The HGV annual test: what fails most, and how to stop it

Brakes decide more tests than anything else

Braking is where an annual test is won or lost. The roller brake test measures what the vehicle actually achieves rather than what it feels like from the cab, and a lorry that stops perfectly well on the road can still be out of balance across an axle or short on efficiency once it is on the rollers.

The causes repeat: worn linings, a slack adjuster that has stopped adjusting, a lazy chamber, a sticking valve, a vehicle presented at a weight the brakes were never going to be measured fairly at. None of those announce themselves to a driver. They announce themselves as numbers on a printout.

The fix is to have a brake performance test as part of your normal inspection routine rather than discovering the figures on test day. We are an authorised service centre for WABCO, Knorr-Bremse and SAF, and we do Haldex ABS and EBS work here, so a fault found on the lane does not need referring to a specialist somewhere else.

Lights, and the wiring behind them

Lighting is the cheapest failure there is and the most irritating, because every one of them is visible from the ground before the vehicle leaves your yard. Bulbs out, a cracked marker lens, a number plate lamp nobody has looked at in a year, a fog lamp that has not been switched on since the last test. On a trailer, add the susie connections and the corrosion quietly building inside them.

Walk the vehicle with a second person working through the switches, and do it in the dark or in a shaded corner where a dim lamp shows itself. Check the trailer on the unit that will present it, because a fault in a connector only shows up on the combination that has it.

Aim matters as much as function. A headlight that works but points into the hedge is still a defect, and it is one of the easiest things to correct in advance — a headlight aim check here is a small charge alongside the test.

Suspension, air and running gear

Springs, hangers, bushes, U-bolts, air bags and dampers. A cracked leaf or a perished bag rarely gives warning; it is found by somebody underneath with a lamp, looking for uneven ride height across an axle, a bag chafing on a bracket, a shock that is wet, and any bracket or mounting that has moved from where it was welded.

Air systems are judged on how quickly they build and how well they hold. The compressor that runs a little more than it used to, the leak the driver has learned to live with and no longer hears — those are defects on the lane even though the vehicle has been working around them all year.

Chassis corrosion belongs in the same walk. Surface rust is one thing; a corroded crossmember, a suspension mounting eaten around its fixing or a tank strap gone thin is another matter entirely.

Tyres and wheels

Tread depth is the obvious one and it is seldom the reason a commercial tyre fails. Sidewall damage, exposed cords, a cut deep enough to reach the structure, mismatched types across an axle and regrooved covers where they do not belong account for far more. Check the inners on twin wheels — the tyre nobody can see is the tyre that fails.

Wheel security is the other half of it: missing or loose nuts, movement marks on the indicators, a cracked or heavily corroded rim, damaged studs. A torque check the week before costs a few minutes and removes an entire category of rejection.

Leaks, and the ones that look small

Oil, fuel, hydraulic and coolant leaks come up constantly. The distinction that matters is between a weep that stays where it is and anything reaching the ground, landing on a brake or dripping onto an exhaust. The second sort will be written up.

Clean the vehicle down and then run it: a clean engine tells you exactly where a leak comes from, and a filthy one hides it. The same goes for presentation — a vehicle that arrives caked cannot be examined properly.

Load security, bodywork and the week before

Body and load-securing equipment is examined too — curtain straps and buckles, ratchets, headboards, rear doors and their catches, twist locks, tail lift condition and its guard rails, and the anchorage points themselves. Damaged or missing securing equipment is a defect in its own right, not merely a haulage inconvenience.

So the week before looks like this. A brake performance test. A two-person light check including the trailer on its own connector. A crawl underneath with a lamp on springs, bags, lines and mountings. Tyres including the inners, and a torque check on the nuts. A wash. Paperwork gathered and the vehicle presented at the correct weight for its class of test. Then fix what you found instead of hoping it will not be noticed, because it will be.

If you would rather have somebody else’s eyes on it, a pre-test inspection here is a fair way to buy certainty — the fitters who would carry out the repair are the ones doing the looking. Ring 01527 870400 and we will fit it in ahead of your test date.