Thus far all of the comments on the BB30 / PF30 design debate have looked at this development only from the BB perspective and have not considered any potential benefits to overall frame design. I purchased a Moots Mooto X RSL frame about a year ago and had some questions regarding their decison to go with a PF30 BB shell and I have attached the response I received from Jon Cariveau at Moots (sp?) below. He certainly has been spot on in prediciting that the PF30 bearing design shortfalls would get sorted out as the design became more widely accepted (Chis King, Enduro and Praxis all jumping in with BB offerings). The tube diameter benefits certainly apply to all metal based frames but I suspect their are similar benefits with CF as well.

From Jon @ Moots:

The pure size of the PF BB 30 or BB30 give us the chance to use bigger diameter down tube and seat tubes, without ovalizing the tube where it lands on the shell, thus keeping the bigger foot print of the tube, which is king when in comes to stiffness. Bigger diameter=stiffer bike. I can feel this going between my regular Psychlo X (with standard) threaded English shell vs. the PF BB30 bike...pure and simple. We see this with the 44mm head tube as well....bigger outside diameter tube (that does not have to be ovalized) gives more foot print on the bigger head tube, thus a stiffer front end.

PF BB30 also has more attributes other than just being bigger. The bearings are kept at a narrower stance, thus decreasing the Q-factor vs. the out board bearings. Again, I can feel this difference when going between the two cross bikes. When outboard bearings hit the market, we lost most, if not all adjustment of Q factor. Remember square taper bb spindles? And being able to choose a width. (Sorry, that might date me a bit)....The BB 30 spec brings the cranks in just a bit in the Q factor department.

Weight is lower on a PF BB 30 assembly as well, aluminum spindle for the crank and a bigger diameter shell that we can machine lighter. Yes, the bearings are can be suspect to wear, but going the PF route gives the face of the bearing more seal that the standard BB30 bearing which is exposed to the outside world.

I would suspect that component manufactures will make progress in the bearing department as this type of set up becomes more common, not only with the small guys building in metals, but even more so as the big guys go this route in carbon.

Thanks,

Jon@Moots

I'm sure the Moots guys knows a hell of a lot more about bikes than I do. I'm still egotistical enough to argue with all of his points...

Perhaps this is true for non-hydroformed metal frames, but this is probably a non-issue for monocoque carbon bikes where tube shaping can be much more varied.

This is not dependant on BB setup, but on a combination of factors. Also, wider isn't necessarily worse for all people.

The weight issue is a questionable claim and hard to prove. Regardless, it's a negligible difference here, this isn't really a valid argument.

I doubt it. No matter what you do a nail isn't going to hold as securely as a screw.

Questionable and hard to prove? Negligible Just compare any manufacturers BB30 crankset with their other systems. Red for example, complete system, crank and BB. BB30 comes to 610g, while GXP weighs 714g. 104 grams are saved. I don't know where you come from, but if 15% is negligible, I wouldn't want to be paying your taxes.

Regardless, BB30 really wasn't designed for recreational cyclists(myself included). The added stiffness, and a substantial weight savings makes it great for pro's, who's bottom bracket bearings are replaced after each race anyway.

A little Loctite 609 and most of everyone's complaints are solved.

I got to chuckle at Moots' response. Self serving.
For the record this is a straw man for carbon fiber which comprises much of the road bike industry and dominates the pro peloton.

Ti BB shells are relegated to a single thickness sleeve. By contrast, carbon fiber isn't even close. If the BB is the heart of the bike and some believe it is in terms of power transmission...the biggest difference between Ti and carbon is the connection of rear triangle, seat tube and downtube to BB...an argument against Ti in general. With modern carbon fiber bikes...all connections and BB are oversized for section modulus aka resistance to twist/strength and much larger than a Ti bike. It is 'independent' of BB type.

See my '12 Roubaix SL3 Pro BB below with Campy cups threaded in place. It is a threaded BB. Overall BB dimensions are identical to both Specialized BB30 and PF30 available on SL3 Roubaix. Carbon tubeset and BB which is effectively a very large ball and much larger than any Ti BB is what gives the bike such incredible power transmission. The only thing that differentiates a threaded BB, BB30 and PF30 is the 'interior of the BB'.

Lastly the benefit you state in Q-factor of baving bearings closer together is really a weakness in terms of BB stability and strength. Opposite bearing forces are higher due to greater moment aka Force X distance applied due to opposite crank arm.

