15x12 on 12.5 tires? backspacing measurements?

[broncoman6524]

ok i bought that truck im builidin its got 2 15x12 steel wheels that i wanna put on my dd k5. its got 33x12.5 bfg all terrains.

how do i measure backspacing on these wheels? i gotta order 2 and i want them to match LOL. is it front of wheel lip to mounting surface?

or back of the wheel lip to the back of the mounting surface?

 

[scooter122983]

Inside wheel lip to the mounting surface use a straigh edge and a tape mesure to get a good mesurement.
Inside/ Axle
I I
\_I__I_/
I I
I I
/------\
outisde
Its kind of a poor drawing with the key board but hope fully you get the idea
also measure the bolt pattern for the lugs so the wheel mfr can give you the same wheels.

 

[broncoman6524]

theyre 6 on 5.5 came off a d44.

ok so the lower the number of backspacing (5" 4" or whatever) the FARTHER the wheel sticks out form the hub?