Why did the MK3 (and maybe others) have the triangular plate for the seats?

[NiceGuyEddie]

I removed the seats to install the 5th point on the belt which has been in the box since 2004. I remember how odd it was that the plate under the seats was a triangle and you could not bolt the seat down in 4 places. May also have been true for the MK2, MK1, and for all I know the MK4.

Sadly, I don't know why this was so and it's been bothering me.

Obviously, the inspector at the track won't know the 5th point is into thin aluminum, but why the triangle?

(YES, I know the belt has expired but at the 1/8 mile track they don't care.)

[Dave M]

Personally I think it was an after thought. After designing the triangulated tubing floor structure they stuck a piece of plate in the hole to bolt the back of the seat bracket to. I made an adjustable bracket to bolt my seats to so was able to easily drill holes as needed to hit solid structure for all 4 corners. Luckily I’m only 5’ 8” so raising the seat up a little didn’t hurt.

[mikeinatlanta]

Obviously, the inspector at the track won't know the 5th point is into thin aluminum,

An inspector may not catch it, but one day a photo may show up on the internet and on another forum as another example of why one should never buy a used FFR. Please don't install a safety restraint system with a massive and hidden defect.

[john42]

An inspector may not catch it, but one day a photo may show up on the internet and on another forum as another example of why one should never buy a used FFR. Please don't install a safety restraint system with a massive and hidden defect.

diddo this!

on my MK3.1 Challenge car I redid the underneath seat mounting area by welding in a new steel plate to the frame so I could properly bolt down the Kirkey seats and the 5 point seat belts. Figured my life with worth the effort to do it right. :-)

[gbranham]

My MkIII was the same way. My MkIV, delivered in July of this year, has a fully squared plate for the seat to mount to. Don't know why the earlier cars have the triangular plate, but it appears to have evolved on the later MkIV chassis, anyway.

I've also noticed the front x-brace on the frame is round tube now, while my MkIII and earlier had a square tube. I guess things slowly evolve as time goes by. Same with the round tube that defines the floor of each footbox; the curve is less dramatic, and it's more 'squared off' on my MkIV. I assume this is to give folks more foot room in the footbox.

[weendoggy]

Seats to aluminum is a disaster waiting to happen. Had a customer give me his car to do some (a lot) of work. One thing I found was the builder (not the new owner) bolted both seats to aluminum only on three, and one of the bolts was sorta' tapped into the 4" round tube. While he was there I told him to watch this, then just pryed by hand the passenger seat out! Needless to say, all 4 were bolted back to the frame including new welded in plates. I did the same on my MKI when installing the Cobra Classic seats. Even have the sub belt bar welded in. I gues the triangle was to strengthen the chassis, just like the trunk "V". :rolleyes:

[NiceGuyEddie]

In my case I have the roadster seats, so the 5th point doesn't do anything since it does not go thru the seat. The tech at the track just said that since I have expired belts he'd like to see my 5th point next time. To be honest, it doesn't even reach the clamp, it's just for show. I understand what you mean that it looks bad if you want to sell the car. I'll be sure to remove it if I ever sell it.

It looks like so far nobody knows why the seat mount plates were triangular. I'm just "one of those people" where if it bothers you, it's stuck in your head forever so I'd really like to know.

[gbranham]

In my case I have the roadster seats, so the 5th point doesn't do anything since it does not go thru the seat. The tech at the track just said that since I have expired belts he'd like to see my 5th point next time. To be honest, it doesn't even reach the clamp, it's just for show. I understand what you mean that it looks bad if you want to sell the car. I'll be sure to remove it if I ever sell it.

It looks like so far nobody knows why the seat mount plates were triangular. I'm just "one of those people" where if it bothers you, it's stuck in your head forever so I'd really like to know.

If the tech wants you to add a belt because the other bits are expired, why not just refresh the belts you have, and not worry about the 5th leg/nutcruncher?

[john42]

In my case I have the roadster seats, so the 5th point doesn't do anything since it does not go thru the seat. The tech at the track just said that since I have expired belts he'd like to see my 5th point next time. To be honest, it doesn't even reach the clamp, it's just for show. I understand what you mean that it looks bad if you want to sell the car. I'll be sure to remove it if I ever sell it.

It looks like so far nobody knows why the seat mount plates were triangular. I'm just "one of those people" where if it bothers you, it's stuck in your head forever so I'd really like to know.

If you have the 5 point belts the submarine belt is intended to keep the lap belt at your waist. If it creeps up and you get in a wreck that lap belt is going to crush your internals instead of staying around your hipbone where it's supposed to be. It's actually worse to use a 5 point harness without the submarine belt. Please get the right belts for your car and seat. Especially if you're racing.