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Wheel back spacing and off set.

2K views 11 replies 9 participants last post by  ericnova72 
#1 ·
Hello All
Kinda at a stand still on my 41 build ,so I thought I would start looking at wheels and tires. Thinking about old school Cragar SS nice and wide in the back and skinny in the front .
Can some one explain to me ,in laymans terms what back spacing and off set mean and how to measure them .
There are no Cragar dealers close by me so Ill be buying online and do not want to make a very costly mistake .
Thanks
Jeff
 
#2 · (Edited)
Backspacing is measure from the inner wheel edge(no tire on rim) to the wheels center contact surface where it would meet the drum or disc hat. Lay the wheel down on it's outside edge on the floor, take a straight edge and lay it across the inside edge of the rim and measure from the mounting surface of the center to the straight edge and you have measured the backspace.

Offset is measured relative to the center of the wheel rim. Take say an 8" wide rim, no offset (zero offset) would be the mounting point to the brake drum or disc is right in the center - 4" from inner or outer edge. Move the wheel center 1" toward the outside of the rim, and that is 1/2" positive offset...negative offset is moving the center inboard towards the inner edge of the rim from the center point of the rim. Just remember that offset is measured relative to centerline from tire bead seat to tire bead seat, and not outer edges of rim...Confusing, I know - this is what trips a lot of people up

Qkay ? ;)

Here's a link : https://www.rsracing.com/tech-wheel.html#backspace
 
#9 ·
Also to find the exact section width of a tire you can look at the manufacturers page. This will show a range of wheel widths for that size tire. It also shows the section width along with the wheel width they used to come up with that measurement. Any variation in the rim width they used will change the section width to a small degree.

Here is a link to a page for the tire specs I am talking about. This also lists other important info like tire diameter, max load, tread width, etc...

http://www.tirerack.com/tires/tires...all=Blackwall&partnum=74YR8GFTAKDW2&tab=Specs
 
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