UN300 - less than 300 miles and it's toast
- Thread starter Ugo51
- Start date
Mmmh. Have fun reading this time warp thread: https://www.retrobike.co.uk/threads/un52-killing-me-softly.178735/
The short story is sort of and that it can be done, but could potentially be an utter waste of time.
You can only replace the grease and ball bearings. It's something to try more for the fun fiddle factor.
fastpedaller
Dirt Disciple
I've found the RPM ones last well (but I'm only a fairweather rider now), if I get caught in rain whilst I'm out, so be-it. I also came up with an idea that can probably be used to eliminate any pre-load on the bearings. When 'cartridges' rely on the cups being tightened into the frame, some of the designs lead to a preload on the bearings (which can be felt when 'maximum torque' is reached). Some (such as UN55 IIRC. don't suffer from this design feature, as the NDS bearing is 'captured' within the cartridge if that makes sense. Anyway, my idea (which I confess I've not had the opportunity to try yet, although I have a part ready should the need arise) is to use a 73mm cartridge in a 68mm bb shell, which means it can just be 'nipped up' and a traditional NDS lockring is then used (in the old-fashioned way 
) err....as a lockring. As highlighted by an earlier poster, there is much info on the CUK forum, and Brucey explains how grease can be added.
) err....as a lockring. As highlighted by an earlier poster, there is much info on the CUK forum, and Brucey explains how grease can be added.It should be possible to do with UN72 or UN91, but you will need to prise off the dirt guards that are pressed on the axle so you can get the plastic dust caps off. Not done it myself, but if you are going to try it would be great if you posted up your efforts.
Early Decathlons had some dreadful FAG copies with plastic cups made in Slovakia, not pretty.
It's a bit sad seeing what Stronglight is actually doing with re-branding.
Early Decathlons had some dreadful FAG copies with plastic cups made in Slovakia, not pretty.
It's a bit sad seeing what Stronglight is actually doing with re-branding.
Rank_21
Retro Guru
I can do a video, I started a channel on youtube a few months ago (I’ve done nearly all the retro shifters, rebuilt etc) and post it somwhere here. Those decathlon FAG copies remind me of the SKF version that was on my Kona explosive. And yeh I agree With stronglight - their in survival mode for the last 20 years. Only thing they had going were chainrings (maybe cranks) and many bikes are going single chainring! The website is outdated too if you compare to say the Hope tech Website
Jonny69
Senior Retro Guru
You can kind of do this. The only two issues might be 1) if you want a very narrow bottom bracket and 2) where the 73mm bb is not centred in a 68mm shell (like a BB52). It’ll be sticking out quite a lot on the drive side, where you normally use 2 spacers.Anyway, my idea (which I confess I've not had the opportunity to try yet, although I have a part ready should the need arise) is to use a 73mm cartridge in a 68mm bb shell, which means it can just be 'nipped up' and a traditional NDS lockring is then used (in the old-fashioned way
I have basically semi-done what you described. I have a Russian bike which is right-hand threaded on both sides of the bottom bracket shell. I used two Neco bottom brackets, which you can tap apart and separate the cups. I put it back together using both the right-hand threaded cups and put a lock ring on the drive side to fix the position.
Ugo51
Retro Guru
Brief update.
I got a UN55 and fitted it in place of the UN300.
Same problem.
Now, I honestly cannot believe 3 different bottom brackets can all have the same issue, so sadly I am starting to think I am doing something wrong.
What can be done wrong in installing a sealed cartrdige botto bracket, I do not know, but I guess I'll find out as soon as I take it off and examine it. The only thing I can think of is that I didn't tighten enough the NDS, but really, if that's the case for 3 bottom btackets, I'm really going to be ashamed of myself.
I got a UN55 and fitted it in place of the UN300.
Same problem.
Now, I honestly cannot believe 3 different bottom brackets can all have the same issue, so sadly I am starting to think I am doing something wrong.
What can be done wrong in installing a sealed cartrdige botto bracket, I do not know, but I guess I'll find out as soon as I take it off and examine it. The only thing I can think of is that I didn't tighten enough the NDS, but really, if that's the case for 3 bottom btackets, I'm really going to be ashamed of myself.
