 Poster: A snowHead
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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At Christmas we noticed that the fuel consumption on our "naked" estate car was 42 mpg on the way south and 46 on the way back. We even managed to get from Les Arcs to Calais in 9.5 hours as opposed to over 10 on the way down. Three reasons for this:
a really stiff head wind on the way south
heavy traffic around Chambery on the way south.
Going up the mountain on the way to Les Arcs and down it on the way back. It is amazing the difference this makes.
Back to the original post. In our previous car - a 170ps 4x4 skoda superb estate - Skis in plastic box raised the fuel consumption from 45 to 43 mpg. A board bag as well reduced this to 41 mpg but the increase in wind noise made us reduce speed as well. I suspect "naked" skis will be even worse for fuel consumption
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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There was a thread on this subject a few years ago, there was a test that showed no difference but it emerged that the average speed on the test was just 30mph. My own experience is with a 2.0tdci S-max driving to Andorra
CC set at 130kmh for about 80% of the journey
With roof box~35mpg
Without roof box ~40mpg
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One of our cars is a pure electric which produces quite good efficiency data. The efficiency impact of putting two bikes on the roof is about 15%, though I’ve not done skis or a box.
My petrol car sees a similar effect of about 15% with the official aero ski box (long and thin so limited frontal area) although I tend to drive a bit slower with a box on so I’m not sure what the real effect is.
Both tests at motorway speeds which are 65-70mph in the electric and somewhat higher in the petrol one.
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Don't forget the impact of roof boxes on ferries, tolls, and car parking fees (under 2m vs over). Possibly insurance premiums too.
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The impact of roof boxes/racks rises with speed, a garden shed on the roof won't make much difference at 30 mph but £40 extra for fuel is better than 4x ski carriage or hiring in resort.
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Zafira Tourer diesel averages 44 on UK motorway journeys, and 41 with a Kamei Delphin roof box through Belgium, Luxembourg and Germany to Austria. This may be due as much to autobahn speeds as to the drag from the box - the box is known to be good to 160kph, which my wife was doing when I woke up and reminded her that the roof box was on...
Eurotunnel cost is the same for high vehicles, and we have no need to use multi storey car parks, fortunately
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@crosbie, insurance is unaffected by use of roof boxes, bike racks, and trailers - all are approved accessories
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 You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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@crosbie, tolls are also the same - Class 1, parking in resort we visit is free, don't think we pay anymore for Eurotunnel but can't be sure
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I was over the 1.85 limit for VT covered parking, but the guy just lifted the bumper thing and let me in. I could have removed the rack of course , but was too tired to bother
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 snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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 And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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@Boris, when tolls start feeding you tickets out of the upper 'lorry' slot then your roof box is probably costing you a tad more than aerodynamic drag.
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Quote: |
One of our cars is a pure electric which produces quite good efficiency data. The efficiency impact of putting two bikes on the roof is about 15%, though I’ve not done skis or a box.
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That's very interesting, is have thought two bikes would have had more effect. Still, I'm sure your data is good. (I drive a plug in hybrid and love an opportunity to obsess over data)
Otherwise, driving our S-Max 2l diesel, I find the roof box made about 10%, and driving fast about another 10%.
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 You know it makes sense.
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I do 120km each way to get to the local mountain, 2.5l Subaru Outback - around 60 days a season.
Nothing on the roof averages about 6.8l/100km including a 20km off road uphill climb, the rest is highway about 105kmh
Ski racks + 4 snowboards gets that number to about 8l/100km
Roof box + 4 snowboards is about 7.2l/100km
It’s a pretty significant difference - maybe 10% extra fuel to use ski racks.
Roof box all the way for me, although may depend a bit on the vehicle. Didn’t make that much difference when I had a land cruiser
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 Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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We always noticed a big difference between UK and France, in heavy but moving traffic from home to the tunnel, 45 mpg, overnight driving on French autoroutes, 35 mpg
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 Poster: A snowHead
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That's interesting, I never considered that the time of day you set off/ drive might affect fuel consumption - good point!
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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All about wind resistance. Get a good draft behind some trucks and it’s much more efficient. Ditto with well designed boxes etc. Anyone who has ridden a cycle time trial or been in the wind tunnel will understand.
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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@Orange200, think the difference @tangowaggon, experienced might be more to do with speed than time of day. Heavy moving traffic probably 40-50mph while night time autoroute closer to 80mph?
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@crosbie, Always go through the Telepeage lanes so no tickets - periodically it gets picked up as Class 2 but email to request adjustment sorts it.
Only time I've been picked up as HGV is when towing caravan and having 4 bikes on roof - can understand the radar picking us up as lorry. Gate wouldn't open automatically, pressed call button and (I assume) they then check camera as it was opened immediately and tag beeped
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Quote: |
Anyone who has ridden a cycle time trial or been in the wind tunnel will understand.
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True that. All those tail-gating Belgians are channeling their inner Eddy Merckx.
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@Boris, it seems to me that Telepeage is only worth getting for less than 2m high lanes. If your car is over 2m high with 40cm high roofbars+box, then either you find an over 2m lane with a human being who can see that you have a car+roofbox or you just enjoy the hassle of getting out of the car to reach up to the lorry driver's slot. Given it's not usually obvious where the human being is, I just put up with paying over the odds.
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My trip through from home to alps is usually the more fuel efficient (even fully loaded, 4 adults and roof box (long slim one) giving about 37-38 mpg) than the 34mpg usual use at home, so i usually see this as a win.
frustratingly i can't quite get back from the Alps to Calais on a single full tank and bottling out and stopping for a top up short of the channel...an extra couple of mpg would see me there, slowing down might help but ........
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