Harness installation

Choosing a harness

The rules are pretty much the same across sanctioning bodies (ARA/CARS/NASA/SCCA), a five, six or seven point unmodified safety harness of proprietary manufacture, meeting the specifications below, shall be fitted for both crew members:

- FIA Standard 8853/98 or 8853/2016

- SFI 16.1 Specification

- SFI 16.5 Specification

FIA harnesses are usually valid for 5 years whereas SFI are only good for 2 years. Given the price difference, it is usually more cost effective to go with an FIA harness. Harnesses come in 2" or 3" width, they have to pass the same tests for certification so a 2" is as strong as a 3". 2 inch harnesses sit better on Hans devices, they offer better adjustments and pressure where it is needed. So we definitely recommends 2" harnesses.

All harness systems must be capable of being released through one latch, most modern harness use a camlock. Most of them have pull down belts, you might want to consider pull down lap belts adjustments that make it much easier to tighten the belts once in the seat. Top of the lines harnesses will also have a anti-submarine belt adjustment that will be easier than can be done without having to go under the seat for adjusting which is very convenient if the seat is shared between several individuals (especially in endurance racing or rally with different codrivers).

Below are pictures of a 6 and 7 points harnesses (5 points are being phased out due to their inferior performance in preventing submarining).

Good instructional video from Simpson on belts and other restraints:


The ARA rule 2.3.4. says 'The locations of the safety harness anchorage points must be as shown in the SFI Seatbelt Installation Guide (available from www.sfifoundation.com), section 6.2 (Installation) of FIA Appendix J, Article 253, or the harness manufacturer’s instructions. If the manufacturer’s instructions are used, they must be provided upon demand at scrutineering'.

Make sure the seatbelt attachment points are going to give the right angles to the belts. Check your harness manufacturer manual for correct angles and mounting instructions, see below some examples from the Schroth installation manual and the FIA 253-61 diagram on seatbelt angles.

Using eye bolts will clip on buckles will be much easier to install and get the correct angles than bolts on that will keep the belt in a fixed position.

The FIA is updating the belt angles for 2023 with a minimum distance of 90mm between the seat and the pivot point of the belt. 

Anchoring points

The most common mistake is to attach the belts to the seat mounts or support. The other common mistake is improper anchoring points when stock mounting points are not used. Here are the main rules about the anchoring points:

Shoulder belts

From FIA Article 253 (2020 edition): 'The shoulder straps may also be fixed to the safety cage or to a reinforcement bar by means of a loop, and may also be fixed to the top anchorage points of the rear belts, or be fixed or leaning on a transverse reinforcement welded between the backstays of the cage (see Drawing 253-66) or on transverse tubular reinforcements according to Drawings 253-18, 253-18B, 253-26, 253-27, 253-28, 253-28B, or 253-30.

In this case, the use of a transverse reinforcement is subject to the following conditions :

It is typical to have a 10 degree angle, make sure you have your seats test fitted in the car before your cage builder welds the harness bars in as they will have to match with the height of the holes in the seat for the proper angle once the driver is seated.

Make sure your belts are wrapped properly, you are supposed to go 3 times through the buckle. Check the tutorial below:

Lap belts

The rules state that 'It is prohibited for the seat belts to be anchored to the seats or their supports.' The easiest solution is usually to re-use the factory mounting points in the chassis for the lap belts. However, on some cars, the 3 point belt anchor might have been attached to the factory seat. In this case, it is necessary to create a new anchoring point. The rules specify 'For each new anchorage point created, a steel reinforcement plate with a surface area of at least 40 cm2 and a thickness of at least 3 mm must be used'. 

The configuration below uses the stock anchoring point of the car, note that the mounting point near the transmission tunnel also sandwiches the seat mount. This is a legal installation.

The install below taking from this YouTube video of a Ford Fiesta build (https://www.youtube.com/watch?v=dgvur5SlUEY) shows a welded plate attachment point

Anti-submarine belts

This is where we see the most mistakes with incorrect mounting points or angles. These belts are also commonly called sub belts or crotch belts. Once again, the rules state 'It is prohibited for the seat belts to be anchored to the seats or their supports.' so you need different anchoring points than the seat mount or bars the seat is attached to. You cannot use any of the components in the red area in the picture below to secure your lap belts or anti-submarine belts (not that any of those components would offer a correct mounting angle anyway):

The angle for a 6 point harness is about 2" rearward of the hole in the seat as shown in the pic below from the SFI Foundation installation guide.

