Track and Wheelbase definition?

[strictlypersonl]

Unfortunately backspacing is not measured from the bead, it's measured from the outer edge of the casting. Typically a wheel is 3/4"-1" wider overall than its "nominal" width. Your 6" wheel might be 7" total width so that 3.25" backspacing puts the wheel mounting surface 1/4" in from the centerline of the wheel. Which is why I much prefer to specify mounting-surface-to-centerline rather than backspacing.

[speed220mph]

Bob: That includes you and me. Problem is when you're starting with a wheel and don't have the specs like in your drawing, you've got to measure the bead from the edge of the rim.

[Jim Holden]

I hit the wrong key, obviously 1/4 x2= 1/2".

...and Bob comes through with the 8x12.

For the sake of the discussion I was omitting consideration of wheel flanges, etc. and essentially viewing this as Bob has suggested i.e.; that the centerline of the 6" wheel is 3" in and (inasmuch as I don't have any other dimensions than the backspacing) the backspace is 3.25", I would have to add the negative offset number, less the centerline number to the track to get the flange to flange number.

Maybe I can coerce Bob into going into his data base and coming up with the magic number for the 6" Dayton 70 spoke wire wheel... and even a diagram.

Jim