The tyre dimension should be the same for your winter tyres and your summer tyres. The dimension is set by the car manufacturer as the optimal dimension that the car is designed for. This is the dimension used for all the safety and performance tests, so if you alter the dimension you will also alter the behavior of the car plus that some of the readings from key instruments might be incorrect. This is true for the odometer and speedometer at least.
If you prefer to have another dimension of summer tyres on your car due to a sportier look, you should try to make sure to try to compensate a lower height dimension with a larger rim to make the overall dimension the same. If you want to put in extra wide tires you need to make sure that they fit in the wheelhouse and that movement when turning isn’t constrained. It is always advisable to discuss this with experts at your tyre shop to get their advice on what changes would be possible.
If you have 225/50R17 winter tyres you should change to 225/50R17 summer tyres and not try to deviate to lower height dimension with the same rim, so a 225/45R17 would not be a good change, as the outer dimension, i.e., the circumference would be smaller resulting in that each rotation would result in a shorter distance versus the original dimension. This is why the odometer and speedometer will show an incorrect reading.
Change to summer tyres at the end of the winter and when spring has arrived, and the weather will not change back. If you have studded tyres, the change to summer tyres is both dictated by the weather and by date restrictions which indicates the last day that you can use the studded tyres during the spring and when the change has to be completed. This is though contingent on that that there are no winter conditions in place when the change should have been done. You can still use the winter tyres as long as you have winter conditions.
If you believe that there is a chance for the winter to return it is advisable to wait with changing until you think that the winter has passed for good. The more dependent you are on your car for daily transport the longer you will probably want to wait so that you don’t get stuck in a situation where you have summer tyres on your car and you have snow covered streets. The summer tyres are dangerous to use when you have winter conditions as they will not be able to provide enough grip to be able to safely get you to your destination. It can also be against the law to maneuver a vehicle on roads when you don’t have the proper tyres for the availing conditions. Make sure that you change to summer tyres, but do it at a time when it is safe to do so.
For more information regarding different dimensions of summer tyres, visit: https://www.nokiantyres.com/