SL-C Manual: Interior
The dash is commonly attached to the chassis with small button head screws in tapped holes in the aluminum on the outside tabs (as shown in the photo) and also in the middle behind where the middle switch panel goes. To fit the dash you will need to trim the fiberglass to fit around the front roll cage bars. Carefully trim the dash so it can slide into the body opening from the interior side. Save the trimmed piece so you can use it later after it has been trimmed to re-insert into the opening by the front roll hoop. If you are using the factory A pillar covers you can use the bottom portion of them as a template to trim the dash. Also check clearance around the steering column. Depending on how you want to cover your dash, make sure you have extra clearance to take into account the covering material. The picture below shows the front edge of the dash padded with thin high density foam. This padding may be required in some jurisdictions.
The dash needs to be supported in the front, around the windshield edge as well. The easiest solution to this is to make small sheet metal brackets and epoxy them to the body as shown in the picture below (ignore the object to the left- the bracket in question is in the upper right of this picture.)
It is vital that the dash be aligned properly with the optional door panels if they are provided. Don’t permanently attach the dash until you have verified fitment with the door panels if you are using them.
To maximize head clearance you should position the seats as far inboard as possible. This tends to better align the centerline of the seat with the center of the steering column as well.
If you would like to fit seat sliders, use side-mounts instead of bottom mounts to maximize headroom. It is possible to use side-mount sliders with no loss of headroom. The use of side-mount sliders will influence your selection of seats. Carefully check head clearance as there is limited height available in the cockpit.
It is also possible to incorporate the optional adjustable pedal box to suit different size drivers.
The standard seats are shipped with a set of seat brackets that bolt into the sides of the seat.
The picture above shows the standard two-piece seats in a Superlite Le Mans. They are the same seat for all versions of the car. Note that the seat may not appear to have 2 pieces, and is rigid (i.e., it doesn't have a way to adjust the recline angle without also changing the seat bottom angle. That is because they are made in two pieces, one a front, and the other a back. The two pieces are then bonded together at the factory to make a single, very rigid but light seat. This is in contrast to a single piece seat that doesn't have a finished back.
The following photo shows the original factory seat, but fully upholstered. Also, note the 3-point belts in this picture. The upper belt attaches to custom receivers welded into the roll bar. These were builder-made changes to this SL-C, instead of the normal 5 or 6-point harnesses. These factory seats were further modified to have a hand-operated bulb which can be pressurized to adjust lumbar support. These lumbar support systems are available on eBay and other places.
Although this seat does not have them, it is also possible to fit seat heaters, which are typically carbon sheets that fit under the upholstery. An example is available from Sports Imports Ltd. .
Here is an example seat heater kit from Dorman (part 628-040):
While there are a plethora of aftermarket seats, most of them are unsuitable for taller drivers as the seat cushion is too high.
A related problem is that most aftermarket seats are designed to accommodate large drivers and are thus too wide to fit in the car with the driver centered with the steering wheel.
The stock seats can be mounted with the bottom cushion part resting on, or almost on, the floor.
If you are contemplating using aftermarket seats, be sure they can be mounted low enough in the car to fit your requirements. The vast majority of aftermarket seats are unsuitable for taller drivers in the SL-C, and many of them are also too wide at the top. Don't buy an aftermarket seat without checking the fit first.
The typical way to allow for a taller driver is to recline the seats. If you have a two-piece seat, try it in different recline angles to see if that improves headroom. If you have a single-piece seat, reclining works, but at the cost of raising the front of the seat bottom. This will limit ingress and egress, so choose carefully.
The picture below shows the original one-piece factory seat’s flat bottom, essential for the lowest possible mounting height.
Finally, when considering seats, select seats that will allow shoulder harness to be used at the correct angles as discussed below. If you are using a 5 or 6-point belt, you must have an appropriate hole in the seat bottom, as specified by the belt manufacturer. You may cut such a hole in the stock seats.
The use of seats with high sides will make ingress and egress much more difficult. If you can find a seat that holds you in the seat while driving, but has low sides, it will be more usable, especially on the street. One such seat is the Tillett B5, shown below
Note the low sides, very low seat bottom position, and narrow design. This is one of the few aftermarket seats that fits well into the SL-C.
There are other seats that may fit, but they may need to be modified, and often the cost to modify a seat that is close, exceeds any savings from getting a seat that fits correctly from the beginning.
Seat Belts & Harnesses
The SL-C can be fitted with traditional 3-point belts, or with competition harnesses. You are responsible for selecting and mounting the harnesses in a way that is safe and meets whatever local regulations you may have in your jurisdiction. For example, most US states require street-driven cars to have DOT-legal belts. In practice, this means that the fastening device (e.g., the cam lock, latch link or other connector) needs to meet DOT rules. A few suppliers like Schroth sell DOT legal harnesses for some cars (though not for the SL-C); most of the competition harnesses are not DOT legal.
