Infinite life RD bearing!
So I had some problems with the bottom RD bearing on my x9 RD. Its a really low quality bearing and it only lasted me about 6 months of commuting through snow and rain and lots and lots of dust. I thought that was unacceptably shitty.
I tore the RD apart and upon inspection it seemed like it wouldn't really matter what quality bearing I put there, it will last like 6 month anyway regardless of ceramic this and ultra double seal that...
So I came up with a solution. It took me about an hour of building including measuring everything and cleaning.
So its a simple little tube made of bearing quality bronze and the pice that goes in the plastic roller is stainless steel, super duplex in this case. You can use almost any metal you want but having one part made out of bearing bronze is good is you would want to run it completely dry for a year or so (or you forget to lube it), otherwize you can make both part of stainless. Avoid Ti and aluminum, Ti galls and aluminum will definitely just magically disappear.
So what you do is you measure the width of your current setup when its removed and this will be the width/length of the tube, the rest just have to be less that that. Make sure to sand it flat when its mounted in the plastic roller, I use 150 grit paper, but 240 will do just as well I suppose.
I don't actually remember what play i put in there but I think 0.1 to 0.3 mm is good enough. You just need to get some grease in there. I avoided doing this as a real gliding bearing and to rthose tolerances since it only takes like a week of dust and rain and such to be out of spec anyway.
Now you might wonder why do a thing like this in the first place??
0: It will last at least 10 years!
1: Well it has 1 moving part.
2: No seals to break, you just grease it every 6 months, or oil it or whatever you have really, as long as you put something in there it spins smoothly. I do this twice a year and I have only actually opened it twice since I installed it including this time, I just wipe it off with a rag and put some oil on it from the outside, thats it!
3: There is nothing to break down.
4: The tolerance is so wide (0.1-0.3mm or so) so it doesn't matter what you ride through, it won't break or wear out anyway, it just spins and spins and spins.
5: You can run it dry in emergencies.
6: It has lasted me 3 years now and the only thing I have done is to inituially put white lithium grease in there and then oiled it 2 times a year. It has lasted about I don't know maybe 5-10000km and it has been -20C snow and winter, industrial parks full of abrasive dust, rain and rain and rain, and mud, and cities.
7: Its as idiot proof as you possibly can make something.
8: Its easy to transplant it to a new set of rollers when the old ones wear out.
9: The maintenance is minimal, hell its even less than minimal.
In one of the pictures you see the wear of the bronze tube, thats 3 years of almost daily wear! The wear is at most 0.1mm (probably half but its hard to see in the pic) and now when I tore it apart I just rotated the little bronze tube to take the load to the "unworn" side.
Judging from the wear I have accumulated I'd say mine will last about 15-20 years if I use my bike the way I currently do.
Good luck with you own (almost) infinite life bearings.