Yeah it can be a very big deal in a hard braking event (braking imbalance) especially on wet pavement. The tire on one end of a axle can have different traction for several reasons ie; different tread pattern......different load ranges (psi)....different tire sizes.....different tire types.
This is the 5th wheel trailer forum so I assume your talking about a trailer although its rare to find a 19.5" tire on a rv trailer.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides