[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
My comments below. Toby Erkson air_cooled_nut@pobox.com <-- Please use this address for email '72 VW Squareback 1.6L bored and stroked to 2.0L, Berg five-speed '75 Porsche 914 1.8L, R.I.P., ORPCA member '95 VW Jetta GL 2.0L, boringly bone-stock Portland, Oregon, http://www.pobox.com/~toby_erkson/ > -----Original Message----- > The backspacing (measured from the inside wheel rim to the mounting > face) will change by half the difference in the widths. Yup, sounds easy enough. > The other problem > is that you have now moved the inside edge of the tire and wheel > in about 3/4 ". Where did this 3/4" number come from? -=-=-=-=-=-=-=-=- New material -=-=-=-=-=-=-=-=- 15"x5.5" rim should have an offset of what? 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 The equation: ( (c - b) / 2) + a = d The solution: ( (139.7mm - 114.3mm) / 2) + 43.0mm = d ( (25.4mm) / 2) + 43.0mm = d 12.7mm + 43.0mm = d The answer: 55.7mm = d So a 55.7mm offset is what one would aim for when going up one inch in width. In fact, for every inch great$ , esser) than stock add (or subtract) 12.7mm to (or from) the stock offset to get the new offset. Thus, a 15x9.5" rim would have an offset of 106.5mm ((5x12.7)+43). Naturally one may not be able to get *exactly* the desired offset so try to get as close as possible. Thanks John! Now, I wonder if Jake's AutoMath spreadsheet can calculate offset and backspacing for us..? (hint, hint :) ------------------------------------------------------------------- Search old messages on the Web! Visit http://www.vwtype3.org/list/