Reader DIY: How to build a dual spare-wheel carrier
Shortly after purchasing my Mazda Drifter, I wanted to increase my vehicle’s long-range capabilities by fitting a Front Runner auxiliary fuel tank. Unfortunately, in the Drifter’s case, the fuel tank lowers the height of the spare wheel under the vehicle.
In my view, this places the spare wheel at great risk when tackling tough off-road terrain; so I started thinking of a sparewheel carrier for the back of my Drifter. However, it was only after I’d had the opportunity to visit Botswana (a long-time dream of mine) that the motivation to build my very own sparewheel carrier got me cracking on the job. In my case, I wanted a dual-wheel setup for extra tyre assurance in Botswana. But before I started with the design of the dual-wheel carrier, there were a few things I had to consider. Weight was a major concern for me; some of the spare-wheel carriers I’ve seen look hugely heavy. Throw in the weight of two big off-road tyres, and it goes without saying that certain weight reductions have to be made when designing a rearmounted wheel carrier.
Another theory I had was that bearing supports were likely to fail, given the offset direction of the load and the fact that bearings are made to rotate, not bounce up and down in a stationary position. After seeing other wheel carriers shear their stops, I opted for my wheels to drop down rather than swing to the side. This arrangement also allows me to keep the wheels out of harm’s way when parked on a narrow track or road-side shoulder. What’s more, side-opening carriers are a hindrance when you’re trying to access the load bay in a tightly packed car park or an off-camber slope.
Once I had an idea in mind, I started with some prototype pieces – to gauge if the angles would work. My basic plan was to have a triangular arrangement with two hinges at the top and bottom of the frame; this would be fixed via a dropdown latch to the top bar, anchored to the bakkie’s old tie-down points.
I started the build process by focusing on the lower horizontal bar; this strut was made from 3 mm steel channel bent up by a local metal shop. The bar was mounted from the towhitch extension plate to a purpose-made bracket bolted to the bumper. The two bottom hinges were then attached to this channel length.
The hinges were made from heavy-duty steam pipe, sized to accept a polyurethane shackle bush. The wheel carrier itself was made from 50 x 25 mm steel tubing. The two top supporting points were made from 3 x 25 mm angle iron, which housed the drop latches mounted on polyurethane shackle bushes. The wheels are easily placed on the bottom step and held in place by a single bolt through the centre. A unique wheel nut (the type used to prevent the theft of mag wheels) was used for the same reason.
It was at this point that I experienced a rather worrying problem: I couldn’t find a bolt that was long enough and which matched my wheel’s thread type. This meant I had to ask an engineering workshop to turn a threaded bar that would screw into my wheel’s thread. To be on the safe side, I added a clamping back-up bracket for good measure. I did all the welding work off the vehicle. The criss-cross design of the carrier frame is very sturdy. Other design elements were that the drop-down latch was mounted on a polyurethane bush and attached to the top supporting angle-iron section, and that the cable attached to the drop-down latch was fastened to a short piece of aluminium pipe to allow the carrier to swing open for access to the canopy door. Alternatively, the aluminium pipe can pass through the frame to allow the carrier to open all the way down and access the tailgate.
To keep the weight as close to the vehicle as possible, I made sure the wheels faced inwards, so that the tail-light clusters, number plate and reversing light could be placed inside the rim. (These items would otherwise be blocked from view by the two spare wheels.)
The total cost of the carrier was R2 200 for the dual spare-wheel setup. After completing our Botswana trip, I realised that the only downside of the carrier’s design is the potential for you to klap your ankle on the lowered frame. But this just gives me more to think about for a future upgrade!
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