Mark in Baltimore

BTW, GT3 shell seats don't offer any additional headroom over stock seats.

Red rooster

Jordan,
I had to raise the passenger seat because my wife at 5 ft was not happy with the view !! Therefore top priority !!
I made four one and a half inch tube spacers to go between the seat runners and the floor. Six axle joint bolts took care of the longer fasteners.
That extra inch and a half of height made a big difference.
Hope that helps

Geoff

shattergard

Thanks Bull

Felix

I might have missed something but...

I don't thinking using the rear mounting holes gains you any headroom. The plane of the mounting holes is almost horizontal; moving 1 inch either way changes virtually nothing. Legroom yes; headroom no.

Bull

Well, try it some time. You will gain just about an inch of headroom, as I did and the scores of cars most of the shops in my area have done it for. The seat moves both rearward and down.

Felix

The holes are an inch apart. To gain an inch of headroom by moving the seat back one inch the rails would need to be in a plane with a 45 degree angle to the horizontal. Sorry but I just don't see how headroom can be gained.

Bull

Sorry you can't see it. BTW, there are other factors in play with the move, and the seat mounts are no on a horizontal plane. As I said, if you want to "see it", try it. I'll let others explain the geometry of something that is accomplished often.

Felix

Indeed, I can confirm that with Sparco sliders and Brey Krause brackets there's little to no change in headroom from the standard 8 way power seat.

Standard 996 GT3 sliders are about 38mm from flange to flange; the Sparco's are about 30 mm.

Standard GT3 brackets are about 100 mm from the lower face to the center of the bolt hole for the rear fixing bolts. The BK brackets are about 80 mm for the same distance.

Felix

There's about an inch of drop between the rear most front hole and the rear most rear holes.

What are the others factors that I'm missing?

BTW have been playing around with seats and brackets and the like so I'm reasonably familiar with the seat mountings.

Jarg1

I have to agree with you on this one. The math is pretty straight forward, and I don't think you gain an inch of headroom. I did this modification, and appreciate the extra legroom, but at 6'4" I'm still slouching down to fit with a helmet.

Scott

Bull

I don't really know as I never spent the time to figure out why I, and others, get close to an inch more, I just take it and run. Maybe something in the roof/sunroof/headliner profile as you move rearward?

BlkC4S

I have this combination (GT3 seat + BK/Sparco). Without a helmet, my headroom is fine. When I wear a helmet, I remove the bottom cushions (it's actually still pretty comfortable), and I gain about 1" of headroom or so.

Bull

Ok, whatever you do DON"T move the seat back to the rear holes and expect any improvement in headroom! Once again on the Internet and particualrly the 993 Forum, it has been proven to be impossible by statement!

Felix

No need to get sarcastic; we're all friends here.

Moving the seat back by one inch and gaining an inch of headroom by doing so means the seat must be an inch lower or the roof must be an inch higher. That just doen't seem possible. I'm not trying to score points or claim I'm right or that you're wrong; I'm just trying to find a logical explanation for the claimed extra headroom and I can't.

Backrest angle obviously play a big part in perceived headroom, at least with "normal" seats.

Bull

BTW, I have never measured the gain. It "seems close to an inch" to me and others, but it could be closer to .81997993 inches. Or, maybe wrestling with those rediculously heavy stock power seats just causes one to become shorter?