Could be tires rather than bearings but you probably won't be able to tell until you remove and inspect the bearings.

Remove the wheel. Remove the caliper and hang it from the front spring with a piece of wire. Don't let anyone step on the brake with hanging calipers as it will spoil your day for sure. When my boys were young I locked the car to be sure no imaginary car trips ended with the caliper pistons laying on the concrete. Remove the rotor.

Remove the dust cover, cotter pin and nut; catch the bearing as you pull the hub towards you. Wipe excess grease off of bearing and then drop it in some kerosene.

Remove hub and lay it on a clean piece of newspaper backside down. Use a drift or smaller hammer handle to push the inside bearing out along with the grease seal that was holding it in place. Wipe off excess grease and drop it in the kerosene.

Remove the grease from the spindle and from inside the hub. Inspect the surface of the cups where the bearings ride. If it is discolored blue or pitted the cup and the bearing will need to be replaced.

Wash the bearings in the kerosene until all the grease has been removed. Inspect, looking for blue coloration (evidence of heat) or pitting in the surface of the rollers. If they are bad enough to be heard you should not have any trouble seeing evidence of damage.

If one bearing/cup assembly needs replacing it does not mean the other one does. Resist the temptation to replace the bearing without replacing the cup. The surfaces work together and just like a rotten apple....

To remove a cup for replacement be sure you have the right tools. Don't attempt to remove it using a screwdriver rather than a punch or drift of the correct size. On the back side of the cup you will find an edge that will allow you to get the flat surface of a punch or drift to rest on. You will be working on the backside of each cup. Strike the punch or drift sharply with a heavy hammer. Move 180 degrees and strike it again. Keep moving around the edge and keep striking making every effort to have it remain parallel to its original position (don't drive too much in one area and get it crooked). It will eventually come out.

Cleanliness is absolutely necessary upon reassembly.

To install a new cup I find it helpful to place it in the freezer for awhile. A cold cup is smaller than a warm one. Grease the outer surface and tap it with a hammer face to get it started. Again move around so as not to get it crooked. Be sure you do not have it turned backwards. Once you have driven it as far as you can with the hammer face you will need to go to work on it with the drift. Be careful to keep the surface of the drift flat against the edge of the cup; do not let the drift slip off of the small edge surface and strike the polished surface where the bearing rides. Drive it in until it stops dead in the correct position in the hub.

Cover the inside surface of the hub and cup with a layer of new grease. Be sure the grease you are using is designed for wheel bearings and for disc brakes.

Take the clean bearing for the back of the hub and force grease through the back side all the way around. A wad the size of a golf ball in the palm of one hand while manipulating the bearing with the other works well. Keep forcing grease in the back side of the bearing until it is squeezing out the front. Then give the surface of the rollers a coating of grease and lay the bearing in place on the greased cup. Some people like to put the bearing in a ziplock bag with the grease and force it in that way, but for me it is difficult to see the grease gets through the bearing; you do not want any internal dry areas.

You should have cleaned the grease seal carefully or purchased new ones. Seldom do I find it necessary to replace the seals. Opinions vary. Give the rubber edge a thin coating of grease and push it into place on the back side of the hub.

Take the clean bearing for the front side and repeat the packing process described for the one in the back. Set it aside where it will remain clean. Make sure the nut and washer are clean.

Resist the temptation to reuse the old cotter pins, purchase new ones of the correct size. Diameter is more important than length; you can always cut them if they are too long.

Lift the hub into place and push it onto the spindle. Insert the outside bearing into place against the greased cup. Place the washer overtop the bearing and finally start the nut onto the spindle. Tighten the nut by hand. Using a socket of the correct size or a pair of adjustable pliers continue tightening the nut while rotating the hub until you can no longer rotate the hub.

Loosen the nut without disturbing the position of the hub, and then tighten the nut finger tight, Install the cotter pin and spread the ends enough to prevent it from falling out. Install the clean dust cover and continue reassembly of the remove components.

Doing one side at a time prevents the possibility of mixing bearings from one wheel with the other, they are old friends working as a team; keep them that way.

Good luck.