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Bottom Bracket adjustment

Old 08-30-16, 01:12 AM
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Bottom Bracket adjustment

I took apart a bottom bracket and upon inspection decided the adjustable cup and the spindle were a little worn. I took it to a shop and asked the mechanic if it warranted a replacement to a cartridge. He agreed with my diagnosis of the wear but told me a replacement wasn't needed yet. I purchased new bearings, greased it up, and put it back together. I finished the job with no play in the bb. After a couple days of riding I checked to make sure things were good and noticed a very small amount of play, but only when the cranks were in certain positions, and even then it would only happen sometimes. The lock ring is tight and the cranks are fully attached to the spindle. Could the light pitting on the cup and spindle cause the sensation of looseness?

When I originally found it to be loose, it was really loose. I am not sure how long it had been ridden like that. Could that have caused an uneven wear that would lead to this? Any help is appreciated.
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Old 08-30-16, 01:21 AM
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Its not unheard of to have to readjust a bb after a few rides post overhaul. Personally considering how cheap and reliable the sealed cartridge BB's are I would have I would have purchased one and installed it, just nip your existing one up a little and ride on or bite the bullet and buy a sealed version
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Old 08-30-16, 05:30 AM
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The symptom you are experiencing would indicate that perhaps the wear is not even. The fact that it is not always there or in the same place would further indicate uneven wear. The other possibility is that the fixed cup is not fully tightened, and is shifting on occasion. I would say that if there is actual pitting (rather than smooth wear) it should have been replaced. As a side note, a properly worn in bearing runs smoother than when new.

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Old 08-30-16, 05:43 AM
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Run the tip of a ballpoint pen over the pitted areas, if you can feel roughness the part in question should be replaced. In my experience once you have pitting the bottom bracket will go downhill fairly fast even with new bearings.
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Old 08-30-16, 06:02 AM
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If you can only feel play when the arms are in certain positions, that is often an dictation that the faces on the bottom bracket shell are not perfectly parallel.
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Old 08-30-16, 04:55 PM
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Originally Posted by JohnDThompson
If you can only feel play when the arms are in certain positions, that is often an dictation that the faces on the bottom bracket shell are not perfectly parallel.

+1. Andy.
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Old 08-31-16, 12:16 AM
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Originally Posted by Andrew R Stewart
+1. Andy.
Can you explain this further?

Thanks to everyone that has responded, btw
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Old 08-31-16, 07:31 AM
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Misaligned bearing "rolling surfaces" (some call these "ball tracks") are a classic cause of tight but still loose adjustment results. Anyone who has spent time in a shop (or at home w/ enough experience) trying to adjust loose ball bearings AND then also has been able to true up said rolling surfaces (as in chasing and facing head tubes or Bb shells) knows this as the improvement in bearing adjustment results after are easily seen.


Bent axles and their misaligned and now worn cones being replaced with straight axles and axially worn (or new) cones are another common example of this.


BTW the angular contact cup and cone (the usual loose ball bearing design) are quite good at making the misalignments less problematic. Why do you think the bike industry has clung to this design for so many years? It allows loose tolerances in the manufacturing of both frame/fork as well as the components being fitted to them. The increasingly common radial contact preassembled cartridge (mistakenly called "sealed bearings" by those who don't study this stuff) bearing design is actually far more sensitive to misaligned bearing installations. This is why so many hubs using "cartridge" bearings have oversized axles. What is a marketing claim of rider benefit ("stiffer axles) is really a design need with these bearings.


John, like some of us, has spent enough time in the trenches to know this. hense my +1 to his post.


This is not to say that this is the OP's problem but this is a common contributor to said problem.


headasunder also makes a good point. The need to readjust bearings after initial use is one reason why better bike shops have had a free after purchase 'tune up" offer for many decades. Those shops that don't adjust the loose ball bearings to spin freely when first assembling the bikes, hoping that the bearing will "wear in" are only creating a situation where the bearing starts it's life with too much preload and the wear right from the beginning is more rapid then need be. Unfortunately this is FAR too often the case. Since most riders don't know this or know how to check for this and the bearing won't feel "loose" the rider mistakenly believes that all is well. Andy.
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