Roof boxes - do they alter the towing dynamics

Oh dear I knew i'd be entering into the lions den by mentioning the towing ratio somebody would quote the obvious ;-)

Maths is still maths so by increasing the weight it still changes the ratio!

No it doesn't. It's the kerb weight of your car that matters as stated by the manufacturer. If the kerb weight is 2000kg, it will still be 2000kg even with 6 roof boxes on top. 85% of your kerb weight will always be the same figure.

I have to agree that it is not going to change the towing performance. If you have a hatchback or estate and have the box finishing near the back of the car it might improve the airflow and give you a small increase in fuel consumption.

Probably the most noticeable effect will be keeping dead flies off more of the front of the caravan.l

Deleted User by, posted in error

peedee

Not quite the same set up as you are talking about, but I tow a Knaus Starclass with a Touareg which has a spare wheel mounted on a roof rack.  Anything less aerodynamic, I can't imagine! It makes no difference whatsoever, other than for a slight increase in fuel consumption.

I can be less aerodynamic than you! We tow a Swift Charisma 230 with a VW Tiguan and stopped at our French Hovel on the way to Spain in December just past to stick 2 bikes up on the roof bars of the car. Reduced the braking effort on the descents in the Pyrenees and probably added 5%-7% to the diesel consumption. Glad to be able to drop the bikes off in France on the return leg because we drove from Newhaven to Scotland on the day of the violent winds, 24th February! Turning onto the A27 dual carriageway from the Newhaven exit and struggling to reach 40mph as the headwind encountered Swifty was not very pleasant!

Steve

Remember those wind deflectors from the 60s ,what happened to them ?

Melted down, recycled into Top of the Range Caravans I suppose 

Windslammer I think was a brand name. Good in theory but something else to add to the caravan list and not everyone had access to wind tunnel to optimise the flow.