Roof boxes - do they alter the towing dynamics
My out fit is a vw tigian and a elldis affinty 554 . Im quite happy with the set up although the tiguan has, in my opinion , steering that is too light.
If i add a 420 litre roof box, to the tiguan, how will it alter the towing dynamics ?
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I can't comment on your particular car but for some years I towed with two Kia Sorento's on which I used a roof box on our longer trips to Europe and certainly didn't notice any effect on the driving of the cars. There was a slight advantage (other than providing a lot of extra stowage) in those countries with lower speed limits like Germany and Austria I actually got better economy. However that benefit was soon wiped out at the higher speeds allowed in France.
David
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The roof box will undoubtedly have some effect on fuel economy, but it could go either way depending on its shape, size and for/aft location relative to the roof of the car, so it is impossible to pass comment which would in any way tell you very much.
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We find that towing with our Mondeo estate we get slightly more MPG with the top box on, but as soon as we go solo that changes and we get less! Add to that the technical issues of physical size, and shape as Lutz mentions, means the only way to find out for yourselves is to try it and see. However, you'll have to make sure you check on the same journey, with the same wind conditions.............. because these will also affect the results!!!
We now take a top box if we absolutely need to - rather than on every journey as we used to, because there is a problem storing the top box whilst at the caravan so removing it to drive without it whilst on site isn't really an option!
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As others have said when we had a full complement we towed with a rigid roofbox and there was no apparent change in anything. However I didn't like the fact that when not towing it was empty and the car didn't look as good (vanity). I've now got a semi rigid one which I use when necessary. Its made of fabric but that means its easily fitted in literally minutes and you can take it off when you've arrived on site and its fold away to be stored in your car boot (which does seem strange). Google Thule Ranger 90 or see here for a video:
https://www.thule.com/en-gb/gb/cargo-carrier/car-top-carrier/thule-ranger-90-_-601100
There is a cheaper version from a company called Handiholdall which my brother uses and its seems just as good, wished I'd seen it before I got the thule one
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We didn't notice any change at all in the aerodynamics and the caravan towed no differently with or without the roofbox. It certainly didn't 'induce snaking' with a roofbox on. The only thing we noticed was that we got less squashed insects on the caravan front window with the roofbox fitted on the car!!!!
Our caravan has shock absorbers fitted anyway, so is very stable when towing.
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It would raise your centre of gravity but increase the weight of your vehicle favouring the towing ratio.....position is essential to prevent whistling too!
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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!
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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.
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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
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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.
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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
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Remember those wind deflectors from the 60s ,what happened to them ?
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