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PCA Member
Posts: 393
Registered: August 2006
Location: Florida


GT3 Seat Installation

Reviews Views Date of last review
2 37260 Mon April 2, 2007


Recommended By Average Price Average Rating
100% of reviewers None indicated 10.0


GT3 Seat Installation

The installation of GT3 seats is a popular modification for the track-rat crowd. The GT3 seats are more supportive than stock seats – even sport seats - and more importantly, have the appropriate holes for a proper multi-point racing restraint. In this article, I’ll share my experiences installing GT3 seats and Schroth racing harnesses in my 2007 Cayman S.

I ordered my seats from sponsor, Suncoast Motorsports, who also performed the installation. While I’ve installed racing seats in other cars, none of them had side impact airbags in the seats. Therefore, I left the job to the professionals. They need to plug into the Cayman’s computer and disarm the airbag and tell the car that the side impact airbags would no longer installed be installed in the car. If you don’t tell the computer that the airbags are missing, you’ll get an airbag warning light on the dashboard.

Removing the stock seats was a snap. …but boy are they heavy! I wish I had taken the time to weigh them. They’ve gotta be over 50lbs each!

Before we can drop the GT3 seats into the car, we have to mount the racing harnesses to the seat – and that brings us to the choice of restraints.

Choosing Restraints
There are all kinds of racing restraints on the market – Scroth, Simpson, Impact Racing, G-Force, etc. The choice of manufacturer turned out to be pretty simple – Scroth is the company that makes the restraints sold by Porsche Motorsport and what you’d find in a factory fresh GT3 Cup car. Scroth is the only manufacturer with a lap belt specially designed to work with the Porsche GT3 seats. I called HMS Motorsport, the US distributor for Scroth, who directed me to Schroth’s GT3 Profi II 6H kit. (about $425) This is a 6-point belt designed to work with the GT3 seat’s lap-belt mounting hardware and a HANS device.

The GT3 seat mounting hardware includes a special “peg” (If you conjure images of the bolts sticking out of Frankenstein’s neck you’re getting the idea) onto which the lap belt is designed to mount. The Schroth harness kit I ordered use a lap belt with a special end designed to fit the GT3 seats special “Franken-peg”.

At the track, I wear a HANS device. Typical 3” shoulder belts are wider than the HANS device and can spill-over the edges of the HANS and possibly slip off the device entirely while driving. Scroth has addressed this problem with a special “HANS-friendly” shoulder strap. This strap is 3” wide near the camlock and then narrows to 2” over the shoulder & HANS device. The 2” wide belt fits the shoulder belt “channel” in a HANS device very nicely.

You can see in this photo how the Scroth 3-into-2 inch belt fits nicely over the HANS device.

If you’re not using a HANS device right now, (why not?) Scroth’s got you covered. They make a version of the GT3 Profi II with standard 3” shoulder belts. …and it’s a few bucks cheaper than the HANS compatible kit.

Lap Belt
As I mentioned, the lap belts attach to the “Franken-pegs” on the sides on the seat rail. On the “tunnel-side” of the seat, the pegs also accommodate the stock seat belt receiver so that you can still use your OEM belts when driving around town.

Mounting the anti-submarine strap
The anti-submarine strap is a critical safety feature. It’s job is to keep the lap belt low across the hips so that it can properly restrain the driver. In a frontal impact, the anti-submarine strap prevents the driver from sliding “under” the lap belt. Keeping the lap belt in place across the hips prevents it from riding up into the sternum during a crash.
The anti-submarine strap (hereafter referred to as just the sub-strap) is threaded through a cut-out in the GT3 seat. But what does it attach to?

As part of our installation, I asked for a sub-strap “truss”. (Porsche part number 996.521.933.90)

This “W” shaped bar is bolted between the seat mounting brackets. Because it’s attached to the seat bracket and not bolted to the floor, it moves fore-and-aft with the seat and therefore stays perfectly centered with the hole for the sub-strap and won’t lengthen or shorten as you move the seat.

The use of the sub-truss means that you don’t have to punch a hole in the floor of your car to accommodate a sub mounting location.

The sub strap is threaded through the hole in the seat shell and wraps around the sub strap truss.

Stowing the Camlock
When you’re not at the track you’ve got a cam lock sitting between your legs on your way to the office. While it’s not really intrusive, you might want to get it out of the way. Since the GT3 seat cushions are velcroed to seat shell, you can pull the seat cushion up and let the cam lock hang over the edge of the shell and then secure the cushion over it.

The Harness Bar
So what do the shoulder straps attach to? That’s a good question! The automotive-aftermarket doesn’t yet (March 2007) offer a bolt-in roll bar for the Cayman. If you want one, you’ll have to have one custom fabricated by a race shop. However, the automotive aftermarket does offer a few different harness bars. I installed the DMC harness bar sold by FarnbacherLoles. Ken Smiley did a great writeup on his harness bar installation – check it out here – so I won’t dive into the installation details in this article. The DMC harness bar is a great piece. It installs at the “hard-point” where the stock seat belt mounts at your shoulder and runs along the top edge of the engine bay. At the mid-point of the car, it attaches to a hard point on the engine bay. The DMC bar features a pair of harness guides so that your belts won’t slip to the left or right.

Reinstalling the stock seat belts
Since our Cayman is used on the street regularly, I left the stock 3-point seat belts in the car. However, they need to be “threaded” through the new seats. On the drivers side of the car, the seat belt is threaded through the left-most shoulder hole. I left the stock seat belt receiver on the “outside” of seat – between the seat and the center console - since it’s tall enough to clear the side bolster. (See photo) From the seat belt receiver, the belt travels across the lap and is threaded through the lap-belt hole in the door-side of the seat and finally attaches to the factory mounting location.

The Completed Installation

Seat & Belt Close Up
Keywords: GT3 Seat Installation



Porsche Orator

Registered: January 2007
Location: Maryland
Posts: 1661
Review Date: Sun April 1, 2007 Would you recommend the product? Yes | Price you paid?: None indicated | Rating: 0 
Have you installed this Product or Mod?:
Do you have any pictures of the actual installation or removal at all with directions? Does the seatbelt warning light/chime come on while on the track,was it disabled? Or do you use both belts?

Techart GT (X51)
2012 Panamera 4
2012 VW GTI 2.0T
2010 VW GTI 2.0T
2009 VW Touareg T2
2007 VW Passat 2.0T
2006 Techart Cayman GT
2002 ALMS Audi TT 225
2001 Audi A4 1.8TQ (RIP)
2001 VW Jetta 2.0
some people like the regular stock factory look, cool people modify the car.
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PCA Member

Registered: August 2006
Location: Florida
Posts: 393
Review Date: Mon April 2, 2007 Would you recommend the product? Yes | Price you paid?: None indicated | Rating: 10 
Have you installed this Product or Mod?:
I didn't shots of the seats coming out - they had already completed that part of the job before I arrived. It's important to make sure the shop disarms your airbags first!

Go Fast, Brake Late, Don't F*ck Up!
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