Fuel on roof. Fore or aft?

pskhaat

2005 Expedition Trophy Champion
I get it. Not the best place for fuel, atop the roof. I need a minimum of 10 extra gallons and don't have a larger/auxiliary tank.

Due to weight and sloshing would you advise to mount them towards the front or the rear of a full length roof rack. Why?
 

eatSleepWoof

Explorer
Due to weight and sloshing would you advise to mount them towards the front or the rear of a full length roof rack. Why?
I would put it 1) where it made sense according to the other gear I carried on the roof, and 2) as close as possible to hardware that supports the rack and is mounted to the roof. Given the option, I'd put the 10 gallons/2 jerry cans such that they are not in a single spot, but rather spread out, to balance out the load a bit.

Outside of those factors I really don't see any reason for prioritizing front/rear of the rack.

In the real world, regardless of where you place the load, there is likely to not be any difference at all.

And for what it's worth, I've had 80-90L water tanks (along with two 20L jerry cans) in vehicles on many occasions, and have never noticed the "sloshing" that everyone on ExPo seems to be terrified of, despite frequent, spirited driving through twisty roads.
 

billiebob

Well-known member
The heaviest item, put it in front of the rear axle, think 2/3, 1/3. Put the lawn chairs and sleeping bags at the ends. Think polar moment.

ps, if the tanks are full.... or empty.... there will be no sloshing. And unless you know you will need the extra fuel... leave them empty.
 

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Cabrito

I come in Peace
I get it. Not the best place for fuel, atop the roof. I need a minimum of 10 extra gallons and don't have a larger/auxiliary tank.

Due to weight and sloshing would you advise to mount them towards the front or the rear of a full length roof rack. Why?
I've done both with no noticeable differences. I go heavy on the roof rack so it all comes down to how I'm loading up with also taking into account weight distribution. I usually only carry five gallons of gas max, but also have had water up top too.

I tend to default to the rear of the vehicle so I can access them easier from the tailgate. I also like the 10L or 2G cans because they are easier to work with.

This old shot from the early 90's was five gallons of gas up top on my X-tra cab SR5. I had to put the gas upright when full and it was sketchy so I would empty it as soon as possible.
Canyon de Guadalupe Baja



2x 10L cans up top in front.


2x 10L Fuel and 2x 10L Water up top on the rear.



These days I'm only running 2x Two gallon RotoPax



My last trip to Baja I went with 2x 10L in the rear.



In Baja my FJ was our chase vehicle and we were carrying 25 gallons of gas on the roof!



 

pskhaat

2005 Expedition Trophy Champion
Maybe ask your insurance underwriter what they recommend...
Will just be me and known vehicles off-highway. Wont travel with them full on populated roads. Plus, I can't afford anything but State minimum liability anyway.

Bloody literal highway robbery, those insurance premiums.
 

pskhaat

2005 Expedition Trophy Champion
And for what it's worth, I've had 80-90L water tanks (along with two 20L jerry cans) in vehicles on many occasions, and have never noticed the "sloshing" that everyone on ExPo seems to be terrified of, despite frequent, spirited driving through twisty roads.
I'm employing Waivian'ish cans this time. I am much more concerned with leakage than sloshing. I've had terrible luck with leaking cans in the past.
 

The_Hoff

New member
I put mine at the rear so I can siphon straight to the tank without removing the Jerry cans. Also, I empty them asap, i.e as soon as I’ve used about 20L of fuel from the tank I empty a Jerry - that way you minimize the time you have the weight up top.


Sent from my iPhone using Tapatalk
 

DaveInDenver

Expedition Leader
Seems to me a consideration is the weight shifting. So if you have stout mounts, like cages, they won't move then anywhere it makes sense. When I carry jerry cans I put them in a small basket on the roof with ratchet straps. I put them against the front so in a panic stop or hard-stop over obstacles they won't come skidding forward.

IMG_1389_mid.jpg
 
Depends on your setup.
I built a custom rack for 4 5 gal jerry cans. I was really nervous with all this weight that far back. Everytime we stop on the 1st day of our trip I would check and double check to make sure everything was secure and no leaks. I thought there would be a noticeable sway with the extra weight so high and when turning or on off camber terrain but with my suspension setup I did not feel anything. A testament to the FJ and Icon suspension.

In my case I don't think it would have mattered it the fuel was fore or aft.

Here is my setup. And yes I need all 28 gallons of gas, 10 days and 300 miles from asphalt to asphalt.

Parashant FJ Picture.jpg
 
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alanymarce

Active member
As you can see we put the cans at the rear of the roof rack, mainly (as noted previously) to allow fuel transfer without having to take down the cans. Not ideal from the point of view of load distribution nor polar moment of inertia, however... we filled them only for a couple of trajectories of this particular trip, and gave them away (to the fire department) when we no longer had any likely need. FOr the trajectories for which we needed extra fuel we drove appropriately for the increased CoG/PMoI until we had used enough fuel to tranfer the contents to the main tank. We had the same set up on the previous "big trip".
 

krick3tt

Adventurer
I have a LR3 and carry my two 10L cans where the spare tire used to be under the vehicle. On the rr I carry my extra water in two 5L Scepter cans. I sometimes do carry extra fuel on the roof in a holder I fabricated, on their sides (it is lockable) to cut wind resistance. They are Nato cans and do not leak so that is not a worry. I carry them toward the rear for easy access as a Nato can with 20L of gas is about 55+ pounds and extremely awkward to handle.
I know there are those that would not carry fuel under the vehicle but that is where most stock fuel tanks are. My cans are protected by a 3/16 inch plate and uses the LR spare tire winch to lift them into position.
When full they equal the weight of the spare tire.
IMG_0017.jpg
 
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