NB There is an edit to this post added 06.02.2017

I need to replace the 68/118 BB on my Giant Rock (made around 2000 I think). It has a locking ring on one side only as shown in the photos. The problem is I can't find one like this online. The nearest I've found was on Sheldon Brown's website but I can only post two links/photos with my reputation so you'd need to google "Cartridges with a lockring on each end" if you're interested.

I want to order the right spares and tools the first time round (to avoid paying for two deliveries) so my questions are:

  1. Do I need to get any special tools other than the obvious: BB tool and lockring tool?
  2. What replacement part do I need? Can I use a BB without lockrings, a BB with two lockrings, or does it have to be a BB with just one? Specific model recommendations would be welcome but not essential - it's the type I need to figure out.

If it helps, the thread on the chainside crank (used to attach the crank remover) had some wear on it, so there may have been some work done on this setup in the past, but I don't know how to tell if there used to be a locking ring on both sides. Please do let me know if further info is needed to answer the questions.

bottom bracket right end (nearest to the chain) Giant rock bottom bracket right end

bottom bracket left end (furthest from the chain) Giant rock bottom bracket left end

Edit on Tue 06.02.2017

Hello, I have browsed the web for a bit longer, and came across some info which I'd like to share here. Hopefully it helps someone make a more specific judgment of what the crack is with my bike.

There are some shops and ebay listings offering a "semi sealed" bottom bracket: http://www.ebay.co.uk/itm/BICYCLE-BOTTOM-BRACKET-VINTAGE-BALL-BEARINGS-STYLE-118mm-or-126mm-IN-BLACK-ONLY/331915747544


There is also this youtube video which I gave its 76th view and which leaves more questions than answers:

The sales listings quoted above don't seem to explain clearly what the difference is between an average cartridge bottom bracket (like a shimano bb un55) and a "semi-sealed" unit. In fact, most results I get on google for >>"semi sealed" bottom bracket<< are from ebay and shops. The main point however is the fact that there is indeed a locking ring on one side only on these.

Now then, I can get a NECO B910 sold with the BB tool for £12, whereas a semi-sealed unit and a BB tool have to be bought separate and add up to at least £16. So the cheapest semi sealed is a few GBP more than the cheapest model without the single locking rings, and I'm not totally clear if I can use either, or only the semi sealed. I don't have the budget for error, so I would really do with some hints here. It seems I have four options really:

  1. Buy a BB tool on its own, get my BB out and take it from there - I might do that if I don't get a definite response on here in a few days, but this will cost more if it turns out I could have bought the £12 BB combo in the first place
  2. If someone is able to positively identify that the unit I've got can only be replaced with a semi-sealed BB, I will buy one of those from a source where it's cheapest to buy the part and a BB tool (with delivery)
  3. Ebay listing 331915747544 linked above seems to suggest this type can be taken apart and bearings can be replaced while keeping the rest of the assembly - if someone can confirm that , I will probably end up buying just a BB tool first to identify bearing size etc, but at least I will have a reason for it.
  4. If someone is able to positively identify that the unit I've got can be replaced with that NECO B910 or another similar BB without a lockring on one side, I will get that £12 set. This could in effect be what CardMechanic says (thanks for your response), but he hasn't mentioned "semi-sealed", so I'm not sure he considered the option that one of these might be required.

Thanks in advance for any input!

  • 1
    It is fairly normal for the lockring to be on one side only. The cup on the other side has a flange built into it that snugs up against the edge of the bottom bracket housing, and the position of the BB cartridge is not adjustable left-right. On a few styles of cartridges there are lockrings on both sides. This allows the cartridge to be adjusted left-right by a few mm. Commented Jun 1, 2017 at 12:15
  • By "lockring" are you referring to the notched ring on the OUTSIDE in the bottom photo? I think that you probably want a splined BB tool that engages the INNER splines. My guess is that this is a shimano splined BB tool similar to the Park BB-32. It's not an ISIS because ISIS doesn't have a square taper spindle. Commented Jun 1, 2017 at 17:25
  • 68 mm is the diameter of the whole cartridge, and 119 is the width of the axle in mm. This is a totally common part, and is not super expensive. Just buy a cartridge bottom bracket and you're good to swap it out. I've not seen one with a lockring, but then I buy cheaper ones.
    – Criggie
    Commented Jun 3, 2017 at 5:08
  • Thanks for all your comments guys. @DanielRHicks, you've got me thinking. I think I can picture how the adjustment would work with locking rings on both sides, but if there isn't one on one side, what would be the purpose of having one on the opposite side on some, but not all models? In other words, what is the difference between mine and a model without locking rings? For a moment I thought about the brake wire adjustment screw but its action seems opposite to what the lockring would be doing. I've put some more of my thoughts in an edit added to the bottom of my original post.
    – pateksan
    Commented Jun 5, 2017 at 23:56
  • 2
    And your BB appears to be a bog-standard one, the only "upgrade" being rubber seals. Likely it's a loose bearing unit, and can in theory be disassembled and rebuilt. But if it's feeling loose or gritty then, at the very least, the balls need to be replaced, and replacing the entire thing (with either another loose bearing unit or a cartridge) would be the wiser choice. Commented Jun 6, 2017 at 0:33

3 Answers 3


Your standard cartridge and "loose bearing" bottom brackets have two threaded "cups".

