When a load is heavier than the rules allow, weight gets spread across more axles. Jeeps, boosters, and multi-axle configurations turn an RGN or lowboy into a superload rig that keeps the heaviest freight legal.
Quick answer: Multi-axle transport adds axles — jeeps ahead of the trailer and boosters behind — to spread the weight of superloads across more tires and stay within per-axle limits. It's how transformers, vessels, and the heaviest machinery move legally.
Every road and bridge has a per-axle weight limit. When a load's total weight would overload a standard trailer's axles, we add them: a "jeep" between the tractor and trailer, "boosters" behind, and extra rows under the deck. Spreading the weight keeps every axle legal even when the total climbs into the hundreds of thousands of pounds.
These are superloads — moves that exceed standard oversize/overweight limits and demand engineered routing, bridge analysis, and often police escorts and utility coordination. We build the axle configuration to the load and the route, working from an RGN or lowboy base.
| Deck / well height | Follows the base RGN / lowboy deck |
|---|---|
| Usable deck length | Configurable — stretchable |
| Legal payload | 200,000 lb+ |
| Max cargo height (legal) | Route-engineered |
| Loading method | Drive-on or crane, per base trailer |
| Axles (base) | 4–13+ (jeeps + boosters) |
Extreme-weight electrical units
Heavy industrial process equipment
Freight beyond standard overweight limits
The heaviest welded and cast structures
Deck height is what decides most loads. The lower the deck, the taller the machine you can carry and still clear 13'6" without a height permit — which is why the heavy stuff rides in a well.
| Trailer | Deck height | Legal payload | Max cargo height | Pick it when |
|---|---|---|---|---|
| Flatbed | ~5 ft (60 in) | 48,000–52,000 lb | ~8'6" | Load is under legal height and width and can be loaded from any side. |
| Step-Deck | ~3.5 ft (42 in) lower deck | ~48,000 lb | ~10' | Freight is too tall for a flatbed but still under ~10'. |
| Conestoga | ~5 ft (60 in); ~3.5 ft drop-deck | ~44,000 lb | ~8' interior (~10' drop-deck) | Load needs weather protection but still has to be crane- or side-loaded. |
| Double-Drop | ~18–24 in in the well | ~45,000 lb | ~11'6" | Freight is tall enough to need a well, and may need extra length. |
| Lowboy | ~18–24 in | 40,000 lb base — 100,000 lb+ with axles | ~11'6"–12' | Height clearance is the binding constraint and the load is crane-loaded. |
| RGN | ~18–24 in | 40,000–50,000 lb base — 150,000 lb+ with axles | ~11'6" | Equipment drives on and off under its own power. |
| Multi-Axle / Superload you are here | Follows the base RGN / lowboy deck | 200,000 lb+ | Route-engineered | Weight exceeds what any single trailer can carry legally. |
Ranges cover standard builds — exact capacity depends on the trailer, the axle spacing, and the bridge formula on your route. Send dimensions and weight and we'll tell you which one your load actually needs.
Before trailer choice matters, the load has to be measured against the federal legal envelope. Stay inside it and the load moves as ordinary freight. Break any one of these and it becomes an oversize or overweight move that needs a permit, and often a routed corridor and escorts:
Height is where trailer choice earns its money. Cargo height is measured from the pavement, not the deck — so a 12-foot machine on a 5-foot flatbed stands 17 feet tall and is illegal everywhere, while the same machine in a 2-foot well stands 14 feet and clears most routes. That single difference is why heavy equipment rides on a lowboy or RGN instead of a flatbed.
Weight works the same way, but the ceiling is the federal bridge formula, not just the 80,000 lb gross — it governs how much weight may sit on a given axle group over a given distance. That's why heavier loads get more axles rather than a bigger trailer: spreading the weight across jeeps and boosters keeps each axle group legal. Some western states allow 14' height without a permit, and every state writes its own overweight rules, so we check the actual route before quoting rather than assuming the federal baseline.
A superload exceeds standard oversize/overweight limits. Multi-axle transport adds jeeps and boosters to distribute the weight across more axles so the load stays within per-axle limits and moves legally.
With enough axles, well past 200,000 lb. The exact configuration depends on the load weight, its footprint, and the axle limits along the route.
Engineered routing and bridge analysis, state superload permits, and usually police escorts and utility coordination. We manage the whole package.
As early as possible — superload permits and route approvals take time. Send weight and dimensions and we'll start the routing.
Related field guide: How to Ship a Generator →
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Send dimensions, weight, and pickup/drop — we'll match the trailer and quote it fast.
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