PF30 Advice

[bpsmith]

Thanks @Yellow Saddle, I have researched this a bit and found how it all works. The interesting bit is in regard to the aluminium reaction. This kind of goes against the Chris King option then.

Some suggest loctite on the bearing cup before installing in the frame. Is this pointless based on the above then, as creaking will always occur?

 

[outlash]

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.

Is this one of those 'opinion presented as fact' type of posts?

 

[Yellow Saddle]

Thanks @Yellow Saddle, I have researched this a bit and found how it all works. The interesting bit is in regard to the aluminium reaction. This kind of goes against the Chris King option then.

Some suggest loctite on the bearing cup before installing in the frame. Is this pointless based on the above then, as creaking will always occur?

The aluminium I'm talking about is a threaded sleeve built into the frame at the time of manufacture. Companies like FSA also make one that can be retrofitted, but it is actually a conversion to 24mm cranks. It is a good option but it is vital that the frame has a drainage hole to prevent water building up around the sleeve and causing the galvanic reaction.

I don't understand your Chris King comment though.

Loctite will not work. It cannot prevent the precession.

 

[Yellow Saddle]

Is this one of those 'opinion presented as fact' type of posts?

By asking the question you demonstrate your ignorance of the topic. If you really want to expose me as an opinionated fact-monger, why not point directly to the flaws in my argument?

 

[Globalti]

Yellow Saddle has explained it and I've cured it.

My pal and I both have BB30 with FSA and we've found the same problem occurs on my FSA K-Force and my pal's Gossamer. In both cases the creaking noise under load was cured, permanently, by cleaning everything up and refitiing with Bearing Fit compound smeared on the FSA alloy axle to prevent it from fretting in the inner bearing races. I came up with this solution when I dismantled my BB to find this:

Look carefully at those machined areas of the axle which fit inside the bearing inner races - what do you think has caused the fretting and erosion of the polished surface exactly where the axle sits in the bearing races? It can only be microscopic movement under the very high stresses of pedalling. My first attempt to cure the noise was by smearing green grease on the interface; this lasted less than a hundred miles and when I dismantled it, the grease had turned black, indicating metal wear. So next I tried Bearing Fit compound, which worked. Smear the bearing fit compound on the inside of the LH (non-drive) race and on the axle on the RH (drive) side so that it doesn't get wiped off as you push the axle through the RH bearing. Bearing Fit takes up the microscopic gap and isn't so hard that it prevents dismantling. As soon as I did disturb it, when I needed to remove the LH crank and knock the crankset a couple of mm to the right to free the chain when it got jammed between rings and frame thanks to careless handling, the cure failed and I needed to dismantle and reassemble clean with fresh compound.

Interestingly, the erosion is less marked on the drive side and I attribute that to the stabilising effect of the drive chain on the pedalling forces.

Clearly the success of this solution tells me that the creaking is not coming from the bearings in the alloy sleeves or the sleeves in the frame. The BB has now been silent for over 1000 miles.

 

[Yellow Saddle]

Yellow Saddle has explained it and I've cured it.

My pal and I both have BB30 with FSA and we've found the same problem occurs on my FSA K-Force and my pal's Gossamer. In both cases the creaking noise under load was cured, permanently, by cleaning everything up and refitiing with Bearing Fit compound smeared on the FSA alloy axle to prevent it from fretting in the inner bearing races. I came up with this solution when I dismantled my BB to find this:

Look carefully at those machined areas of the axle which fit inside the bearing inner races - what do you think has caused the fretting and erosion of the polished surface exactly where the axle sits in the bearing races? It can only be microscopic movement under the very high stresses of pedalling. My first attempt to cure the noise was by smearing green grease on the interface; this lasted less than a hundred miles and when I dismantled it, the grease had turned black, indicating metal wear. So next I tried Bearing Fit compound, which worked. Smear the bearing fit compound on the inside of the LH (non-drive) race and on the axle on the RH (drive) side so that it doesn't get wiped off as you push the axle through the RH bearing. Bearing Fit takes up the microscopic gap and isn't so hard that it prevents dismantling. As soon as I did disturb it, when I needed to remove the LH crank and knock the crankset a couple of mm to the right to free the chain when it got jammed between rings and frame thanks to careless handling, the cure failed and I needed to dismantle and reassemble clean with fresh compound.

Interestingly, the erosion is less marked on the drive side and I attribute that to the stabilising effect of the drive chain on the pedalling forces.

Clearly the success of this solution tells me that the creaking is not coming from the bearings in the alloy sleeves or the sleeves in the frame. The BB has now been silent for over 1000 miles.

This is a nice explanation and good cure. I omitted to add the additional problem of BB30 which is the metal-on metal interface between bearing and axle. My explanation deals with the casing-to-frame interface. Shimano's Hollowtech BBs don't have metal-to-metal but also creak, as explained above.

The erosion will be less on the right hand side since torque on that side is not transmitted through the tube. It goes directly from crank to chainring. On the left side, it goes from crank, to (flexible) tube, through to the right, into the chainring. It is the flexibility of the tube that causes the fretting on the left.

I like the suggested use of Bearing Fit, it is something I have not yet tried.

However, I think BB30 sucks. It creates more problems that what it solves and is purely the result of patent right fights and corporate jealousy and pride.

 

[bpsmith]

Yellow Saddle has explained it and I've cured it.

