356C wheel offset dimensions

[Robin]

Can anyone tell me what the offset dimensions should be for 5 1/2 inch steel wheels to fit a 356C ?
The standard 4 1/2 inch wheels show 112mm, will 125mm fit ok?

 

[Lightweight_911]

I think the backspace of the 4.5in steel wheel is actually 100mm (ET=42mm)

The 5.5in steel wheel has a backspace of 112mm (ET=42mm).








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[Robin]

Measuring from the wheel inner mating face perpendicular to a straight edge across the rim outer lip, gives the following dimensions :-

KPZ 1964 standard size 356C wheels, 4 1/2 inch x 15 steel wheel measures 112 mm (a nominal 4 inches backspace)

Lemmerz 1967 early 911/912 5 1/2 inch x 15 steel wheel, measures 126mm ( 5 inches backspace)

KPZ 1984? early 911 steel wheel 5 1/2 inch x 15 listed ET42, measures 126mm (5 inches backspace )

I have two KPZ 944 spare wheels part number 477 601 030 B, steel 5 1/2 x 15 wheels, dated 1987 marked ET53 and with a backspace of 137mm (about 5 1/2 inches backspace).
These are having the centres cut out and rewelded to give an offset of 126mm, to match the ET42 wheels making a set of 4 wheels and a spare, all will be painted silver.

Does anyone know what the "ET" in ET42 or ET53 actually means ?

At least If they don't fit the 356C then I will have a set of "Steelies" for someone with an early 911 or a 912 to buy.

 

[Lightweight_911]

Robin - my mistake ... I was neglecting to take into account the actual overall width of the wheel.

ET is the offset ... the 'deviation' of the hub mounting face from the centre-line through the wheel.

For example, a 5.5in wheel - which is actually approx 6 5/8in wide - (6.625 x 25.4mm = 168.275mm) has a centre-line approx 84mm from the edge of the rim.

If the backspace is 126mm, then the offset (ET) is 126 - 84 = 42mm











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