offset/backspacing- whos good with this stuff!!!???

[PUR PONY]

ok- I get confused a little when it comes to this stuff. I am looking for a new set of rims for my old car and trying to figure out fit....... the new ones i really like dont come in the offset/backspacing i need

is this math correct to anyone that under stands this...
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9" wide rim
36mm (1.41in) offset

9"/2 = 4.5+36mm = ~5.91 backspacing.......

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so if i then got a:

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9" wide rim
12mm (0.47in) offset

9"/2 = 4.5+0.47mm = ~4.97 backspacing.....

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SO TO MAKE BOTH RIMS BE EXACT THE SECOND RIM WOULD NEED ABOUT A ( --- 1" ---- ) SPACER........


IS THIS CORRECT?????

thanks a million guys

 

[RangerX]

Lotsa fancy rithmatic, there! Here's what I would do. Take one of each rim and lay it down on the ground, outside-face down. Take any staightedge, like a ruler, and lay it across the top edge of the rim, from one lip to the other. It does not have to cross the widest part. It just needs to cross over any part of the mounting surface (where the lug holes are). Measure the distance from the straightedge to the mounting surface. That is your Backspacing. Compare to the other rim. The difference is how much spacer you need, although I would just run the set with the smaller number up front. You'll have a slightly wider front track, which is a good thing.

 

[PUR PONY]

thanks for the reply but i dont have the new wheels and not sure i can get one to look at around here.... basically a mail order wheel.... so i would like to figure this out on paper first.

The way i figure it.... if the wheel has a smaller offset then the front end is wider......

if the wheel as a larger offset the front end is narrower..... which means i can use spacers to widen it- and make the rims correct backspacing