The Carrera 4 came
as standard with 16" diameter "Design 90" alloy wheels
- 6J on the front and 8J on the rear. Standard tyre size was 205/55 and
225/50 respectively. The wheels are designed to match the placement of
the wheel bearing in the hub and, as such have a mounting face with a
positive offset (as shown to the right) of 52.3mm. When replacing wheels
it is important to maintain the correct offset to preserve the loads placed
on the wheel bearing. Offsets (also referred to as "ET" or ' EinpressTiefe' ) may be varied with the aid of shims or
spacers in cases where the replacement wheel is a different width to the
original. Note that spacers/shims can only REDUCE an offset of a wheel,
never increase it.
In 1992 the Carrera
2 and 4 got the "Design 92" wheels - also called "Cup"
or "Cup 1" wheels in 16" and, optionally, 17" diameter.
The 17" wheels were standard on the Turbo cars from launch in
1991 (in 7J/9J sizes) and from 1992 on the RS in magnesium alloy in 7.5J
and 9J sizes.
Another term related
to the wheels is the bolt pattern. Most Porsche wheels use 5 bolts on
an imaginary circle around the hub which has a diameter of 130mm - this
is called the Pitch Circle Diameter, or PCD, often
shown as 5x130. |