My pal and I both have BB30 with FSA and we've found the same problem occurs on my FSA K-Force and my pal's Gossamer. In both cases the creaking noise under load was cured, permanently, by cleaning everything up and refitiing with Bearing Fit compound smeared on the FSA alloy axle to prevent it from fretting in the inner bearing races. I came up with this solution when I dismantled my BB to find this:

Look carefully at those machined areas of the axle which fit inside the bearing inner races - what do you think has caused the fretting and erosion of the polished surface exactly where the axle sits in the bearing races? It can only be microscopic movement under the very high stresses of pedalling. My first attempt to cure the noise was by smearing green grease on the interface; this lasted less than a hundred miles and when I dismantled it, the grease had turned black, indicating metal wear. So next I tried Bearing Fit compound, which worked. Smear the bearing fit compound on the inside of the LH (non-drive) race and on the axle on the RH (drive) side so that it doesn't get wiped off as you push the axle through the RH bearing. Bearing Fit takes up the microscopic gap and isn't so hard that it prevents dismantling. As soon as I did disturb it, when I needed to remove the LH crank and knock the crankset a couple of mm to the right to free the chain when it got jammed between rings and frame thanks to careless handling, the cure failed and I needed to dismantle and reassemble clean with fresh compound.

Interestingly, the erosion is less marked on the drive side and I attribute that to the stabilising effect of the drive chain on the pedalling forces.

Clearly the success of this solution tells me that the creaking is not coming from the bearings in the alloy sleeves or the sleeves in the frame. The BB has now been silent for over 1000 miles.

Interesting. Any links to the specific product that you used?

Incidentally, I don't have any marks at all on the shiny area where the crank spindle and bearings meet.

 

[bpsmith]

The aluminium I'm talking about is a threaded sleeve built into the frame at the time of manufacture. Companies like FSA also make one that can be retrofitted, but it is actually a conversion to 24mm cranks. It is a good option but it is vital that the frame has a drainage hole to prevent water building up around the sleeve and causing the galvanic reaction.

I don't understand your Chris King comment though.

Loctite will not work. It cannot prevent the precession.

Chris King comment was in reply to you saying that the Alu reacts. CK BB being Alu cups.

 

[Globalti]

Interesting. Any links to the specific product that you used?

Incidentally, I don't have any marks at all on the shiny area where the crank spindle and bearings meet.

Bearing fit compound is commonly available. Here for example:

http://uk.rs-online.com/web/p/retaining-compounds/0514559/

 

[bpsmith]

Bearing fit compound is commonly available. Here for example:

http://uk.rs-online.com/web/p/retaining-compounds/0514559/

Cheers.

 

[outlash]

By asking the question you demonstrate your ignorance of the topic. If you really want to expose me as an opinionated fact-monger, why not point directly to the flaws in my argument?

How exactly do I demonstrate my ignorance? You're the ignorant one by calling me that when you know nothing about me. As for flaws in your 'argument', who's arguing? You're presenting your opinions as facts, all I've done is point that out.

For someone who's quite happy to advertise their own work in their sig, you're bedside manner leaves a lot to be desired. Whilst I'm sure your advice is sound, your attitude is frankly shocking and puts many off from reading it.

For the record, I've replaced 4 press fit BB's including one of my own and the only time I've had problems is when someone bought the cheapest available bearings and they didn't fit correctly. No creaking, no fuss, done in under an hour. IMO, if you're having problems when fitting, you're not doing it right.


Tony.

 

[Yellow Saddle]

How exactly do I demonstrate my ignorance? You're the ignorant one by calling me that when you know nothing about me. As for flaws in your 'argument', who's arguing? You're presenting your opinions as facts, all I've done is point that out.

For someone who's quite happy to advertise their own work in their sig, you're bedside manner leaves a lot to be desired. Whilst I'm sure your advice is sound, your attitude is frankly shocking and puts many off from reading it.

For the record, I've replaced 4 press fit BB's including one of my own and the only time I've had problems is when someone bought the cheapest available bearings and they didn't fit correctly. No creaking, no fuss, done in under an hour. IMO, if you're having problems when fitting, you're not doing it right.


Tony.

Like I said, point out the flaws in my explanation rather than blanket-condemn it as mere opinion. Skip the ad hominem, it makes no valuable point at all.

 

[outlash]

You want input? You called me ignorant without any provocation. I expect an apology.

 

[Citius]

You want input? You called me ignorant without any provocation. I expect an apology.

Maybe you could prove that you are not ignorant first? Answer the question put to you.

 

[Yellow Saddle]

Chris King comment was in reply to you saying that the Alu reacts. CK BB being Alu cups.

I wasn't aware of CK's PF BB30 cups in aluminium. It is a strange choice and I would expect a lot of creaking from it. As I explained, the reason the cups on PF BB30 are plastic is to accommodate the imperfectly-machined carbon frame. This problem is not there with normal BB30 in aluminium frames. In alu frames the BB shell is welded onto the frame and then machined to high enough tolerances to not squeeze the bearing out of round. The welding causes the shell to distort, hence the expensive machining afterwards.
Making the cups from aluminium is problematic, I'd say. The anodizing does however protect the cup from the aforementioned galvanic corrosion (to an extent). But because this is a removable part, it is not an issue should it corrode. The sleeves I mentioned are permanently bonded to the frame. Corrosion then spells new frame.