# Prepping a carbon fiber frame for pressfit-30 bottom bracket with aluminum cups?



## Waspinator (Jul 5, 2013)

I think it's safe to assume that one does not face or ream the bottom bracket shell of a carbon fiber frame prior to pressing in the aluminum cups. But is there any way to maximize the fit between the carbon fiber shell and aluminum cup?

And what material does one use on the cup when placing it? Some say anti-seize paste, others say Loctite (green), and nobody specifies which type of frame material their instructions address.


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## Peter P. (Dec 30, 2006)

What brand frame do you have? It's not clear to me; is the BB shell carbon or aluminum?

What brand BB cups do you have?

In the absence of the above information, I would only use anti-seize on a threaded fit. If you must use a loctite, then start with a low strength RETAINING compound for press-fit applications; a compound that's removable.

Look down on the lower left of the link provided and you'll see an Applications selection. Choose plastic to metal if the BB is carbon. Choose metal to metal if both surfaces are metal. Loctite 641 is one removable compound for press-fit, cylindrical applications.


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## Waspinator (Jul 5, 2013)

BB shell is carbon fiber. 

And what about prepping the frame? Is there any sanding to do to remove paint or stray pieces of epoxy? Frame is a Ridley Noah.


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## ruckus (Apr 1, 2014)

Maybe, just pay a trusted LBS $15 to do it? Just so if anything goes wrong, they are liable, sort of safety net.


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## cxwrench (Nov 9, 2004)

Waspinator said:


> BB shell is carbon fiber.
> 
> And what about prepping the frame? Is there any sanding to do to remove paint or stray pieces of epoxy? Frame is a Ridley Noah.


It's a PressFit. If you sand it you're removing material and it then becomes 'sort of a PressFit'. With the Cervelos they recommended a sleeve retainer loctite w/ primer. We found they still made noise, if not immediately then within a month or 2. We now use grease. It will still make noise eventually but it takes a lot longer for it to become noticeable. Check w/ your frame manufacturer and see what they recommend, but the only thing we've used that works for any length of time is plain-ole grease.


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## ewitz (Sep 11, 2002)

It is Press Fit 30.

No loctite or compaound required just some grease on the bearing races.

See Workshop: How to service BB30 & Press-Fit bottom brackets - BikeRadar for some decent instructions.


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## Waspinator (Jul 5, 2013)

cxwrench said:


> It's a PressFit. If you sand it you're removing material and it then becomes 'sort of a PressFit'. With the Cervelos they recommended a sleeve retainer loctite w/ primer. We found they still made noise, if not immediately then within a month or 2. We now use grease. It will still make noise eventually but it takes a lot longer for it to become noticeable. Check w/ your frame manufacturer and see what they recommend, but the only thing we've used that works for any length of time is plain-ole grease.


My understanding is that the creaking comes from movement caused by inexact fit between bb shell and bearing cups. With metal frames about to have bearing cups pressed into or screwed into them the expectation is that head tubes and bb shells are faced and reamed to exact dimensions in order to maximize fit between bearing cup and metal. What I'm wondering is whether or not this sort of frame preparation should be (or even can be) done for a CF frame when something is going to be pressed into it.


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## JoelS (Aug 25, 2008)

IMO, this is about the worst possible BB solution. I've never had success and have tried all sorts of different compounds. 

That said, there's a better PF30 BB on the market now. This one works. It's installed in my wife's bike and she's never had a problem. Praxis Works | Conversion Kit


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## Waspinator (Jul 5, 2013)

JoelS said:


> IMO, this is about the worst possible BB solution. I've never had success and have tried all sorts of different compounds.
> 
> That said, there's a better PF30 BB on the market now. This one works. It's installed in my wife's bike and she's never had a problem. Praxis Works | Conversion Kit


I disagree. For pressfit 30 bikes, Praxis' conversion bb requires the use of a plastic sleeve into which the aluminum bb is placed. While it does accomplish connecting the left and right sides (which probably does help with creaking), you're still riding on plastic, and expecting all of you weight and pedaling forces to be sustained by that plastic sleeve without it being compressed and negating the stiffness the bb30 and pf30 standards were designed to deliver. 

