bottom bracket change: BSA 68/73, is this all I need ?

[Cbetronic]

Hi,

I got myself a new bike a recently, but I may already have an issue with the BB making clicky noises.

The crankset is a Gates CDC S301 (really a ProWheel) and the BB description says BSA 68/73.

A quick look online produces lots of results, so I'm at loss what to pick. Would any BB with the above description fit ?

 

[Jameshow]

Hi,

I got myself a new bike a recently, but I may already have an issue with the BB making clicky noises.

The crankset is a Gates CDC S301 (really a ProWheel) and the BB description says BSA 68/73.

A quick look online produces lots of results, so I'm at loss what to pick. Would any BB with the above description fit ?

I believe it's included. The 68/73 is it's max /mum width!

 

[Big John]

You shouldn't have any issues with the BB on a new bike and if you do then you should be returning it to be put right by the seller. You shouldn't need to put it right yourself. You may even be running the risk of invalidating any warranty that's in force if you do start working on it yourself.

 

[Jameshow]

You shouldn't have any issues with the BB on a new bike and if you do then you should be returning it to be put right by the seller. You shouldn't need to put it right yourself. You may even be running the risk of invalidating any warranty that's in force if you do start working on it yourself.

It's possibly a s/h bike new to him?

 

[figbat]

The BB will need to be a BSA screw-in type, with a 68/73 width capability and for a 24 mm crank spindle.

 

[Ajax Bay]

I got myself a new bike recently

Share what bike and how 'new' please.

 

[fossyant]

So, 68mm refers to what is usually road bike width BB shell, 73mm is more on MTB.

You need a Shimano Hollowtech II BB - these are cups that screw on each side. You'll also need the tool to fit it (all are under £30).

https://www.merlincycles.com/shiman..._medium=Affiliates&utm_campaign=genieshopping

https://www.merlincycles.com/icetoolz-bb-tool-for-external-bearings-71966.html

 

[Cbetronic]

You shouldn't have any issues with the BB on a new bike and if you do then you should be returning it to be put right by the seller. You shouldn't need to put it right yourself. You may even be running the risk of invalidating any warranty that's in force if you do start working on it yourself.

I bought the bike online unfortunately. I'm not totally sure yet that it is the BB but there are very few parts there... I would probably bring it to a repair shop and verify that it is actually the BB.

It's possibly a s/h bike new to him?

Share what bike and how 'new' please.

C*be editor 2025, you can't really buy those s/h yet, I have used it for less than 6 months and I have put a few thousand km on it.

 

[Cbetronic]

I believe it's included. The 68/73 is it's max /mum width!

'mum' as in 'min' ?

So, 68mm refers to what is usually road bike width BB shell, 73mm is more on MTB.

You need a Shimano Hollowtech II BB - these are cups that screw on each side. You'll also need the tool to fit it (all are under £30).

https://www.merlincycles.com/shiman..._medium=Affiliates&utm_campaign=genieshopping

https://www.merlincycles.com/icetoolz-bb-tool-for-external-bearings-71966.html

Thanks for the links.

68mm is the min width and 73 is the max width with spacers I assume ?

I already changed the BB on my previous bike but it was a Shimano so I just picked the same model. There is no brand on this one so I'd rather ask people who know.

I did buy the tools for screwing that BB and I remember how tightly screwed it was, probably because I used a spanner around the tool.

That Shimano BB seems quite cheaply priced, almost as cheap as a copy on AliExpress! Shimano being a reputable brand, it's going to be fine but I wonder if it is worth investing in something a little more robust/durable ?

Thanks for the help!

 

[Cbetronic]

One more question, is it possible to identify the source of noise knowing that I can only hear it when I hit the pedals firmly. I have to be riding, it can't be on a bike stand.

I tried recording it with a phone while riding, moving the phone close to different suspicious parts but it wasn't conclusive.

 

[figbat]

Noises are as tricky to track down on a bike as they are in a car!

Off the top of my head, noises could come from:

- bottom bracket
- seatpost
- saddle
- suspension (if fitted)
- cables
- hubs
- stem/bars
- wheels/spokes
- cranks
- pedals
- chainring
- frame…

Worth giving the bike a good once-over, checking everything is tightened to the required torque and nothing is flapping or rubbing. It’s easy to fixate on one possible cause and ignore or overlook something else.

 

[Ajax Bay]

Drivetrain​

• Crankset: Gates S31 CDC, 45.5mm Beltline
• Bottom Bracket: Gates BSA
• Belt: Gates CDX, 113 Tooth