“When assessing a modified/rebuilt vehicle, DVLA’s main interest is to establish whether the original identity has been compromised by the changes made. If a vehicle has been modified from the original manufacturer’s specification or if not enough of the original components have been retained in the build, the vehicle identity will change and IVA will be required to register with an alternative registration number.

Due to the very nature of rebuilding or modifying vehicles from their original manufacturer’s specification, DVLA assesses each vehicle on its own merits based on the documentary evidence provided and a physical inspection of the vehicle.

The INF 26 information leaflet, and the information given on the website, is issued as a guideline to the registration of rebuilt, radically altered or kit converted vehicles. They are not meant as technical guides. However, both clearly indicate that if modifications are made to the chassis or monocoque bodyshell, or if the build does not include enough original, major components (as listed) the identity of the vehicle will change.
The information on www.direct.gov.uk is regularly reviewed to reflect changes in legislation

VOSA have provided the following response to your questions;

Chassis.

Q) What is classed as chassis? Is it purely the outer longitudinal rails or are the crossmembers between these also a part of the chassis?

A) Chassis should be taken to include crossmembers.

Q) We know that cutting or shortening a chassis is classed as modification but is this relative to the vehicle wheelbase i.e. the chassis must remain uncut between the 2 axles but anything forward of front or aft of rear suspension mounts can be removed?

A) Chassis includes the full original length of the longitudinal members including to the front of the front axle and to the rear of the rear axle.

Q) Is it acceptable to remove bodymounts, which contribute no strength to the chassis when changing a body to a different style /make?

A) Yes, providing they are additional to and are not an integral part of the chassis structure.

Q) Is it acceptable to strengthen a chassis by the addition of boxing plates a process that involves turning a 3-sided open chassis rail into a fully enclosed ‘box’ chassis?

A) Yes, providing the original structure remains unchanged.

Monococque.

Q) What is the definition of a monococque ?

A) A design in which body and chassis are all one unit.

Q) Why does cutting into a monococque affect the vehicle identity if it retains the same shape /profile as before.

A) Cutting is considered to be modifying the vehicle from its original specification. Any modification to the chassis/monocoque body is considered to render the vehicle no longer original specification or of original identity.

Q) Is it acceptable to modify a vehicle bulkhead and/or transmission tunnel when performing an engine change or fitting another make?

A) No, Assuming this is in relation to a monocoque structure. This would be considered a modification to the structure.

Q) Is it acceptable to fully weld sections that are spot-welded as part of the original construction methods, to increase the strength of the body?

A) Yes, providing the original structure is retained.

ACE felt that further clarification was needed from VOSA so we sent more questions.

The following responses are from the VOSA Press Office:-

The answers to our chassied vehicle rules queries seem mainly straightforward, However, we have further questions based on the answers supplied.

Q) As chassis strengthening is allowed, are we correct in assuming that additional crossmembers would also be allowed?

A) It is important that the original chassis structure is retained unmodified, and while it is acceptable to strengthen areas and include additional brackets or crossmembers, It would be limited to additions within the existing chassis frame structure. Additional chassis structures, i.e. extending the outward parameters of the original chassis structure would be considered a modification.

Q) It is the monococque rules that need the most clarification.
Your reply states that any cutting of the monococque” is considered to render the vehicle identity no longer original specification or of original identity “. This would suggest that any crash repairs necessitating cutting and removal of panels or chassis sections, or restoration work would call the vehicle’s identity into question?

We presume that the point should really be that any cutting… other than in factory designed joining areas…would be the actual criteria?

A) In this respect it is necessary to differentiate between modification and repair. Any repair process that is in line with manufacturer’s recommendations and that returns the structure to its original specification would not be considered to be a modification.

Q) Would the modification of wings to allow clearance for larger wheels fall foul of the regulations?

We presume not as the common fitment of sunroofs does not create issues as this is a non stressed item of the monococque, the same as wings?”

A) When considering a monocoque structure, it is necessary to consider what constitutes cosmetic panels that do not significantly add to the structural strength and which panels provide structural integrity. In general front wings modified in this way would not constitute a modification to the monocoque structure.

With reference to the further query, VOSA have advised that they would prefer the following statement:

What constitutes a monocoque is that of how an OEM manufacturer would view it. The chassis or `cage` assembly and all components that form it, less any cosmetic panels or infills that make no structural consideration to the monocoque or its component parts.
However, we must emphasis that this information is given for general guidance and each case will be judged on its merits.