Shop for a trailer jack and you'll run into two different load numbers — a big one and a smaller one — often without much explanation. Pick based on the wrong number and you'll either overpay for capacity you don't need or, worse, buy a jack that bends the first time you move a loaded trailer on soft ground. Here's exactly what each number means and how to size a jack correctly.
Static load rating: what it holds while parked
Static load rating is the maximum weight a jack can support while the trailer is stationary — parked, unhitched, sitting still. It's the larger of the two numbers and the one manufacturers put front and center. The ARK XO750, for example, carries a 1,650 lb static rating.
Static rating tells you whether the jack can safely hold the front of your trailer up while it's parked. Useful — but it's not the number that protects you when things actually get hard.
Dynamic load rating: what it handles while moving
Dynamic load rating is the weight a jack can handle while you're rolling the trailer on the jack wheel — walking it into a campsite, repositioning it in a driveway, nudging it off the ball. It's always lower than the static rating because a moving load shocks and side-loads the wheel, yoke, and bearings far more than a parked one. The XO750's dynamic rating is 1,100 lb against its 1,650 lb static.
This is the number that matters off-road. The whole point of an off-road jockey wheel is moving a heavy trailer by hand over mud, sand, and gravel — which is exactly when dynamic load applies. A jack with a high static rating but a weak dynamic rating will still fold when you put it to work.
How to size a jack: match dynamic rating to tongue weight
The figure you're sizing against is your trailer's tongue weight — the downward force at the coupling, not the trailer's total weight. As a rule of thumb, tongue weight runs about 10–15% of the loaded trailer weight. So a 6,000 lb loaded camper puts roughly 600–900 lb on the coupling.
Steps:
- Find (or weigh) your loaded trailer weight — packed for a real trip, with water and gear.
- Estimate tongue weight at 10–15% of that.
- Choose a jack whose dynamic rating comfortably exceeds it, with margin for rough ground.
Don't size to the bare, empty trailer — size to how it sits when you're actually heading out.
Quick reference: the ARK XO range
| Model | Static load | Best-fit trailer |
|---|---|---|
| XO350 | 770 lb | Teardrops & small utility trailers |
| XO500 / Black Edition | 1,100–1,102 lb | Mid-size off-road campers |
| XO750 | 1,650 lb | Tandem-axle & fully loaded rigs |
Bottom line
Static rating tells you what a jack holds while parked; dynamic rating tells you what it can move — and off-road, dynamic wins. Estimate your tongue weight, then pick a jack whose dynamic rating clears it with room to spare. Browse the full ARK XO off-road trailer jack collection, all in stock and shipping from Upland, CA.