Moreover, the bb to which you're referring is meant for using 24mm spindles in bb30/pf30 frames. I have a 30mm crank. 

I do agree, however, that the pf30 standard, which was borne purely out of a need to cut manufacturing costs and little else, is far and away the worst development ever to come to bicycle design. Far and away worse than integrates headsets. Bb30 isn't much better either.


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## Dunbar (Aug 8, 2010)

Waspinator said:


> you're still riding on plastic, and expecting all of you weight and pedaling forces to be sustained by that plastic sleeve without it being compressed and negating the stiffness the bb30 and pf30 standards were designed to deliver.


I'm having one of those Praxis adapters installed on my BB30 bike as I type this. The plastic sleeve (which wasn't needed on my bike) is pretty rigid and, once installed in the shell, with the metal adapter pressed inside of it, probably can't compress much (if any). And frankly, the sleeve is probably stiffer than a bare carbon fiber PF30 BB shell that it's sitting inside of. From what I've read most of the creaking is a result of bearings or adapters walking out of the shell. Not because the sleeve is compressing. By loctiting bearings in place or using a threaded adapter like Praxis you fix that issue.

I agree that BB/PF30 has proven to be way more hassle than it is worth in terms of weight/stiffness. I went through two sets of Wheels Manufacturer adapters in 5k miles. There are few things more annoying on a bike than listening to a creaking noise 4-6k times per hour!


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## redondoaveb (Jan 16, 2011)

I've got a Ridley Noah Pro and installed a Wheels Manufacturing PF30 BB (picture below). I used grease for the install. Got a ton of miles on it and no creaking at all.


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## Waspinator (Jul 5, 2013)

Dunbar said:


> I'm having one of those Praxis adapters installed on my BB30 bike as I type this. The plastic sleeve (which wasn't needed on my bike) is pretty rigid and, once installed in the shell, with the metal adapter pressed inside of it, probably can't compress much (if any). And frankly, the sleeve is probably stiffer than a bare carbon fiber PF30 BB shell that it's sitting inside of. From what I've read most of the creaking is a result of bearings or adapters walking out of the shell. Not because the sleeve is compressing. By loctiting bearings in place or using a threaded adapter like Praxis you fix that issue.
> 
> I agree that BB/PF30 has proven to be way more hassle than it is worth in terms of weight/stiffness. I went through two sets of Wheels Manufacturer adapters in 5k miles. There are few things more annoying on a bike than listening to a creaking noise 4-6k times per hour!


I have to disagree with you there. I seriously doubt that the compressibility (ie modulus of elasticity) of that plastic sleeve is higher than that of the bb shell and frame, and certainly not the metal bottom bracket itself. Although the frame may flex elastically a little bit with each pedal stroke, I'd bet money that the wall of the plastic sleeve compresses as well - especially if/when the frame is no longer flexing (ie when all the flexing the frame is going to do in a pedal stroke has been done, eg at the frame's yield point). I'm sorry, but the bottom bracket is an absolutely lousy place to put a material with a lower modulus of elasticity like Delrin, which is basically plastic.

I've said this before and I'll say it again: I seriously doubt there are more than a handful of people in the entire bicycle industry designing frames or components who have any actual engineering training. And it shows. This whole integrated headset nonsense, and now the pf30 and bb30 reeks of engineering ignorance.


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## Dunbar (Aug 8, 2010)

Waspinator said:


> I have to disagree with you there. I seriously doubt that the compressibility (ie modulus of elasticity) of that plastic sleeve is higher than that of the bb shell and frame, and certainly not the metal bottom bracket itself. Although the frame may flex elastically a little bit with each pedal stroke, I'd bet money that the wall of the plastic sleeve compresses as well - especially if/when the frame is no longer flexing (ie when all the flexing the frame is going to do in a pedal stroke has been done, eg at the frame's yield point).


