Does fitting a tow bar affect my insurance?

If you have fitted, or are planning to fit a tow bar to your vehicle, you need to inform your insurance company in order to prevent your insurance policy being invalidated. The insurers need to be informed of any modification made to your vehicle as this will affect your insurance policy.  

Fitting a tow bar enables you to tow trailers or caravans, which increases your vehicle risk.

Many companies do add charges, and there are several that offer specific policies for caravan owners.
There is the possibility you incur a small policy amendment fee, although there is no industry standard for this, and will depend upon your current insurer.

Where can I have a tow bar fitted?

You have the option to specify a tow bar to be fitted by the vehicle manufacturer, although in practice many dealerships will involve a specialist outsourced fitter as this is a specialist area they do not participate in.

There are many specialist fitters and auto-electrical engineers that have a premises set up for tow bar fitting.

Is a mobile tow bar fitting service available?

Mobile tow bar fitting is a popular choice as it provides time flexibility and is often popular in rural areas where travelling to a fitter and leaving your vehicle for several hours is problematic.

Most mobile fitters carry all the necessary tools and equipment to supply and fit a tow bar and harness, they can also perform the reprogramming necessary on some vehicles.

Can I fit a tow bar myself?

Self-fitting is an option, provided you are confident enough. Most harness kits come with installation instructions, although a sound knowledge of vehicle electronics will give you a significant advantage.

The bars themselves have a variety of options with swan neck, detachable and swing out options available for many vehicles. Most tow bar kits come with fitting instructions and it is important select the appropriate harness arrangement for both the vehicle and the tow bar assembly.

Lower cost Universal Kits often have unprepared wiring so you will need to cut and attach cabling, as well as ensure the relays are the appropriate type for your installation. As the term Universal suggests, often the same components are in the box, which may or may not be appropriate for your vehicle.

Many tow bar and harness suppliers are happy to give advice for self-fitting and there is a wide library of YouTube information. As with all things, buyer beware, as once a tow bar harness fitment has been started, if it proves to be incorrectly installed or not the right kit for your vehicle it will usually take a professional (or in the worst case the main dealer) to put things right.

Another consideration is maintaining a constant charge / supply to the vehicle battery. As installation can take several hours it is commonplace for vehicle batteries to run down, or in some instance to suffer a power dip caused by a surge in electrical current drawn. It is recommended to fit a suitable Battery Support Unit whilst installation takes place. This both protects the systems from spikes and power dips, but also helps keep the battery charged.

Why is maximum towing and Tow Ball (nose) weight important?  

This will indicate the maximum weight the vehicle manufacturer believes your vehicle can tow, which becomes the legal towing limit. Towing above the vehicles maximum towing weight is illegal as it poses a significant danger to both the vehicle occupants and other road users, and pedestrians.

How do I work out the maximum towing weight?

The maximum towing weight is a specific weight per vehicle, and is usually stamped on the Vehicle Identification Number Plate (VIN Plate). These are usually an alloy plate, although some are stickers, and a commonly located on the door pillars, or under the bonnet. The details are also available in the vehicle handbook.

Once located, the VIN usually shows 3 or 4 weights that you can use to calculate your maximum towing weight. The first is usually the Maximum Allowable Mass (MAM) which is the gross vehicle weight when full of occupants, fuel and payload. The following number will be the gross train weight, which is the combined (MAM) of the vehicle and a trailer. The next number is the maximum axle load for the front and the final number is the maximum axle load for the rear.

To calculate your maximum towing weight, you’ll need to subtract the gross vehicle weight from the gross train weight.

It is important to remember, not all vehicles are permitted by the manufacturers to have a tow bar fitted, for the purposes of towing. Some (EVs and hybrids) only permit the fitment of a tow bar for cycle rack purposes only. As the onboard electronics and systems are not set up for towing trailers. It is vital to remember this when purchasing a second hand vehicle with a tow bar already fitted, as you will not know if this has been fitted just for a cycle rack, and could cause considerable damage to your vehicle if used for towing.

Although there is a maximum weight, this does not account for height and when you add the height of a caravan the maximum weight will be lower.  As a general rule of thumb, the 85% rule should apply.  There are some good websites for working this out, including The Caravan and Motorhome Club. 

The 85% Rule

The '85% rule' is not legislated, but a recommendation that states that the weight of the loaded caravan should be no more than 85% of the cars kerbweight. Those who are experienced caravanners may go up to 100% of the cars kerbweight, but no-one should tow a caravan that is heavier than the towing limit of the car.

I’ve found the VIN Plate but the first number is 0000 or blank?

Generally, this indicates the vehicle is not designed for towing, although it is worth checking with the vehicle manufacturer or specialist tow bar fitter, as sometimes this can be misleading.

What are the advantages of using a vehicle specific harness?

By effectively by-passing the vehicle electronics with the use of a Universal kit, the trailer or caravan is essentially hidden from the towing vehicle. Whilst a Universal kit will usually enable the trailers indicators and brake lights to function, along with other convenience functions such as parking sensors to cut off, and in some, but not all cases the fog lamps to work, a universal kit (or by-pass) kit by-passes the ADAS systems and other systems such as, cruise control and lane assist.

Most modern vehicles will now adapt themselves when towing, with the engine cooling system and ABS braking electronics both adjusting to having to work harder with the greater load. Many vehicles now have a Trailer Stability Program (TSP) fitted as standard. This is activated when the vehicle specific harness is fitted, and the vehicle reprogrammed, this assists the vehicle in reducing and correcting a ‘snaking’ trailer.

Systems like Adaptive Cruise Control will be able to reset the safe distance between vehicles as it will be aware of the trailed unit.

In conclusion

In our opinion, there seems little sense in purchasing a vehicle with so many additional safety and beneficial features, to then by-pass these when fitting a tow bar. Usually when people tow a caravan or trailer tent, they have their nearest and dearest with them, and why would you put them at unnecessary risk by disabling or bypassing some of these safety features?

If, as a vehicle owner you were asked to sign a fitters indemnity form acknowledging you were offered a fitment that would enable all of the safety features on your vehicle to still function when towing, but you elected to have these systems by-passed as it’s a bit cheaper, would you sign it?


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