Part 6 The Wheels cont

8) PCD - this is the abbreviation for 'pitch circle diameter or 'bolt circle diameter. It denotes the diameter of an imaginary circle passing through the centres of (in our case) the four nuts securing the wheel to the hub face. For the TR7/8 this dimension is 3.75inches (95mm).
9) Offset - this is the distance between the wheel mounting surface and the centre- line of the rim. If the centreline is outboard of the mounting surface, positive offset (and a wider track) results; if it's inboard of the mounting surface, negative offset (and a narrower track) results. In the case of the TR7/8 there is a negative offset of 30mm (1.19 inches). Obviously if the offset is changed and tends towards the positive aspect, then the wheel will be farther out and closer to the outer edge of the wing. This could ultimately result in the tyre hitting the wing. Often when buying after market wheels this fact is not taken into account and can be made worse by fitting bigger tyres with a larger section width. One final thought to bear in mind if buying after market wheels and tyres; if the offset is increased or decreased from the car manufacturers stated figures then the loads on the wheel bearings and steering/suspension joints will increase. Similarly, excessive offset can cause heavy steering and kickback through the steering wheel.

I have deliberately refrained from suggesting any particular make/model of after market tyres or wheels, as this is up to the individual. However, I hope that the above will help in making an informed decision. Remember, the larger the section width the more rubber on the road and hence the more weight on the steering. Similarly, the lower the aspect ratio the firmer (harder!) the ride.

As I know many members who have carried out V8 conversions have also opted for after market tyres and wheels, perhaps they could let me know the manufacturers names and their specifications so that a database can be set up for new members contemplating this aspect of the conversion.