Trying to get my head around the offset of wheels, if I have a wheel which is quoted at 42-50 56.1, does that mean from the edge of the rim to the mounting face of the rim and which one would be the inside or outside measurement, in this case is the rim 92mm wide? can't be as this is the quoted details for the standard rims on my Soob Forester, and what does the 56.1 represent, I assume it's the diameter of the hole in the center of the rim.
Thanks in anticipation
Don

http://www.1010tires.com/wheeloffsetcalculator.asp  < play with that

56.1 is the centerbore size for hubcentric mounting.

the lower the number offset the further out the wheel will go, between 2 wheels the same width anyway.

rough numbers.
a 15x5 +30 compared to a **x8 + 30, will be 1.5" more wheel inside and outside the original wheel
change that +30 to a +5, you get more like 2.5" further out & not much extra inside.
make it a +55 and you have 1" outside and 2" extra further in, also affects track measurements & opens a can of legal worms.

hope that kinda makes sense, gotta go to work! good luck

Thanks for that STIDUB, as it happens I had that same site opened plus this one http://www.carlsalter.com/wheel_fitments.html  what has me stumped is why the second site gives 2 figures for each wheel regardless of make

Bugger, had my hopes up, damned cheep I reckon.
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=160679881802&ss...

2 numbers may be from the various options fitted from factory, 16s on a tig are +33 19s are +45, it has to change with the width to keep the wheels inside the body