 Poster: A snowHead
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It depends:
As said above a guideline would be about 10 - 20 % reduction.
But
If you have a large torquey diesel engine and you drive at a modest motorway speed at say 60mph for arguements sake the effect will less pronounced than if you have a small petrol engined car that you hammer down the autoroute. When drag is increased Mpg tails off dramatically with higher speeds esp with engines that are being pushed closer to their capability.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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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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You need to Login to know who's really who.
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| midgetbiker wrote: |
Does anybody out there use a back box? I'm thinking about one for the back of my Navara, and the blurb reckons it will have no effect on mpg (which is sub 30 @ 75mph anyway), any feedbak on these claims would be appreciated. The idea is to have a platform out the back on which i can mount 2or3 bikes or a box for extra load carrying or even both at once.
Please don't ask me to explain why I would need extra luggage capacity when I have about 3 cubic metres in the boot. If you want to know ask my wife! |
Change your Navara for a Pathfinder
Not even my wife can fill that up, she has tried, but you can just drop more seats and you can get a Thule bike rack that is a semi perm fit on the tailgate, i can fit my 177 skis in the back ar a 160 snowboard or both, boots luggage kids and stuff.
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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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Simonsays - I'm amazed that trial reported minimum impact from a roofbook on MPG..... 
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I've driven to the French Alps twice with 2 roof boxes on, the long thin ones, side by side. Getting access to the far side one is difficult, but they both fit on a Galaxy comfortably. The drop in MPG on a 1.9 Diesel was about 10% (down from 31 to about 27), averaging (if I'm honest) over the 130kph limit. With 7 people in the car I think that's quite good going. Felt the weight up some of the long hills but otherwise all went smoothly. Compared with the cost of taking another car the extra fuel is nothing.
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[Interesting with the roofbox results from the trail and the experiences here differing. Though the study shows that the worst is combining the extra drag with extra weight, and I would imagine if you have a roof box on it's because the car is also full up with stuff adding quite a lot of weight, for example most average MPG readings will be with 1 adult in the car. Say you add 2 adults(or a teenager) and 2 children on top thats probably another 200kg (50-70kg per adult, 30-35 per child?) plus all the associated luggage, say 20kg pp (going off aircraft allowance) thats another 100kg. Is it not the extra weight that is dropping the fuel consumption?
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The Autoexpress test route at an average of 29mph is not what I would hope to achieve on an Autoroute so it really is not a representative test! On the other hand the point about the weight (anotherproblem) is well made!
Perhaps a forum member would care to do a more realistic test one Sunday, i.e. drive up and down a motorway (at 70 MPH ) with and without an empty roof box ( sounds fun I know ! I would but I think I am washing my hair  )
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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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| Bode Swiller wrote: |
| Anyone any view on the effect of a roof box on MPG? |
I just noticed this thread was about to drop off the bottom of the page, so I bumped it.
Hardly surprising that it was about to be relegated to p.2, since it's such an unbelievably boring question.
Does anyone have any view on the effect of panniers on my pushbike, in terms of the number of calories-per-hour burned?
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The Abominable snowHead, I think you need to worry about wind generally.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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The Abominable snowHead, your wit amazes me
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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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My findings... put roofbox on this morning (Thule Atlantis 900) and have driven about 60 motorway and dual carriageway miles. It has made no difference whatsoever to the mpg - if anything, according to the trip and comparing to a journey I made at the weekend along the same route, the mpg has just slightly improved by 0.2 mpg! This on a full size 4x4 with 3.0 V6 turbo diesel. So, there you have it, a definitive sample of 1.
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Bode Swiller, Winter or summer tyres 
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You know it makes sense.
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Boredsurfing, winter. And, before you ask... yes, chains, warning triangle, hi-visibility underpants etc etc
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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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Bode Swiller, so indeed it probably is the weight added, not the roof box that must make the difference? I'd always assumed that they would suck your mpg but after reading the test, the point about them being quite aerodynamic is probably correct
One thing I would ignore with these fuel saving leaflets you get off the highways agency is in a diesel "change gear at 2000rpm" thats all well and good but my car (Fiat Stilo 1.9JTD) has a very good diesel engine but the turbo isn't properly in till about 2250rpm so is sluggish as hell if you change at 2000 rpm! I only tried this as an experiment, I only change gear when the power starts to fall off, near the red line 
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Poster: A snowHead
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anotherproblem, might be a different story with a more streamlined car. Most 4x4s are like flying bricks and the engine has to deal with wind resistance all the time. Adding a roof box to such a car might make no difference but adding one to a more aerodynamic package like yours might have a large effect on mpg.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Bode Swiller, But surely some 4x4 are more streamlined than others. An Audi Q7 is dog ugly but I guess quite aerodynamic, whilst others like any Landrover product is probably less aerodynamic than a brick.
