backspacing? offset? what????

this isnt directly an explorer question but i NEED help.

i have a 1999 expedition with AP racing brakes.
these new calipers and rotors are too big for stock ford rims. i know that i need at least 17'' rims for them to fit. the back of the stock rims hit the caliper. how can i measure the NEW "backspacing" or "offset" of my truck so i can get the right size rims...?
also what is my trucks stock "offset"?


thanks and PLEASE help..

Tony

 

[SIGMAPIRATESHU]

backspace

ok forget everything that i said about backspacing i got my answer...all i need to know about now is OFFSET.

what is my trucks stock offset..how can i figure out what it is now.

thanks

 

[addkev]

back spacing and offset are the same thing, but back spacing is measured from the back of the wheel and off set is measured from the centerline of the wheel, but they accomplish the same measurement.

There is a good write up onm tirerack.com


Offset

 

[SIGMAPIRATESHU]

offset

thanks alot...btw i went threw hell to find rims that would fit my expedition...

thanks

tony