fuel consumption with a roof rack

Submitted: Sunday, Jan 16, 2005 at 11:31
ThreadID: 19427 Views:2198 Replies:9 FollowUps:4
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HI all
My 2002 TD Prado Auto uses 15% more fuel with a TJM steel roofrack than without. Seems to be irrelevant whether rack is loaded or not, maybe the unladen rack acts like a big air brake with the mesh floor, and just a big lump with it loaded. I wasn't expecting such a big increase. Anyone else with similar result? Now looking at taking rack off and only putting it on when doing a trip, pain in the butt as its a two person jopb to get it on and off...

Rich
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Reply By: Brew69(SA) - Sunday, Jan 16, 2005 at 11:43

Sunday, Jan 16, 2005 at 11:43
Sounds about right mate...mine ,ay even be a bit worse than 15%. As for taking it off the only thing wrong with that is you never know how handy it is until its not there. I did this once and quickly realise i used it around town more often than i thought i did. Then you need to have somewhere to put it. Member eric uses one of those cheap boat winches to lift his off and store it hanging in the shed.(makes it a quick one man job to put on and off) My uhf arial is on the rack too, so it means relocating that if its off. For me the extra fuel is worth the convenience of having the rack.
AnswerID: 93374

Follow Up By: Member - Roachie (SA) - Sunday, Jan 16, 2005 at 11:56

Sunday, Jan 16, 2005 at 11:56
I'm with you Brew,
I've had my rack on since about day 3 of owning it (& I bought it brand new). It has never been off since and I do wonder what sort of condition the roof gutters are in under the supports.
I've got cables to power the rear lights, power and air hose for the horns, Shovel is there all the time, plus I keep the PVC pipe with kids stretchers rolled up inside.
I'd like to be able to remove the rack and see how much quieter the truck is without it; but it simply ain't gunna happen, cos it'd be too much of a hassle.
With my old GQ, I was able to remove it by using a small hand winch (from a boat trailer). I'd use it to lift the front end of the rack up to the rafters and secure it with a couple of steel hooks. The rear end, I was able to lift it manually by standing on the rear step and then hooking onto similar steel hooks. I didn't have any "permanent" gear on that rack though.
Brew is right about the rack being used every week or so (at least it is in my case, cos I've got the back all decked out with shelves and fridge etc).
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FollowupID: 352352

Reply By: ev700 - Sunday, Jan 16, 2005 at 11:57

Sunday, Jan 16, 2005 at 11:57
Bullbars must have a similar effect. Anyone tested fuel usage pre and post-installation?
AnswerID: 93376

Reply By: GO_OFFROAD - Sunday, Jan 16, 2005 at 12:21

Sunday, Jan 16, 2005 at 12:21
If 15% extra fuel is going to rain on your parade for the intended use of a very fuel efficient vehicle already, then perhaps you either need a bigegr vehcile, so no roof rack required, or, re assess what you need to take, that the rack is needed for.
AnswerID: 93380

Follow Up By: Willem - Sunday, Jan 16, 2005 at 12:56

Sunday, Jan 16, 2005 at 12:56
I came to the same conclusion. My truck probably uses 20% more fuel with the roofrack on. I find that I use the rack for a variety of transport purposes so after removing it once and then refitting it I now live with it and dont stress about the extra fuel consumption!
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FollowupID: 352368

Reply By: Member - Sparkie (QLD) - Sunday, Jan 16, 2005 at 14:19

Sunday, Jan 16, 2005 at 14:19
G'day everyone.

It's amazing what you can learn on this site.

I have a heavy duty home made roof rack on my Mitsu Express and now I know why my fuel economy is up to putty!

I thought my van was using to much fuel and been very unhappy with it, so much so I took all my equipment out of it and everything of the roof rack and drove a full tanks worth with just me behind the wheel and wondered why my economy still sucked.
Now with what I am reading it is a common problem. ;-/

Another thing learned of this site.

Sparkie(IE not Y) ;-)
AnswerID: 93401

Reply By: ROTORD - Sunday, Jan 16, 2005 at 15:18

Sunday, Jan 16, 2005 at 15:18
Hello All

Aerodynamic drag is proportional to the square of the speed of the air over the object . Double your speed and the drag increases fourfold. So the good news is that using the roof rack around town and at slow cross country speeds there will only be a minor drag effect . The time to remove the roof rack is when considering a long high speed highway trip . The other way of reducing drag is by streamlining. A full roof rack with a taut smooth cover will have far less drag than an empty or uncovered rack .
AnswerID: 93406

Reply By: Member - Jeff M (WA) - Monday, Jan 17, 2005 at 14:32

Monday, Jan 17, 2005 at 14:32
That's why the basket is SO good, not only can you remove it very easily between trip but when it's on it sits back further creating a heap load less drag.
AnswerID: 93599

Reply By: Moose - Monday, Jan 17, 2005 at 14:47

Monday, Jan 17, 2005 at 14:47
G'day Rich
Getting it on & off isn't too difficult for us. I only ever put it on when we're heading off camping otherwise it's hoisted up under the garage roof. I've set up a pully system and it's a breeze - still a two person job, me on pully & missus on unhooking and guiding it onto vehicle (or opposite when storing). Takes a couple of minutes max. Another reason I take mine off unless it's needed is that I've put a solid floor in it (thin ply over the mesh floor). So it wouldn't go too well in the rain. We carry all the bedding etc in it so the solid floor and a canvas fitted cover means it's a waterproof container when travelling.
AnswerID: 93601

Follow Up By: RichieK - Tuesday, Jan 18, 2005 at 10:00

Tuesday, Jan 18, 2005 at 10:00
Hi Moose

Unfortuanetle my garage doesn't have provision for attaching a hoist - just a flat roof. Could get a stud locator but will resort to muscle power I think.

Cheers
Rich
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FollowupID: 352705

Follow Up By: Moose - Tuesday, Jan 18, 2005 at 10:10

Tuesday, Jan 18, 2005 at 10:10
G'day Rich
Mine's only a flat roof too. I just attached a couple of double pulleys to the studs and hey presto - makes lifting it on and off so easy. Also it's out of the way in space that would normally be wasted. Even with a single vehicle in a double garage space always seems to be at a premium.
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FollowupID: 352707

Reply By: Alan S (WA) - Monday, Jan 17, 2005 at 15:23

Monday, Jan 17, 2005 at 15:23
I have an ARB rack and noticed an increase when first put on, although not as high as 15%. I removed it once and then realised the amount of wind noise it generated.

When i put it back on next time i located it about 2 inchs furhter back so the front of the rack was furhter away from the wind deflecting of the windscreen. This has certainly reduced the noise level and consumption is also a little better.

AnswerID: 93608

Reply By: flappan - Monday, Jan 17, 2005 at 15:34

Monday, Jan 17, 2005 at 15:34
I never bothered to measure the difference with/without Roofrack , but assumed it to be around 1 or 2/100.

Just the noise of the damn thing would tell you it would have some effect.

With a Racksak though , I recon its worth an extra 3 or 4/100. Have to look into a wind deflector I think.
AnswerID: 93610

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