348 Three-Point Seat Belt Conversion

This thread will show you step-by-step how to convert your US-spec 348 (with mouse belts) to a three-point setup. Total cost is under $25, it only takes an hour or two, and it is fully reversible.

The basic concept is to convert the existing shoulder belt into a center-mounted three-point belt. The end of the shoulder belt is anchored on the inboard side of the seat bottom, and a sliding male belt clip is added that mates with a female latch on the outboard side. The belt is detachable at the inboard anchor, so that TS owners can still get the belts out of the way while stowing the roof panel. Other than the sliding belt clip, the mod uses the existing seat belt hardware.

To give credit where due, in the course of researching this mod I came across this post from No Doubt, circa 2005: http://www.ferrarichat.com/forum/135394345-post9.html. He outlined the concept, and suggested it could be implemented simply by swapping the driver and passenger seats. I tried that, but was not able make the swap due to interference between the seats and the center console. Thus this slightly more complicated method…

There are a few minor issues with this mod:

1. The outboard mounted female belt latch projects above the height of the side bolster. It makes getting in and out of the car a little bit (more?) awkward.

2. The stock shoulder belt is barely long enough. When I’m buckled in, I can only lean forward about 6” before it reaches the end of its travel. If you are a very large person, you may not fit.

3. There ended up being minimal clearance between the inboard seat anchor and the center console on the passenger side – I can barely get a finger in to disengage the belt. On my car, the driver's side is fine, so your mileage may vary. Since you only need to disengage the inboard latch when you stow the roof panel (if you have one), I consider this to be only a minor nuisance.

Disclaimer: The information in this thread is for information only. I strongly recommend that you do not modify any of the safety equipment of your car, including the seat belts. If you choose to make any of the modifications described in this thread, you do so at your own risk.

- Eric
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The key parts needed are the sliding belt clips. Search ebay for “seat belt buckle alarm stopper eliminator Ferrari”. They are available from several different vendors. Expect to pay around $10 (including shipping) for the pair.

Optionally, you can add belt web stop buttons to hold the sliding belt clip at a convenient height when the belt is unbuckled. I bought mine here ($13 including shipping): https://www.gotbelts.com/mounting-hardware-misc/m.products/84/view/21.

You will also need a couple of long (14”) zip ties.

Tools needed are:

6 mm hex tools (standard and ball-end)
Med Phillips head screwdriver
17 mm socket
4 mm hex tool
8 mm deep-well socket
Small vice grip (6” needle nose, or similar)
Magnetic pickup tool
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Remove the seats from the car using the 6 mm hex tools. Search F-Chat for details on how to do this.

Once the seats are out of the car, lay them face down so that you can access all of the hardware on the sides and bottom. Remove the leather trim panels from each side of the lower seat assembly (2 screws for each panel). You won’t be able to reinstall the smaller trim panels from the inboard sides, so bag and tag them for storage.

The details of the stock seat belt hardware are called out in the photos below. Fortunately, all of the mounting holes are symmetric from one side of the seat to the other, which is what makes this mod possible.
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Remove the lap belt assemblies from each seat. You will need to use a 17 mm socket and a 4 mm hex tool.

The hardware removed is shown in the photo. Carefully bag and tag this hardware for future reinstallation.

The lap belt hardware weighs almost 3 lbs per side, so you do get a little bit of a weight savings with this mod.
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Using a 6 mm hex tool, remove the shiny bracket that holds the microswitch electrical connector. After the bracket is removed, reinstall the hex fastener, as it also is used to help secure the black mounting plate.

Next, using a 17 mm socket, undo the bolt that holds both the microswitch and the male belt latch. The microswitch assembly is now free. Bag and tag it for future reinstallation.

Reinstall the male belt latch and associated bolt onto the inboard side of the seat, in a mirror image to the original installation.

Note that the electrical connector bracket (which is not being reinstalled) includes a keying pin to properly orient the male belt latch. Since you don’t have this keying feature, simply align the male belt latch so that it is perpendicular to the edge of the black mounting plate.

Repeat these steps for the other seat.
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Using a 17 mm socket, undo the bolt that holds the female belt latch, and reinstall in a mirror-image position on the outboard side of the seat.

Repeat for the other seat.
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Reinstall the outboard trim panels for each seat using the two screws.

Since the lap-belt guide bar was removed previously, the “long” end of the trim panel will be free with nothing to attach it. I solved this by simply zip-tying the flat metal hook on the trim panel to the seat adjustment bar. The zip tie passes between the seat bottom and the seat rails.

As mentioned earlier, the inboard trim panels will not fit. You could alter these trim panels to allow them to fit, but since they are not really visible when the seats are in the car, so I chose to leave them off.
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Moving on to the car itself, the interior trim panels along the rear shelf need to be removed in order to access the shoulder belt inertia reels.

