Yet another bottom bracket standard

[jon_norstog]

Well here it comes. Sounds like T-47 may be the mother of all bottom brackets.T47- More standards-more problems, or one bottom bracket shell to rule them all?

I hope they can double up on bearings. My own take is the BB30 sealed bearings that T-47 will use are kind of marginal. Here is how they compare with the bearings used in 2" American and "mid" sized BMX bottom brackets. The 19mm spindle has held up quite well in competition, and is available in a number of spline patterns, hollow drilled, and in Ti. mid_vs_BB30.jpg

There is a third BMX standard, "Spanish" that uses a smaller shell and smaller bearings than American and mid, but is still more robust than BB30, PF30 et al.

jn

"Thursday"

[Andrew R Stewart]

I really hope that this "standard", if it is accepted by the industry, lasts a long time. More because I'm tired of keeping up with new designs and then explaining to customers why their expensive bike is so hard to get parts for.

But your point about the actual bearing capacity is one that I've made for years (since the advent of splined threaded BBs). Load capacity of a bearing is most dependent on rolling element (ball) diameter, not element number. So the larger the elements get the greater the load and often the life. This need to package tiny bearings inside of frames was always a stupid marketing driven path, IMO.

We had very well working examples of pressed in shell, cartridge bearing, BBs many years ago that lasted for thousands of miles in harsh conditions. I point out Burley tandems and Fisher ATBs as two examples. While working with these "classic" (hey at least I didn't say "vintage") systems was a hassle, given the lack of prior exposure and therefore the lack of comfort and readily at hand tooling, it was understood that once replaced these bearinged systems wouldn't need servicing for a long time. Andy.

[devlin]

Why didn't they make the Shimano 24mm version use a bigger OD bearing and hence bigger balls? They would have had a huge winner on their hands there for Shimano cranks and similar users. IMO. I always thought about making cups for the BSA threaded shell and machine cups to take a bigger bearing while taking the req'd length off the shell. Would have ended up with a 63-64 long shell.

[progetto]

Weight ( we can't have something heavier than last years model) and aesthetics (matching in with 40mm bb shell which were /are common.

Why didn't they make the Shimano 24mm version use a bigger OD bearing and hence bigger balls? They would have had a huge winner on their hands there for Shimano cranks and similar users. IMO. I always thought about making cups for the BSA threaded shell and machine cups to take a bigger bearing while taking the req'd length off the shell. Would have ended up with a 63-64 long shell.

[devlin]

That is one plus about the new option though, is making cups that will take the bigger 24mm axle bearing and have the room to fit it. Might mean getting a new lugged bottom bracket designed and made. More dollars or building lugged BB's from scratch or just FB the BB. I see it as a step in a more sensible question which gives a nod to saving current frames instead of making them obsolete in one foul swoop.

[Clockwork]

Can't wait to see the price of those big taps.