[GLHS60]

To understand OEM wheel patterns, one needs to understand and measure the 'bolt circle"

If an axle etc was spun and a line scribed between the stud hole centers it would measure 4.75"

The "bolt circle" is the diameter of the circle made thru the stud centers.

If one actually scribes the 5 on 4 3/4" wheel, the circle will measure exactly 4.75

Old timers look a the studs and see the imaginary circle the studs/holes form.

Typically they measure from the center of any stud to between the farthest 2 studs.

Not directly between the farthest 2 studs but allowing for the curvature of the circle.

 

[GLHS60]

Wheel bolt patterns are measured as a bolt CIRCLE, regardless of the number of studs involved. This means that all of the studs are placed exactly with their centers corresponding to the center of the bolt circle. Then the spacing of the studs is calculated (geometry again) according to the number of studs, for example a five lug application will have the studs placed every 72 degrees (360 divided by 5). It is pretty hard to measure bolt circle with a tape measure when an uneven number of studs is involved. The best choice is to invest in an inexpensive bolt circle measuring gauge .

EXACTLY Bill !!!

I've never before read such dumb answers as some of the ones in this thread.

Its not even that hard with a tape measure if one remembers to measure the CIRCLE.

Its little wonder so many guys call their Engines motors

 

[GLHS60]

This is still dumb!!

Can't anyone post a diagram showing how to measure a circle??

Say a 4.5 or 4.75 or 5 inch circle ...

Correct. Everyone knows the bolt circle formula for a 5 bolt is: boltcircle = 2Rsin(72) + wheelstuddiameter/2
Or, just use a tapemeasure like this:
View attachment 49562