This is the first bike build I've attempted, so far the process has been pretty difficult but I'm especially struggling with the Bottom Bracket installation.

Firstly, I have a frame with a threaded BB shell, so I bought a threaded bottom bracket, like this one: Threaded Borrom Bracket. This went horribly though, I wasn't sure what to expect in terms of force when screwing it in, I think I ended up with it misaligned and forced it, destroying the threads on my new frame in the process...

To work around that, I bought a BB that doesn't engage with the threads on the frame but threads together instead. Here it is: Bottom bracket number 2.

I have 2x 16 notch tools I can use for installation (1 to hold the other side) but I can't even get it in the shell all the way.


Do I need something to press it in, or is this just a case of my second bottom bracket being not suitable for a frame with a threaded shell?

Any help with this would be appreciated, despite a lot of niggly issues and incorrect part selection on my part, I'm quite enjoying the whole process.

Here's an extra picture of the empty shell which is threaded (well, crossthreaded now...)

Empty shell

Each side of the BB is fitted with a silver notched cup, that I can remove. If I take this off, the BB does fit into the shell and I can thread it into the other half. I just can't seem to get it tight enough to stop the BB from spinning in the shell.

Split from washer

I also noticed that when I full tighten the BB, the square pegs won't spin anymore.



As requested in the comments, here is a close up of the original threaded bottom bracket I purchased originally (Link at the top) and a picture of the side of the shell that it won't screw into. It looks very neatly cross threaded to me, I was really angry at myself for doing that...

Original BB

Crossthreaded BB shell

** Hopefully the final edit **

So I've managed to screw in the Tange BB, it actually went in 99% of the way by hand very easily. I tightened it with reasonable force at the end using a Torque wrench but I didn't want to over do it. I notice the non-drive side I can still see 1 thread but it doesn't seem to want to go in any further easily. The drive side is all the way in and flush to the shell. Does this look correct and as expected? I consulted a few video guides from ParkTool but not much was mentioned on expected "flushness" of the cup on that side.

Here are some pictures:

Drive side:

enter image description here


enter image description here

  • Something must be stopping it going in, can you photograph inside the shell with the cartridge removed?
    – Swifty
    May 16, 2020 at 16:34
  • 1
    Sure, I've added it to the original post. The only thing I can think is that the new thread together BB I have either isn't going to fit because of the threads in the shell or needs pressing in somehow?
    – DL3001
    May 16, 2020 at 17:30
  • If you have calipers, measuring and writing down diameters of parts involved might shed some light on what fit tolerances you have. May 16, 2020 at 17:55
  • I don't have any calipers unfortunately, I've added another picture of the BB where I've removed the metal notched ring. With that removed, it fits in the shell but I can't tighten it. If I tighten it so far it also stops the square ends from spinning. Using a tape, the black main body of the BB pictured is around 34mm. What I can tell you for sure is that with the metal ring on, it doesn't fit in the shell. That's why I was unsure if it should be pressed in or not using some other tool.
    – DL3001
    May 16, 2020 at 18:24
  • 1
    @NathanKnutson - I've added a pic of the original threaded bracket and a close-up of the damaged shell threads. The frame is this in a different colour: santafixie.co.uk/leader-cure-2016-frameset-blue.html
    – DL3001
    May 16, 2020 at 22:14

3 Answers 3


Threadless cartridge BBs have their place, and that place is where the threads are destroyed. Thankfully you're not there yet. They are a compromise because they tend to have creak issues sooner or later no matter what.

You should take the frame to a shop with a proper piloted BB tap set. One side of your shell looks fine. The fix is to install the pilot into that side all the way and use it to start the other side. At that point one can use some force to confidently get through the cross-threaded section. (One shouldn't necessarily go all the way through with the second tap without partially removing the first, because referencing one side to the other isn't really how the tools are intended to work, but that's a tangent.)

You have enough good thread in there remaining that things should be fine at that point. The risk is continuing to mess with it and starting to lose threads completely, which could happen from the spot you're in now.

In the scheme of things, bike bottom brackets use a fairly long section of very fine threads. Its pretty common for low end cartridges such as Sunrace to not get things right and have problems with starting rough, going in rough, etc. It may work fine after chasing the threads, but if it doesn't, there's a lot to be said for just getting a Shimano UN-55. It will go in right and last a ton longer, and they've gotten really cheap.

