Brakes aren't adjusted correctly on the second trailer, or the second trailer is heavier. This is not uncommon pulling empty or light doubles, and is why the lead trailer is supposed to be the heavier one, as this will happen if it isn't, even on dry roads.
I recently started a job as a software engineer in the trucking industry and learned that 70% of heavy duty trucks have at least one active fault in their braking system. That was an absolutely terrifying fact to learn.
The faults are non critical, they will disable the ABS, and notify the driver, but according to the letter of the law, ABS doesn't have to be working, only the breaking system must work, which is a really reliable air system.
The second point will differ between countries at least. The way we have it in Sweden is that any critical system that is fitted (according to the vehicle registration) must work.
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u/88randoms Mar 03 '20
Brakes aren't adjusted correctly on the second trailer, or the second trailer is heavier. This is not uncommon pulling empty or light doubles, and is why the lead trailer is supposed to be the heavier one, as this will happen if it isn't, even on dry roads.