Do I need an 8.5mm or a 10mm size wire if my original wires are just 7mm (or smaller)?

If you don’t intend to upgrade your vehicle’s original ignition with a high-output ignition, you may not need larger size wires.

Magnecor KV85 and R-100 Race Wires have been designed primarily for race engines that will be run with high-output ignition systems, and contain high-capacity 2.5mm conductors that require extra insulation when used with extreme-output ignition systems. Magnecor Race Wires will also be exposed to heat an unmodified production vehicle will never experience.

However, the major advantage Magnecor Race Wires have over conventional 5mm, 7mm and 8mm wires is that neither the high-capacity conductor nor the insulating jacket will wear out during the life of the engine.