Accuracy Of Bottom Brackets From Major Brands Analyzed

[goodboyr]

He also commented on poor knock-off bearing tolerances, mentioning FSA also, as contributing to the overall "out of tolerance" issue.

I didn't go back and check, but the BB30 standard had published tolerances (in terms of diameter anyway), and I'd assumed this is what he was referring to in his charts.

If the "go" and "no go" used in manufacturing resulted in BB shells that were within spec, then why the results, and variation between brands?

Here's the drawings with the BB30 and PF30 standard including specs. Note that the shell can be 41.96 -0, + 0.025 so the range is 41.96 to 41.985 on BB30 and 46 +0, -0.05 or a range of 45.95 to 46.0 for PF30.

[spud]

interesting analysis. I've got an 8 year old Cannondale that only creaks when it gets above 80 degrees or so. my theory is that with heat, the aluminum BB shell expands enough that the bearings can walk on the seat area. I'm guessing the frame has done near 40K miles, so maybe the BB has just stretched out.

[hambini]

The guy is measuring BB shells. Incidentally, he doesn't say how he is doing this in what seems to be his back bedroom. But measuring is not how the industry tests its BB shells because even with BB30 there is actually a tolerance range. With PF30 there is a wider tolerance range.

The industry uses 'go' and 'no go' tools. I believe FSA market these.

I measure with a laser or with a faro CMM and in some cases both.

A go/no go gauge is only suitable for measuring the hole tolerance. It is no good for measuring misalignment.

I would be interested to know how you think the industry should be measuring it's BB Shells.

Thanks

Hambini

[pyrahna]

I measure with a laser or with a faro CMM and in some cases both.

Let's take the silliness of using a go/no-go gauge out of the conversation for a second as it is not applicable to the type of analysis you did.

My only suggestion is to include the repeatability of the arm in your presentation. According to Faro @ http://www.faro.com/en-us/products/metr ... m/overview it could be anywhere from .016mm to .1mm. Faro arms (and romer arms) are fantastic tools but are at the less precise end of professional measurement tools. But we are getting close to the realm where environment control is almost as important for decent measurements.

I have nothing against what you did and am glad for the information and the presentation as it adds intelligence to a topic that is sorely lacking in hard cold numbers. My only critique is to provide a little more information as to how the numbers were obtained.

[bikerjulio]

I'd say the industry should give up trying to make precision pressfit shells altogether and just supply a 46 mm dia x 86 mm long tube.

Into this the owner can insert the BB of choice for the crankset being used. Preferably threaded together.

Let's face it, BB30 was introduced in 2000, 17 years ago, never took off as any kind of universal standard, and now appears to be on it's way out.

[hambini]

I measure with a laser or with a faro CMM and in some cases both.

Let's take the silliness of using a go/no-go gauge out of the conversation for a second as it is not applicable to the type of analysis you did.

My only suggestion is to include the repeatability of the arm in your presentation. According to Faro @ http://www.faro.com/en-us/products/metr ... m/overview it could be anywhere from .016mm to .1mm. Faro arms (and romer arms) are fantastic tools but are at the less precise end of professional measurement tools. But we are getting close to the realm where environment control is almost as important for decent measurements.

I have nothing against what you did and am glad for the information and the presentation as it adds intelligence to a topic that is sorely lacking in hard cold numbers. My only critique is to provide a little more information as to how the numbers were obtained.

I take on board what you are saying but on youtube, I don't want to create a video which has a large segment on the methodology as it will switch the vast majority of people off as they are not interested. There will always be the ones who want the technical nitty gritty (like yourself) but that is a definite minority.

Thanks

hambini

[Imaking20]

Wow, these videos are fantastic. Now I need some NTN bearings

[pyrahna]

I take on board what you are saying but on youtube, I don't want to create a video which has a large segment on the methodology as it will switch the vast majority of people off as they are not interested. There will always be the ones who want the technical nitty gritty (like yourself) but that is a definite minority.

Thanks

hambini

Maybe a single web page as to your measurement methodologies and tools and just link to that?

[hambini]

I take on board what you are saying but on youtube, I don't want to create a video which has a large segment on the methodology as it will switch the vast majority of people off as they are not interested. There will always be the ones who want the technical nitty gritty (like yourself) but that is a definite minority.

Thanks

hambini

Maybe a single web page as to your measurement methodologies and tools and just link to that?

I think that is a good idea, In future I will go for that.

[Valbrona]

I measure with a laser or with a faro CMM and in some cases both.

A go/no go gauge is only suitable for measuring the hole tolerance. It is no good for measuring misalignment.

I would be interested to know how you think the industry should be measuring it's BB Shells.

Thanks

Hambini

They don't have time to accurately measure every BB shell.

This video shows the tools they would typically use when making a frame: an ID go/no go gauge, and an alignment gauge.

https://www.youtube.com/watch?v=77ljRAZFPYc

[WinterRider]

I take on board what you are saying but on youtube, I don't want to create a video which has a large segment on the methodology as it will switch the vast majority of people off as they are not interested. There will always be the ones who want the technical nitty gritty (like yourself) but that is a definite minority.

Thanks

hambini

Maybe a single web page as to your measurement methodologies and tools and just link to that?

I think that is a good idea, In future I will go for that.

Progression of this thread shows best of WW. Sure like your thinking and ideas testing data etc... very well done. Kudos!

[pyrahna]

I think that is a good idea, In future I will go for that.

Sounds good!

As an aside...if you ever have a chance to measure one of the full ceramic SKF bearings, do it....they are marvels. Not the hybrid bearings, but the ceramic ball + race ones.

[53x12]

Definitely would be interesting to see Hambini do more testing for the future and include the likes of Colnago/Trek/Canyon/BMC/Giant...etc. Definitely interesting to see the data that he has gathered. Definitely would be interested to learn more about his methodology and testing methods.

[Bogan]

Loctite 609 or Loctite 638

[53x12]

Loctite 609 or Loctite 638

That's all fine and good for the install. But still doesn't help if you have a parallel misalignment or a BB with a diameter out of spec.

You take a generic/no name/knock off Chinese BB30 bearing and say you get one that measures at the lower quartile and try to install it in a Boardman or Cannondale with a BB diameter at the upper quartile as measured, you are going to run into problems. Regardless of Loctite 609 or Loctire 638. Neither of those will fix the underlying issue.