I came across an old thread saying that the boxed section on the floor, where the front of the seat adjustment is, is not structural and can be removed. They just mentioned that they did this for the purpose of mounting their race seat flat on the floor in their race car.

1) Just want to confirm that structurally that this is true.

2) Has anyone done this?

3) How difficult is it? (besides just hacking away at it with a girder)

I am interested because I am running an after market seat and being a giant, I could use every inch I can get.

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Are you referring to the cross member there? I'm not sure it's NOT structural. It connects across the longs, anchors at the center tunnel, and helps secure the floor pan. It's spot welded on each long and boat load of places underneath with the floor plan and then tack welded about 6 or 8 places on the center tunnel. To remove it cleanly takes some time drilling out spot welds. Of course with a grinder....

I'm not a structural engineer, so I'd defer to others, but I personally would be careful. Put it this way: with my car on a rotisserie I welded in a 1 inch square tubing across between longs to provide integrity when I removed it for replacement.

I've seen it taken off of many race cars, and I am considering the same (as soon as I get my car back).
I BELIEVE (and hopefully others that know better can chime in) that it provides some structural rigidity to the floor itself, otherwise the expanse from front to back firewalls might be too great to not sag with weight.

Is your car a race car? Does it have a roll cage?

My plan was to weld a 1/4" plate from long to center tunnel, about as wide as the boxed section being removed. Again, that's what I've seen on a lot of vintage race cars

On a race car with a welded in roll-cage? No Problem, cut it out.

On a street car? Not so much ...


In your case, you would still want some sort of cross member support there. You could replace it with square tubing that has a lower profile.
Some have even lowered the floor in that section to gain another inch or so.

Whatever you do, make sure it's triangulated/boxed for stiffness. That cross-member is right at the main flex point of the chassis.

I just replaced mine in my restoration project, if it's nonstructural then it's only function would be for a place to install the seat height adjuster and route the ebrake-on switch. I'm not sure of the effect that it'd have on chassis stiffness, but one thing it definitely does is to keep the floorpan from sagging under the weight of the driver as naro914 mentions.

Have you tried fitting the seat with it in place? I'm 6'1" and have my aluminum Butler seat pretty much all the way toward the rear firewall and pretty much mounted directly to the floor. Plus, I like the seat to be tilted back slightly. installed this way, my seat does not interfere with that lateral box frame in any way.

Even if it did, I would not like to have my seat laying flat on the floor; I'd be sitting too bolt-upright and would have no lower support for my thighs. It takes just a slight tilt to clear that lateral.

If I were 5'5" it might create a conflict, but not for "a giant".

I suggest trying to fit it as-is, see how it works out.

It's not for a race car, but I am having to run 5 point seat for AX and TT events. Im 6'6 265, so really no aspect of this car is to scale with me But that is why it is so fun once I am in it.

Its not caged but I am flirting with doing a hoop and lower cross brace, much like the old style GT cage...

I would leave the passenger boxed section, and was thinking I could just run some extra plating laterally in place of the boxed section and weld it in.

The main issue I have is if I scoot my but back, my head goes up, which is an issue with a helmet, if I tilt it and scoot my butt forward my knees come up, then its an issue with shifting and the steering wheel. Right now its OK, but I am always looking to improve my seating position and dropping down 2" does not seem like much, but could make all the difference.

Any time you have sections of steel with a 90 deg. bend in them welded to the overall structure, you are adding some resistance to bending, and thus adding to the "structure" of the whole. As some have pointed out, with a cage, or other added bracing, you may get away with it, but in stock form, I'd never take it out.

Or lower the whole floor pan like this? I saw this post on facebook a little while back.

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Spec Miata guys are starting to lower their seats in the floor pan (recently allowed for 2016). I'm betting there's some "off-the-shelf" built parts you could modify for that, should you decide to pursue it.

I'd like to get my seat down about 1 more inch or so, so that I can run it open-top. I'm *just* above the required 2"-below-top-of-main-hoop. Maybe if I scrunched down during scrutineering...maybe I'll let Mr Foley perform some of his madz skillz on my floorpan.

Removed most of it on a project recently. Here's the comparison.

Mine are both cut out; sidemount seat brackets bolted directly to/thru floor with steel flat stock reinforcements in between. It's really the only way to get low enough with race seats and helmet. My car is fully caged tho...

Pictures by chance with the seats out?

I need sliders, so gotta mount those directly to the floor first.

Sorry - I did not find any pics of the floors/seats during assembly.

Hmm that's a pretty good idea. I might do this on mine as those parts are trashed on my car anyhow.. I could easily just weld square tubing in that is smaller and still retain the strength.. I am 6' 1 so that extra room would be appreciated.

That's what I did on a different car I built in 2001:

http://www.kakashiracing.com/floor.html