How to fit BB30 cranks to bike with a threaded BB shell?

[ColinJ]

I had a set of powercranks donated to me a few years ago but have never used them because they are designed for BB30/PF30 bottom brackets and I don't have any bikes with those BBs. I was just thinking though that it might be possible to get screw-in external bearings, like Hollowtech II but for the wider spindle?

I had a quick search and have found a few likely-looking products but am not confident that I would buy the right thing...

The bike that I want to convert has a standard English-threaded square taper BB.

This is what I want to fit...

I don't know what the little collar on the left with an arrow on it does. I thought that it might be to hold what appear to be 2 spacers in place?

The drive side has a screw with a torque figure marked on it so I assume that once the bearings and cranks are in place, I just tighten that and all should be okay?

So... advice please!

 

[Cycleops]

What is the spindle diameter? Hollowtech is 24mm but I think BB30 is 30mm so won't work with Hollowtech bearing cups.
So what you want is screw in bearing that will accept a 30mm spindle but there might be other problems.

 

[chriswoody]

That collar looks similar to the pre-load adjuster on SRAM DUB cranks, after fitting the crank arms, you use a 2mm hex socket to remove the play before tightening up the pinch bolts.

As Cycleops mentions above though, BB30 crank spindles are a larger diameter than normal Hollowtech ones, so check the diameter of them.

What make are the cranks?

Edit: just had a quick nose around the internet and found this that may help explain what you need to measure and weather it's possible or not with your cranks, it seems spindle length is also important.

https://bikerumor.com/aasq-45-how-can-i-fit-a-bb30-crank-in-a-threaded-bsa-frame/

 

[ColinJ]

What is the spindle diameter? Hollowtech is 24mm but I think BB30 is 30mm

30 mm.

So what you want is screw in bearing that will accept a 30mm spindle but there might be other problems.

Indeed, which is what worries me!

That collar looks similar to the pre-load adjuster on SRAM DUB cranks, after fitting the crank arms, you use a 2mm hex socket to remove the play before tightening up the pinch bolts.

Ah, of course - that makes sense! I notice that the arrow points the other way on this crank. I wonder if it has been fitted the wrong way round, or if that makes any difference?

What make are the cranks?

Quarq Riken powercranks. Ah, I just found THIS very detailed DC Rainmaker review from 10 years ago - it looks good! (On my set though, the spindle/axle is attached to the non-drive side and the screw holding it on is marked 'do not remove'.)

I don't want to spend too much money or time on this. I could buy a power-measuring pedal for about £300 which would be much simpler, but it seems a shame not to use the Quarq system if I can.

 

[Proto]

Looks like a standard SRAM BB30 crankset to me. You can buy a BSA threaded bottom bracket which this will fit.

Something like this: https://www.biketart.com/products/w...bracket-steel-bearings?variant=40809742401715

Note the ball bearings are tiny and I’m guessing would not last very long before failure.

 

[Jameshow]

https://www.ebay.co.uk/itm/36451013...tixoXeJTeO&var=&widget_ver=artemis&media=COPY
Any good!

 

[Jameshow]

You'll be disappointed with the numbers..!!

 

[Proto]

For assembly have a look here, I think page 14 or so onwards.

https://www.sram.com/globalassets/d...cranksets-and-bottom-brackets-user-manual.pdf

 

[ColinJ]

Looks like a standard SRAM BB30 crankset to me. You can buy a BSA threaded bottom bracket which this will fit.

Something like this: https://www.biketart.com/products/w...bracket-steel-bearings?variant=40809742401715

Yes, that's the kind of thing I was looking at. I don't really want to spend as much as that though...

Note the ball bearings are tiny and I’m guessing would not last very long before failure.

... especially if the bearings wouldn't last long!

https://www.ebay.co.uk/itm/36451013...tixoXeJTeO&var=&widget_ver=artemis&media=COPY
Any good!

Funnily enough, I was looking at that about an hour ago. I dare say that the bearings in that wouldn't be super but presumably the sealed bearings could be replaced if/when needed?

You'll be disappointed with the numbers..!!

I'm sure that I will be! I would be very happy indeed if I could manage 3 W/kg after a few months of hard work, but I suspect that at my age and with my health history those days are gone. Still, whatever I measured, I would make it my target to improve that figure by 10% and see how I got on with that.