"I have 245/45R17 low profile tires on my car, and I want to make sure these new tires I'm looking at are low profile, too. Also, can I replace low profile tires with 'regular' tires?" These two questions are asked often by customers we deal with when discussing tire options.
If the tires you're looking at purchasing are the same size, in this example it would be 245/45R17, then they will have the same dimensions and the tire's profile will be at the same level.
The term "low profile" is a relative term. It does not describe a specific type of tire. If you consider 245/45R17 to be low profile, then every single tire available in that size is low profile as well. Some will say anything lower than 50-series, some will say anything less than 40-series is considered low profile. It doesn't really matter what you consider to be low profile, what really matters is that you have the right size tires. Yes, a 245/45R17 is lower profile than a 245/50R17 tire, but they aren't interchangeable.
Some people want to take their Original Equipment (still using 245/45R17 as an example), and put a "lower profile" tire on their car and drop it to 245/40R17 to lower their vehicle. While going from a 45-series to a 40-series will give you a lower profile tire, it will also change several other things. The lower profile also decreases the overall diameter of the tire, which will cause a harsher ride, increase your probability of damaging a tire and change the accuracy of your speedometer and odometer. The propensity for damaging a tire comes from the decreased load carrying capacity of the smaller tire.
Other people will go the opposite direction with this and say that they don't like the ride of these "low profile tires" and they want something that isn't low profile. While taking that 245/45R17 and moving up to a 245/50R17 may sound enticing to get a smoother ride and protect your wheels from potholes, this may not be a good idea either. That change in size gains you almost a full inch of overall diameter, a 4.4% increase. This may not sound like much, but it is outside the 3% variation range that is normally recommended, so it will affect your speedometer and odometer adversely. The other part of this is that while some vehicles may be able to handle a one inch diameter increase in tires, most can not. Vehicles are being built to more exact tolerances these days, and often times there simply isn't enough room to turn a bigger tire inside your wheelwells without rubbing.
If you want a lower profile tire for aesthetic reasons, what you need to do is get a larger set of wheels. A 245/40R18 is lower profile but the same diameter as a 245/45R17. If you want a higher profile tire to get a smoother ride, you should get a smaller set of wheels and something similar to 245/50R16, which is higher profile with the same diameter. When you want a higher profile tire to fill your wheelwell out better, you're going about it the wrong way. You should lower the suspension of your car to close that wheel gap.