Just dusted down my roofbox for next week - can anyone tell me how far back on the car I need to mount it to minimise air resistance? I have a Skoda Octavia Estate if it makes any difference.
I really shouldn't cross the top of the windscreen. Ideally it should be set back a little way.
If you follow the line of the windscreen up and back over the top of the car it should sit behind that imaginary line. That will give you least wind resistance as the screen naturally deflects wind upwards.
Surely you are governed by where the cross roof rails go. On all the cars I have had with fixed rails the manufacturer marks where to fit the cross rails. The box then goes wherever they are.
------------- Nigel
March 2012 - Dove Meadows
6th July Moving to Hayle
True, but most roof-boxes allow you to place the brackets in a number of different places, so for a fixed cross bar the box can be positioned a few notches forwards or backwards.
also the thule boxes with the quick grip fixings have a slot in the box which allows about four inches of movement
I tend to try and fit mine so that the wind flow up the slope of the screen hits the front slope of the box to minimize the aerodynamic disruption, you do see with some of the long narrow boxes that the front of the box is out over the top of the screen so the wind flow up the screen will hit the bottom of the box creating lift and drag
We used a roof box for the first time this year, we have a Volvo V70 estate, we set our box so it started about 3ins from where the sun roof ended. OH took all petrol brought and used etc, and he reckons that we did 1 mile less per mile per gallon than with out the box!
I couldn't possibly comment though well outside of my area of authority!
Thanks everyone, I guess following the line of the windscreen makes sense. There's nothing in the Skoda user manual about location of cross bars, although a Renault I had a long time ago was very specific regarding their location.
I also have an Octavia Estate and, last weekend, placed my Farad roofbox so that the rear clamp was just in front of the upright above the rear passenger door. This meant that the front of the box was about halfway over the sun-roof.
Importantly, this places the box in about the middle of the roof for handling and balance.
In a near 400 mile run I averaged about 52mpg, a little less than my normal commuting average of about 60mpg but, with a fully loaded car, I am not going to complain - especially as I wasn't hanging about on the motorways, either.
A little extra wind-noise (turn up the radio) but no particular problems.
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Topic: Fitting a roofbox
