SHIMANO BB-UN300 bottom bracket British thread, 68-122.5 mm (LL123), silver, One Size, EBBUN300B23X

This bottom bracket is for my e bike which I use pedal assist on extensively. As it's a legal 250W motor I have to put in a bit of personal oomph, especially on hills so the mechanics of the bike are very important. The bracket on the bike in comparison (Chinese bike) was a loud mess although it's rotation was adequate and would have lasted longer, however eyeing the corrosion evident on it, decided to replace the bracket and I'm so glad I did. The Shimano one is silent and very smooth with excellent build quality. I've been gradually replacing the original parts on the bike with more upmarket replacements as time goes on and it'll last for many years as a result. This bottom bracket is very good value for money and raises the bar quite a bit compared to the lousy original part.It didn't last for many years as hoped, just a little under two years. Bearings corroded on chainring side. Disintegrated with complete collapse on one side. Having said that, I've replaced with this item again. It did run well up until the failure point, it's reasonable price for two years of constant use won't break the bank.

Excellent Shimano quality, exactly as expected really.

Good quality, easy to fit. All nasty noises and movement gone.

These look the part, and appear to be a genuine part. Quality in the hand felt good, and it fitted nicely. A quiet smooth ride with no play in the pedals.Alas after only 500 miles, mine started to show accelerated wear. At 800 miles it had significant slop in the bearings - the crank ends had 4-5mm of "side to side" play at the ends, and you got a fair bit of creaking when riding.Initially I thought this must be a quality issue. However I bought another to replace it, and having now replaced it, I suspect the problem may have been the result of a fitting error and not the bracket. The end with the free shell, was not fully engaged in it, and hence the alloy shell had worn rather than the bearings in the bracket (those still seemed tight). So the bracket could then wobble at one end where the bearing was no longer adequately supported.When fitting the replacement (same make and model) the free shell screwed quite a bit further into the frame than the previous one, leaving me with more confidence that the end bearing will now be fully supported in the shell.

I've had a BB-UN300 in my commute bike for about the last 4,000 miles. Still as smooth as the day I installed it. Needed a new BB for a friend's bike, so this was an easy choice. For a relatively cheap component it's feels well made. Installation is easy (the hard work is getting the old one out first!).

Excellent just what I needed !

I needed a replacement in a hurry and there's not a huge choice of branded bottom brackets with square taper for next-day delivery. Never really sure if you're getting genuine Shimano from amazon though - it arrived in a brown rather than blue/grey box, but I don't have another example to compare it with. After a few short commutes at only moderate effort the BB started clicking loudly indicating a cracked bearing or race. Didn't feel like dismantling it, but noticed that the width of the actual bearings is much narrower than on the Sunrace BB I then fitted (but haven't used that one enough to know if it's any better).

Well made service part