Hambini T47 BB tolerances

Hello builders!

I built a Ti gravel frame that has a T47x68 shell. I have made a bunch of frames with T47 shells, but I’ve never had anyone try to use this BB.
Frame was finished as usual - faced and chased with Park Tool cutters and handles.

Customer is unable to get the Hambini to fit.
It threads in no problem until the last ~5mm and then it “hits a wall.”

If you’re unfamiliar with this BB, it’s unlike any other machined aluminum BB that I’m aware of. Instead of having a removable center sleeve (for protecting the insides of the bearings from water getting in the frame) the Hambini sleeve is part of the drive side cup itself. Dirt and grime isn’t the intended purpose but instead he claims it makes for a higher performance BB.
See photo and website if interested.

Hambini is blaming my construction for the BB not fitting. I am blaming his unrealistically tight tolerances for a metal frame that inherently deforms a little while welding. Even though I used sharp Park cutters, it’s still not close enough to use his BB.
In order to achieve his tight tolerance, we would have to have a blank/unthreaded T47 shell and cut threads after welding.

What are your thoughts on this?
Has anyone else had this happen?
Has anyone tried this BB?


I don’t have any useful input here and I don’t mean to derail this thread, but this is the first I’ve heard of a BB center sleeve for performance. Is the logic that it will keep the bearings in plane?


You’d have to ask Hambini but it’s something like that. Max efficiency of the bearings…?

I’d love to hear from bearing manufacturers like Enduro to hear what their thoughts are on this especially since they don’t feel the need to do it on their own BB’s|


Here’s long shot:

73 - 68 = 5 Have you checked that the BB assembly is actually for a 68 mm BB shell?

Otherwise, I think you’re on the right track that Hambini may be overtolerancing things for the real world. This is from their website;

They are correct in saying that, “you generally shouldn’t try to do both criteria in one feature”.

An often overlooked feature of all threaded BB shells is how important it is to have the faces parallel to each other and square to the BB centerline. This geometry is part of what aligns the bearings. Granted, it may not be the best solution, but it’s one that can be done well with a minimum of tooling and effort. Hambini has added the center sleeve as an alignment feature, which is sound from a mechanical viewpoint. However, there are now THREE criteria that must be met for a good fit: Thread size and concentricity, parallellism and squarness of the BB faces, and the tolerance and fit of the center sleeve. If any one of these is on the edge or out of tolerance, proper fit will be difficult or impossible.

If the Hambini center sleeve is to be used to full advantage, the cups are probably better off not touching the BB faces. That poses a new set of problems, like how are the BB cups held in place if they are not securely tightened against the BB face?

Ideally, all BB shells would be finished precisely after fabrication. The time and cost associated with this is far higher than typical thread/face tools that are easily and (relatively) cheaply available. That means builders are stuck with a less than perfect solution. The question is, is this solution good enough?

If the BB cups are not precisely aligned, it will put stresses in other parts of the assembly. If it’s a 30 mm aluminum spindle, the spindle will deteriorate. We’ve all seen a well used aluminum spindle that is worn at the bearing contact. If it’s a 24 mm steel spindle, stress is directed at the bearings. We’ve all seen Shimano bearings get loose, but these BBs are so cheap that they are a throw-away maintenance item.

So what’s the answer? Considering real-world tolerances and the physics that distort hot metal, I feel the answer is to not expect tight tolerance BB components to fit well. Hambini is using sound mechanical principles, if all the tolerances are correct. That just doesn’t happen, and the reality is that we’ve all been struggling to get a fabricated assembly to work well with bearings that require accurate geometry to work well and a long time.

As much as the customer in this case wants the Hambini BB, the best course may be to suggest another BB. It will work well, and can be easily installed and serviced by the rider or mechanic.




Agreed with everyone - this seems like an overengineered “solution” that tries to solve a “problem” by further over-constraining it. I can’t see a world in which a standard BB fit onto a frame works doesn’t work well but this one does - especially for $200+ more than a standard BB.

I’m curious - is the customer having an issue installing both sides of the BB? Or when installing one side at at a time?

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Thanks for the thoughtful response Mark!

I thought the same thing but unfortunately it’s the 68 version for a Shimano spindle.

With Ti, every post-weld process would ideally be done by dedicated machinery and fixturing. I know that the “big” domestic builders do this - singlepoint/boring the seat tube and head tubes instead of using hand tools; facing chasing threads on at least a lathe and at most a CNC cutting the threads after the full bike’s been welded (i.e., Seven…?).

For those of you that have not worked in Ti yet, it’s crazy how much it moves, distorts, undercuts even with the best heatsinks and technique. I’m no Brad Bingham or Steve Potts so I have no doubt I have a ways to go to improve, but I know i’m not too bad either.

No other BB does this, I assume for a reason (other than it’ll cost more). The Hambini doesn’t even provide a taper on the driveside sleeve to help ease into the NDS cup!