See below:

I test-rode a couple of '13 bikes recently with BB30's and I noticed that they seemed squeaky/noisy near the crank. I wasn't sure what it was, but after reading this thread, perhaps it was the BB30. I also test rode a model that did not have a BB30 and it was quieter/normal. Perhaps it was something else, but I can think of what else it might have been, since I was not shifting and all of the bikes were by the same manufacturer.

...and that's when they're brand-new..... Imagine a year or two down the road!

I have a giant defy advanced and the wife has a trek 5.2 and both have ultegra cranks on them, and neither has an outboard bearing...so I assume they are bb30....does that just mean they have an adapter?

This is important but hasn't been mentioned as far as I can tell.


"Lastly the benefit you state in Q-factor of baving bearings closer together is really a weakness in terms of BB stability and strength. Opposite bearing forces are higher due to greater moment aka Force X distance applied due to opposite crank arm"


I would wager if you rigidly mounted any type of BB shell in a fixture, fully assembled the different crank types and measured deflection at the pedal you would find PF-30 to have the most flex and a quality external bearing BB to have the least.

How hard is it to remove BB30 bearings if they've been glued in with the loctite 609 ?

I started but didn't finish reading the thread there was just way to much...whatever to wade through.

I do agree that PF30 will replace BB30 in short order. But as to BB30 being a cost saving measure I don't understand why all the frame manufacturers I spoke with as this was really hitting the masses HATED BB30. My conclusion was that it placed the burden of tolerance on the frame maker.

They not only need to align the cups to each other but they must be perpendicular to the frame as well. I've had several carbon frames where the alloy inserts that were bonded into the frame for a BSA BB where two separate pieces tack welded together. I'm not sure of why this would be easier than molding in a complete BB shell but frame makers assured me it was.

It may have something to do with how alignment can be affected by heat when cured or exactly at what point the BB30 she'll gets bonded in but something about it is more difficult, more costly, has a higher rate of QC failure and increased tooling cost. In short. It is NOT less expensive and was driven by the design people and NOT the manufacturers.

Case in point. We are working with a new factory that has all the latest greatest equipment and is really hungry to get product into the market place. They haved STOPPED offering their frames in BB30 and now only offer them in BSA because there were enough problems in production with final alignment that they have decided to skip over BB30 and go straight to PF30 for MY2014 frames.

As to what may actually be better? At this point I think the weight savings and design possibilities with PF30 may prove out over time.

Yup...the basis for my assertion. From a percentage standpoint...bearings outboard a 68mm shell versus inboard...it ain't small change.
The torque moment percentage wise is likely on the order of 10-20% more torque on inside of shell BB30/PF30 bearings for same pedal force because spacing is quite a bit less. Although unsubstantiated, this may contribute to reduced bearing life as well...which is often reported versus outboard bearings which in my experience have good durability life.

Very simple. No fancy tools required. A narrow wood dowel is the least invasive. Remove crank. Dowel through one bearing and resting on backside of opposite bearing. Tap, tap, tap around the backside with small hammer blow and they will knock right out. Servicable greeen Loctite 609 is deliberately forumulated to be weak in shear. The Loctite however helps substantially in keeping the bearings in place and from creeping...which causes creak.

Yup...they are BB30. An Ultegra crank is one of the most popular and effectively adapted external bearing crank that will adapt to BB/PF30.
Most bike makers use Wheel Mfg. spacers...which space radially from 24mm spindle to 30mm BB30 ID and outboard to take up axial distance between bearing being mounted inside aka BB30 versus outside the shell as is the case with outboard bearings.

^^^ Hence 386BB EVO

86.5mm bb shell, and the bearings as far apart as with external bearing cups on a 68mm bb shell.

https://road.cc/content/news/34738-up...80%A6-bb386evo

Working well on my bike so far (other than a clearence issue with the Quarq).

I agree with your post and comments about frame makers being challenged by making a reliable BB30. Co-axial bore centers side to side is a big manufacturing challenge...especially if insert molded alloy cups aren't connected as you state. Best practice is to perform a finish hone after separate alloy cups are captured in the carbon to ensure bearing bores will be in proper alignment and bore ID's will provide correct level of press. Making BB30 is expensive as you say and offers no cost advantage to frame makers. Move to BB30 is driven by design which does pose the question...is it better? I say no.

Also agree that PF30 is the future as I stated in an earlier post. PF30 is cheaper and easier for the frame maker...but does place onus on a properly designed BB which are starting to become available as aftermarket suppliers seize on this opportunity based upon the current clear deficiencies of using plastic bushings which are pretty pitiful in concept and execution.