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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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Boredsurfing, well I did say "most"... and don't call me Shirley.
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| Boredsurfing wrote: |
| Bode Swiller, But surely some 4x4 are more streamlined than others. An Audi Q7 is dog ugly but I guess quite aerodynamic, whilst others like any Landrover product is probably less aerodynamic than a brick. |
I quite like the Q7. Better than a Porsche Cayenne anyway.... 
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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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X5 = Footballer or testosterone-driven corporate cock
Cayenne = Drug dealer or wife of X5 driver
Q7 = Footballer or corporate cock trying to avoid people thinking they are a footballer or corporate cock by buying an Audi
Discovery = unimaginative dinner party bore and hero of the hard shoulder
Toureg = unassuming, probably OK person
Defender = serial killer
Shogun = close pal of Mr Discovery Driver or suicidal school run mum
Patrol = wants everyone to think he clears mines for a living
Grand Cherokee = discerning, practical type, they never clip wing mirrors
Range Rover = the Defender driver's perverted lawyer or one of those really hard up farmers
Land Cruiser = wants you to think they are a UN weapons inspector
There you go. Where do you fit?
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Help me out, I forgot Discovery Sport
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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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Boredsurfing, nope, mine's not on that list either.
Darn, thought you were in the Defender club.
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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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anotherproblem, I'm too frightened to say
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Roof box's are very useful things but do bring up the cost of fuel! If you do get a box remember to check its long enough for your skis!!!! (if thats whats going in it!)
Roof box's are particularly useful for skis if you are driving on a daily basis as well because all that snow/water doesn't have to go in the car....however careful you are at cleaning off your skis before they go in the car there is always some snow/water left on them!
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You know it makes sense.
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I'm assuming Scarpa has a Defender? He seems the type
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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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| Bode Swiller wrote: |
| anotherproblem, I'm too frightened to say |
Rav 4
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Poster: A snowHead
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| Quote: |
Roof box's ...do bring up the cost of fuel!
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alexchapman, according to my in-depth scientific survey, apparently not.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Boredsurfing, That's the kind of childish thing a Merc ML or GL driver would say.
Nope.
Last edited by Obviously A snowHead isn't a real person on Wed 16-12-09 19:40; edited 1 time in total
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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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| Bode Swiller wrote: |
X5 = Footballer or testosterone-driven corporate cock
Cayenne = lovely people
Q7 = Footballer or corporate cock trying to avoid people thinking they are a footballer or corporate cock by buying an Audi
Discovery = unimaginative dinner party bore and hero of the hard shoulder
Toureg = unassuming, probably OK person
Defender = serial killer
Shogun = close pal of Mr Discovery Driver or suicidal school run mum
Patrol = wants everyone to think he clears mines for a living
Grand Cherokee = discerning, practical type, they never clip wing mirrors
Range Rover = the Defender driver's perverted lawyer or one of those really hard up farmers
Land Cruiser = wants you to think they are a UN weapons inspector
There you go. Where do you fit? |
fixed it
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You need to Login to know who's really who.
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Bode Swiller, ah! Volvo 
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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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Shimmy Alcott, SURELY NOT  EWWWW!
Boredsurfing, either that, or maybe the Lexus RX
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Boredsurfing, Technically I wouldn't call that gopping thing a 4x4 but it should be in the list. That's the other school run mum car. But it's psychotic school run mums as opposed to the Shogun's suicidal school run mums. Important hormonal difference.
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anotherproblem, One of the range of Lexii? No.
Shimmy Alcott, Can you cut me an ounce of skunk please.
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Bode Swiller, sorry, hun, I've smoked it all
anotherproblem, I LOVE my car and I can't fault it at all - except that it only comes with a 2 year warranty - what's that all about?
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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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| Quote: |
what's that all about?
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that's all about a grand to extend it
And then, talking of Huns, there's them Merc ML drivers - hard to pidgeon hole but a funny lot.
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FAQ
