If you’re building a camper conversion, this article might be the most important one you read; it’s not about colour coordinating splash backs or which insulation is better for you no, it’s about what you can do for free to improve your safety and braking distances.
Remember at school we learned of Newton’s formula of F=m*a or Force is equal to mass multiplied by acceleration?
It’s a universal that applies to everything from solar systems to snooker balls, from big bangs to Bacteria, and basically means that energy, weight, and acceleration are all interlinked.
Why are we talking about this when we really want to know about adding extra payload to our van or motorhome?
Well, the most critical consideration to the weight of our vehicles is how they are going to still be able to brake safely.
Rearranging the above formula gives us (a=F/m ) or acceleration is equal to the force applied divided by mass or weight.
So if we visualise a sports car on the starting line, the acceleration is a result of the force it can apply between the wheels and the track (grip) and the weight of the vehicle; a light weight sports car is going to be faster than a pickup truck with the same power right? Simple.
But what if we look at slowing down again? After all braking is deceleration or negative acceleration.
Ok, so a heavy vehicle is going to take much longer to slow down, as it has more force (momentum) due to its higher weight.
This all makes perfect sense right? and would tell you that if two identical vans are braking on the motorway, and one is empty and one is full, the empty one is going to brake much sooner than the full one? Common sense, and this is what all braking requirements are based on.
But funnily enough that’s not true, and I’m going to try to explain why below.
Braking in the Real World
Back in 2019 (or as I prefer to call pre-2020 “the good old days”) a bunch of scientists in Slovakia named Skrucany, Vrabel & Kazimir decided to challenge this conventional wisdom and after performing pages and pages of calculations decided to buy a Peugeot Boxer L4H3 van and do some real world testing.
They connected sensors, and calibrated distances, and factored in things like wind speed and the effect of the sun's gravitational pull on the steering wheel (I might’ve made that last bit up) before going out on the test track. They got the van up to 75mph and braked to a stop and measured the braking distance.
They then repeated this experiment with some dummy weights raising in 250kg increments from 0kg up to 1,000kg, but here is the important bit, they also repeated the braking test with the weights in 3 different positions too; right up to the bulkhead behind the driver, in the middle of the load floor, and right at the back of the load floor.
In graph 1 is the results of the braking tests, and the dotted line is what you’d expect to see, a nice constant of “more weight = longer stopping distance” but that isn’t reflected in reality and the stopping distances appear all over the place.