Packers or Bump Rubbers
Packers or bump rubbers can be used to prevent the springs or torsion bars compressing too far. This allows the suspension to be soft, but it means the bottom of car can only get a certain distance towards the ground until the springs hit the bump rubbers.
Cars often run on these bump rubbers under the influence of high speed aerodynamic load, but they must not come into play around a corner. If the suspension is soft enough for the car to ride the bump rubbers around a corner (not just a flat out curve) the movement in the suspension cannot give the wheel the desired grip, so the car's handling in the corner is compromised.
They are useful on modern F1 cars to preserve the wooden plank under the car.The rules stating that no more than 1 mm can be worn during the race.
Hence Schumacher's exclusion from Spa 1994 happened because wooden plank on his car was worn to much.
The most famous part of the SPA circuit is the Eau Rouge / Raidillon combination. Having negotiated the La Source hairpin , drivers race down a straight to the point where the track crosses the Eau Rouge stream for the first time, before being launched steeply uphill into a sweeping left-right-left combination of corners with a blind summit. The Eau Rouge corner requires a large amount of skill from the driver to negotiate well and the long straight ahead often produces good overtaking opportunities for the best drivers at the Les Combes corner. It is a crucial corner for the timed lap, and also in the race, because you have a long uphill straight afterwards where you can lose a lot of time if you make a mistake. It makes a special impression every lap, because there is also a huge compression of few g-s on driver's body and car as you go through the bottom of the corner. During this compression, car suspension give up, and without packers, underbody of the car can start to slide over the track. And that mean worn plank and less aerodynamical grip because diffuser can lose air to feed him.
The challenge for drivers has always been to take Eau Rouge-Raidillon flat out. Regular racing touring cars can take the corner at 160–180 km/h, prototipe racing cars at 250 km/h and Formula One at over 300 km/h.