I have the Delrin sleeve in my hand right now (it wasn't needed in my BB30 install.) You have to remember it's sandwiched between the BB shell (on one side) and the metal Praxis Sleeve (on the other.) There should be basically no torsional load on the sleeve when it's physically pressed into the BB shell with the metal sleeve installed. The only way for it to move would be in compression and it feels very hard to the touch. Plastic bushings have been used in automobile applications for many years and see much higher loads than a bicycle would.

I do agree that the widespread issue of BB/PF30 creaking is not something bicycle consumers should have to put up with at this point. It really is a disgrace that manufacturers and shops haven't got the noise issue sorted out by now.


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## Waspinator (Jul 5, 2013)

Dunbar said:


> I have the Delrin sleeve in my hand right now (it wasn't needed in my BB30 install.) You have to remember it's sandwiched between the BB shell (on one side) and the metal Praxis Sleeve (on the other.) There should be basically no torsional load on the sleeve when it's physically pressed into the BB shell with the metal sleeve installed. The only way for it to move would be in compression and it feels very hard to the touch. Plastic bushings have been used in automobile applications for many years and see much higher loads than a bicycle would.
> 
> I do agree that the widespread issue of BB/PF30 creaking is not something bicycle consumers should have to put up with at this point. It really is a disgrace that manufacturers and shops haven't got the noise issue sorted out by now.


Of course the plastic sleeve feels hard to the touch! Your fingers are soft, and the muscles that give us our pincer grasp are relatively weak. Plastic is not a hard material in general.

Not only that, you're mistaking hardness with stiffness (eg modulus of elasticity). I also think you're not considering exactly what sort of forces that plastic sleeve will be enduring. The material will be squeezed between the lower half of the metal bb and bb shell, both of them objects that are much less compressible/deformable (eg much stiffer) than the plastic. Basically, some of your pedaling energy will be spent on elastically deforming that plastic sleeve.


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## Dunbar (Aug 8, 2010)

I guess we'll have to agree to disagree. Not all plastics are created equal. I don't see a bottom bracket as a particularly challenging application for a material like Delrin. It's a bicycle being propelled by a human and not a 2-ton vehicle. Losing energy to flex in the frame or components has basically been shown to be undetectable in modern road bikes. The thickness of the sleeve is just over 1mm so any "flex" would be a fraction of that which is insignificant.


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## Waspinator (Jul 5, 2013)

Dunbar said:


> I guess we'll have to agree to disagree. Not all plastics are created equal. I don't see a bottom bracket as a particularly challenging application for a material like Delrin. It's a bicycle being propelled by a human and not a 2-ton vehicle. Losing energy to flex in the frame or components has basically been shown to be undetectable in modern road bikes. The thickness of the sleeve is just over 1mm so any "flex" would be a fraction of that which is insignificant.


You're forgetting about the very significant mechanical advantage over which the forces are applied to a bottom bracket (or a plastic sleeve). I mean, that's why the square taper standard is gone and replaced with thicker and thicker spindles and larger bb shells. Consider this: the average rider weighs 70kg. Now let's consider this rider out of the saddle in an all-out sprint. With each pedal stroke, almost his entire weight will be on the down-going pedal, producing a downward force of 700 Newtons, and applying a torque of 119 Newton-meters about the bottom bracket (700N x 0.17m). Some of that torque will be used to push the bike forward, but some of it will compress that plastic.


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## Dunbar (Aug 8, 2010)

Waspinator said:


> Some of that torque will be used to push the bike forward, but some of it will compress that plastic.


How much can a sleeve with a ~1mm thickness compress? The answer is a tiny fraction of a 1mm which means it's insignificant. If it compresses too much it cracks and the manufacturer is not going to release a product that cracks every time a rider sprints.