The pictures in this section show a 3-point, DOT-legal belt system that one builder created. Superlite makes no representation as to legality, suitability for use or any other claim for this installation.
The builder is responsible for selecting and installing a safe harness system that meets whatever rules and requirements to which the car is subject. The belts and their installation are examples only.
When fitting seat belts or harnesses, consider the mounting points, and follow carefully the instructions you receive from the seatbelt manufacturer. In no case should you mount the shoulder harnesses at an angle of less than 80 degrees from vertical (in other words, no more than a 10-degree slope from the top of your shoulder to the mounting point).
Fasteners should be a minimum of 7/16" Grade 5, or as specified by the manufacturer of the seatbelts.
Inexpensive belts can be obtained from suppliers like Crow Enterprizes, RJS, Simpson and others. Lighter, better, and more expensive belts are available from suppliers like Schroth and Willans. No matter where you source your belts, select them with care in terms of the buckle type, whether the adjusters are pull-up or down, whether or not you need to have a DOT-legal assembly for street use, and whether or not you will be using a HANS or similar device.
Note that the factory seats may not have a hole in the seat bottom (as they are not in the pictures on this page). If you use the factory seat and a crotch belt (and you must use one, if you are using a competition harness, as the risk of submarining is very high with a laydown seating position as in the SL-C), you must modify the seat to allow the crotch belt to come up through the seat bottom as shown in the manufacturer’s instructions.
Under no circumstances use a crotch belt that extends over the unmodified seat bottom- this is unsafe and contrary to all manufacturers’ instructions.
The lower seat belt mounts can be put through the floor using 7/16” Grade 5 or higher bolts or the hardware that came with your belts. Put the head of the bolt underneath the car to reduce the likelihood of it catching the floor scraps on the pavement. Also use a 50 x 50 mm 3mm thick steel plate under the bolt head as a shear plate. If these belts are for competition use, check your rules for the sizes and methods permitted for these plates.
In general, you should never use 4-point belts on the SL-C, as they don’t offer a way to stop submarining. There are no approved 4-point belts that are certified for the SL-C. The seating position for almost all drivers in the SL-C is very reclined, and the risk of submarining in a frontal accident is very real. Always use either DOT-approved 3-points, or 5 or 6-point race belts, properly installed.
The inside buckles can be secured through the chassis center tunnel. Drill straight through the chassis and use a long bolt to secure both driver and passenger side buckles.
The pictures below show retractable Seat Belt Mounts and harness mounts created by a builder- these are not part of the standard roll bar, but are shown for those who need to attach belts differently than a wrap around the horizontal bar in the picture. They are simple in concept, however, and can be fabricated and welded to the roll bar as desired.
These are unnecessary if you choose to use competition belts. If you are planning to use competition belts, the shoulder harness ends just wrap around the bar and lock in place- no changes to the bar are needed. The belts in this car were done for regulatory purposes.
Most SL-C builders will use competition belts and will not need to make these modifications.
The optional side panels can be attached using plastic Christmas tree clips or by bonding on tabs that slide under the edge of the main cab. You can then just put a couple of discreet screws at the lower edge to affix the panel to the side of the chassis. These screws in the photo below would blend into the carpet if painted black.
Photo below shows a side panel with tab method of affixing.
Depending on the look you want and the purpose of the vehicle you can create very simple flat panels to finish the door off and provide a surface to mount the interior door locks as shown in the next two pictures.
Fully-shaped inner-door panels are available as an option from Superlite Cars. These continue the line and shape of the dash into the door panels. These panels can be attached to the doors by using plastic Christmas tree clips or traditional screws. The panels need to be test fitted to the vehicle before trimming. It is also recommended that you keep the thickness underneath the door to a minimum. To improve fitment, you may need to grind the lower portion of the door panels down.
When upholstering, because of the tight fit of the door panel at the bottom, it’s usually best to just apply the leather directly to the underneath edge of the door without any padding. Always check for clearance when you are fitting doors and upholstery. Use modeling clay to get a close feel for gaps in doors that you can’t easily see, and allow enough clearance to permit the use of door seals. If the door hits the sill when closed, there will be no room for a seal, and the upholstery, to the extent that it contacts the sill, will be quickly marred.
Rear Bulkhead Panel
The rear bulkhead panel is available as an option. It will need the seat belt boss holes cut into it. It might also need trimming at the top corners where it slides between the body and the roll cage. Also check your door clearance as you might need to cut the main cabin back further in the top corner of the door openings. If this is the case, you might need to extend the rear panel top corners back a little further.
The center console is available as an option. When fitting the center console please ensure you provide the clearance holes necessary at the bottom rear edge where the seat belts need to be mounted.
The console can also be trimmed to bring it back an inch or so, in order to adjust the shifter opening. Be sure to locate the shifter in such a way as to insure shifting comfort. It’s easy to mount it too far forward, ending up with knuckles hitting the dash.
