A light film of greasy dirt can happen with freshly packed wheel bearings, especially when the dust caps are more of a shield than a true seal, but you definitely shouldn’t see excessive grease constantly flinging out from both sides. If the TBS bearings were overpacked at assembly, the heat from use can force extra grease past the caps, so checking the packing amount and making sure the caps fit snugly is a smart move before it turns into overheating or contamination issues.
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