Paraphrased from Continental’s website:
The lateral stiffness of air bellows differs greatly from type to type. For the individual air bellows types, the following lateral stiffness values – relative to the axial stiffness – can be expected. The specified percentages are for the recommended operating height for vibration isolation.
Single convolution 30 to 60%
Double convolution 5 to 30%
Belted 30 to 50%
Triple convolution 0% (not recommended)
Rolling lobe 0% (without restraining cylinder)
Sleeve type 0% (without restraining cylinder)