I'm thinking of buying a roof box but have never driven with one. For those who have, what are your experiences, opinions, prejudices, etc.
I'm especially interested in effects on handling, noise and economy. Alternatively, if you know of any good data on the web testing their effects that would be excellent (I've only found a very limited amount of reliable info).
When/if we buy one it will be fitted to a 3 series BMW and most often used on long trips at motorway speeds.
Many thanks
D
The fuel economy takes a 10-15% increase but the handling of the car will not change that much if you don't overload the box.
We put/wrapped the straps around the roof bars as well (both sides) to give some added security as the clips that keep the box on the roof bars seem a bit on the light side. We had the box (450 L) filled to the brim.
The Mammut straps are available at Obi, Coop Brico, Hornbach etc.
Go slower and the hit on fuel consumption isn't nearly so great.
I read something a while back that said that fuel consumption is affected by some factors as much as previously thought.
Opening windows, air-con, roof boxes (not bars) etc really don't make much difference.
The big difference is with speed. Drive a bit lower and save loads.
To the OP:
We sometimes use a roof box:
It's a bit noisy (no loud whistling though)
Be careful in some low car parks if you have a tall box and a tall car.
It's amazing how much you can get in them but be careful of the weight limits.
And yes, a roof box is a huge drag factor.
handling = no different
economy = less km per litre
noise = slight low pitched noise at higher speeds..............
This article ( http://www.autoexpress.co.uk/news/au...thbusters.html ) is the best I have found up until now and agrees with everything said here (pretty much). I would say that there is a big difference between windows open and top down but I'm not arguing with anything.
The difficulty I'm having is quantifying the impact on economy as it will depend on so many factors but thanks for the personal experience information, that's about as good as it gets.
The jury is still out then on the noise issue though. Can't say I fancy driving 8 hours with some nagging whine going on but I guess that was what Sandgrounder was recommending...
Looks like a "suck it and see" approach is needed if I can accept the cost impact if I have to get rid of the box.
Cheers
But simplified, doubling the speed, quadruples the drag. i.e. driving say at 100Km/hr will be much, much for efficient than going at 140Km/hr.
So, a roof box is a huge drag factor if you go faster.
I wonder if you mount it upside down, the lift produced will decrease your rolling resistance
Anyway:
Here's the article I mentioned. I don't know how accurate it is.
Additionally an empty roof box will increase fuel consumption than a (overladen) one - 100kg?
Anyway, with or without the roof box, the speed makes the greatest difference to fuel economy so driving like an old lady isn't such a bad idea.
Although my grandmother drove a BMW 3 series when she was 80 until the Police managed to catch up with her and promptly took it away
For a recent trip to the UK I bought a full width 580l box and the difference was marked. At 130Kmh on the Autoroutes I would say it knocked the normal range from 900km down to 750 adding to the worry of finding petrol in France.
Nevertheless the difference that a 580L box makes to carrying capacity is amazing to an ordinary family car with 5 passengers and a dog. As other people said just try not to put the heavy stuff in it.
The Thule Alpine 500 is for sale by the way for 200CHF. It is more suitable for the winter season but I just don't want 2 boxes.