Here's a popular notion for track driving enthusiasts; Installing Racing seats in your car. They offer much improved lateral support, and the opportunity to properly route and retain your racing harnesses. However, anyone who has ever tried to do one of these installations has already run into the buzzsaw of competing and conflicting systems that vie for a piece of the usually limited space available. Add to that the fact that one-piece race seats do not offer the infinite adjustment available in a stock articulated seat, and the installation of such equipment can be exceedingly tricky.
This project will be the installation of Kirkey Road Race Deluxe seats in a 2001 Porsche 911 Aero Coupe. The Road Race deluxe is Kirkey's top line road seat, and features shoulder wings for upper body support, increased seat base length for thigh support, dedicated side mounting points, increased thickness milled side and back panels for increased rigidity, and a fairly deep padded cover. Their main architectural advantages are light weight, just the right stiffness, and a compact exterior. They sell for about $600 each.
This car previously had Sparco Torino seats installed. They did not work very well at all with this car. Not only did I find them rather uncomfortable, but these seats are fairly wide at the rear, and the 996 side sills are fairly narrow, and turn in dramatically past the door opening. This area was far too narrow for the seat to slide back far enough even for the moderate-height 6'1" owner to use effectively. At 6'5". I could barely get IN, let alone drive it! It simply did not work well at all.
This car's previous setup utilized a set of quite nice Sparco sliders, and a steel adapter plate. The Sparco sliders look to be quite up to the task, but the adapter plate was downright flimsy! I could easily fold it right over
996 Race Seat Install
my knee. Since the sliders bolted to this adapter entirely, not to the OE holes in the floor, how anyone thought that was a sufficiently strong mounting platform I'll never know.
Once the old components were removed, the first order of business was how to mount the new seats? Stock seat rails bolt to the heavy tubular seat frame at the bottom. Most articulated sport seats - like the previous ones - offer the same provision. However, with a race seat where there is no heavy steel frame, bolting through the seat base has the disadvantage of not being terribly strong because the loads are transmitted to the fasteners and mount points in tension, not shear.
Most people owning dual usage cars will want to have sliding seat tracks to maintain more daily convenience. With this you run into the first of many technical challenges. Big Problem #1 - How to interface between the mount holes in the floor, the sliders, and the seat?
It would offer far superior strength if the sliders could bolt directly to the mount holes, but the lack of available long sliders and the shape of the mount pads on the floor prevent this. The common solution is to buy or make an adapter
plate. At right is such an adapter plate. I fabricated this out of 3/16 x 3 flat steel.
You can clearly see the four holes at the corners where the plate bolts to the stock seat holes in the floor. The rear mount holes in the sliders are picked up by the rear seat bolts. The arrows point to the holes where the front of the sliders will be bolted down. Incidentally, I used Grade 12.9 Socket Head Cap Screws (Allen bolts) throughout this installation.
The previous adapter plates were laughably flimsy! This explains the fairly heavy gauge of the metal I used to give added strength to the unsupported distance between where the adapter plate bolts to the floor, and the slider mounts to the adapter.
The passenger seat adapter you see above was relatively simple to make, but not the one for the driver's side. At left you see the completed driver seat rail assembly. Proper reach to the steering wheel is obviously critical, and because of these seats laid-back design, I needed every degree of rear seat back incline that I could find. To add to the difficulty, the mount areas on the floor are significantly higher in the front than in the rear, and actually form a raised pedestal. The combination of declined seat design and declined mount points offered a very difficult scenario to overcome. This was Big Problem #2.
The red outline on the bottom picture shows the actual shape of the adapter plate, which
allowed the area where the slider bolted in front to be about 1/2" lower than on the "flat" passenger side adapter. This tipped the driver's seat base down in front a precious few degrees. This 1/2" at the bottom doesn't seem like much, but at shoulder height it got me about 2-3" closer to the steering wheel, which the owner desperately needed.
At right is a top view of the finished driver's seat frame assembly. The double-locking seat tracks from JAZ Products are pretty rugged, and offer a very positive locking mechanism and solid construction for under $30/pr. Unfortunately, this brings us to Big Problem #3. The raised portion of the seat adapter on the driver's side blocked the path of the slider from moving all the way forward. The red arrows point to relief slots that I had to cut in the adapter plate to allow the sliders enough clearance to extend fully forward.
