REMOVE THE SHIELDS
The shields on your bearings do a good job of keeping most debris out of the bearings, but they also do a good job of slowing down the bearings slightly due to friction between the shield and the inner and outer race of the bearing. Removing one or both of the shields can reduce friction and let your bearings move more freely. Shields should only be removed from the side of the bearing that isn’t exposed. For example, a bearing in a hub should have the shield that will be inside the hub removed. If a bearing is completely covered, like the bearings on an idler shaft, you can remove both shields.
Removing one or both of the shields from your bearings is going to allow them to spin more freely.