The main trim panel is secured using two studs that poke through into the engine bay. They are located on each side of the firewall between the coolant tubes. As shown in the photo, use an 8 mm deep-well socket to remove the nuts. Each side also has a small flat washer, which you can remove using a magnetic pickup tool. Once the nuts/washers are removed, the main trim panel can be pulled free of the car. It is also held in place by two press fasteners, so it may take a little bit of force to remove it.

After the main trim panel is off, you will be able to access the two screws (one on each side) that secure the upper leather trims. Remove the screws and push the upper trim pieces up and out of the way – you don’t have to remove them completely.

You will now be able to access the two screws that attach the cover for the inertial reels. Remove these two screws and remove the cover. You should now have full access to the shoulder belt inertial reels.

I believe that the interior trims may vary across different models, so the exact procedure for your car may be slightly different. But the basic steps should still apply.
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Fully extend the belt from the inertia reel, and temporarily secure the reel in place using vice grips.

The belt threads through a slot in the inertia reel, and is held in place by a steel bar that passes through a loop in the webbing. To remove the belt, first pull the steel bar away from the reel. I used a small screwdriver to help pry it out. When the bar is free, pull a few inches of the belt through the reel, and then slide the steel bar out from the loop in the webbing. (In the photo, the steel bar can be seen partially pulled from the loop at the end of the belt.)

Next, pull the belt through the other way until it is completely free of the inertia reel. Since there are several layers of webbing in the belt-end loop, you will have to do some wiggling to get it through the slot.

With the belt out of the car, thread the sliding belt clip onto the belt. Again, because of the thickness of the webbing at the loop end, it will take some force and some wiggling to get the clip onto the belt.

When you install the sliding belt clip, make sure it is oriented as shown in the photos. The metal part of the sliding belt clip must go on the side of the belt opposite to the red latch release button.
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Reattach the shoulder belt by threading it back through the upper anchor, and back through the slot in the inertia reel. Reinstall the metal bar into the belt-end loop, and secure the belt by snapping the metal bar back into the inertia reel. Remove the vice grips and allow the belt to retract.

Important: When you reinstall the belt, you must flip the belt over from its original orientation. As shown in the photo, when reinstalled, the metal part of the sliding belt clip must be facing away from the firewall, and the red latch release button on the buckle must be facing towards the firewall. If you don’t orient this properly, you will end up with a twist in the belt when it is fastened.

Repeat steps 8 and 9 for the other shoulder belt.
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Reinstall the interior trim panels by reversing the procedure from step 7.

Reinstall the seats in the car.

Secure the buckle at the end of each shoulder belt to the male belt latch at the inboard side of each seat.

Add a web stop button to each belt to hold the sliding belt clip at a convenient height. With the belt in the retracted position, the stop button should be positioned about half-way up, as shown in the photo. If you try to put the stop button too high, it will interfere with the tensioning of the belt when it is buckled.

To install the web stop button, mark the location on the belt, poke the button through the webbing (it will go through easily), snip off the pointed tip, and then press fit the donut to secure it. The web stop button does create a hole in your belt, so if you really want total reversibility, you can do without it.

If you haven’t already done so, you will need to disable your seat belt warning lights. Search F-Chat for instructions on how to do this.

That’s it! Crack open a cold one, and admire your handiwork…
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I'm not qualified to perform an engineering analysis on this, but the seat/track assemblies should be designed to handle the forces from the shoulder belt.

The fixed anchor point (the one that was re-positioned in Step 4) was provided by Ferrari in case of failure of the automatic belt system (see pages H-16 and H-18 in the owner's manual). This anchor point is mounted to the seat, not to the car chassis.

My assumption is that the forces through the seat/track assembly are approximately the same for the three-point setup vs the stock belts configured for "manual emergency operation".

- Eric

 

Just a preference for a "standard" belt arrangement...

Since I have owned my car, I have always used the belts in the manual mode, i.e., mad-mouse disabled. This requires separately fastening the lap belt and the shoulder belt. Plus my lap belts did not retract strongly, so I had to either manually feed it back in, or leave it laying on the floor. Basically, I just got tired of messing with it.

- Eric

 

I originally had the same concern. For what it's worth, the parts I bought came in a package that said "genuine safety buckle." After inspecting the parts, and cutting one of them up, I could not find any difference in materials or construction from a standard automotive buckle. Also, after having disassembled and reassembled the entire seat belt system, my belief is that the sliding buckle is far from the weakest link in the chain.

Having said that, if anybody has access to real engineering data on this stuff, I'd love to see it.

Finally, my original disclaimer still applies -- if you do this, it's at your own risk.

- Eric
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