Changing crankset

[kilroy]

Hi guys. I've been looking at potentially shortening my cranks from 172.5mm to 170's. My bike is fitted with 11spd Ultegra cranks (R8000 series) and a BBR60 (BSA) bottom bracket.

I've seen some nice S-Works and SRAM carbon cranks for reasonable money. Some of them mention being compatible with a BB30 bottom bracket. I take it I would need to change the BB as well? I'm assuming my bike would accept a BB30 if required?
Any pointers would be appreciated.

[jaseyjase]

If you're bike currently is running a BSA bb, then you most likely cant run a BB30 bb.

However SRAM make BSA compatible cranks, so you just need to purchase that and the matching BSA bb to suit.

[P!N20]

I'll be amazed if you notice any difference between 172.5 and 170.

[Nobody]

I'll be amazed if you notice any difference between 172.5 and 170.

Yeah, 165 is you want to notice a change IMO. I went from 175 to 165 a decade ago. Yes, I noticed the difference.

[kilroy]

Fair enough, thanks for that. I do remember reading about 165mm cranks being the sweet spot for high cadence climbing but to be honest didn’t really want to make such an extreme change to crank length as I’ve had knee and back issues in the past. It would make sense to pick a compatible crank rather than replacing the BB so I’ll keep that in mind.

[Nobody]

...but to be honest didn’t really want to make such an extreme change to crank length as I’ve had knee and back issues in the past.

The point of short cranks is often to help people who have knee, hip, or other issues that can be related to bike fit (body mechanics) or inflammation issues. Knee problems was the major reason I changed. It marginally helped. One piece of the puzzle.

[Mr Purple]

You won't notice a change from 172.5mm to 170. I started on 170, went to 172.5 and back to 170. No difference.

I have heard of someone making a mistake and accidentally running a 170mm on one side and a 172.5mm on the other. Apparently he noticed no difference either.

[kilroy]

You won't notice a change from 172.5mm to 170. I started on 170, went to 172.5 and back to 170. No difference.

I have heard of someone making a mistake and accidentally running a 170mm on one side and a 172.5mm on the other. Apparently he noticed no difference either.

Wow, I think my body would notice after a couple of hours!

[kilroy]

...but to be honest didn’t really want to make such an extreme change to crank length as I’ve had knee and back issues in the past.

The point of short cranks is often to help people who have knee, hip, or other issues that can be related to bike fit (body mechanics) or inflammation issues. Knee problems was the major reason I changed. It marginally helped. One piece of the puzzle.

Sweet, might have to look into the 165’s. I kinda wish I still had my Assimo power meter pedals as my 4iiii power meter will be a bit too long!

[Duck!]

If your bike currently is running a BSA bb, then you most likely cant run a BB30 bb.

However SRAM make BSA compatible cranks, so you just need to purchase that and the matching BSA bb to suit.

No ifs, buts or maybes, a BB30 crank cannot be fitted in a BSA frame. BB30 uses the same 68mm shell width, with a larger bore to allow internal fitting of the bearings; the crank spindle is only long enough to fit through the internally-mounted bearings.

BB386 format cranks can be an option though. They use the same 30mm diameter spindle as BB30, but the spindle is longer in order to fit through 86mm press-fit shells, and also BSA shells with suitably larger outboard bearings.

SRAM's "DUB" crank & BB set is similar to BB386 in that it can be adapted to fit most frame formats, however it uses a pointlessly unique spindle diameter that requires a compatible bottom bracket.

[WyvernRH]

If your bike currently is running a BSA bb, then you most likely cant run a BB30 bb.

However SRAM make BSA compatible cranks, so you just need to purchase that and the matching BSA bb to suit.

No ifs, buts or maybes, a BB30 crank cannot be fitted in a BSA frame. BB30 uses the same 68mm shell width, with a larger bore to allow internal fitting of the bearings; the crank spindle is only long enough to fit through the internally-mounted bearings.

BB386 format cranks can be an option though. They use the same 30mm diameter spindle as BB30, but the spindle is longer in order to fit through 86mm press-fit shells, and also BSA shells with suitably larger outboard bearings.

SRAM's "DUB" crank & BB set is similar to BB386 in that it can be adapted to fit most frame formats, however it uses a pointlessly unique spindle diameter that requires a compatible bottom bracket.

Interesting... I must admit I have difficulty (ie no real interest) in following all the BB bracket variations but I do have a BB386 bottom bracket on my FELT gravel bike and I bought the chainset shown below which has 'BB30' written on it to convert it to a triple, being assured it would fit by the shop (sucker...). As Duck mentions, this didn't work as the axle was not long enough to prevent the inner ring fouling the large BB386 bottom bracket.
So to the point.. I repurposed this chainset for my early 90's TREK road bike which has a standard (BSA) bottom bracket using an outboard bearing kit made by <Edit -Rotor IIRC-Edit.> Sorry, checked the box, it was a conversion kit by FSA.




As you can see it worked fine, apart from requiring some creative thinking to get the front derailleur outboard a little further.
So, was I just lucky or are these really BB386 cranks?

Personally, I've taken an oath never to buy another bike that does NOT have a standard bottom bracket shell....

Richard