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## Waspinator (Jul 5, 2013)

Dunbar said:


> How much can a sleeve with a ~1mm thickness compress? The answer is a tiny fraction of a 1mm which means it's insignificant. If it compresses too much it cracks and the manufacturer is not going to release a product that cracks every time a rider sprints.


I knew someone would make that point! And that's not a good thing.

It's not an issue of how many millimeters or micrometers or nanometers the plastic will compress. It's an issue of how much energy is expended on compressing it rather than being transferred to the chain and the rear wheel to move the bike forward. Understand?


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## Dunbar (Aug 8, 2010)

Waspinator said:


> It's an issue of how much energy is expended on compressing it rather than being transferred to the chain and the rear wheel to move the bike forward. Understand?


And the point you're missing is that energy is so minuscule as to be meaningless. In a 1000W+ sprint you shouldn't be worried about tiny fractions of a watt lost to fraction of a mm of BB flex. Anyone who does worry about such things needs to get a sense of perspective.


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## Waspinator (Jul 5, 2013)

Dunbar said:


> And the point you're missing is that energy is so minuscule as to be meaningless. In a 1000W+ sprint you shouldn't be worried about tiny fractions of a watt lost to fraction of a mm of BB flex. Anyone who does worry about such things needs to get a sense of perspective.


Are you kidding me? You still don't get it? Boy, someone here certainly failed high school physics!

The amount of compression in terms of length may be tiny but it can certainly translate into an appreciable amount of lost energy, specifically because of its location - ie ground zero for the transfer of all of the rider's energy into the bicycle. All of these new bb standards came about for the purpose of stiffening up the bb area. Did you think that the square taper standard disappeared because it flexed like a rubber band or something? Even _minimal _flex in that area of the bike saps energy - enough energy to compel these bike manufacturers (right or wrong) to come up with thicker and thicker spindles and shells. So why take a step backward in stiffness by putting a less stiff material in the mix there?


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## Peter P. (Dec 30, 2006)

I have to side with Dunbar. Unfortunately, cycling tends to attract a lot of techno-geeks and engineering types who love the comfort of "the numbers".

In real world application, bicycles and the various components have been strong enough and stiff enough for decades. And 10 years from now we'll look at present day bikes and comment on how flexy they were...


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## QuattroCreep (Nov 30, 2009)

I agree with waspinator. Thinking of all of the fractions of watts I was giving up in my drive train was keeping me awake at night. I started a quest to make the most efficient drive train I could. I read every study about waxing a chain instead of lube, ceramic bearings, oversized pulleys, oil not grease in my wheel bearings. After many years of research I think I have developed the most efficient drive system on the planet. Direct drive unicycle, takes awhile to get your balance but once you do there is no going back to chain drive. I give it a few more years before it pops up in the MTB scene, then in cross, finally one of the big three will market it to road bikers even though it is not UCI approved. Then there will be like 1000 posts about is it worth the change, some guys will get it and make the change, some will be retro grouches and say it is all marketing hype. One wheel direct drive is the future. Remember you heard it hear first.


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## Waspinator (Jul 5, 2013)

QuattroCreep said:


> I agree with waspinator. Thinking of all of the fractions of watts I was giving up in my drive train was keeping me awake at night. I started a quest to make the most efficient drive train I could. I read every study about waxing a chain instead of lube, ceramic bearings, oversized pulleys, oil not grease in my wheel bearings. After many years of research I think I have developed the most efficient drive system on the planet. Direct drive unicycle, takes awhile to get your balance but once you do there is no going back to chain drive. I give it a few more years before it pops up in the MTB scene, then in cross, finally one of the big three will market it to road bikers even though it is not UCI approved. Then there will be like 1000 posts about is it worth the change, some guys will get it and make the change, some will be retro grouches and say it is all marketing hype. One wheel direct drive is the future. Remember you heard it hear first.


Hey...if I can reach just one person!!


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## redondoaveb (Jan 16, 2011)

Waspinator said:


> Hey...if I can reach just one person!!


