My porsche 1984 944 has 7x15 wheels which I am wanting to replace with
17inch Porsche Cup alloys. I have looked at a few web sites which all show that the 17 inch wheels come as 7.5Jx17 for the front and 9Jx17 for the rear. Can anyone explain why there is a difference in the width of the wheels for the front and back? Will they just bolt straight on? Surely the rears would protrude slightly?Also, what does the letter 'J' stand for in the wheel size?
TIA
-- David Speir (remove NO.SPAM to reply)
Gives a different shape tyre/road contact patch at the back, very common setup on performance cars.
With the "correct" alloy offset the wheels should stick out in both directions by an extra inch - you'd need to check if that will cause it to protrude on one side or foul anything on the other.
I'm not familiar with the wheels or car in question, but if your 944 won't take the wider rears then it should be possible to obtain the same size all round by buying replicas (assuming Porsche won't sell a set of
4 7.5" rims.)
It designates the shape of the tyre bead seat, IIRC.
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