Take the modification of suspension spring as an example. If the spring belongs to [designated parts], the car owner is not required to declare under any number of circumstances. For [non designated parts] conforming to [security benchmark], if the load capacity of the vehicle changes significantly after modification, the vehicle owner must change the vehicle registration data. In other words, as long as the spring modification does not touch the range of [modified vehicle] (i.e. change the suspension form), it is not difficult to pass the verification of the relevant department in most cases. In fact, most of the existing street car suspension modification parts do not fall into the category of [modified vehicles].
Take engine modification as an example. As the compression ratio of the modified cylinder does not involve the change of the exhaust volume, even though the vehicle has increased the power output, it is not necessary to register it as a [modified vehicle] or replace the vehicle registration data in Japan (unless it does not meet the [security benchmark] after modification)
