Advice: Inspecting ten-stud wheels

Whenever the phone rings this late at night, it could only mean something is wrong. The driver said his problem was two blown drive tyres, or so he assumed after the loud bang had set his heart pounding fast than a Cummins signature at full noise.

After a few more late-night calls, the nearest tyre service field truck agreed to head out within fifteen minutes.

After a couple of hours, my phone rings again. It was the tyre service technician; the news wasn't good: "I'm sending you some photos," he began. "The wheel nuts were loose, and the rim's stud holes elongated or flogged out. The marks on the mating sidewalls of each blown tyre indicated that they'd been rubbing together for a while, causing them to overheat and eventually go bang." He concluded.

The following morning revealed the extent of the damage to the wheels. Sadly, however, the evidence indicated that this truck had been operating with loose wheel nuts for a considerable time.

Surprisingly, with the wheels flapping around in this condition, you’d think there would have been some form of strange noise, vibration and indeed a change to the way the truck handled.

So why didn't the driver stop to investigate the problem earlier?

Was the driver simply lazy and couldn't be bothered? On the other hand, maybe he did check the wheel nuts every day and pulled over when the vibration occurred but failed to recognise the problem due to a lack of training.

But not all disc wheels are the same. Therefore, it is essential to recognise the different types of disc wheels and understand how they are mounted and the correct tightening torque for each.

There are two different alloy disc wheel mounts: ball-seat-cap-nut (stud piloted) or hub-piloted.

Ball-seat-cap-nut mounts rely on the cone-shaped end of the nut and chamfered hole in the rim for location.

This style of alloy rim is easily distinguished by large chamfered edges on either side of the stud hole. An inner and outer nut is used on dual wheels. Left hand threaded nuts and studs are on the nearside, and right hand threaded nuts and studs are down the far side.

When mounting the inner nut, it is essential to ensure enough thread engagement to tighten up onto the wheel rim without bottoming out on the end of the stud's thread. This can be checked by tightening all the nuts in a regular manner. Then by loosening one nut to hand tightness and counting the number of turns it takes to disengage. For example, for a 1-1/8th inch stud, there should be at least five full turns, or seven turns on a ¾ inch stud.

Hub-piloted mounts use pilot pads on the hub to locate the rim and feature a straight stud hole without the large chamfer. But before mounting a hub-pilot wheel, it pays to clean the seat with a wire brush and coat either the wheel pilot or hub pads with a lubricant (Freylube or equivalent) to minimise corrosion build up between the wheel and hub pads.

Related reading:
Changing truck tyres safely
How to manually release truck brakes
The real cost of mismatched tyres

These wheels use a two-piece flange nut with a right-handed thread around the whole truck. When reinstalling the flange nuts, it's also recommended to lightly lubricate the stud thread and the contact area between the nut and flange washer with a SAE30W oil.

With either type of mount, the recommended tightening torque on an alloy Alcoa disc wheel is 600Nm (450 ft/lb), re-torqued after 50-100 kilometres. (It pays to refer to the vehicle operating manual for individual torque valves).

While every wheel manual suggests that you should use a torque wrench, the thought of carrying such a high-priced item in the truck's tool box for a roadside wheel change is somewhat daunting, to say the least.

Another roadside problem is that the short-handle wheel brace that comes with a new truck or trailer is virtually useless unless you're packing twenty stone or more in weight. Loosening a 600Nm (450 ft/lb) tensioned nut is impossible.

Even if your budget did extend to carrying an expensive tension wrench on the road, the chances of it staying in the truck are slim. Sadly, in this day and age, many people in the transport industry often need your equipment more than you do! Also, imagine having to explain to the boss how you left behind his brand new expensive tension wrench somewhere on the side of the road when you changed that last flat.

Many spare parts outlets sell a torque multiplier dedicated for loosening and tightening truck wheel nuts. One inch-drive truck wheel-nut torque multipliers retail for around $150. Cheaper tension wrenches start at about $880.

There are several ways to get around the problem of tensioning wheel nuts accurately – without a costly wrench. And following method is one of the simplest.
• While your truck is in the workshop, use a tension wrench to torque the wheels to the recommended 600Nm (450 ft/lb).
• Now get a sturdy pipe, roughly 800-900mm long, that will fit over the truck's standard wheel brace handle. This length should be sufficient to achieve the required 600Nm (450ft/lb) torque.
• Tighten the wheel nuts using the pipe and check the torque against the tension wrench while in the workshop.

The pipe should fit neatly in a trailer's toolbox, and if it gets lost or knocked off, it doesn't matter that much.