Overlanding Water, Fuel & Storage
Water and fuel for a self-sufficient trip, what they weigh, how many jerry cans — and whether your roof is already over its limit.
Water
Fuel
Roof load
The roof limit is a moving limit
Manufacturers publish a dynamic roof load — what is allowed while the vehicle is moving — and it is commonly 150 to 165 pounds. Critically, it includes the rack, and on many vehicles the rack alone is a third of the allowance before anything goes on it.
It is also the worst weight on the vehicle. Roof load acts on the longest lever from the roll axis, so it degrades handling and rollover margin far more than the same weight in the back. The rule that follows is simple: the roof is for bulk, not for weight.
Things worth knowing
- Water and fuel are the two heaviest things you carry and the two people plan last. Forty gallons of water is 334 pounds, and it does not get lighter until you drink it.
- The published roof limit is a DYNAMIC limit — what is allowed while moving — and it includes the rack. On many vehicles the rack alone is a third of the allowance before you put anything on it.
- Weight on the roof is the worst weight on the vehicle. It acts on the longest lever from the roll axis, so it degrades handling and rollover margin far more than the same weight in the back.
- Off-road economy is not a small correction. Rough trail can cost 40% and deep sand more than half, so a range figure taken from the highway is close to useless for planning.
- Carry the means to make water as well as to store it. A filter weighs almost nothing next to the water it replaces, and it turns any stream into a resupply.
- Fuel in cans is heavier than the fuel alone. A 20-litre can is about 32 pounds of gasoline plus 7 of can, and four of them is a passenger.
How to use
- Enter party size, trip length and route distance.
- Pick a water rate and the terrain you will actually be driving.
- Check the roof section — the rack counts toward the limit.
Frequently asked questions
How much water per person per day?
A gallon covers drinking and cooking only. Normal camp use with washing up is around 1.5, comfortable use with a proper wash is 2.5, and hot or desert conditions push it past 3. Most people underestimate, then ration on day four.
How much does the water weigh?
8.34 pounds a gallon. Forty gallons is 334 pounds, and unlike most gear it does not get lighter until you drink it — which is why it belongs in the payload calculation from the start rather than at the end.
How much economy do I lose off road?
Graded dirt costs about 15 per cent, rough trail around 40, and deep sand or mud more than half. A range figure taken from the highway is close to useless for planning a trail route.
What is a roof rack weight limit?
Manufacturers publish a dynamic roof load — what is allowed while moving — commonly 150 to 165 pounds. It includes the rack, and on many vehicles the rack alone is a third of the allowance before anything goes on it.
Why is roof weight worse than weight inside?
It acts on the longest lever from the roll axis, so the same pounds degrade handling and rollover margin far more up there. The rule that follows is that the roof is for bulk, not for weight.
How much does a jerry can weigh full?
A 20-litre can is about 32 pounds of gasoline plus seven for the can, so roughly 39. Four of them is a passenger, which is worth knowing before you bolt on a fifth.
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