Why Brake Adjustments Are Often Bad?

Every year there is a large focus on air brake adjustments or lack thereof. And throughout the year there is news and all sorts of talk about brake adjustments and associated fines and penalties handed out by government inspectors. Add to this mandatory training in some places and all manner of tools and accessories to make brake adjusting and checking easy and it just doesn’t make any sense. So, what is going on?

The headwinds against good brake adjustments

Before talking about solutions, you need to know what the problem is. Not only is it plural, but the list is very long and each one could be its own article. The main culprits are poor greasing and bad grease, imbalances in brake application from the valve, hose and boosters to the automatic slack adjustors, sub-par slack adjusters (you can’t tell how well one is built by visually inspecting it), brake linings wearing uneven for its own set of reasons, and of course, bad brake adjustments by mechanics, technicians and drivers.

The point is, there is a lot that can go wrong, and it usually does, and our main tool to combat all this is the occasional brake adjustment. Add to that the fact that most brake adjustment intervals are sporadic, and often pointless and you get a situation where incredibly high percentages of trucks and trailers get fines and penalties.

How brake adjustments are done wrong

As mentioned, often the brake adjustment, you know, the solution to poorly adjusted brakes, is useless. That sounds crazy but it's the foundational problem. The average adjustment is done with the wheels on the ground, often before a greasing, sometimes after sub-par grease is used, and without any measurements being taken. Not only are measurements rarely taken, only a few fleets do, but they’re rarely properly interpreted. If it was properly followed, by the second or third time a slack adjustor is way off, it should be understood that another adjustment is not the solution. But almost no one can know about the problem, fewer will act on it.

There’s a real expense to managing brake adjustments, and although everyone knows at least on some level that it’s extremely important for such heavy trucks to be able to brake as well as possible, it’s often neglected. No one will let an inexperienced apprentice adjust engine valves, but the brakes responsible for stopping thousands of pounds, no problem. And what’s funny is that one is as hard to do right as the other.

So, what is the solution to brake adjustment problems?

It takes a commitment and it takes a team effort. We have to be willing to say “a brake adjustment may take 10 minutes, and cost nothing more than labour, or it may cost a few hundred dollars and take hours”.

There are two reasons mechanics don’t adjust brakes properly, because they don’t know, or because they are lazy. I’ll only talk about the former. To adjust brakes properly one needs to know how to safely take measurements. Those measurements then need to be stored where they can be followed up on with future maintenance. Once measurements are taken, and everything is reasonable (one or more adjustors are not completely out of range requiring further inspection of problems in the system), the mechanic MUST lift the truck on jack stands. You cannot know if brakes are well adjusted by feel nor by “it’s always gone well when I did it this way in the past”. It’s mostly that attitude that led to the sorry state we now find many of ourselves in today.

Once the vehicle is lifted safely and securely, and we feel confident that the system is working well overall, then the adjustors may be tightened all the way, without forcing t the end. Most times a half-turn or so is enough to get the adjustment right. The trick however is to loosen the adjustors until the wheels turn freely. This is the trick. Without the vehicle in the air and the mechanic checking for the wheel to turn freely, the odds of the adjustment being too loose or too tight are huge. This leads to an imbalance in brake lining wear. Which leads to further bad adjustments. Automatic slack adjusters can only do so much. Measure to assure adjustments are equal and within spec, and you are done. If adjustments cannot be made equal and within spec, other issues need to be resolved.

Conclusion

This is a slight simplification of the work needed to get brake adjustments right. There is the quality of grease, of parts, and the proper management of information. There is a need for training and practice. Even drivers have a part to play. By every shift filling the air to the maximum pressure and applying the brakes all the way, then repeating 2-4 times, the slack adjusters have a chance to work properly. A slack adjuster is a ratchet, a ratchet needs to work to function properly. In this scenario that work comes from braking hard, which hopefully the driver rarely if ever needs to do.

I once inspected a school bus, the epitome of not braking hard (hopefully), and the first time I pushed the brake pedal all the way to the floor (this on a hydraulic system) the brake fluid line burst. Translate this story to: had the driver, God forbid with kids, been put in a situation where he did have to brake as hard as possible to avoid a collision, his brakes would have completely failed him. He didn’t know because he never drove hard enough to have the problem. This is the same ‘problem’ with any professional driver. The better they are, the less often they need to jam the brakes hard. Barring bad luck.

I hope this has opened your mind to looking at brake adjustment management as a lot more than a simple necessary evil that the new guy can just “get done with”. I hope you can find a way to approach the serious need to maintain braking capacity as much as I hope you never need it.