Can we talk about how much grease is actually in a sealed cartridge bearing?

I was rebuilding an old Shimano hub last night and decided to pop one of the sealed cartridge bearings open just to see... I was shocked to find it was maybe only 30% full of grease. I always assumed they were packed solid. Found a tech document from Enduro Bearings online that basically said under-filling is normal to prevent overheating. Blew my mind a little. Anyone else run into this and have a preferred re-packing method, or do you just leave them as-is?

3 comments

3 Comments

troythompson1mo ago

That explains the dry sound some new hubs make.

felixramirez1mo ago

I packed my new DT Swiss hubs with a heavier marine grease and it quieted them right down.

tarar271mo ago

Yeah, my buddy did the same thing on an old Chris King hub last year and had the same shock. He was sure it was worn out because it felt a bit gritty, but when he cracked the seal it was just... not much grease in there. He ended up cleaning it and re-packing it with a light bike grease, maybe 50% full. It worked fine, but he said it felt like a gamble. That tech note makes sense though, about the heat. I guess @troythompson is right about that dry sound meaning they're just running lean from the factory. Makes you wonder if a little extra grease for quiet is worth the risk of it getting too hot.