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Actually I think we are still confusing offset and backspacing.... Offset is measured from the centerline of the wheel to the mounting face of the wheel with positive being away from the centerline of the car. Backspacing is measured from the inside wheel rim to the mounting face. Therefore the backspacing is equal to the width of the rim plus the offset. Backspacing will always be positive unless you have a negative offest wheel with the offset greater than half of th rim wi/㮚 Are we all confused now....:^) So using Toby's nomenclature... a = Stock offset = 43.0mm b = Stock width = 114.3mm ( = 4.5" x 25.4mm ) c = New width = 139.7mm ( = 5.5" x 25.4mm ) d = New offset = ??.?mm and adding two.. e = Stock Backspacing f = New Backspacing you have to decide what your goal is. a) Do you want the load on the bearing to be the same? b) Do you want the inside edge of the rim to be the same distance from the inner fender well? c) Do you want the outside edge of the rim to be the same distance from the fender? The solution is different for each goal. a)Here the extra width is split evenly inside and outside. a = d = 43mm e = (b/2)+a = 100.2mm f = (c/2)+d = 112.9mm b)Here the extra width is all on the outside. d = a-((c-b)/2) = 30.3mm e = (b/2)+a = 100.2mm f = (c/2)+d = 100.2mm c) Here the extra width is all on the inside. d = a+((c-b)/2) = 55.7mm e = (b/2)+a = 100.2mm f = (c/2)+d = 125.6mm Both a) and c) move the inside edge of the rim and tire in towards the inner fender well. a) moves it in 12.7mm and b) moves it in 25.4 mm. Both of these will probably cause rubbing on the inner fender well when you corner. b) keeps the inside edge of the wheel/tire in the same relative position and moves the outside edge outward. You have to watch the wheel well opening on the fender with this one. There is no free lunch. Hope this is clear. Take a look at www.tirerack.com in the Wheel Tech section for a picture that might help. Later, John Jaranson '71 FI Auto Fasty(now what offset did I need????) ------------------------------------------------------------------- Too much? Digest! mailto:type3-d-request@vwtype3.org Subj=subscribe