 Poster: A snowHead
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Anyone any view on the effect of a roof box 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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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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It depends on how you usually drive - if you're a steady 70mph kind of driver, and you do the same with a roof box on, it will reduce your MPG by 8-10 on an average family car. On the other hand, if you're a 100mph outside lane all the way person, the roof box will make so much noise that you'll not go any faster than 80 (or you will, and it will detach itself all over the motorway), and your MPG will be nearly identical.
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You need to Login to know who's really who.
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Boredsurfing, Ah, just the answer I wasn't looking for. I was thinking more towards the Bugatti Veyron end.
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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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I reckon about 5-7mpg drop on our VW Sharan with a steady cruise of 80mph on motorway. Usually would expect to average 45mpg (diesel) but drops to around 40 with roofbox on
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On a typical run to the Alps having the box on drops my mpg by about 10%, i.e. from about 39.5 to 35.5.
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ousekjarr, I'll be a family-onboard-cruise-control kinda guy. 8-10 mpg would put me down into the low 20s. Probably an extra £80 in fuel just for the roof box then? Plus the roof box hire. Dilemma is that I CAN fit everything inside but do I really want to have to? Hmmm
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Boris, Yoda, thanks. That's good info. I'll go think about it.
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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: |
| Boredsurfing, Ah, just the answer I wasn't looking for. I was thinking more towards the Bugatti Veyron end. |
Ah if you are putting a box on the Veyron dont forget to you won't be able to use the toll gates.
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.. and watch out the air brake doesn't snag on the roof box
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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Bode Swiller, I like to have good visibilty out the back so we go with a roofbox & vacuum bags in the back for all our clothing so the car isnt crammed full. Reckon the box only drops fuel consumption by 5 mpg or so in the S-Max.
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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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| Frosty the Snowman wrote: |
| .. and watch out the air brake doesn't snag on the roof box |
voice of experience eh! 
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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!
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You know it makes sense.
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midgetbiker, a back box on a Navara would:
a) Make it slighty longer than an artic
b) Make loading the hardtop space very difficult
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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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Frosty the Snowman,  agreed but:
a) Still short enough to be a 'standard vehicle' on P&O NSF (got to be under 6 metres), whereas a roof box makes it too tall to be standard (got to be under 1.8m I think)
b) The canopy door should still open with the box in situ, and I should be able to open the tailgate if i get a system which allow the box to slide back on extender bars for loading/offloading
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Poster: A snowHead
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just have to watch the overswing, but i have been used to that inthe past and should adjust pretty quick.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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I think it also depends a lot on whow much the fit on your car affects the aerodynamics. I had one which on a Vectra Hatchback sounded as if it was about to take off but on the next car, Laguna Estate, it was very quiet and smooth. Biiger reduction on MPG on Vectra.
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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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Colin B, agreed, on an estate with a flat back the change will be less pronounced whereas a box will mess up the smooth rear slope on a saloon or hatch more. the area of low pressure at the back of a car 'pulls it backwards' and effects mpg adversely. Putting a canopy on a pick up improves mpg as despite adding weight it fills in the bed at the back of the truck and eases the big no pressure area that otherwise develops there.
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You need to Login to know who's really who.
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Also on an estate people tend to mount the box further back (because of the longer roofline) and so the air pushing up over the windscreen continues over the box and doesn't smack into the bottom of it.
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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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| ousekjarr wrote: |
| It depends on how you usually drive - if you're a steady 70mph kind of driver, and you do the same with a roof box on, it will reduce your MPG by 8-10 on an average family car. On the other hand, if you're a 100mph outside lane all the way person, the roof box will make so much noise that you'll not go any faster than 80 (or you will, and it will detach itself all over the motorway), and your MPG will be nearly identical. |
On one really bad traffic day up through germany we thought we would miss the boat (a big deal when the next one is 24hrs later), when the autobahn cleared we were hitting 120mph+. We had strapped the box onto the roofbars to supplement the mountings but began to worry the rails would pull off the roof!
we still missed the boat by the way 
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On my car the top box never made much of a difference to the MPG, but then again I have a BMW M5. 22 mpg without, 22 mpg with. Performance is affected once aerodynamics come into play above 80 or so, which is plenty fast enough with the topbox on. I reckon the lack of change in MPG is down to driving more slowly.
Don't forget that all that space means you are tempted to take more, which means more weight and worse MPG from acceleration. More weight means longer braking distances and cornering will be affected with more roll. Check out the weight limit for the roof loading in the handbook.
Overall take care. Best to try to pack everything in the boot. The art of careful packing meant that I took my wife, youngest son and parents on a trip to Denmark and back with just the boot full up, and the car I have has a tiny boot compared to the monsters I have seen in similar sized Renaults, Fords etc.
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Makes very little difference for me. I have a big 540 litre box on a Subaru Legacy estate but it only makes a couple of mpg difference.
