Thread: Towbars and motorcycle carriers

Hi Lucas,

Prior to buying my d4 last December I was very close to getting a bike carrier myself but was worried about it being on the back of my then VE GTS. In the end I opted for a D4 and made a bike carrier that bolted to the draw bar of my camper trailer.

The D4 tow bar set up appears to be a very good piece of engineering and i cannot see an issue with putting a bike carrier on the back. We now have a 2.5 ton jayco base station and the 220kg plus tow ball weight is no issue so your 155kg bike and carrier would be safe as houses.

There was a post about the tow bar attachment falling out on an RRS which was a bit of a worry however it would seem that this may have been as a result of other contributing factors. I know that I take care to make sure mine clicks in well and it works!

You are going to love the D4!!

i would check with the police to see if its legal

I haven't looked it up, but they are made in Australia and have lights and number plate brackets, so I assume they are legal....

Generally, it can't protrude more than 150mm from the sides, can't obscure the tail lights and can't obscure the number plate (which must be illuminated at night). Have a look at the vehicle standards bit on the RTA website.

I always thought the weight on a tow ball should not exceed 80kg. Can't find a legal reference for that, but I know what it's like trying to hitch a car trailer, and the importance of balancing the load in terms of how the car feels when towing.

Matt.

Originally Posted by irondoc

I haven't looked it up, but they are made in Australia and have lights and number plate brackets, so I assume they are legal....

By no means is everything designed and/or sold in Australia is legal to use in Australia, or in all states. This may well be fine as it does have the extras you mention.

Originally Posted by MC D4

Hi Lucas,

The D4 tow bar set up appears to be a very good piece of engineering and i cannot see an issue with putting a bike carrier on the back. We now have a 2.5 ton jayco base station and the 220kg plus tow ball weight is no issue so your 155kg bike and carrier would be safe as houses.

I can't get my head around the maths, but it seems likely that if the centre of gravity of the bike/rack combination is behind the centre of the tow ball, 155kgs may seem like a lot more.

With a trailer, the weight is straight down through the centre of the ball. From the picture posted, it looked as though the centre of gravity would be well behind the ball, effectively adding leverage to the weight.

Anyone skilled in maths able to comment?

What Wilbur said does need to be carefully considered.

The problem relates to a rotational force (engineering term 'moment').
Basically the further from a pivot point that a force is applied, the less force that is required to achieve the same result. Hence the 'leverage' advantage achieved when using a high lift jack, hydraulic bottle jack, etc.

For those who like the math approach to things, and have the inclination, a good description of the concepts can be found at:
Introduction to Statics: Moments.