Usually the right (drive) side cup has a lip on it, so it will only screw so far into the bottom bracket housing. There is no adjustment, and no need for one, since the distance that the shaft should project outward is determined by the design of the parts. And if the bottom bracket is a cartridge one often the right side cup is permanently attached to the cartridge.

However, nothing is perfect. If the cups do not tightly restrain a cartridge unit it will move about and make annoying clicks. And if the cups are loose in a loose bearing style unit the axle will wobble around in the bearings.

So one side (at least) is made adjustable, without the lip on the cup, but instead with the threads extending a few mm outward beyond the expected distance it should be screwed into the BB shell. This adjustable cup is then screwed in "tight enough" to achieve the desired pressure on the bearings. But "tight enough" is not generally so tight as to cause the cup to "lock" in place like a regular bolt, so the lock ring is added to allow the cup position to be preserved, in spite of the various mechanical pressures that would attempt to turn it.

Note that this "adjustable cup" is generally on the left side, allowing the adjustment to be accessed without interference from the chainrings.

The vast majority of "3-piece" BB setups, at least on lower-end bikes, are of this variety, with one "fixed cup" and one "adjustable cup". For the most part these units are interchangeable, so long as the style of the axle end matches (and there are 3.5 different styles). There will be a modest variation in the length of the right-side shaft, between 2-ring and 3-ring fronts, but most 3-ring bearing assemblies will fit 2-ring bikes, and likely a fair number the other way.

A few bottom bracket bearing assemblies have adjustable cups on both sides. This allows for various things, such as a BB shell that is wider or narrower than normal, or desire to adjust the "chainline", moving the sprockets closer to the frame or farther away. It also allows a single BB bearing assembly to fit several (slightly) different setups.

  • Wow, I can see now how you earned all these user awards! I hadn't realised who I was talking to, thank you very much, I really appreciate it. So am I right in assuming that "semi sealed bb" and "loose bearing bb" are in effect two terms for the same engineering concept?
    – pateksan
    Commented Jun 6, 2017 at 1:06
  • 1
    @pateksan - I only deal with old stuff, so I'm not real familiar with "semi sealed". But I gather it's basically a loose ball unit with rubber seals where the axles poke through, and a plastic body around the shaft and bearings proper. This in only slightly fancier than a standard unit. A "cartridge" unit, OTOH, is metal cartridge that encloses the bearings and shaft and which comes as a single unit -- "no assembly required" (sorta). Commented Jun 6, 2017 at 1:24

The BB you have there is a sealed mechanism but loose ball one. It's very common for those to have one or two lockrings to allow for tensioning of the bearings. It can be replaced with any BB that has the same threads. I would probably just go ahead and replace it with a cartridge BB, they aren't very expensive. As long as you're keeping the same crank, make sure you get the same size or within a mm or 2.

  • 1
    I didn't really understand your answer until Daniel provided his extensive one below - thanks anyway!
    – pateksan
    Commented Jun 6, 2017 at 1:09

Ok, I've been meaning for weeks to write a proper post and never got a chance, so here's a brief summary.

  1. Based on the very valuable answers I got here, I took the risk and bought the NECO B910 supplied in a kit with a BB tool. It fits perfect.

  2. The old BB was sitting really tight and a few teeth on it cracked in the process of removing it. I used a 250mm spanner to undo the cups and had to lean on it to get it to move. Also, the thread is very fine and took forever to come out, for a while I thought I had broken the thread and it was just spinning loosely.

  3. The old BB was indeed what some people seem to call "semi sealed" BB, very much like in these photos Ebay - I mean, it looked exactly the same to me. And I couldn't see an obvious reason why the BB became so badly loose. So in theory, it may have been possible to fix the old BB but I didn't have the time to experiment.

  4. I meant to put up a video of the process, but my phone battery died while filming, and the video file is corrupt. One day I might try to fix it on my linux laptop.

  5. I used some cheap copper grease from ebay, and an improvised torque wrench: I attached some luggage scales to my 250mm spanner. I was aiming for 50 Nm, which is 50 N on a 1 m lever, or 200 N on a 250 mm lever, so I pulled on the scales until it showed 20 kg (which corresponds to 200 N weight on Earth). This seemed about right - slightly less force than it took to undo the old one, but similar order of magnitude. I had to use my other hand to keep spanner on the BB tool and my legs to keep the bike steady, but it wasn't as awkward as it sounds.

  6. For the record, I still can't see what the purpose of the locking ring was. It was threaded onto the cup, and came off without too much work. Was it supposed to be helping to stop the cup from undoing itself? I can't see how the ring would make any difference, it really seemed to be the cup's thread that kept it in place.

I hope this helps someone. I'm well chuffed with how cheap it was to do. I've ridden about 200km and it all sits nice and tight. If anyone has questions, please feel free to ask.

  • Great work - re (6) the lock ring should have been snug up to provide tension between the cup and the frame. You can't do the cup up tight on the threads because then its binding on the bearings. And now you own some bike tools :)
    – Criggie
    Commented Nov 1, 2017 at 21:40
  • 1
    Mainly the lock ring keeps the cup from TIGHTENING over time, due to precession. Commented Nov 1, 2017 at 22:49

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