Legal lowering before needing certification

[keen 6]

I have an E34 i want to lower a bit. Can someone advise me of the maximum that can be done without certification?

Edited February 8 by keen
spelling mistake

[Vass 925]

My rough understanding is you have to maintain a minimum 100mm clearance to the lowest point of the underside. Cert is automatically required if you're putting in adjustable suspension so stick to traditional springs. Cutting springs is also a no-no. 

[thorburn 121]

Cut n paste from the lvvta cert threshold doc

▪ the springs or shock absorbers are direct replacements, and:

 replacement springs are contained within unmodified OE seats throughout full

suspension travel; and

 replacement springs are self-retaining in their seats at full extension, without use of

non-standard devices such as wire-ties, straps, or external spring locators; and

 replacement springs have not been heated or cut; and

 springs and spring seats are not height adjustable by any means (unless OE); and

 suspension maintains sufficient travel for safe operation; and

 suspension components maintain sufficient clearance from unmodified bump-stops

when fully laden; and

 a minimum of 100 mm ground clearance (un-laden and without driver) exists below

any part of the vehicle structure, or any steering, braking or suspension component

(does not include such items as exhaust pipes and exterior body panels that do not

contribute to the structural strength of the vehicle); and

 the normal relationship between front and rear suspension height is not unduly

affected; and

 clearance is maintained between all components, when tested from lock to lock at

full droop; and

 suspension retains at least 40 mm of rebound (droop) wheel travel (Note 6).

Note: Strut or spring spacers always require certification.

Note: The only other allowable methods of adjusting vehicle ride height without LVV certification are

leaf spring blocks (as per below requirements) or adjustment of OE equipment (torsion bars or OE

adjustable air suspension).

Note: When determining if there is sufficient suspension travel remaining, consideration must be given

to the vehicle being in use and fully-laden.

Note: Sufficient clearance must be maintained from the travel-limiting bump stop (not an OE spring

aid). The spring aid and/or bump stop must not be modified. A spring aid is a low-density conformable

material that is fitted inside a coil spring or above a leaf spring by a vehicle manufacturer to assist the

spring, and acts as the bump stop only once it is fully compressed. The spring aid may be contacted at

any loading condition to increase the vehicle’s spring rate, but the vehicle must retain sufficient wheel

travel. A bump stop is a small high-density rubber bumper that is designed to stop vehicle suspension

or driveline components from coming into contact with the vehicle structure at the extremes of its

suspension travel, and is not designed to carry the load of the vehicle for sustained periods of time.

Note: Rebound wheel travel should be measured as the difference between the distance from the top

of the tyre and the wheel arch with the vehicle resting on the ground, and the top of the tyre to the

wheel arch with the vehicle lifted so that its tyres are clear of the ground (suspension hanging in full

rebound). This difference must be greater than 40 mm.

Note: A vehicle can be LVV certified with less than 100 mm ground clearance provided that there is

sufficient suspension travel.

[Cement 905]

Yuuuur here is the document: https://lvvta.org.nz/documents/suplementary_information/LVVTA_LVV_Cert_Threshold.pdf

You're looking for the section 'Springs and shock absorbers (Including modification of ride height)' on page 16.