zlacker

>>LinuxB+(OP)
So much WTF in this article, like the regenerative braking thing as if the torque for both regular braking and regenerative braking doesn't have to be put through the tyres to slow things down.

I definitely buy people with EVs hooning it around the place wrecking their tyres. It is really easy and fun to make use of all that torque. But it's not actually required.

>>mehele+H2
By design, braking introduces drag onto the brake disc and in turn creates drag on the wheel. This drag is in opposition to forward momentum and so the rubber of the tyre flexes and gives to these forces a little at a time - resulting in slowing your forward momentum.

A rail car without rubber takes 10x-50x the distance to brake due to steel on steel friction.

Rubber is consumed from the tyre during acceleration, deceleration, and turning. Little rubber granules will roll off. The only time this isn’t happening is when the tyres aren’t in motion.

This is why you bring extra tyres to track day.

>>reacto+G4
In motion the friction coefficient of rubber on asphalt (0.67) is not that far off from steel on steel (0.57) according to the internet [0]. That orders of magnitude difference in braking distance is more a result of train cars weighing 30-80t.

This comment does feel like talking to ChatGPT though, with the detailed clarifications the discussion didn't really require.

[0] https://www.aplusphysics.com/courses/honors/dynamics/images/...

>>buran7+27
The mass of a vehicle does not determine the braking distance, assuming the braking is coefficient of friction limited.

>>london+Q8
It does but not because it influences friction at the wheel contact point (the mass cancels out in that formula). If braking is done entirely in "wheels locked" fashion then all that matters is the friction coefficient between the wheel and the track. But most braking is not like that. A train will only lock the wheels in emergency braking as that will apply larger braking force than otherwise available.

In normal braking the friction between the pads and the wheel is the important one and in that case the stopping distance is determined by how much of the energy of the moving vehicle you can bleed through the force you apply with the braking pads. More mass/speed, more energy, more time needed to apply the xxxxN of force to the wheel and convert the energy to heat. The energy of the moving vehicle scales with its weight while the maximum force a friction braking system can apply doesn't.

The science of braking is even more complicated than that, materials heat up or melt, friction coefficients change, tires behave differently under different loads, ABS systems kick in, etc. These are deceptively complicated topics.

The formula for friction also doesn't contain surface area and yet we use wide tires and big brake pads. But the bottom line is that in a real life scenario (as in not in simplified formulas on paper) the weight of the vehicle very much influences the braking distance.