PF30 Advice

[bpsmith]

Been trying to track down a creak when in the highest 4 gears on my Bianchi with FSA Gossamer crank and PF30 BB. Doesn't happen in any lower gears and doesn't happen when in same gears on the back and on inner ring on front.

It's a weird noise that I cannot replicate on the stand, so can't show anything in a vid of it. It would definitely fall under the creak definition I reckon.

It happens when I push hard on the pedals and only on the drive side as I put power down or deliberately on a hill and at slow speed to put pressure on it.

I have tried everything I can think of, looked at the usual sides that get posted up on here too. Checked and greased cassette, hanger, rear dérailleur, jockey wheels, chainring bolts, front dérailleur, cables, etc. chain has been replaced, but same noise before and after. Decided to remove crank earlier, to clean and re grease. Checked the BB and non drive side feels a tiny bit smoother than drive side, but not majorly different.

Any ideas?

Toying with getting the BB replaced. Only done 1,500 miles, mostly in the dry too. What's an idea on mileage in such conditions? What sort of cost is this to get done at my LBS?

My other option is to buy the tools and do it myself. I am pretty good mechanically. Is this something straight forward with the right tools? Can I remove the PF30 BB to clean thoroughly and then grease and refit, or not worthwhile? Trying to gauge whether worth the tool cost to use regularly, or just better to pay my LBS this time?

 

[Citius]

Have you had the cups out? That's where the problem is.

 

[screenman]

Seat pin or saddle rails are both big causes of creaks

 

[Citius]

Seat pin or saddle rails are both big causes of creams.

You might want to edit that...

 

[screenman]

You might want to edit that...

Blast this spell cheeker

 

[bpsmith]

Have you had the cups out? That's where the problem is.

Nope, not yet. Not got the tools, as above. If I buy the tools, can I remove and refit the current cups and bearings without damage?

Have you done this job yourself?

 

[bpsmith]

Seat pin or saddle rails are both big causes of creaks

I have recreated the noise from on and off the saddle. Have also put weight on saddle and twisted and flexed to see if I can hear the noise and can't. Still likely to be this?

 

[Citius]

Nope, not yet. Not got the tools, as above. If I buy the tools, can I remove and refit the current cups and bearings without damage?

Have you done this job yourself?

I have done it, but with a borrowed shop tool. The job is either straightforward, or a pain in the ar5e, depending on how keen the cups are on staying in place. If you are going to remove the cups, I would fit new ones anyway - as the job is not something you are going to want to repeat too often

 

[screenman]

I have recreated the noise from on and off the saddle. Have also put weight on saddle and twisted and flexed to see if I can hear the noise and can't. Still likely to be this?

No. But if course moving your weight off the saddle puts more on the bars. In 45 years of cycling I have seldom had a noise from the BBC, not saying never though.

 

[Citius]

No. But if course moving your weight off the saddle puts more on the bars. In 45 years of cycling I have seldom had a noise from the BBC, not saying never though.

Screenman - where can I buy a spellchecker like yours?

 

[screenman]

Bottom bracket cups

 

[bpsmith]

Is it worth buying the Chris King version, as has 5 year warranty and is serviceable from fitted within the bike?

It is costly, but appears to average out as similar price over time.

Planning to keep this bike long term btw.

 

[Hacienda71]

I am sure you have, but have you checked the pedals?

 

[bpsmith]

I am sure you have, but have you checked the pedals?

Yes. Sorry, missed that. Also had new cleats and greased when fitting.

 

[Yellow Saddle]

PF30 is problematic, as is any press fit bottom bracket. It comprises a bearing housed in a plastic cup. The cup is then pressed into a carbon frame in what is assumed to be a rigid fixture. It is far from rigid. The frame's BB shell is flexible and the cup is flexible. The cup material is specifically chosen to be flexible because a carbon shell cannot be milled to the perfect dimensions required for bearing placement and the flexible cup between the bearing and frame is supposed to take up the gaps and accommodate the imperfections. Further, a BB precesses rather badly because of the crank's imperfect rotation. This causes relative movement between cup and frame. Imagine the shell as something made of rubber. Now imagine you pushing on the crank and how the rubber stretches and ovalises in the direction of the pedaling force. That is not imaginary movement, only exaggerated and in reality, this is what happens. This means there is a constant fight between cup and shell. The shell distorts and snaps back towards the cup, but, not in perfect position. A little movement in another spot causes the previous spot to re-seat itself and the result is creaking.
Add a bit of dirty water with dust into the mix and you'll quickly see that a flexible shell, with dust on its surface, with a flexible plastic cup squeezed into it, is actually just a creaking machine with a large carbon speaker in the form of the frame.
The creaking does not emanate from the bearing (in most cases) but from the interface.
The solution seems obvious - remove the cup, clean it, grease it and replace it.
Reality is cruel. The cup can only be removed destructively. There is a tool available from the German tool company, Cyclus, that can remove it safely, but that tool costs as much as the bike frame itself.

The reason we are stuck with pressfit BBs is because of "progress." People are in love with carbon but carbon is difficult to engineer at the BB interface (and in other situations too, such as T joints). The first carbon frames had a threaded aluminium insert into which a standard BSA threaded BB would screw. That doesn't work because of strong galvanic action between the carbon frame and alu shell. Within a short time the alu shell is corroded to the point where the BB just falls out. Carbon itself cannot be threaded in a way to make it strong enough for BB use. So pressfit it is.

If you don't want a creaky BB, get a steel frame. Progress is not always forwards.