it is quite hard to say how strong they are.
but i can tell you that BBS makes all wheels that conform to some of the highest levels of testing in the industry.
Cyclic bend check
This test simulates the side pressure that is applied to the wheel when cornering. A tension ring is rigidly mounted to the inner rim shoulder and is subjected to a cyclic bending moment.
Two axial wheel test
With this test BBS is able to simulate both the side and normal pressure applied from the vehicle to the wheel. For example, using the Nürburgring or Hockenheim test, BBS can bring Formula One circuits 1:1 into its test facility so that it can put its wheel types through its paces under the hardest of conditions.
This test simulates the impact of hitting the curb from the side. A falling weight is dropped several times onto the outer rim shoulder of a tyre-covered wheel. It is important that there is no sudden loss of air from the tyre.
BBS wheels can withstand pressures of between four and ten times more than that defined in the European ECE regulations