At left is the seat bolted to the fabricated side plates which are welded to the sliders. You can see the front of the seat is slammed as low as it will go, and the rear is raised up to the point that the top of the seat clears the headliner by about 1/4"!!
And... oh by the way, we're not nearly done with the problems yet. Big Problem #4 - Belt Mounting. Proper seat belt mounting allows for free rotation so that the seat belt can pull straight from it's mount flange on the end of the belt, regardless of the angle at which the belt is run. Unfortunately, the OE mounting bolts are only designed for one set of belts. When you put a set of race belts on the same bolt, they will be trapped and will not pivot! Usually the best you can do is to assure that the trapped race belt is placed at such an angle that it pulls straight when the driver is belted in his preferred position. Not ideal, but about all you can do.
When you get to the inner belt mounting, you run into REAL headaches. First, there is essentially only room for one belt. Second, the OE belt mounts to the seat frame, not the body, so there are no mount holes pre-made. The solution was to incorporate a mount flange on the adapter plate. Both of the belts are mounted with earlier Porsche 11mm seat belt bolts that have a shoulder under the bolt head that allows the belt to pivot at the mount. This allows the belt not in use to be swung out of the way.
All of this stuff must be done with the seat out of the car, because there is no way in $%@# to get at this when the seat is in!
WELCOME TO BIG PROBLEM #5
This seemingly innocent little fellow is a factory 996 seat mounting bolt. Other than the fact that it has a 6-point external head, and a "self-centering" tip, it doesn't look much different than most bolts.
Looks are once again deceiving!
This car came to me with "regular" 10mm x 1.5 thread pitch grade 8.8 bolts in place of most of these OE bolts. Inexplicably, two of the OE type were still used in the passenger's seat. I noted that the replacement bolts did not seem to move particularly freely in the holes when I took them out, and that the threads were slightly rounded off on their edges. I ran the threads with a die, and the situation did not seem terribly urgent.
I had the seats in and out at least a-dozen-and-a-half times trying to get all of these Big Problems worked out, and by the time I could see the light at the end of the tunnel, I suddenly found that I had
concurrently reached the end of the life span of the threads in the floor!
This on top of everything else?! #@%&@# !!
After the shock wore off, I got to looking at these odd little bolts. I tried to clean one of them up by running the threads with a die. It lurched in a tight-loose-tight rhythm. Strange. I threaded it into my finger tips. This does indeed not have a regular thread! It is sort of triangle-shaped. A trip to the local pro fastener outlet put order to my findings. These bolts are not normal, not even self-tapping. They are THREAD FORMING BOLTS. "Triodal" by name, if I remember correctly (?). The holes in the car floor are blank inserts, and these bolts, with their self-centering tip and special shape form their own threads as they are FORCED into the holes in the floor. These are not normal threads, and only work to whatever degree that they do with the OE bolt in them. Other bolts will not quite interface well with them, and if they are asked to come in and out too many times... POOF! Goodbye threads!
Oddly enough, the failures only occurred on the front holes. The rear threads remain rock solid. ???
Problem solved by drilling out the inserts and re-tapping them to the next closest size... 1/2"-20 SAE.
REAL THREADS this time. SOLID!
not work well. I had much the same trouble installing them in my 944. They are built with far too much recline, approaching 20 degrees. Couple that with the fact that most cars have reclined seat mounting points (front mount points higher than rears) and you can see part of the problem. They just lay back way too far!
If you try and lower the front of the seat to incline the seat back forward, you hit the floor immediately. If you raise the rear of the seat, you better hope the driver is short because you will run out of headroom quickly. That, and the seat base becomes much too level with the floor, or even tipped down from back-to-front. This is not good for reasons of driver retention in an impact. I have been in contact with Kirkey to see if they would like some help with their seat designs. More to come on that front... once they get through with their busy season.
And so, the ordeal is ended and the finished product is revealed. Nearly 25 hours of labor to get this all to work! Truth be told, these seats are not properly designed, and do