If you have a 7 point harness, the 7th point must be installed like a 5 point belt anti-submarine belt, 20 to 25 degree FORWARD of the seat hole (not behind like the 6 points).

In the 2022 revision of FIA Article 253, a new confusing diagram 253-61-a has appeared that shows acceptable crotch belt angles from 20 degree forward to 90 degree rearward (see picture below left). This does not mean that you can attach a 6 point harness with a 90 degree rearward angle as depicted by the green lines in the picture below in the middle. In case of an impact the harness would tear through the seat hole and release tension (red curved line) allowing the occupant to move and most likely sustain back injuries. The only reason we can think of the 90 rearward angle is for some 7 point harness configuration where the anchoring points of the crotch belts are aligned with the should mounts like in the testing described in SAE papers 2015-01-0739 and 2015-01-0740. At this point we are not aware of any manufacturer providing belts requiring those angles for saloon cars.

A common option is to use an eye bolt with a washer and a backing plate under the floor. You can find eye bolts at http://www.jegs.com/i/G-FORCE/471/109L/10002/-1 and backing plates at http://www.jegs.com/i/JEGS-Performance-Products/555/70017/10002/-1) for submarine belt mounting.

Note that the bottom nut might still be exposed to impacts and might require additional underbody protection.

Subaru GD chassis have a reinforcement just under the seat that will protect the bolts but might require the backing plates to be bent to conform the to the shape of the reinforcement depending on the location of your eye bolts.

A better option is to have a dedicated bar (as shown below) that is welded to the chassis like the seat mounting bars. This way you don't rely on the floor pan for securing any belt. You just loop the anti-submarine belts around the bar like you would do for the shoulder belts. This is particularly useful on older cars like Subaru GCs that don't have any floor protection and let the nuts and backing plates exposed under the car.

Common issues

Here we list few issues that have been seen in forums or at tech.

Counterfeit harnesses

There have been a number of counterfeit harnesses over the years, most of them are sold on eBay. Be careful to get your harnesses from reputable vendors. There is a viral video of a crash with a counterfeit Sabelt harness below. Make sure you get quality hardware 

Improper mounting points

Improper anchoring points include using the seat mounts or bars to secure the belts, or not using the proper reinforcement plates.

On the picture the nut is welded directly to the floor without backing plate, this is not safe or legal.

Here the 2 crotch straps of the 6-point harness are secured to the same anchroring points. Two anchroring points 4 to 6 inches apart should be used.

This lap belt mount is not secured to a mounting point that is welded to the chassis or sandwiched through the chassis with a backing plate of 6in2 and 1/8" thickness.

This is a proper lap belt anchoring point (often necessary for modern car on the transmission tunnel side where the stock seat belt is actually attached to the seat and does not provide an anchoring point on the chassis). The place is welded to the chassis with a welded nut on the back to hold the eye bolt. The weld ring on top of the eye bolt in the picture below is the inner anchor point for the pin stand tube in the rocker. 

Photo courtesy of Dave Clark.

The picture to the left shows an example of an improperly mounted crotch belt. First the angle is wrong being mounted in front of the seat instead of 20 degrees rearward, second the space between the mounting points should be 4 to 6" and finally straps are not allowed to pass over the seat but have to go through the seat as the FIA rule below states:

Improper angles

This is most commonly seen with bolt-in brackets where the brackets are not oriented properly as shown in the examples from the Schroth installation manual below:


Unsecured locking bale

The rules state 'If the manufacturer provides for safety wiring the locking bale to prevent accidental unfastening of the belts from their anchorage points, then it shall be necessary for the all such components to be safety wired.'

People often forget to re-secure the locking bale after they service their belts, especially on the sub-belts that are hard to reach under the seat. A cotter pin / split pin or safety wire must be used to prevent the snap-on bracket to open (picture source: Schroth installation manual)

Expired belts

This sounds stupid but the most common cause for failing tech is an expired belt. FIA certified belts are on calendar years and they expire on Dec 31 of the expiration year written on the belt, but some belts expire on a specific month which can give some surprises mid-season if you forgot about it. Make sure you check the dates, and especially when you buy new belts, make sure that all the tags have the exact same date!

Damaged harness

Always check your harness for possible damage (see picture from the Schroth installation manual below). Sun exposure or chemical spills can also discolor and alter the strength of the harness and require replacement. 

Another issue is when using a seat mount bracket that is not compatible with the seat lap belt holes and it causes a point of laceration with the belt as shown below (source: Schroth installation manual)

Remember that harnesses should only be cleaned with fresh water and never dried up with forced heat (picture source: Schroth installation manual).