There is no definitive answer to this question as it depends on a number of factors, such as the type of vehicle, driving conditions and personal preference. However, a good starting point would be to check the manufacturer's recommendations for your specific vehicle and tire size. In general, tires with a lower aspect ratio (such as 35) will require higher pressure than those with a higher aspect ratio (such as 45). Additionally, if you frequently drive in hot or cold weather conditions, you may need to adjust your tire pressure accordingly.