29th March, 2019

How to retro-fit seat belts

When the three-point seat belt was introduced in 1959 it saved lives overnight and changed road safety forever. With occupants of cars travelling belt-free or just wearing a simple lap belt at the time, Volvo’s introduction of the patent-free, three-point safety device is reported to have saved at least one million lives worldwide.

Of course, today, not all classic cars are fitted with three-point seat belts and it’s a source of ongoing debate with enthusiasts whether to retro-fit seat belts to their vehicles. With the argument of aesthetics and keeping originality to one side, the cost of fitting can be prohibitive for many.

In this guide, we look at ways you can fit seat belts to your car at home, whether it be for a vintage car without seat belts or to replace a lap belt with something safer. We recommend that you have moderate mechanical knowledge and can weld to a safe standard before tackling this task.

To do this, you’ll need a tape measure, protractor, drill, spirit level, marking tool, welding equipment (to make the safety brackets), time and patience.

The first stage is to look for the current or possible mounting points within your car. If your vehicle has a wooden frame (predominantly pre-war) or another material, then this is harder than traditional metal framed cars. Regardless of what your car’s frame is built from, you must make sure it’s structurally sound as there mustn’t be any degrading of the car’s body within at least 30cm from the mounting points. This is a MoT requirement, but if your car’s exempt we recommend sticking to this safety measurement.

Did you know that fitting front seat belts became a legal requirement for UK registered cars built from October 1964, but it wasn’t compulsory until 1983?

Secondly, you should then look at the feed angle of a three-point seat belt and measure it up within the cabin. The feed angle is the angle where the belt is anchored and feeds over an occupant’s body. If the feed angle is too low (mounted in line with the bottom of the seat) then it will push the lateral force down the driver and passenger’s spine. But if the feed angle is just higher than the top of the seat (and an adult’s shoulders) then it will push the lateral force in the direction of travel, which is much safer. Your instruction manual should recommend feed angles, or contact the supplier if you are unsure.

Did you know that The Royal Society for the Prevention of Accidents state that three-point seat belts are safer, but wearing a lap belt is far better than wearing no seat belt at all, because the greatest risk of injury to car occupants in an accident comes from being thrown about inside the vehicle or being ejected from it?

If you’re fitting lap belts, then the same rules apply. You must ensure correct mounting to make sure that they’re secure. If the points are too high up, then they are likely to dig into the stomach rather than lower in the hip area.

Once you have your mounting points measured and marked up, it’s then time to devise a mounting point and/or a plate. Creating a safe, secure and large enough welding patch to your car is crucial to give the belts an anchor to the body of the car. Once you’re happy that the points have the right feed angle, as well as not placed within a 30cm radius of rust or degrading, it’s then time for fitting.

Most seat belts come ready to mount, depending on the product, but always check with your supplier. Before you attach the seat belts, we recommend that you do a quick test to check the belts will be flush with each occupant’s body and that there aren’t any kinks and knots.

Did you know that if you’re involved in an accident then you should also replace your seat belts as they can be weakened and won’t perform to the same safety standard again?

If you’re looking for help, advice or parts then there are many specialists that can assist. We’ve found that Quickfit Safety Belt Service has a range of belts that have been designed to be period-correct so that your aftermarket alterations look like they belong. If you’re looking to install seat belts but don’t want to do it yourself, there are companies that can help, including Seat belt Services.

Have you ever fitted seat belts to your own car? Let us know if you have any hints and tips in the comments section below.