I know there's no real science in this so don't be getting all cross about it but it's at least interesting to those who take note of such things.
Some here will know I do a fair old mileage. More or less a thousand miles a working week when I'm busy, sometimes more.
Anyway, my car doesn't have roof rails and most of the time it has a pair of roof bars on it with bike racks bolted to them. I tend to leave them on because we use them a lot and it's a bit of a faff taking them on and off. Couple that with a full sized glass panoramic roof which fills me with horror when lifting the bike rig on and off and the line of least resistance seems to be to leave it well alone.
Last week though I decided to take it off to give the racks a proper clean up and grease etc. Never got around to putting it back on at the weekend as for once we didn't go mountain biking.
The odd thing though is that just for the curiousity value I re-set the fuel consumption trip thing on the dash display. I expected to see at least a slight mpg improvement. My experience with running with three bikes on top of the car for long runs is that can have up to a 20% negative effect on fuel consumption particularly if much of he journey involves motorways as when heading across France etc.
This though is just a comparison of fuel used with empty bike racks in place versus no roof-rack at all.
My car is a 2.0 diesel 4x4 auto Qashqai and normally returns ( with the racks on ) 36.4 - 36.8 mpg in mixed but mainly long distance with a bit of London driving. Over the past week and a half and some 1200 miles with the racks off it has recorded, yes ladies and gentlemen....36.5 mpg.
Odd eh? Now I know these things aren't 100% accurate but it ought to be consistently innaccurate I'd have thought wouldn't you? Maybe the car is just so brick-shaped it simply doesn't make any difference?
Last edited by: Humph D'Bout on Tue 16 Aug 11 at 21:50
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Roof-racks and mpg. new
Roof-racks and mpg. new