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So after about 10,000 miles with my bike I bought in 2015 the bottom brackets have had enough. I need to switch them out, and considering they're quite cheap in retail and also does a lot of the heavy lifting I thought I could upgrade to a better series.

And here's where my problem is, I have no idea whether a BB I'm considering will fit the bike or not.

Here's the bike I have enter image description here It's a 2015 Nishiki Hyper Pro


The original Bottom Brackets are Shimano SM-BB4600, which seem to be the Tiagra series. (https://www.chainreactioncycles.com/se/en/shimano-tiagra-4600-bottom-bracket/rp-prod67221) enter image description here


The Bottom Bracket I hope to upgrade to would either be

Shimano Dura Ace BB-R9100 (https://www.wiggle.se/shimano-dura-ace-bb-r9100-vevlager/) enter image description here

Or the Shimano BB-R60 Bottom Bracket (Ultegra, 6800/105 5800, Hollowtech II) (https://www.wiggle.se/shimano-bb-r60-vevlager-ultegra-6800105-5800-hollowtech-ii/)

enter image description here

Would you say these bottom brackets are interchangeable? And if so, for me who mainly use the bike for a high pace 12 mile commute (in sun, rain or snow) each day, what BB would you recommend? Never mind the price difference, I only focus on durability and performance.

  • The best way to pick Shimano bottom brackets is by the color. Which one matches your bicycle the best? IME there isn't any difference in any of the Hollowtech II bottom brackets other than the color. – Andrew Henle Mar 22 '19 at 13:48
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There are three current Hollowtech II road threaded BB designs (different model numbers of identical designs also exist).

  • BB-RS500 - this is the 44mm 16-notch cup design and weighs 92g
  • SM-R60 - this is the 41mmm 16-notch cup design and weighs 77g
  • BB-R9100 - this is the 39mm 16-notch cup design and weighs 65g

These measurements refer to the diameter of the bottom bracket cup, which is only a concern during fitting/removal. The bottom brackets themselves all fit the same frames.

Technically only the R9100 is considered 'Dura-Ace', the others are 'non-series'. In any case they are all interchangeable - you can use BB-RS500 with an R9100 crankset.

In general weight savings are the primary driver of the higher BBs. It would not be reasonable to assume that they are more durable.

However Shimano advertise that SM-BBR60 & BB-R9100 use 'small ball bearings'. This is not necessarily a good thing, in that smaller bearings are weaker. However there are more of them. Still it would be reasonable to assume that the RS500 will be DIFFERENT in durability from the other two, but not necessarily worse.

My money would be on the RS500 if durability is a concern as the extra weight does not seem to be a bad thing in this context. It is possible there are design differences such as seals between the models, but I would not assume this without evidence.

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  • Thank you for educating me! I'm now convinced to keep on with the RS500 and instead put my money towards maybe a better chain that @Argenti Apparatus recommended. Thanks a lot! – AndroidHustle Mar 25 '19 at 7:33
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All Shimano Hollow-Tech II road bottom bracket cups are interchangeable, that is they all have the same bottom bracket shell threads, fit in same shell width, have the same axle diameter and overall width.

I personally wouldn't bother with the Dura Ace or Ultegra units, I'd put the price difference between those and a Tiagra or 105 unit into a better quality chain.

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  • The 105 would already be a huge upgrade. Given that the Tiagra lived 10.000 miles. The second unit is likely to outlive the frame. – Carel Mar 22 '19 at 18:58
  • Really like the argument to use the price difference towards upgrading something else, I mean I haven't switched out the chain either during this time. Only my break pads. – AndroidHustle Mar 25 '19 at 7:34
  • @AndroidHustle I'm stunned by that revelation! Chains are not supposed to outlast bottom brackets! You chain is probably very worn and so is your cassette (worn and elongated chains kill sprockets). Unless there is something demonstrably wrong with the BB (roughness, play), I'd prioritize a new chain and cassette. – Argenti Apparatus Mar 25 '19 at 11:18
  • @ArgentiApparatus hmmm... I'm going down to my bike now after lunch to fix a flat tire, gonna have a close look at the chain and cassette, but I really haven't suspected them to be the problem. The resistance in the crank have I suspected came from the BB since it's crackling when turning the crank. – AndroidHustle Mar 25 '19 at 12:01
  • @AndroidHustle yeah, I'd bet real money your chain and cassette are toast and the BB is fine. Check the chain rings too – Argenti Apparatus Mar 25 '19 at 12:08
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The bottom brackets are interchangeable as long as you go for the same bottom bracket type which in your case seems to be the standard english threaded road bottom bracket.

However, I don't think that at your level of cycling that it would make much of a difference to simply upgrade the bottom bracket itself. You can just replace it with a new Tiagra and will probably notice a good enough difference simply because it is new.

If you want something that will give more longevity, you'd have to go to a different system such as square taper which moves the bearings inside the bottom bracket and away from the rain. But this would require changing out your crankset.

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  • Big thanks to your input! I never really considered switching out the crank set since I felt quite satisfied with the setup. If I were to convert to a square taper or Octalink system I suppose I may have to replace my shifters also? I have the Shimano 105 FD-5800, 31,8 mm front shifter now. – AndroidHustle Mar 22 '19 at 13:11
  • No, the shifters and the derailleur would be fine. Most people consider the hollowtech 2 to be superior to a square taper or octalink, but it really depends on your priorities and riding style. You might be better off just replacing your bottom bracket more often to keep it running better. 10,000 km is a long distance for an external bottom bracket considering they are so cheap to replace. – Kibbee Mar 22 '19 at 18:40
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    I have to take exception with the assertion that internal bearings have better longevity. Bearings are really no more protected on an internal cartridge BB than external. Internal bearings have smaller diameter and therefore have less cup and cone surface area. The bearings are further inboard and experience higher pedaling forces. For these reasons Internal bearings are likely to wear faster than external ones. – Argenti Apparatus Mar 22 '19 at 19:05
  • Thanks to both of you! I think I'm sticking to Hollowtech II and try to replace BB's more often. Probably should have replaced it almost a year ago... – AndroidHustle Mar 25 '19 at 7:24
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All Shimano HollowTech 2 chainsets have 24mm axles so the bottom brackets will be interchangeable.

The higher quality BBs have smoother more polished bearings which generally makes them last longer.

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