So what is reasonable?
Remember we need to be able to justify our views on the basis of road safety, enginnering reality and the expectations of the general public.
What has been permitted or restricted in the past is in the past, what is reasonable mo-ving for-ward (julia)
.AND this does go further than wheel sizes and lifts.
So lets start with unengineered lifts.
I think by far the most practical proposal is a 3 inch or 75mm maximum total un-engineered lift consisting of an increase in tyre diameter of up to 50mm and either or, or a combination of body or suspension lift of up to 50mm.
The tyre size being judged from the tyre manual, the body lift being measured by the size of the blocks being inserted or substituted and the suspension lift being measured at the chaisis rail ( some how).
I justify this by saying, it is not chainging the ride height a great deal, bumper off set should not be much of an issue, and all vehicles should withstand this within enginering tolerance.
And most of the general public would not regonise a vehicle lifted thus as being lifted.
And it is practical because a lift and a trye size increase are commonly done hand in hand, AND this is a popular, common and moderate combination.
Of course all the usual conditions apply, such as wheel coverage, % of suspension travel, ADR complainace and so forth.
Some states like QLD may require inspection but not engineering of a body lift..this is probably reasonable.
This sort of lift would be well within the capability of the average home mechanic and on most vehicles it would not require further modifications to make the steering or suspension behave correctly
This sort of combination I am sure is very very popular even among the conservative and would represent thousands upons thousands of vehicles.
Making people engineer lifts up to 3 inches would simply clog the system.
Seperating the tyres from the other lift, I think is a practicality...because tyres can be easily changed in a few minutes, where the other lifts can not.
Thaughts.
cheers