Well, what did you end up doing with your shell and BB?


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## Waspinator (Jul 5, 2013)

redondoaveb said:


> Well, what did you end up doing with your shell and BB?


I sawed off the bb shell, and decided to ride the bike Flintstones style!

I'm going to use blue loctite. I'd like to be able to remove the cups without trashing the frame.


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## choirboy (May 24, 2014)

Waspinator said:


> Are you kidding me? You still don't get it? Boy, someone here certainly failed high school physics!
> 
> The amount of compression in terms of length may be tiny but it can certainly translate into an appreciable amount of lost energy, specifically because of its location - ie ground zero for the transfer of all of the rider's energy into the bicycle. All of these new bb standards came about for the purpose of stiffening up the bb area. Did you think that the square taper standard disappeared because it flexed like a rubber band or something? Even _minimal _flex in that area of the bike saps energy - enough energy to compel these bike manufacturers (right or wrong) to come up with thicker and thicker spindles and shells. So why take a step backward in stiffness by putting a less stiff material in the mix there?


OK, I've done the sums and assuming that it is Delrin with a Young's modulus of 800 MPa and 20 degC (http://www2.dupont.com/Plastics/en_US/assets/downloads/design/DELDGe.pdf) , and assuming uniaxial loading of the bearing element of the sleeve which has a cross sectional area of ~400 mm2 (40 x 10), a 75 kg rider applying his full body weight to the pedals (at a Q value of 110mm ) would compress the 1mm thick Delrin by 3.6 microns. At a cadence of 100 this would sap the rider of a mammoth 3.7 nanoWatts.

Frankly it's a miracle that anyone riding a bike fitted with the Praxis converter makes any progress when all their energy is taken up bouncing on this massive mattress of a component....

Back in the real world I have one on my bike and it results in a noticeably stiffer crank than the factory-fitted FSA adapter. I believe this is because the collett mechanism actively compresses on fitting rather than relying on passive components.


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## goodboyr (Apr 19, 2006)

Post of the week. Nicely done......but I have a feeling you still haven't convinced him.


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## dracula (Mar 9, 2010)

Waspinator said:


> I
> 
> I do agree, however, that the pf30 standard, which was borne purely out of a need to cut manufacturing costs and little else, is far and away the worst development ever to come to bicycle design. Far and away worse than integrates headsets. Bb30 isn't much better either.



What is wrong with integrated headsets? Please elaborate.


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## Waspinator (Jul 5, 2013)

choirboy said:


> OK, I've done the sums and assuming that it is Delrin with a Young's modulus of 800 MPa and 20 degC (http://www2.dupont.com/Plastics/en_US/assets/downloads/design/DELDGe.pdf) , and assuming uniaxial loading of the bearing element of the sleeve which has a cross sectional area of ~400 mm2 (40 x 10), a 75 kg rider applying his full body weight to the pedals (at a Q value of 110mm ) would compress the 1mm thick Delrin by 3.6 microns. At a cadence of 100 this would sap the rider of a mammoth 3.7 nanoWatts.
> 
> Frankly it's a miracle that anyone riding a bike fitted with the Praxis converter makes any progress when all their energy is taken up bouncing on this massive mattress of a component....
> 
> Back in the real world I have one on my bike and it results in a noticeably stiffer crank than the factory-fitted FSA adapter. I believe this is because the collett mechanism actively compresses on fitting rather than relying on passive components.


Hold on a second there, cowboy. You need to make sure your calculations are in order before you start in with the condescending, sarcastic remarks. They are not.

Where are you getting the 400mm2 cross-sectional area of the Delrin bearing sleeve? I think you may be considering the footprint of the bearing against the sleeve, but you’re missing something important.

The bearing sleeve is circular, as is the bearing that sits in it. That means that the part of the sleeve at the base of the circle (i.e. at the 6 o’clock position) will feel much more pressure than the parts of the sleeve at the 3 o’clock and 9 o’clock positions, which will feel none. Or have you never heard of ovalized head tubes under rough riding conditions?

