It is not a closed space, the extra grease works it's way out of the space the first time the wheel is turned and gets the grease hot. Front wheel bearings are tapered roller bearings, there is no possible way that you can over pack them by hand. Most ruined bearings are caused by over tightening, not over packing with grease.

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Karl B
95 E300 D
2006 Mazdaspeed 6
2001 GMC Yukon XL
1997 Contour SVT
Mazda RX-7 SCCA race car