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Working Out Offsets Help


26 Jan 2019
Am very much thinking about getting some BBS E88's for the 6.C4S and I could do with the collective brain on sizes etc.

I currently run the standard wheel (albeit turbo) with Cup2's on 7mm spacers front and 15mm spacers rear which is just right. I shall probably change to 4S's on these if I can find the right sizes.

Q1: How do I convert that into a offset for new wheels given I can specify so I don't need to run spacers?

Q2: Is there any merit in going smaller or wider at either end and if so is their any good/favourite alternatives out there? It is pretty over tyre'd for the power so I don't want to run any more rubber at the rear, arguably front could do a size larger etc

Can't get gold E88's out of my head. Such lovely looking wheels but I don't want to spend all the money and get the wrong size!
Standard wide body wheels are as follows
Front : 18x8 et50
Rear: 18x11 et63

The equivalent with your spacers are front et43, rear et48.

My 996.1 C2 had 235s on the front when I got it (which is standard on wide body), I changed for the correct 225 and can see why the previous owner made the change, but it isn't much different really. I'd suggest sticking to standard sizes.
Those are not the standard offsets for a wide body car. 45 is right for the rears, before knocking off the spacers.
Spinner said:
Q1: How do I convert that into a offset for new wheels given I can specify so I don't need to run spacers?

The wheel offset eg ET63 is the amount in mm by which the mounting face of the wheel is offset outwards from the centre line of the wheel (ie how much the centre line is displaced inwards towards the car). The spacer effectively moves the mounting face inwards towards the centre line of the wheel ie it pushes the wheel outwards from the hub. So to recalculate the effective offset with the spacers fitted you subtract the spacer thickness from the wheel ET. In your case if the original is ET63 then the effective new rear offset is ET(63-15) = ET48.

You need to be sure what your current ET is before specifying new wheels.

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