Hot Rod Forum banner

Picking wheels for 67 LeMans (offset measuring)

3K views 14 replies 6 participants last post by  curtis73 
#1 ·
I'm planning on welding up a wheel offset measuring tool; the kind you bolt onto your hub and use to measure what offset/backspace you need. The ones I found online are expensive, and some require that you buy the tire to put on the checking tool, but I want one that will measure everything I need at once.

Having said that, I wondered if anyone knew off the top of their head what might fit my 67 LeMans. I'm going with 17" wheels. I thought I'd pick your brains first and maybe you folks already know what fits and what doesn't.
 
#11 ·
Agreed, but I want to make one with the measuring arm perpendicular to the hub. Then I can mark it with diameters and slide the all-thread up or down. I do this frequently enough that I want an actual precision tool instead of a piece of steel and a tape measure

I have one of those bolt pattern gauges that I can transfer to a steel disc and then weld on some channel.
 
#6 ·
Offset is the deviation of the wheel hub from center, and the backspacing is the amount of space from the center to the inside edge of the wheel Or ???
A 7 inch wheel with no offset would have a 3.5 inch backspace Yes or no?
Or am I thinking all wrong about it? Not trying to be flip.If I am wrong I need to know as I am looking at the same project in the future Joe. Thanks.
I see I also co mingled the term , so that is confusing . Backset. My bad.
 
#7 ·
Offset is the deviation of the wheel hub from center, and the backspacing is the amount of space from the center to the inside edge of the wheel Or ???
A 7 inch wheel with no offset would have a 3.5 inch backspace Yes or no?
Or am I thinking all wrong about it? Not trying to be flip.If I am wrong I need to know as I am looking at the same project in the future Joe. Thanks.
No, you got it. My point is that you can't specify a backspacing without also specifying a rim width. The added complexity is that backspacing is measured from the absolute inboard edge of the rim lip, whereas width is measured between the bead sealing surfaces. The shape of the lip can vary by wheel, especially between steel and aluminum wheels. For example, assuming zero offset on both wheels, a 7" wide wheel would have about 3.75" backspacing (half the width plus the extra thickness of the lip). An 8" wide wheel would have about 4.25" backspacing.
 
#12 ·
Being an ex-draftsman, I always use a piece of large cardboard (box) to lay out the tire/wheel I suspect will fit, then cut it out and see. If you were clever enough, you could build this template in two pieces that slide (with measurement markings) for adjustability...

Russ
 
#13 ·
Here was my quick and dirty drawing of what I had in mind.

I would take a bolt pattern gauge, lay it on a steel disc and trace the pattern onto the steel. Then cut and drill it to make a steel copy. Then take some 1/16" wall sqaure tubing (let's say 1") and notch the bottom of the tubing such that it sits behind the disc by 1/16". This way, the inside face of the smaller tubing that slides up and down should represent the wheel mount face since it is spaced 1/16" by the wall thickness of the bigger tube.

Weld a nut on the bigger tube for a thumbscrew to hold the smaller tube in place. Measure and mark the smaller tube at increments that correspond to overall diameter of the tire. At the very top of the smaller tube, weld on two adjusting collars with thumbscrews. Insert some solid rod through those collars. Slide one rod out to simulate the inner-most distance, and the other out to the outermost distance. Run the suspension through its limits and adjust up/down, in/out as necessary.

Then measure the overall width of the rods to find max section width, and measure the difference of inside/outside to find offset. Then its just a matter of finding the tire/wheel combo you want within those parameters.

The only thing I noticed I would change is the thumbscrew for the square tubing should be on the front face so it hold the smaller tube square against the back of the bigger tube.
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top