[Stroker]

When you measure a wheel's backspace, I assume you start from the back side of the wheel that mates with the hub. But do you measure to the outer-most point of the wheel or inside where the tire bead would sit.

 

[74 hatchback]

most outer part

 

[supr78nova]

not all wheel manufacturers measure backspace the same way. To make sure, contact the manufacturer and ask how they measure before you order.

Dan

 

[NOGO]

not all wheel manufacturers measure backspace the same way. To make sure, contact the manufacturer and ask how they measure before you order.

Dan

Dan is absolutely correct. Never assume when you are spending hard earned $$$ on your wheels!

 

[Tim_D]

not all wheel manufacturers measure backspace the same way. To make sure, contact the manufacturer and ask how they measure before you order.

Dan

Yeah, I may have found this out the hard way...

I ordered my wheels for my '63 wagon in size 17x7 with 4.5" backspacing. I assumed that, since the wheel width measurement is from bead to bead, that the backspace measurement was from mounting surface to bead. At least that's the way I would do it.

Well, I got my wheels and they are measured to the outer lip, not the bead . Now, after measuring the wheels outside-to-outside mounted on the rear axle and comparing to the minimum measurement on the inside of the wheel houses, it looks REEEEAAAAL CLOSE. I'm looking at 1/2" clearance min on each side, assuming the axle is perfectly centered (which is a leap of faith in itself).

The measurement from bead to rim lip is 1/2". The extra 1/2" per side would have given me plenty of clearance. Now, I'm looking at the probability of narrowing the axle or heating/pounding the outer wheelhouses.

 

[justin72nova]

I have always thought backspacing was measured from back edge of wheel to where the rotor touches the wheel (in inches)

and offset is the middle of the wheel to where the rotor touches the wheel (in mm)