Brake testing: How to choose the right load simulation system

By Pavan Jheeta

With the DVSA’s new laden testing in full effect since 2023, more workshops than ever are getting equipment in place to start simulating loads on their in-house brake testing.

But if you’re looking at options to improve your brake testers, it’s not always clear what the best choice is.

Here’s what you need to know about the different load simulation systems — and how to pick the system that’s right for your setup:

 

Which brake testers do you use?

This is the first big question you need to ask — especially if your workshop uses several types of brake tester.

Some types of load simulation work better with specific brake testers. And some brake testers are simply unsuitable for certain types of load simulation.

In practice, that usually means you’ll be looking at:

  • Axle load simulation for a Mobile Brake Tester
  • Chassis load simulation for an In-ground Brake Tester that’s installed over a pit
  • Direct load simulation for an In-ground Brake Tester
  • Hydraulic load simulation (if it’s built into an In-ground Brake Tester).

Those are the general rules of thumb. But there is one exception that can cover every base:

Direct load simulation (like our Nodding Donkey) can be used with any type of brake tester.

 

Because the Nodding Donkey works as a completely separate unit — one that doesn’t attach to the brake tester — it doesn’t matter which type of brake tester you use with it. The pressure is applied directly to the top of the vehicle, and the brake tester isn’t involved in applying that force.

Most other types of load simulation work by using some version of the ‘pull-down chain’ method — including Axle, Chassis, and Hydraulic load simulation.

That means the vehicle is attached to the brake tester with chains — and that can affect whether that type of brake tester is a good fit.

 

What types of vehicles are you testing?

As well as the different types of brake testers, you also need to think about the vehicles themselves.

While the Nodding Donkey can work with any type of brake tester, it won’t work with every vehicle. It needs a sizeable flat surface to apply its downward pressure, which means it’s best for:

  • Vehicles with open flat-beds
  • Tractors where a load is applied to the fifth wheel
  • Closed box trailers and trailers with an opening
  • And semi-trailers.

Similarly, load simulations using a ‘pull-down chain’ won’t always be right for every type of vehicle:

While Axle and Hydraulic Load Simulation will work for most vehicles (they’ve all got axles!), Chassis Load Simulation won’t always be a good fit.

Depending on the vehicle, it may be difficult to find a connection point on the chassis that’s strong enough for the forces applied by the chains. And in some cases, we’ve seen workshops that have caused damage to their vehicles by improperly attaching chains to the chassis.

 

What kind of brakes do they have?

This is a smaller point — but it’s one worth thinking about.

Most commercial vehicles use a load-sensing valve in their braking systems. It’s designed to help the vehicle adjust its braking pressure in response to the load it’s carrying.

So why does that matter when you’re choosing a load simulation system?

Because some types of load simulation bypass this valve completely.

With a pull-down chain method (such as Axle or Hydraulic Load Simulation), you’re not apply pressure to the body of the vehicle. This means the load-sensing valve doesn’t get activated, and it won’t adjust the braking power according to the ‘load’ you’re simulating.

You won’t achieve the 65% DAW (Design Axle Weight) that’s required by the DVSA — and your brake testing won’t give you results that reflect the true performance of your brakes.

So if you’re servicing vehicles that use a load-sensing valve, you may be better off with a load simulation system that affects the entire vehicle — such as Direct or Chassis Load Simulation.

 

Still not sure?

There are lots of options for load simulation systems — and lots of factors that affect your choice.

If you’ve got a mixed fleet (or a mixed set of brake testers in regular use), the best place to start is with the advice of an expert:

We’ve spent decades helping workshops and fleet owners to make the right choices with their brake testers — with customers that use every type of equipment, and every type of vehicle.

So if you’re looking to expand or upgrade your kit, we’re here to help:

You can look through our full range of brake testers in our online shop — or start a chat with a workshop expert to get the advice you need to make the best choice for your business.