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I want to upgrade my bikes groupset to a Shimano 105. I currently have a "sealed cartridge, square taper, steel spindle, steel cups" bottom bracket. Will this be an issue upgrading to a new groupset? Will I need to get a press fit or just the Hollowtech II BB60?

More generally, are there other considerations when getting a new groupset? I currently have:

Bike: Marin Toscana CX (2010 or so) Crank: FSA Vero Front Derailleur: Shimano Sora Rear Derailleur: Shimano Tiagra Cassette: SRAM 11-26 9 Speed

I am up for basically ripping everything off and replacing it as needed, just need to know if there are any dealbreakers with compatibility.

2 Answers 2

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There are a lot of parts to this question.

  1. A "press fit" bottom bracket is a name for a whole class of bottom-bracket standards, but it describes the interface between the bearings and the frame, not the bearings and the BB spindle. With a press-fit BB, cartridge bearings are pressed directly into the BB shell. There is a similar class of bottom brackets where there is a thin plastic cup between the cartridge bearing and BB shell. This is a confusing topic. Here's a guide to BB standards.
  2. You probably have a British/ISO/BSA (different names for the same thing) bottom bracket. This uses threaded cups. Not compatible with press-fit.
  3. You do need to pay attention to the interface between the bearing and the BB spindle, because there are multiple options here too. You've got a traditional square-taper spindle, which is 15 mm in diameter and probably profiled to fit loose bearings, but Hollowtech II uses a 24-mm straight cylinder instead. British BBs that fit HT spindles move the bearing cups outside of the BB shell, and use cartridge bearings.
  4. Buying a new groupset is usually disproportionately expensive. You might want to price new bikes (if you can find one in this market) just to make sure you're satisfied with the value/money ratio.
  5. From what I can tell, your bike might have been specced with cantilever brakes or cable-actuated disc brakes. 105 cable brake levers should work with cantis, and if you've got cable-actuated discs, I think they'll work with those too. But 105 disk brakes are hydraulic; if you're getting disc brakes, you'll also need mounting adapters. And if you're switching from cantis to discs (I assume the frame has disc-brake mounting tabs even if it is not using them), you'll need to make sure your hubs can fit disc rotors—or get new wheels/relace these rims onto new hubs.
  6. Your bike looks like it has a top-routed derailleur cable. I'm not sure if that's a top-pull derailleur, or it uses a pulley on the seat tube to turn the cable around. If the former, you'll need to adapt to a bottom-pull derailleur. I'm a little surprised Problem Solvers doesn't have a clamp-on pulley, so the alternative would be to route the cable under the BB.
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  • Thanks for the detailed response. I would probably get a new bike in normal times, but this is the best option given my drivetrain is a wreck. I have cantilivered breaks, but I will be swapping them out for traditionally mounted rim brakes. My front derailleur has a little pulley under it operate as a bottom pull
    – DanG
    Jan 5, 2022 at 18:22
  • Not sure I understand everything you said about BBs - my real question is if I get a 105 crankset, will a professional at my bike shop be able to find a BB that will work.?
    – DanG
    Jan 5, 2022 at 18:24
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    @DanG yes, this will be a straightforward job for a bike shop. As for caliper brakes: consider your tire size. Most calipers can't reach past the fatter tires you might have on a CX bike, and "long-reach" calipers can have poor performance, which is why cantis are a thing.
    – Adam Rice
    Jan 5, 2022 at 18:53
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The SM-BBR60 bottom bracket and any Hollowtech 2 style crankset with 24mm spindle should work fine. Your rear hub is 11 speed compatible. As far as I can tell there is nothing preventing you from upgrading everything to the latest Shimano 105 groupset.

I would ride the current components until the chain and cassette (and ideally chainrings and cables) are worn down and in need of a replacement so you don’t replace perfectly good parts.

Keep in mind that you’ll need special tools to remove the old crankset and bottom bracket (also: Gentle reminder that the bottom bracket non-drive-side tightens clock-wise while the drive side tightens counter-clockwise). You’ll also need (another) special tool to install the new bottom bracket. For the cassette you’ll also need the lockring tool and a chain whip.

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  • Thanks this sounds very promising. I will probably have a professional do the installation, but the bike shop can't source the parts so I am doing that myself. My worry here is that if I buy a bunch of parts I won't be able to use them so I just wanted to check on here
    – DanG
    Jan 5, 2022 at 18:36

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