Butyl rubber material

Butyl rubber material has inevitable physical property so to speak plastic deformation under sustained loading. The frontal strut upper mount on vehicles supports over 500kg all the time in addition to vertical resisting brakeing power. So this part has tendency to deform gradually as time passes, causing frontal height down. As a matter of fact, the caster action reduces because of loosing frontal height. This phenomena happens so slowly as not to be realized by ordinal driver, if the stability is lost while straigh running by loosing caster action.

This is why many of rubber parts in vehicle should be replaced as periodical replacement parts.

In another words vehicles are capable to continue so long time as 200,000km or 20years if the maintenaces are performed properly.