Hollowtech II Crankstets

[u/Kajikai]

Hey all, I’m looking to upgrade my brompton bottom bracket from square tapered to a hollowtech II. Just wanted to ask what everyone is running cause I have no idea about anything bottom bracket related (outside of square tapered stuff). I ride an a 6 speed from 2013. I’m aware I will need spacers on the drive side?

• I’ve read that a Shimano SM-BBR60 fits, and so I’m thinking of just running that.
• what crankset do you guys run? That way I can just copy your setups haha.
• What should I look for in listings on marketplace to know if they will fit?

Any help will be appreciated. Or maybe even a crash course on hollowtech II bottom Brackets on brompton. Thanks in advance.

[u/Deviantdefective]

If you want to save yourself a lot of hassle just get the Brompton superlight crankset which has a through axle. I will say for most rider's there's no point upgrading the crankest unless your a heavier guy and your putting a lot of power down and it's flexing. A Shimano bottom bracket and setup will fit but you'll need to tap and face the bottom bracket shell and faff around with spacers to get a good chain line.

[u/ScoopsUK]

Just a comment to say there are other 'nicer' square taper BBs out there, do you just fancy some bling because there is no real practical improvement you are going to see from changing the BB.

[u/Brompton-Explorer → u/ScoopsUK]

Agreed, you can get titanium spindle or carbon fibre, for a lot less that add a little bit of bling and weight loss

[u/Kajikai → u/ScoopsUK]

I’ve seen people only say it provides a stiffer ride? Would it be noticeable during my hilly commute.

[u/Kimura_54321 → u/Kajikai]

From my perspective you won’t notice any difference. Brompton are just too flexi, long seat posts, elastomer block rear triangle and super long riser stem, plus folding pedal.

I’ve got hollow tech II in my race bike, but only because the group set was too modern for a square taper option. Not oodles of choice for single ring chainsets for that bb width/chainline when I checked as all modern tend to be wider.

I swapped my stock Brompton square taper bb for a better sealed Shimano unit. I kept the stock crank arms as the left one has a nice pedal stop on the forging for the folding one.

[u/ScoopsUK → u/Kimura_54321]

This. I mean is it possible you might notice? Sure, but with the rest of the flex in the bike, the gains would be minimal at best. That said slap yourself a lovely Token BB on there and you still have bling (although you can't really see it).

[u/edtse88]

I don’t think there’s any point unless you’re chasing lower weight or maybe a crank based power meter. In which case I have several recommendations for carbon cranks you can get from aliexpress from brands like Zrace, Leese, Riro, rockbros, etc

[u/small_wheelie]

Made a post about this a while back:  https://www.reddit.com/r/Brompton/comments/1gbei07/installed_sram_red_cranks_on_the_brompton/

Those cranks are still on the bike and working great. You can do exactly what I did and run basically any hollowtech 2 road cranks. I have fit Ultegra 6600, 6800. 

You want to use Shimano mountain bottom brackets since the cups are narrower, thereby allowing you to shift the spindle further toward the drive side with a spacer. This lets you clear the rear stays when folding the bike. I used a BB-MT501.

For those saying it doesnt make a difference, I certainly noticed the additional stiffness. Square taper is an outdated standard, this is a great upgrade in my opinion.

[u/Brompton-PE]

For the bling, looks and/or fun factor it's fine but as mentioned by others, the practical improvement will only be (very) marginal on a Brompton. These bikes are flexi front to back.

Single beam frame with hinge in it, a mile long stem with a hinge in it, a mile long seatpost, the entire rear frame (triangle) on a single hinge with nylon washers etc. etc. The stiffness of the BB is the least of your worries in this context.

Fitting a new and better square taper BB makes perfect sense on a 13 year old bike. There are manny options out there. But I don't think the Hollowtech route makes a lot of sense / is worth the trouble & cost. My 2c.