I’m sure it’s a very nice BB and professionally made. I hadn’t heard of them before this customer so it’s all new to me. Sounds like nobody here as heard of them either.

I’ve offered to send the customer a BB of their brand’s choice so they can get riding!


They’re threading in both at the same time and they “meet” about 5mm apart without going farther in. But they’ve tried all ways - DS first, NDS first, etc, they just don’t want to go in all the way because the sleeve is blocking their path.
If it were me i’d turn down the driveside cup’s sleeve about 5mm or at least add a long taper and call it good :rofl:


From what you are describing it sounds like the threads aren’t concentric or the axis of each thread is at a slight angle to the other. Given the tolerance that Hambini is spruiking it maybe that what you have is just a yiny bit out from what he’s demanding for installation. Funny thing is if the BB shell was to a tolerance that allows a Hambini installation it would mean the Hambini is null as any BB will perform well in such a well prepared shell. :thinking:


That is funny, and true.

BB distortion was the main reason Ti builders hounded @mark_pmw to source thicker raw tubing for their BB’s, which he did, and the thicker wall definitely helps. The shell on the bike in question is the older thinner wall version though, so that’s on me. But if my Park reamers don’t get it close enough for this BB then maybe opening up the threads a little with dull cutters may help…


Hambini is also a major d-bag (IMHO) and has got it in his head that his products are the only bike/engineering product in the world that is actually any good. Personally I would never buy or use his BBs purely for this reason, even if they are 100 times better than anything else. But the way his threaded BBs work is totally redundant for real-world applications - although his PF ones do make sense, I just can’t get past his terrible personality and attitude.


The Hambini looks an awful lot like a low-cost Taiwanese sample I have here in the shop. I have installed the one I have here because I suspected it was over constrained. To my surprise it went together without issue, I did install one cup entirely then the other, but now that I think about it, I suspect the fact that it all went together fine was more luck than anything else.


Great point!

I think the reality of the situation is that something is getting overconstrained and flexing to make up for it:

  • The BB “shaft”
  • The BB shell
  • The threads
  • The spindle
  • The bearings

That is one of the reasons why I am a fan of Shimano’s BB’s. They have a plastic (nylon?) interface that can flex to accommodate imperfect alignment.

To me, engineering is not about finding the best solution, but rather finding the best solution that works within your constraints: cost, equipment, materials, tooling, timeline etc…

You could make welded bb shell to aerospace tolerances by post boring and machining the threads, but it’s going to cost you! And after all that energy, your dirty chain is still going to scream at you after 300mi.

I think these niche explorations into BBs are cool. Maybe the Hambini BB could be improved by allowing the small side to “float” by cutting deeper and shorter threads.

The BB Nick is talking about was this one BB from the Taiwanese company FIRST: m47r - First Components

We ordered a few samples, and I was quite impressed. The cranks spun really smoothly without a chain (which honestly I think is just a gimic). And It has been happily chugging along in my MTB, with no creaks or issues.

It has an interior sleeve that threads into the cups as you tighten it. In theory its overconstrained, but I have a feeling the tolerance is looser on the sleeve.

The best part: it came with more 24mm spindle spacers than you ever need.


When the BB is outside of the shell… can the customer push it together to get 68mm between the faces that touch the shell faces? Or another question, how narrow can you get the shell faces w/ the BB only?

I prepologize if this has already been answered as I didn’t read every word in the post.


This is what I was thinking. A great reason to use the lathe.

Sounds like a case of a part maker not understanding the use case.


Not thinking this would work, I mailed out my “backup” T47 cutters and handles to the customer to take to a bike shop (I sent the reamers sold by Paragon before Park made them).

After another pass of the cutters and the BB went in easy! Just needed a little more thread play.
The older cutters had not been sharpened so being a little dull may have helped. They are also a lot wider than the Park ones but not sure if that made any difference. Either way, problem solved!

Thanks for all the troubleshooting.


I don’t know if hambini is really using sound mechanical principles, his bb’s are over-constrained. Of course, that’s not something that a 5 y.o. engineer would necessarily learn about in their training.


There’s also a pretty glaring error in his description of BB performance.

The frictional loss in a T47 Shimano setup is worse than a BSA Shimano setup. The main loss is through the bearings. The T47 uses the 6806 whilst the BSA uses 6805. The difference is small but measurable.

6805 = 25 x 37 x 7mm
6806 = 30 x 42 x 7mm

So his statement is just not true. At least not as far as my experience goes. I’ve never seen a T47 threaded BB for Shimano spindle with a 6806 bearing.
Those are the bearings used by BSA as well as T47 BBs for 30mm spindles (and DUB w. a reducer).

Which leads me to another gripe I have with the widespread misunderstanding of T47 - so many punters and bike industry folk, incl. tech journalists, seem to think that T47 cups house bigger bearings for 30mm spindles, when in fact they don’t.