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I've heard all over about how important it is that you face a frame before installing a Hollowtech BB, as the cups not being aligned could be the difference between your BB lasting 1k and 10k miles.

Is there is any way of ascertaining how aligned the cups are on an installed unit?

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  • You normally face and chase the frame when you get it if it wasn't done already, but for decent quality frames it shouldn't be much of either process needed (they should come pretty well done). – Batman Apr 26 '17 at 23:30
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No, there's not a way of measuring it on an assembled bike. (On a bare BB shell, one could hypothesize some ways of measuring the parallelism, but it's not something anyone really does.)

In an extreme example you would find it was impossible to adjust correctly for adjustable preload types such as Shimano, or was tight and didn't turn freely in automatic (wavy washer or elastomer) preload systems.

Usually it's more subtle than that though, with the only real diagnostic method being, "Gee, for some reason this isn't spinning as freely as it should, let's face it to eliminate that factor." Or it's suspected someone is wearing out BBs seemingly prematurely, especially if a fresh one seems to not spin well.

Just pre-emptively facing and chasing the BB is really the way to go. That's the only way to actually know it's right.

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  • Ok... so if they weren't aligned well you'd notice that there was play in the cranks through parts of the rotation but not others (assuming the preload was just right)? – BSO rider Apr 27 '17 at 0:40
  • In an extreme example, yes. You would find that as soon as you adjusted it so there's no play, you'd have binding, or as soon as there's no binding, there's play somewhere. – Nathan Knutson Apr 27 '17 at 3:15
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I had a similar thought with my Campagnolo Ultra-Torque cranks (2010). They made a clicking sound and I suspect it was because one of the cranks came out of alingment. After removing the cranks and inspecting the threading on the retention bolt, I noticed some of the grooves were worn down to bare metal, so in effect my cranks were not on properly, and were not tighten properly (using a torque wrench).

After finding this, I went and bought a brand new retention bolt, carefully inspected it, and replaced it. Worked perfectly.

Safety is paramount. I would check the threading under the microscope (any hobby microscope with above lighting will do) and note any imperfections in the threading. If any, replace the bolt entirely.

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