Shoutout to the old guy at the swap meet who told me about grease migration

I was picking through some parts at the Riverside swap meet last Sunday, and this older mechanic started chatting with me about vintage cup and cone hubs. He said something that blew my mind: he claimed that in a properly packed and adjusted hub, the grease can actually migrate away from the bearings and into the freehub body shell over a few hundred miles, leaving the balls dry. I always thought if you packed it full, it stayed put. He showed me a 90s Shimano hub he'd just serviced where the freehub was packed with grease but the race was almost clean. I've been doing this for five years and never noticed that pattern. Has anyone else seen this happen, and is there a specific grease that's less prone to wandering off the job?

3 comments

3 Comments

alex5242mo ago

That old timer is onto something big. It's not just the grease type, it's the whole design of those old hubs. The freehub body acts like a sponge, and centrifugal force from spinning literally slings the grease outwards into that cavity. Seen it a dozen times on 90s MTB hubs people bring in. A thicker, tackier grease helps, but honestly, the real fix is just checking and repacking way more often than the book says.

wren82629d ago

I read a piece in a old Bicycle Quarterly issue that talked about this. They tested a bunch of freehub greases and found the real problem is the seal. On those old Shimano Uniglide hubs the rubber seal just wasn't good enough so the grease would get pushed right past it from the centrifugal force. The thicker grease slows it down but you're right, checking them every six months is way smarter than hoping the factory fill lasts forever.

the_miles2mo ago

Yeah, the sponge thing is spot on. I mean, I've cracked open old Campy hubs that were bone dry inside the races for the same reason.