Additionally, I’m not sure what relevance exactly the q-factor has in this situation (and yes, I know what q-factor is). The contact point between rider and crank - i.e. where the rider’s cleat attaches to the pedal - occurs at around 0.04m lateral the bottom bracket shell (depending on q-factor, pedal spindle length). One would be inclined to multiply the rider’s weight by this number and gravity and say that this is the torque about the outer edge of the sleeve. But the contact point is also displaced 0.175m (e.g. the crank length). The hypotenuse of this triangle - i.e. the moment arm - is about 0.180m, estimating for argument’s sake that the fulcrum (e.g. center of rotation) is just at the inner edge of the contact between bearing and sleeve, maybe half a centimeter in length. So, rider’s weight of 75kg x 10m/sec2 x 0.180m gives you a torque of 135NM about the center of rotation. Take that torque, and now divide it by half a centimeter, and now we see that the outer edge of that bearing sleeve experiences a force of 27,000 Newtons. The crank arm length and lateral displacement create a lot of mechanical advantage.

That 27000 Newtons isn’t being applied over an area of 400mm2, as you said. It’s being applied over a much smaller area, as I said above. What is that area? It gradually increases as you go from the 3 o’clock and 9 o’clock positions until you reach the 6 o’clock position, where it is at a maximum. But let’s say for argument’s sake that the ‘effective’ surface area is 1/5th of what you say it is (i.e. 80mm2). 27000Newtons divided by 0.00008m2 = 337,500,000Pa worth of pressure. The elastic modulus of Delrin is anywhere from 0.6GPa to 1.2GPa. So yes, it won’t compress under static load. But there are some caveats to that point. 1. Static loading ain’t the same thing as dynamic loading. A 75kg rider hammering down on one pedal is going to apply a heck of a lot more downward force on the pedal than 750N, especially if he’s pulling up on the bars. 2. the surface area of the sleeve that must resist the maximal force is probably a heck of a lot smaller than the 80mm2 I mentioned. And finally, 3. if I’m not mistaken, these plastics start to plastically deform under pressure, even when they’re not taxed beyond their yield strength.

So, you were right in that the Delrin sleeve _may_ be fine in a bottom bracket shell, under ideal conditions and with generous calculations But you had absolutely no clue why. Bottom line, metal is still better in that area.


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## Waspinator (Jul 5, 2013)

dracula said:


> What is wrong with integrated headsets? Please elaborate.


It would stand to reason that if you paid $3000 for a frame, you’d want to be able to keep it as long as possible. Having the bearings fit loosely into the frame (as opposed to solidly into bearing cups that are then firmly secured in the frame) is a lousy idea. Now maybe the design flaws and would-be problems never panned out because people replace their bikes/frames before they do, or maybe the problems are just underreported. But you know the saying: if it looks like sh** and smells like sh**, it’s probably sh**.


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## dracula (Mar 9, 2010)

Waspinator said:


> It would stand to reason that if you paid $3000 for a frame, you’d want to be able to keep it as long as possible. Having the bearings fit loosely into the frame (as opposed to solidly into bearing cups that are then firmly secured in the frame) is a lousy idea. Now maybe the design flaws and would-be problems never panned out because people replace their bikes/frames before they do, or maybe the problems are just underreported. But you know the saying: if it looks like sh** and smells like sh**, it’s probably sh**.


I replaced my frame after 30 000 km and would have thought the integrated headset is good for another 100 000 km. They are butterly smooth as on day 1 and this after many rides in the rain (Scotland).

I do not see many people complaining and fretting over integrated headsets. But I am a strong believer that my standard GXP bottom bracket were not up to the job and a big pile of **** which required me to replace it every 6 months or see.

My new frame still features GXP brackets (using my old Rival crankset) although in a BB30 conversion kit with adapters.


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