If you have ordered the interior tub option, a specific console is a part of that option.
The roof panel is available as an option.
You can insert both adjustable and fixed vents into the roof panel. Please note that to draw fresh air into the cabin you will need to cut into the inner roof scoop panel and the air vents will need to be sealed to that inner vent to stop water and debris from entering. It’s a good idea for the vents to sit proud of the inner vent surface to reduce the likelihood of water entering through the vent itself.
Most SL-C builders leave this panel closed, and duct cold air to the engine compartment, rather than using it so supply interior cabin air. Here is an example of a builder using the roof scoop and duct to introduce ambient air to the cockpit, controlled by typical automotive air vents, instead of the typical implementation for engine compartment air.
The kick panels are available as an option. These panels slide in the top and are attached underneath the dash with a retaining screw (see Dash section for photo). can be attached so that they are removable to access electrical fuse box, windshield washer bottle etc. The picture below shows a modified kick panel (it has a lift-up flap to reveal controls for a hidden battery charger) covered in leather and Alcantara.
SL-C interior with modified kick-panel. Note tight fit to the door and lower door panel. This piece is needed only when you haven't ordered the interior tub option- it has its own version of this panel.
A Pillar Trim
The A pillar trim panels are available as an option. The rear mounting flange is cut into and sits flush with the dash panel.
The upper part of the pillar must be trimmed carefully to fit the optional roof panel. Some builders have modified the roof panel to extend downward to the A pillar trim, and built up the join area with fiberglass to create a tight, seamless-appearing fit. The picture below shows an A pillar panel that has been trimmed to better fit the roof.
The kit ships with the Brandwood shifter as shown in the photos below. Other shifters from production cars and the aftermarket may be able to be adapted (you are on your own here), but regardless of the type of gear shifter you are installing, please confirm the position by test sitting in the seating position. Be sensitive to the mounting position so your arm isn’t uncomfortably extended when you need to use the upper gate (i.e., gears 1,3,5), and pay special attention to the risk that your knuckles might hit the center console stack when shifting. This usually requires that you loosely install the dash while fitting the shifter.
As a general rule, the shift knob should be in line with the steering wheel to facilitate hand movement from the shifter to the wheel. Begin with that, and adjust as necessary. Remember that the steering wheel can telescope so you should plan to place the shifter after you have power to the column so you can verify clearance.
The shifter can be bolted directly to the center tunnel using fabricated brackets. The photos below show examples.
The shifter kit is supplied with a cable retaining bracket that is bolted onto the rear of the gearbox using the existing tail housing bolts for most transaxles.
There is also an adaptor piece that slides over the end of the Porsche linkage shaft for the G-series of Porsche transaxles.
You should always use insulation on the shifter cables to reduce heat soak and deterioration of the Teflon liner inside the cable sheath.
The factory demo car went through 3 sets of cables before the problem was completely understood and solved. Be sure to route the cables as far as possible from the exhaust, and use Firesleeve or an equivalent barrier to keep heat away from the cables. Multiple heat barriers can be used to create an additive effect. For example, one builder’s SL-C has Aeroquip Firesleeve around the cables, which is inserted into a sleeve of DEI heat wrap, and that assembly is then wrapped in Technofibra for more protection.
Note the routing of the shift cables in the picture above.
You should always test fit door seals for clearance and fit before the body is painted.
Fitting door seals is part of fine-tuning the doors and other body parts. If you add seals after the fact, the added thickness of the seals will usually push body parts like doors out of alignment. This can sometimes only be corrected with bodywork.
The photo below shows an example installation of the door seals.
The arrows on the photos indicate where the rubber door seal starts and finishes. On final assembly the seal should be attached with silicone adhesive to prevent seeping under the seal and into the cabin.
In general, more sealing can be applied to further reduce wind noise. Many high-end production cars use double or triple seals for the ultimate in noise, odor and temperature control. Such an approach can be taken with the SL-C, but care must be exercised to be sure that adding seals does not change the alignment of the doors. Thus, fit the doors with whatever seals you plan to use, rather than adding them after the door fitment is finished.
It is also a good idea to consider using edge trim on all the exposed edges of doors and front and rear bodywork. These seals minimize chafing, look OEM, and protect paint.
Consider using door pulls on the doors so you can pull the doors down from the inside more easily. You can fit recessed handles into the doors, leather straps or aluminum billet pull handles. Many different types of pulls are available from hot rod shops, or from junk yards.
Carbon Fiber Trim Pieces
As an option you can purchase carbon fiber trim pieces from Superlite to dress up your interior.
The following carbon pieces may be available:
- Door Panels, and door panel inserts
- Recessed Door Pulls
- Console Inserts (version 2 console)
- Dash (usually the two binnacles are covered in CF)
- The interior “tub” is also available in carbon fiber
Attached below are photos of some of the factory carbon pieces.
Door Pull & Door Panel Insert