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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. |
I have been looking at that towbar mounted Thule system too as I could do with a better bike rack. This system: http://www.roofracks.co.uk/main/easybase.htm
Buy base, box and bike rack. That box looks a bit odd though. Aesthetics are more important than mpg sometimes.
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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 wrote: |
| Bode Swiller wrote: |
| Boredsurfing, Ah, just the answer I wasn't looking for. I was thinking more towards the Bugatti Veyron end. |
Ah if you are putting a box on the Veyron dont forget to you won't be able to use the toll gates. |
What toll gates? I'm going via the land of the free autobahn.
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| Bode Swiller wrote: |
| Boredsurfing wrote: |
| Bode Swiller wrote: |
| Boredsurfing, Ah, just the answer I wasn't looking for. I was thinking more towards the Bugatti Veyron end. |
Ah if you are putting a box on the Veyron dont forget to you won't be able to use the toll gates. |
What toll gates? I'm going via the land of the free autobahn. |
Oh, I thought you were going skiing
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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Boredsurfing, good point - Much of Austria is currently looking like Montalbert 
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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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| Nick Dawes wrote: |
| Bode Swiller, I like to have good visibilty out the back so we go with a roofbox & vacuum bags in the back for all our clothing so the car isnt crammed full. Reckon the box only drops fuel consumption by 5 mpg or so in the S-Max. |
Nick how many people are you taking? I'm going to drive this Easter, myself, the better half and 2 kids who will be 10 and 7 by then. I was assuming I can do without the roofbox in my S-Max. Middle seat down for 2 pairs of skis, then I have a safety net in the bag, so I reckon 4 large/medium wheelie bags will get all the gear in for a week, and the car won't be crammed full. That's what I'd take on a flight, so assume driving shouldn't be much different?
cheers,
Greg
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You always take more driving! Just because you can 
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You know it makes sense.
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We can get the 5 of us and 2 sets of skis in the Sharan without need for a roofbox.
But - prefer to have more room in car to stretch out than be crammed in
As Colin B, you do tend to take more cos you can - Mrs Boris always takes her own pillows, cos she prefers them, then the kids want to take theirs, plus a couple of bears each, and a few books oh and may as well take the laptop and 17 changes of clothes (each) 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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| Colin B wrote: |
| You always take more driving! Just because you can |
So true, Mrs Swiller wants to take the halogen oven, the Nespresso machine and the kids (if there's room). Being over Christmas there'll be a few pressies too (sorry folks, Santa doesn't really arrive down the chimney you know).
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Poster: A snowHead
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the car won't be crammed full. That's what I'd take on a flight, so assume driving shouldn't be much different?
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Apart from the tendency to take more because you can, there is also the thing that if you are selfcatering to save money , you do a valley based shop on the way up. We always seem to end up with a car loaded to the gunwales on arrival at the resort in a rental car even if we have not been full at the airport.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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T Bar, when we've had a leisurely trip there, we did the basic shop in Calais and bought all the booze there as well - saved a fortune.
Bode Swiller, well know that would be silly, he just uses magic. Normally he arrives a bit late on Xmas day, when you're out skiing with the kids and just the grandparents are in Apartment, he's late as he's gone to your normal house and see the note you've left and then gone to France last. Now that is perfectly logical ISN'T IT 
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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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kitenski, As Colin B, T Bar, and Bode Swiller, point out you take more because you can! Its our first trip of the winter to our apartment in 3 weeks so we always take more then, coupled with a roofbox full of presents for Christmas and my sons birthday, for a regular trip you should have loads of space!!
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You need to Login to know who's really who.
You need to Login to know who's really who.
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| Quote: |
| (sorry folks, Santa doesn't really arrive down the chimney you know). |
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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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Had to do the 100mph slalom around various items of bedding etc. jettisoned from the roofbox of a Brit car last year, took them a mile to stop and they were surveying the carnage from the hard shoulder. Maybe Ill buy one of those straps this year just in case.
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You'll need to Register first of course.
You'll need to Register first of course.
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| Bode Swiller wrote: |
Buy base, box and bike rack. That box looks a bit odd though. Aesthetics are more important than mpg sometimes. |
If you were genuinely concerned about aesthetics you wouldn't be considering either 
Last edited by You'll need to Register first of course. on Sun 6-12-09 22:22; edited 1 time in total
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I put a big thule roof box on a Discovery 3 and I reckon I get better MPG, either the box improves the breeze blocklike aerodynamics of the discovery. or I drive more carefully, in an effort to avoid shedding the luggage all over the motorway!
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DaveMcSki, probably the later.
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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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| frank4short wrote: |
| midgetbiker wrote: |
Buy base, box and bike rack. That box looks a bit odd though. Aesthetics are more important than mpg sometimes. |
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no i didn't 
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Mondeo 2.0TDCI with a roofbox on one side and a ski rack with 4 pairs of skis on the other, reduced MPG to 34MPG at a steady 80MPH, would usually expect 43MPG on a run. Thats about 12 gallons on a 2000 mile round trip
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FAQ
