[Tigers] Rear tire rubbing

[Tiger Man]

I took the tiger out the other day, its been too long.  A guy at work wanted
to check it out, so we went for a spin.  I eventually pulled off in a dusty
dirt area and let him drive.  At the time when I was switching sides, I
noticed that the passenger rear tire had a big rub mark on it, which was
really evident by the dust everywhere else.  I didn't see any evidence of it
on the drivers side.

The guy from work was a big guy, and I'm not exactly a lightweight either.  So
not sure if that was one of those one time weird things of two big guys
bottoming out the suspension when I left the pavement, or if I truly have a
problem.

The car is running 185/70R13 on stock rims.   I measured the clearance from
the ground to the fender, and the center of the axle, of course I forgot to
write it down, so I will have to go out and remeasure at some point.

Basically I am trying to figure out, are the tires I am running a bit
optimistic on height/width, or is my suspension starting to sag.  There is a
shop locally that does big business re-arching springs for classic cars so not
sure if its time to go see them, but even if I do, not sure the would have the
specs on what the springs should look like.

Also the tires still have plenty of tread on them, but I know they are
probably getting old enough that they need to be replaced anyway.  So I will
be trying to decide on a replacement tire, or the possibility of wheel/tire
upgrade.  But in the mean time, I'd rather not loose a tire though because of
sidewall failure, as I believe my spare is original 1965 issue

Anyone have any experience in that tire size, or the measurement I can use to
check my suspension?

Thanks,
Steve