RE-greasing 7901 cartridges: Which side do I open up?
01-03-13, 09:57 PM
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RE-greasing 7901 cartridges: Which side do I open up?
I'm replacing the cartridge bearings in my Surly "new" hubs, and have been thinking about what grease is in the replacements. So, given that both the originals and the replacement appear to be the exact same thing (7901 RS Max Enduro) I thought that I might refurb the old ones just as practice in the event that I choose to change the grease eventually.
So, here's the thing, these are directional bearings in the sense that I can adjust them with some lateral load once installed. I just can't find which side I should open up if I want to service them.
Anyone know?
So, here's the thing, these are directional bearings in the sense that I can adjust them with some lateral load once installed. I just can't find which side I should open up if I want to service them.
Anyone know?
01-03-13, 10:16 PM
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Which side is easier to pull the seal off of? Ideally you'd pull both side seals. Andy.
01-03-13, 10:38 PM
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Most of the sealed cartridge bearings used on bike hubs are sealed on both sides. However there's zero benefit to a seal on the inside, so remove one seal (doesn't matter which) pack clean and relube the bearing, and press in with the open side to the inside (duh).
BTW- there's no reason for bike hubs to use bearings sealed on both sides. I suspect that they do so, to avoid QC issues resulting from bearings being pressed in open side out.
BTW- there's no reason for bike hubs to use bearings sealed on both sides. I suspect that they do so, to avoid QC issues resulting from bearings being pressed in open side out.
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01-03-13, 11:03 PM
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Except the 7901 has a distinct inside and outside so, according to your theory, it does matter which seal you remove.
01-03-13, 11:18 PM
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What I said still holds, you remove the inside seal, whether it was the inside before or after you removed the seal.
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01-04-13, 01:26 AM
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First off, thanks for the help guys!
Anyway, the 7901's have a blue and a black side, with the blue being on the inside when they come from Surly, so I'll try to pry that side first. And I guess I'll take both off if I can't clean all the goop out with only one side off. I do wonder why I should choose to run them without first replacing the seals: although the inside might not get exposed to much filth or water, I don't quite see the advantage and the weight savings seems negligible.
Now I just need to figure out how to properly adjust the preload on these puppies. They're somewhere between cup and cone and non-directional cartridges and I haven't gotten the hang of 'em yet.
Anyway, the 7901's have a blue and a black side, with the blue being on the inside when they come from Surly, so I'll try to pry that side first. And I guess I'll take both off if I can't clean all the goop out with only one side off. I do wonder why I should choose to run them without first replacing the seals: although the inside might not get exposed to much filth or water, I don't quite see the advantage and the weight savings seems negligible.
Now I just need to figure out how to properly adjust the preload on these puppies. They're somewhere between cup and cone and non-directional cartridges and I haven't gotten the hang of 'em yet.
01-04-13, 09:13 AM
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First off, thanks for the help guys!
Anyway, the 7901's have a blue and a black side, with the blue being on the inside when they come from Surly, so I'll try to pry that side first. And I guess I'll take both off if I can't clean all the goop out with only one side off. I do wonder why I should choose to run them without first replacing the seals: although the inside might not get exposed to much filth or water, I don't quite see the advantage and the weight savings seems negligible.
Now I just need to figure out how to properly adjust the preload on these puppies. They're somewhere between cup and cone and non-directional cartridges and I haven't gotten the hang of 'em yet.
Anyway, the 7901's have a blue and a black side, with the blue being on the inside when they come from Surly, so I'll try to pry that side first. And I guess I'll take both off if I can't clean all the goop out with only one side off. I do wonder why I should choose to run them without first replacing the seals: although the inside might not get exposed to much filth or water, I don't quite see the advantage and the weight savings seems negligible.
Now I just need to figure out how to properly adjust the preload on these puppies. They're somewhere between cup and cone and non-directional cartridges and I haven't gotten the hang of 'em yet.
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