  • Thanks - Just a general question RE having the threads tapped/chased - are they almost as good as new after, or will they forever now be compromised or flimsy? I'm just thinking with regards to future maintenance/repairs, I'll be forever living in fear of touching the BB. Also, I'm open to suggestions on a better BB. I think it has to be 103mm length though, at least as far as my crank documentation seemed to suggest. Seems I can't find a UN-55 at that size.
    – DL3001
    May 17, 2020 at 7:46
  • 2
    They likely won't be significantly compromised. There's a lot of unaffected thread in there. May 17, 2020 at 11:34
  • This is the right thing to do. There is still paint on the shell, There could have been some paint or other stuff in the threads. The threads were probably supposed to be tapped by the bike builder and the attempt to install the BB without that might have been doomed even without any cross-threading. The LBS will also use a facing tool to face the shell surface where the current paint may cause uneven surface for the BB cups. May 17, 2020 at 17:15
  • 1
    @DL3001 I'm sorry it's still not going well. It's not surprising that starting it cross-threaded is still possible or easy, because chasing serves only to clear the path of the original threads; the false one that cross-threading created is still there in some form. Usually in these situations I've had success by carefully but forcefully starting the BB in while looking at it from the other side of the shell and keeping it forced on center. I suspect the Sunrace unit you have is causing problems. There are mid-priced Sugino BBs in 103 you could try that are very nice quality. May 23, 2020 at 17:59
  • 2
    @NathanKnutson - I'm please to report the Tange BB went in very easily... I can't believe the SunRace BB has caused me so many issues (Well, my fault as well for sure...). Thanks so much for the advice, you've totally saved me. I added a couple more pictures of the installation now. I'm quite apprehensive about brute forcing this thing in any way, could you take a look at the installation? I was a little concerned with the left hand cup. I didn't have any threadlock so used plenty of grease.
    – DL3001
    May 28, 2020 at 9:28

First up, there's no shame in getting a local bike shop to do this bit of assembly. Your frame is expensive and damaging the threads would be very bad.

Your frame is threaded - you need to use a threaded bottom bracket. The press-fit adapter you bought is not suitable for this bike.

The cartridge in your tea-towel photo is the correct unit to install.

  1. Start by cleaning the threads on the frame, using rags and degreaser.
  2. Use a bright light and a pointy pick to check the threads carefully. Pick out any metal fines, and look for damaged/rolled threads. Try to reform them with the pick - ideally, you'd run a tap through the threads to chase them clean but those are very expensive and only found in bike shops.
  3. Apply grease or anti-seize to the threads on the frame or the cartridge
  4. You might need to fit a washer/spacer at this point - depends on what your cartridge came with.
  5. Push the main part of the cartridge into the frame from the drive-side, and spin it backwards to tighten. There is a proper tool to fit the flanges, you will need this to get it seated, it's not something that can be bodged.
  6. Fit the small ring on the other side of the bike - it goes on the non-drive-side and is threaded normally, so turn it like closing a bottle top. This side should also have anti-seize paste/grease. It needs to be firm but not supertight.

You may encounter resistance at some points in the rotation due to damage in the threads. Go by feel and take your time. As long as the cartridge is not cross-threaded you'll be okay.

There's a time for finesse and a time for brute force.
BB installation is the art of knowing which to use, and when.

Your LBS would not be expensive, and you will protect your frame. I have deferred some really hard jobs to my LBS, purely because I don't have the tool or can't get it perfect.

  • 1
    Another great answer, thanks. I'm leaning towards taking it to my LBS, which unfortunately means I'll have to carry my frame for an hour on foot... Just out of interest, you mentioned there's a proper tool to fit the flanges on the BB - can you elaborate on this? Not sure I've come across it in my research so far.
    – DL3001
    May 17, 2020 at 11:20
  • @DL3001 Probably a parktool.com/product/bottom-bracket-tool-bbt-22 or similar. It should fit the splines on both sides of your cartridge unit.
    – Criggie
    May 17, 2020 at 13:13

I recently bought a new Surly Cross-Check frameset for a build project. BB (Shimano BB-UN55) wouldn't screw in on the right side. Upon closer inspection there was an excess of paint inside the BB shell covering the first three threads. Paint as deep as the threads. Very disappointing for an expensive frameset. Spent a couple of painstaking hours with a Stanley knife blade carefully scraping it off. After that I was able to screw in the BB no problem. You should be able to screw in the BB with the tool and your hand (no spanner). Only use the spanner when fully in for a final tighten. Never force it. There is a reason why it sticks. Find out Why.

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