Steel or aluminium is the first question in almost every roof rack conversation, and it is usually answered with a preference rather than a number. The honest answer depends on what you carry, how much roof load the vehicle can legally take, and how the rack will be treated over five winters. Here is the comparison with real figures.
The roof is the constraint, not the rack
Before comparing materials, separate the two load numbers that appear on every rack specification, because they answer different questions.
- Dynamic load is what the roof can carry while the vehicle is moving. Our PN103 platform is rated at 100 kg dynamic.
- Static load is what it carries parked — which is when a roof top tent with two people in it is actually loaded. The PN103 is rated at 300 kg static.
The static figure is the one that matters for camping, and it is usually limited by the vehicle’s roof structure rather than by the rack. A stronger rack on a weak roof does not raise the number.
Steel: strength per dollar
Steel wins on stiffness and on cost. For a given load rating, a steel platform is cheaper to build than an aluminium one, and it resists the kind of point loading that comes from recovery boards, jerry cans and a spare wheel bolted down hard.
The cost is weight. The PN103 platform measures 1,350 x 950 mm and weighs 19 kg before you put anything on it. Every kilogram up there raises the centre of gravity and eats into the vehicle’s roof load allowance, which is why the platform size should be chosen against the vehicle rating rather than against what looks right.
Aluminium: weight and corrosion
Aluminium’s advantage is straightforward — roughly a third of the density, and it does not rust. Our RL01 side ladder is aluminium, 6 steps, 5 kg, rated to 150 kg. As a ladder it takes a person’s full weight repeatedly, so the material choice there is about handling and about not adding corrosion points to the vehicle, not about saving roof load.
The trade-off is stiffness. Aluminium tube of the same weight as steel tube is less stiff, so an aluminium rack has to use larger sections or thicker walls to reach the same load rating — which is where the price advantage of steel comes back.
How each one fails
This is the part that matters after year two.
Steel fails at the coating. Our racks are powder coated in matte black. The coating is the only thing between the steel and the weather, so a deep scratch from a strap, a branch or a badly packed load becomes a rust line. It is repairable — clean, prime, paint — but it needs noticing.
Aluminium fails at the fastener. Aluminium does not rust, but steel bolts in aluminium threads do, and dissimilar metals in contact with road salt will corrode the fastener long before the rack. If you go aluminium, ask what the hardware is made of and whether the mounting points are isolated.
Neither failure is dramatic. Both are avoidable, and both are cheaper to prevent at purchase than to fix at year three.
How to choose
- Choose steel if you carry heavy, awkward loads — recovery gear, fuel, a spare wheel — or if the rack lives on a working vehicle where scratches are going to happen anyway and you would rather repaint than replace.
- Choose aluminium if roof load budget is tight, if the vehicle is used mostly on road with occasional trips, or if you live somewhere with road salt and want the structure itself to be immune.
- Either way, size the rack to the vehicle’s dynamic rating first, then check the static rating against the heaviest thing you will put up there — usually a loaded roof top tent.
Fitting and living with it
Two habits decide how long a rack lasts. The first is checking the mounting bolts. A rack that works loose does not fail politely — it moves, and movement wears the roof mounting points and the coating at the same time. Re-check the bolts after the first loaded trip, then at every service interval.
The second is remembering which load number you are using. The static rating applies when the vehicle is parked. A roof top tent with two people in it is a static load; driving with that weight on the roof is not what the rating covers. This is the most common misunderstanding we see, and it is worth repeating to anyone who will use the vehicle.
For steel, touch up chips in the coating before the next wet season rather than after it. For aluminium, watch the bolts rather than the rack.
What we build
Our roof racks and platforms are steel, powder coated in matte black, and mount to the factory roof points — the PN103 is the standard size and we build custom lengths for pickup canopies and van roofs. Side ladders are aluminium, because that is a part you lift every day. If you are unsure which suits your vehicle, send the roof dimensions and what you plan to carry and we will confirm the platform size.