questions

[gpday06]

what does rear spacing mean? and bolt circle? and how can i tell what wheels will fit my '79 C10 how do i do the measurments for rearspacing? any help is appreciated

[roundedline]

By rear spacing I am assuming you mean back spacing?
Back spacing is the distance from the mounting surface to the rear of the rim.  For example 4" backspacing will measure 4" from the mounting surface to the outer edge of the wheel if you placed a straightedge on it.

Bolt circle is the diameter of the circle that the bolts are centered on.  GM pickups are 5 on 5".  Or 5 lugs on 5" bolt circle.

One way to measure for backspacing is to take a rim the size you want with a known backspacing and measure the clearance from the edge to the fenderwell while the suspension is in compression and rebound.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[gpday06]

that helps but a little unclear about the back spacing, but its ok. im planning on these wheels, but dont know what offset and BSM mean? is the offset same as backspacing? thankz  
www.aewheel.com/eagle_all....cfm?id=12

[gpday06]

the 18" X 8"

[DnStClr]

Offset is not the same as backspacing.while backspacing measures from the mounting surface to the edge of the wheel, offset measures from the mounting surface to the middle of the wheel (when it's standing vertically).. Not sure what BSM means, but it probably means backspacing measurement.
Here's a link from Yokahama-
www.yokohamatire.com/utwheels.asp

Don St.Clair
Culleoka Tn