Trailer & Tow Vehicle Specifications – How To Correctly Tow Your Trailer
Factors Affecting Towing, Weights and Tow Vehicles
Boating is a great activity that the entire family and friends can enjoy. To ensure safe driving conditions and optimum towing performance, it is important to correctly set up your boat and trailer to the two go hand in hand at keeping you safe on the road. It is the trailer owner’s responsibility to ensure that the appropriate towing set up, load distribution, and tow vehicle are used for safe and legal towing of your boat or cargo.
Towing vehicles vary in capacities and attributes and these variances must be taken into consideration when towing any form of trailer behind your vehicle. It is important to take your time and to check your trailer / vehicle setup to ensure you are safe out on the roads. Failure to correctly set up your vehicle and trailer can negatively affect your towing performance and cause serious damage and injury. If in doubt, refer to a towbar/suspension/towing specialist. This towing guide should be read in conjunction with your vehicle, trailer and tow bar owner’s manuals.
Tow Vehicle Ratings
The number one rule when it comes to towing any form of product behind your vehicle is that your towing vehicle must be capable of towing the combined masses of the trailer, boat and any equipment it carries, this includes fuel.
The towing capacity and tongue weight rating for most vehicles is found in your vehicle’s manufacturers handbook and should always be referred to before any towing commences. You must not exceed the towing limits specified by the vehicle manufacturer.
The tow bar rating and tow ball rating is normally found on the tow bar it’s self, or on a sticker placed on the side face of the driver’s door near the door latch. The tow bar and tow ball fitted to your vehicle must have the correct capacity equal to or higher than the package you are towing. This is extremely important safety matter.
The Tongue Weight (down force) rating of your tow bar must be equal or greater than the Tongue Weight (down force) of your trailer you are towing. Your specific vehicle set up and other factors (especially tow ball height) will also add to the variation of the tongue weight.
Quick Tips To Remember
- Generally speaking, the bigger the boat the larger the tow vehicle/tow bar rating is required.
- Larger Boat/Larger Car – Correct
- Smaller Boat/Larger Car – Correct
- Smaller Boat/Smaller Car – Correct
- Larger Boat/Smaller Car – Incorrect
Boat Trailer Packages
The tongue weight (down force) is the weight that is transferred on to the car tow ball from the trailer. Most people will be familiar with the towing capacity of the car or tow bar itself; but not so familiar with the Tongue Weight Rating. This factor is very important and can decide how your car performs on the road when towing.
Measuring Tongue Weight
Tongue weight can be measured simply by placing a set of heavy duty scales under the coupling at its normal tow ball height. If heavy duty scales are not available the tongue weight can be obtained by using a public weigh bridge however this method requires the trailer to be weighed twice. The first weigh is with the trailer and load disconnected from the tow vehicle and standing alone on the weigh bridge (actual ATM). The second weigh is with the trailer and load coupled to the tow vehicle and only the trailer axle group on the weigh bridge (actual GTM). The difference between the two weights is the Tongue weight.
As a rule the tongue weight should be between 5% and 10% of the combined weight of the actual tow package (ATM). You must also be aware however, that some car and towbar manufactures’ can recommend a Tongue Weight range different to the industry standard.
Example of Tongue Weight Calculation
Weigh No 1 – 2400kgs (Actual ATM weight)
Subtract Weigh No. 2 – 2200kgs (Actual GTM weight)
Difference 200kgs (Tongue weight)
Tongue Weight Percentage Calculation
(Tongue Weight ÷ Actual ATM) x 100 = TW %
(200 ÷ 2400) x 100 = 8.33% Tongue Weight which is within the industry standard
Factors That Can Affect Towing Weight
- Position of the boat on the trailer.
- By moving the boat forward or back on the trailer your tongue weight will change.
- Moving the boat further forward will increase TW.
- Moving the boat back will decrease TW.
Stowage of gear in the boat
Your boat should not be used to transport heavy items such as camping gear and wake ballast. An allowance has been made for the boat to carry normal water sport items and these should be placed in the boat over the axle group.
- Items placed forward in the boat will increase the TW.
- Items placed at the rear of the boat will lighten the TW.
Tow ball height
Your tow ball height should be such that the trailer sits level when fitted to the tow vehicle. As a guide the centre of the tow ball should be between 400mm and 450mm from the road surface when measured on level ground with the trailer on the vehicle. THIS IS OFTEN GIVEN LITTLE ATTENTION YET IS A SIGNIFICANT FACTOR.
Large boats with large Tongue Weights may compress the tow vehicle’s suspension. In these instances, suspension upgrades, adjustable height tow balls or other towing upgrades may need to be considered to ensure a level trailer-to-vehicle connection. Similarly, any car with soft suspension will have their towball height decreased under load, and this will affects TW.
Tips To Remember
- Increasing the ball height will increase the TW
- Lowering the ball height will decrease the TW
- As these factors are variable, it is the responsibility of the vehicle owner to ensure their vehicle is capable of towing their boat and trailer package; and at a level height; and any additional load is not excessive. A tongue height of a vehicle is an area that may need expertise from towing/suspension specialists.
Fuel Level Of Your Boat
Most centre mount engine boats have a fuel tank located at the rear of the boat. The amount of fuel in the tank will greatly affect the tongue weight.
- A full tank of fuel will lighten the TW.
- Lower fuel levels increases the TW.
- V Drive or rear engine mount boats generally have a fuel tank located above the axle group and as a
result the fuel level does not affect the Tongue Weight as significantly as centre mount boats.
Outboard Boats/Fish Sports Trailers
Generally speaking, boats with Outboard Motors fitted to them are matched to our Fish and Sports Range of trailers. The Outboard Motor creates are large variable load at the extreme rear of the package that varies from dealer to dealer, brand to brand, horse power to horse power. All of the previously discussed factors still have the same effect on outboard packages, however to provide additional adjustment to counter this (if required), this range of trailers comes with an adjustable wheel base. By moving this wheel base towards the rear, the TW will increase; conversely, moving it towards the front with decrease the TW.
Important Safety Tips & Tricks To Remember
Towing Your Trailer
Towing requires a greater degree of knowledge and skill than normal driving in addition to the
driver’s legal responsibilities.
When towing, you should always:
- Allow for extra length and width when entering traffic
- Apply the accelerator, brakes and steering smoothly, especially in wet or slippery conditions
- Maintain extra space than normal between you and the vehicle in front to allow for a longer stopping distance
- Engage a lower gear in both manual and automatic vehicles to increase vehicle control when travelling downhill
- Allow more time and a greater distance in which to overtake. When towing, your vehicle’s capacity to accelerate is reduced
- Be aware that towing can be more stressful than normal driving and is more likely to cause fatigue. Therefore, more rest stops should be planned.
If your trailer begins to sway, try to remain calm and avoid the natural instinct to apply the tow vehicle’s brakes. Don’t try to counter or correct the sway by steering, alternatively hold the vehicle steady and try to stay in the lane. If you trailer is fitted with Electric brakes, gently apply them using the manual control on the tow vehicle’s fitted electric brake controller. Otherwise, where conditions
permit, continue at a steady speed or accelerate slightly until the sway stops. When a condition of sway has been corrected, slow down and pull off the road safely. Check that any additional load is correctly distributed within the trailer and identify what caused the sway.
External factors such as cross winds and overtaking trucks and buses can create significant side thrust forces which can increase the chance of trailer sway.
If you require any further information or advice, consult a towing/suspension specialist
Products Related To This Article
Trailer Tow Balls
This excellent user guide was kindly put together by the folks at Easytow Boat Trailers. To download a copy of this guide, TowVehicleSetUpGuide2013