Guide
Low loader or step frame? Choosing the trailer for a machine
Updated
Trailer choice is not a preference, it is arithmetic: capacity, deck height and how the machine gets on. Understanding the options makes the conversation with a haulier much shorter.
The main types
- Low loader
- A very low deck between the axle sets, usually with a detachable or folding gooseneck so a machine can drive or track straight on at the front. Chosen when the machine is tall, heavy, or both. The low deck is what keeps the loaded travelling height under bridges.
- Step frame
- A stepped deck: higher over the neck, lower behind it. Good general-purpose plant trailer with more usable deck length than a low loader, typically loaded via ramps at the rear.
- Extendable trailer
- A step frame or flat that telescopes for long loads such as booms, beams or long machine beds. Length is bought at the cost of some capacity and manoeuvrability.
- Beavertail
- A rigid or trailer with a sloping tail and ramps, used for smaller plant that drives on. Quick and cheap for machines it suits, and unsuitable the moment weight or height rises.
- Flatbed or curtainsider
- For crated, skidded or palletised machinery loaded by forklift or crane. Fine for a machine tool on a skid, wrong for anything that has to drive on.
Deck height is the real constraint
The number that decides the route is the loaded travelling height: the deck height plus the machine. Every metre of deck you can lose is a metre of clearance gained under bridges, gantries and cables, which is why the lowest available deck is not always chosen for capacity reasons but for route reasons. If you know the machine's height precisely, say so precisely; if you do not, say that too, because a haulier can measure but cannot guess.
What decides the choice
- Weight and axle spread, which set the trailer capacity and configuration required.
- Machine height, which sets how low the deck must be.
- Loading method, since a machine that drives on needs a deck it can climb onto and a machine that is lifted does not.
- Deck length and overhang, and whether attachments travel on the same trailer or separately.
- Site access, because a long low loader that cannot get through the gate is the wrong trailer whatever its capacity.
Leave the choice with the haulier
Customers occasionally specify a trailer type in an enquiry and then get quotes for the wrong thing. Give the machine details and the access instead, and let the operator select. The useful question is not "can you do it on a step frame" but "which trailer are you quoting and what loaded height does that give", because that answer tells you whether the route has been thought about.
Where a machine turns out to be oversize or overweight for normal running, the movement moves into abnormal load territory with its own notification requirements and a different kind of operator. Flag anything unusually wide, long or heavy in the enquiry so the right firms quote it.