- The coils in a spring are crushed into a rigid stack. The tyre casing is squashed against the solid wheel rim.
- The damper squeezes shut or stretches out so far that its inner valves strike the ends of the steel tube they are in.
- That hammer blow hits not only the suspension component itself, but also transmits to whatever it is attached to!
- If a rock or hole or bump is bad enough to do that, of course slowing down will reduce the impact. You should go slowly enough that the suspension moves within its design limits; over extreme obstacles, that can mean a near standstill.
On rough roads, driving very slowly is not necessarily kinder to your car. There’s always a “right” speed to maximise comfort and minimise wear-and-tear, and it is often a moderate cruising speed, not a crawl.
That applies to both a single bump or a continuous surface of rocks or holes or corrugations.
After all, “flexing” is what your car’s suspension (including tyres, springs, dampers and rubber bushes) is designed to do. By flexing a bit, but with enough space and resistance to still keep solid objects apart, it cushions the rest of the vehicle and its occupants from shaking and shocks. All the time.
It will come to no harm while doing that within its intended range of movement, whether the flexing is as fast as a humming bird’s wings or as slow as a chameleon’s walk.
Additional wear and tear or direct damage is inflicted only if any part of the suspension is forced to flex “further” than its design limit; or, in the case of tyres and dampers, when the intensity of movement generates extreme heat.
You’ll know when you have crossed the limit line. There will be a loud bang – as if some part of the car has been hit with a sledgehammer. Because it has. The hammer is the car’s dynamic weight, swung at the speed the car is travelling at. The “cushion” (of air in a tyre or compression of a rubber bush or bending of a spring) has been punched so violently that two solid things that are never supposed to meet hit each other. Bang. The axle hits the chassis so hard that even the rubber bump stop surrenders.
The coils in a spring are crushed into a rigid stack. The tyre casing is squashed against the solid wheel rim. The damper squeezes shut or stretches out so far that its inner valves strike the ends of the steel tube they are in.