wrote in message
...
On Feb 2, 7:15 pm, wrote:
. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Not a completely true statement. Have you ever used a measuring
wheel?

Yes I have; used them for several decades and many miles of measuring. They are
very unstable (but very manuverable) if you use them in the forward direction.
For long straight measurements, I always trailed them.

Vaughn