1

OK. I am confused with all these BB standards. I'd appreciate it if someone points out the correct adapter for my Opus Allegro 4.0 with a bb86.5 monocoque running on a Tiagra 4600 groupset and FSA compact crankset (pressfit) to 105 7000 crankset (53/39T).

Apparently, the bottom bracket which will come with the groupset is SM-BBR60 which is a threaded BBR60 and won't fit anyway, so I thought I keep my current BBR30 pressfit and find an adapter for the crankset and then sell the SM-BBR60. I checked Park Tool guide, but they are just too many variations and namings. Living in Canada.

enter image description here

enter image description here

  • 2
    Your question is a bit ambiguous. "bb86.5" implies you have a frame with BB86 press-fit cups. Installed BB86 bearings have the same dimensions as a Hollowtech II threaded BB and is compatible with Shimano road cranks. You say you have a 'BBR30' by which I think you mean BB30 or PF30 which is used by FSA. You just need to identify what BB standard the frame is and then Google for appropriate adapters. Adding photos of the crank and BB area will help definitely identify what standard your frame is. – Argenti Apparatus Jun 28 at 17:51
  • I see sry for the confusion. Added. – Amir Jun 28 at 23:31
  • 1
    I hope you're not replacing the original 50-34 compact crankset with a 53-39 standard crankset and expect that to make you faster. It won't. If you're pedaling at 100 rpm with your chain on a 50t chainring and an 11t cog, you'll be going 35 mph or almost 60 kph. Even at 90 rpm - which you should be able to sustain for a really long time - you'll be doing 50 kph/32 mph. The Shimano crankset will probably shift a LOT better than the FSA one does, however. – Andrew Henle Jun 30 at 9:45
  • Thanks @AndrewHenle. Sure. I found my max effort sprinting at Tiagra's 12T and my current 50T almost spinning out at around 57 km/h with ~110 rpm. Checked bikecalc.com/cadence_at_speed and found I am almost at the very threshold of its theoretical limits, setting drags and aerodynamics aside, so I thought I'd give it a try on bigger crankset and an 11T which comes with 105 and see if cadence was my limiting speed or my actual sprinting power. – Amir 2 days ago
2

Whoever wrote their product specs was probably confused, because "BB86.5" isn't really a thing.

You have an FSA 386EVO crank. All the bikes in this series seem to have come with them.

You probably have a BB386EVO shell.

If not that, then it's probably a BB86 shell. This would require a fancy adapter bottom bracket to work with those cranks, which would be unusual for stock parts, so I doubt it's what you've got.

The internal diameter of BB386EVO is 46mm vs 41 for BB86. Pull your cranks and put a ruler or caliper up to the shell. 5mm is a pretty big difference so you should be able to figure out which you've got.

In the likely case it's a BB386EVO shell, a bunch of companies make adapter BBs for 24mm cranks for them. The thread-together type linked is nice because it adds a natural hedge against creaking, but they're pricier than some options. Cheap reducer adapter bushings exist too, which in my opinion are a compromise because they waste space that could have been used on bigger ball bearings, and add another set of surfaces that can creak. Those could adapt your existing BB to your R7000 though, in the event it still has life in it and you want a simple installation.

If it's BB86 you just need any Shimano press fit road bottom bracket.

| improve this answer | |
  • Thanks for the info @Nathan. Yes, it is most likely 386 and I need to go for either adapters you mentioned. Do you think those cheap reducers will likely waste Watts cuz the reason for an upgrade was to have a better performance lol – Amir Jun 29 at 15:50
  • 1
    @Amir Not acutely, but the other type will Iikely spin better for longer in terms of wear life, so there could be gains there. – Nathan Knutson Jun 29 at 15:58
  • I see. So basically if I saw my current Tiagra BB is ok, I don't need to buy a 105 SM-BB72-41 pressfit and the adapter. An adapter alone would suffice? – Amir Jun 29 at 16:07
  • 1
    Tiagra implies a Shimano product, and Shimano only makes threaded and BB86/92 press fit bottom brackets. If your shell type is in fact BB386EVO, then what you have inside now is likely an FSA 386EVO bottom bracket, unless by some chance it came with or got replaced by another company's product that does the same thing. But if you have a a BB386EVO shell and the pictured cranks, then yes the adapters I linked to will make any Shimano road crank work. One of the potentially confusing things here is that BB386EVO is both a shell standard and the name for FSA's long 30mm crank standard. – Nathan Knutson Jun 29 at 22:12
  • Thanks for all the info Nathan. Much appreciated. – Amir Jun 30 at 4:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.