If you have them on a 8 inch rim try 18 lbs, if on a 10 inch or wider rim try 20lbs Not all gauges read the same pressures on the same tire by the same person I have more than one tire gauge, two cheap Moroso 0 to15 lbs, a digital bycycle racing gauge and a real expensive low pressure (0 to 12 lbs in 16 of a lb increments) analog gauge. I now use one of them only, don't get your self confused by having multiple gauges Take the time to expermiment to find the best pressure for your car I ran M/T 325x6060x15 ET Street radials on both 12 inch and 10 inch wide rims, I ran them on my 3450 lb Duster, it like between 18 and 22 lbs them according to my notes on my gauge IHTHs