Bike Wobbles

[WillH]

We had a good question from Russell Millar about the impact of attaching bikes to the back of a caravan. Our 'guru' provided a detailed answer. What experiences do you have of attaching bikes on the back of your van?Q:Following up from your recent piece entitled ‘Rack and Roll’, I feel eager to add that my wife and I spend most of our Spring, Summer and Autumn touring on the continent. During our travels we see many caravans with bikes attached to the rear of caravans and have yet to see any form of instability taking place. I look forward to your comments with interest. Russel Millar, by email. A:

Research conducted at the University of Bath with Bailey of Bristol has established beyond any doubt that a towed trailer is far less stable when heavy objects are stowed at its extreme ends. To confirm this claim, the University’s automotive specialists built experimental trailers (like the one shown here) which permit weights to be mounted at different points along their main central spine. When towed on a test track, a trailer’s deflections are then measured using scientific equipment and the effect of different load distribution positions is recorded and analysed.

The tests clearly established that when a heavy object is placed at the rear of a trailer or caravan, a potentially dangerous situation arises. If lateral deflections occur during towing, this instability is far harder to correct than it is when substantial weights are located close or over the axle.

This feature can also be experienced by trying to stop the lateral movements of a horizontal weight-training ‘dumb bell’ that you hold and swing back and forth. When heavy weight discs are mounted near the centre of the bar, it is really quite easy to stop swinging side-to-side movements.

However, when the exercise is repeated with the same discs mounted at the extreme ends of the bar, suppressing the movements is very much harder. Even though you might not have witnessed instability, Russell, towing when a caravan’s weight distribution ignores the laws of physics creates a very unstable arrangement.

Let me know if you have any experiences of 'bike wobbles'!