“by muppets braking in the corner” blah blah blah…. i know.

but how are they produced? why does a wheel being dragged over the same spot create a rippled effect and not a rut in the direction of travel?

is it when the bike is “spitting traction”.. a favourite mbuk’ism

Imagine a cup filled evenly with small stones and sand.

If you tap the cup, over time all the stones appear at the top.

It’s nothing to do with that 😀

Imagine a cup filled evenly with small stones and sand.

If you tap the cup, over time all the stones appear at the top.

It’s nothing to do with that

I wondered where you were going with that lol 😆

Ok, if you lock your rear wheel at high speed, you go into a skid, but the wheel will skip a little everytime it hits a bump, then land back down and create a tiny dip in the ground. Completely unnoticeable for one rider. But when every riders back wheel hits that little bump, skips, then hits the same spot, you start getting that wavy effect.

I should add, that’s my theory anyway. I don’t actually know for certain.

Its caused by suspension dive

If everyone had their forks set properly it wouldn’t happen

And then the ruts hold water which softens them and means they get erroded faster than the bumps.

From vague memory of science class, I suspect it has something to do with resonance of the spring/damper system further enhanced by the extra loads going through the wheel/ground during braking.

Recsonance being the tendency of the system to oscillate at a greater amplitude at some frequencies than at others.

Similary, on the road you may notice that on tight uphill bends the road is corrugated on the inside where the inside driving wheel creates the same effect due to acceleration out of the bend and up the hill.

This even occurs to a smaller degree in a constant state system, constant state being no acceleration or braking. Train tracks develop these corrugations over time.

My text books were discarded a long time ago, so I can’t offer any further explanation.