keep the tire ride height the same.
Different size tires and wheels. The factory size tires and wheels are calibrated with the speedometer. If a different sized tires or wheels are put on the vehicle, the speed can be off.
You may use that size, yet however the accuracy of your speedometer will be less accurate (if used on front wheels).
Yes, but your speedometer will no longer be accurate.Sure, as long as you change all 4.
Larger tires will make the speedo lower than actual speed.
Yes, they will fit. Be aware that if the wheels are not the same diameter your speedometer will be off unless you change tires to compensate.
If by wheels you mean the steel rims, most Catalinas were equipped with 14 inch wheels. You can increase the size of the wheels, but that requires buying different tires. Often times changing the wheels and tires from stock will require calibrating the speedometer. A larger tire spins fewer times per mile which causes the speedometer to indicate a slower speed. A change from 14 to 15 inch wheels won't make a huge difference in speedometer error (8%) unless you are driving at a very high rate of speed. As speed increases, error increases. Mounting wheels above 15 inches runs the risk of a speeding ticket unless you have a GPS unit that can be used as a fallback speedometer.
Different heights of tire will change the speedometer reading.
Should not be a problem. Tires have an almost identical height so speedometer will remain accurate.
Do you have the correct size tires/wheels on the vehicle? Look on the driver's door post or in your owner's manual for the correct size. Incorrect size tires will effect the accuracy of the speedometer. If you are running the correct tires then the vehicle speed sensor (VSS) may need replacing.
Jet Accu Speed Speedometer calibrator. It adjusts your speedometer for bigger tires or gear change. Only works on automatic transmissions.
Not without changing the wheels also. If you also change the wheels to 17 inch wheels then that is an acceptable swap.
Yes, they can be used? To keep it simple, have the people who install your tires match the height of your existing 18 in tires with the new 20" tires. Doing that keeps you from reprogramming the computer to match the new combo and your speedometer will be correct.