have been weakend in a car accident many years ago or anything.

I think they could snap on anyone if they aren't done up tight, any little movement back and forth (small enough that you don't notice it) will weaken that small tab and cause it to snap, for extra precaution you could get another tab attached on the opposite side of the existing piece (welded to the rail underside) that would attach to the back (or the front depending on where you look at it- forth or aft) of the seat rail mount- you could use one continuous bolt which will hold both tabs against the seat rail mount.

I'm in the same boat. I thought it was just me, but in addition to the rail breaking (same place) the rear seat mount has ripped away from the sill, and also cracked/torn the chassis rail. As I said, i thought it was just me, but I've now seen it on a few more coupes. The problem is, with the seat back a fair way (all the way back) the front floorpan bracket (which goes all the way from the sill to the trans hump, much stronger) bears almost zero weight, and it's ALL on the rear ones.

I've repaired the floor pan and bracket, but really it is just going to happen again.

I'm not as tall as you, but my head rubs on the roof lining over bumps, and I desperately need more leg room.

If I just altered the brackets, to move the seat further back, it would stress the 'weak' rear bracket even more.

So the option I've started on is to make custom rail/brackets, that span from that front seat mount bracket (the one that goes all the way across) then running 2 solid RHS beams back from there, all the way back to the crossmember in front of the diff (the one that is directly under the front edge of the rear seat. that crossmember area is MUCH stronger. So by making brackets that go there, and bear the bulk of the weight, it won't re-crack the floorpan in that other area.

It means I can mount the seat back further. the 'support beams' would 'usually' compromise the drivers side rear passenger leg room, but by the time I've moved the seat back where I want it, there's no gap behind the front seat backrest, so nobody could sit there anyway.

I'm going to mount the seat direct to these rails as well. Done carefully, this will mean the original sliding rails are gone. That isn't a big deal, as nobody else needs to drive it. By getting rid of the slide/rails, it lowers the 'bucket' part of the seat (if done 'right' by as much as 1-1.5 inches. SO no only more leg room but also more head room. Due to the angle of the fore/aft rails, the further back the seat is the lower it is. So I might just manage a full 2 inches extra headroom too - but I'll take absolutely all I can get.

The way I'm making this whole 'structure' it will bolt to the front factory rail via the front 2 bolts, but the rear rail will use angle iron to 'sit' on top of that rear crossmember. To give it wider support, I've cut some angle iron, then curved it, and welded a new piece in, so that it can go across the width of the rear crossmember, and slightly up and over the trans tunnel hump section.

If I choose the width right, it will 'sit' on there and wedge itself in, and be quite sturdy without bolts on the rear half. It'll make more sense when it is finished.

I should also warn anyone else trying to do this themselves of a tiny 'trap' you might fall in. don't just make the brackets and the rails 'square' with one another. The problem is the the rear crossmember isn't perfectly parallel. It narrows (which means it travels backward as it travels to the outside of the car). So if you cut the front to rear steel to identical lengths and welded it up, the rear bracket wouldn't sit flush, it'd be hanging forward about 5-10mm off the front of the outside edge of the crossmember.

SO basically you need to make the bits of angle iron first, and then measure the different lengths for the front to rear beams, tack, then weld them to another piece of angle iron, get it all fitting snug, and then welding it to the front angle iron bracket.

This is very early days for mine, and ideally it would have needed bigger angle iron, but I had a lot of 50mmx50mm angle iron spare, so I started with that. I will add a piece to the vertical wall of the rear one, so the front to rear beams can sit low enough.

Anyway, here is the starting point:


it will require that I grind off the driver's side back seat securing bracket off of that rear crossmember/brace/chassis thing, so it can fit snug, but apart from that minor change, it is (once finished) a bolt in option, so that if somebody wanted to, down the track, they could unbolt this thing and bolt a seat with factory rails back in the original position.

I've started with a piece of angle iron for the front bracket
















I have no doubt my ridiculous weight (more like Johnny Vegas than Arnold Schwarzeneggar) didn't help it, but they seem to be a weak link, and the floorpan itself isn't perhaps as thick as we might optimally like. I'd also add that the pics I used for the stripped out shell were not mine, I got them off this forum photo section originally, but used them as they were convenient to do a few ms paint edits on to make it clearer, and certainly quicker/easier than taking a lot of new pics and scanning them etc.

Thanks a bunch Guy's, the info and help has been great, i'll continue to try and source some rails, ute rails were pointd out to me on ebay they would be fine yea?

ute rails im fairly confident are exactly the same

I have been replacing the seats this weekend with s13 seats. Have welded rails made of angle iron to the bottom of the seats, which now bolt in to the original rail bolt holes. The extra rail means extra rigidity (my coupe's rear seat rail mounts had come away from the body too) but also it means I haven't had to mod the original holes. Could bolt original rails and seats in easily.

ANYWAY, means I might have a set of coupe rails for sale if you still wanna go that way.

OK so I have been procrastinating over this too long now, I've basically gutted the interior of my coupe to try and get a better look at the problem, as it turns out it's not just a seat rail snap. The rear driver side seat bracket has punched out the bottom of the floor pan, seems to have started from a small amount of rust..... And then BAM! Right through. (I’ll try to post pictures of later tonight)

I’ve had a couple of people look at it and the conclusion has been to pick off the mount and make up a new panel for the floor pan and weld that it, before I start to attempt to knock up my own panel I thought I might ask if anyone else has had something similar made or been successful. Whilst I like jmac's idea I would like to try and keep it close to original as possible.

Is this of any help?

This member Wayne is a pretty skilled craftsman, here is his website Panelcraft

Cheers Clyson8 looks good but the rear panel picture on the site

shows the panel is made to fit around the bracket, i need to be able to weld the rear bracket to it. the picture shows that it ends arounds the bracket and because i have to cut that whole bit out it really wont work in this instance :S although could be a good starting point.

Attach file:

---

  Rear Floor pan.jpg (33.43 KB)