So there is light an the end of the tunnel. A single, uniform, 46mm ID cylindrical bore aka PF30 provides a myriad of design options...from press in BSA sleeve aka C-bear to effective regress PF30 to BSA...or...long press, captured bearing assemblies aka C-bear and now Chris King and...Praxis which is said to be offering a number of different crank adaptation options moving forward. The Praxis collet BB is the least invasive because it expands versus relying on a press which would clearly degade a carbon PF30 thru bore hole over time. The Praxis solution is the most elegant and the future in my opinion and a legitimate contender to replace an external bearing, BSA BB.

To me, the 86mm wide evolution of BB30 makes the most sense on a couple of levels. Most notably, it capitalizes on lateral frame stiffness by wider section downtube, seat tube and rear chainstays. Bearings are in the same position as external bearing BB's for greater stability. Improved Q-factor is taken off the table but that is OK for most of us.

The weight of the bearings is only part of the story, you need to take into account the entire system. There are many variables involved, which is why I'm saying that it's difficult to prove.

Also, regardless of the 15% figure, no one should be worried about 100 grams of weight savings in a bottom bracket. This is a negligible concern. As my coach in high school used to say: if you piss , you lose a pound.

We agree then, BB30 is only a good idea if you have a protour mechanic replacing your bearings daily.
Or just buy a frame that uses a threaded BB and your problems are solved.

One last point: I get it that BB30 allows manufacturers to squeeze every last dollar out of the manufacturing cost, but clearly BSA isn't that expensive to produce. For example, the vast majority of generic Chinese carbon frames come with BSA bottom brackets. If Hongfu can do BSA (in fact, prefers to offer BSA) and still make a healthy profit at $365 a frame, anyone can.

Campag, I am not disagreeing with anything you have said about BB30 or pressed bearings, or about the carbon assembly process.

However, from a manufacturing standpoint, honing a bearing bore, especially in aluminum, is essentially the worst way to hold position between two opposing features. For size, it is great, but in manufacturing terms, "A hone follows a hole". It is very easy to hone a banana bore, or to push the hone. You will get a sized hole, but not a located hole.

If I had to do a press fit bearing bore in my manufacturing shop, it would be easy. Frame is fixtured stationary, and you use a boring head through one side. If I had to hold 50 millionths, I could jig grind with the same fixture.

If I had to do a threaded BB in a blank shell, I can tap, and position will be uncontrolled (on PD), and I have to have access from both sides (two fixtures). I could single point from one side, which puts the frame in a lathe spinning. Or I could thread mill. which will be the most accurate PD from the left thread to the right thread. Thread milling is slow and expensive, comparatively.

Now, none of this may be the actual method used. They may simply fit finished BB's into the mold. But from a machining cost stand point, I believe this to be accurate.

Good points Roll...I know your background is machining and honestly there can be healthy debate as to best practice. There are two tenents at play here as you know:
1. Sizing of the bore on each side for appropriate bearing press.
2. Co-axiality of bores such that when you press in bearings the crank spindle will spin freely. Perfect alignment of the axial centerline 'relative to frameset' is less critical than bore to bore alignment as you know...even if the spindle is a full degree off relative to vertical centerline of the bike...just as long as bores align. As Bob stated, this is more managable with a one piece insert that attachs both bores. This is in fact how many carbon BB's are manufactured like my BSA Roubaix. A full sleeve with internal threading on each side is insert molded. This ensures cylindricity and is relatively simple.

A cylindrical hone may work...it really comes down to tolerance stack up of rough bores...whether you use additive stack or root mean square for your calculation and how perfect you want to make the design. The tradeoff is cost. Bearings have a degree of axial freedom as you know...there is no such thing as perfectly co-axial bores.

No cost spared...best method to ensure precision machining of bores on each side is to hard fixture the BB as I believe you are stating. This creates primary datum and finish bores which will not 'walk' compared to a hone....and is independent of true position of rough bores.

There are many ways to machine a BB30 to ensure bores will have adequate integrity to address not only alignment but press.

Very well said, and again, I have never seen a drawing for a frame, so I may be picturing a positional tolerance that is unnecessary for a functioning assembly.

From personal experience, honing aluminum is a funny bird. I spent a great deal of time in a previous job working on honing aluminum manifolds (6061 and 7075) in an environment where everyone believed that honing was the best finishing method for size and position. I did some very detailed design of experiment to prove that it is all about L over D, amount of stock removal, and finish of the bore prior to the hone. It became fairly easy to mathematically determine which features may be at risk, and where positional movement could be expected.

But in general, I have no first hand experience with any of the press fit bores, largely because I like the easy of assembly and dis-assembly of threaded BB's. I defer to your practical expertise on the pro's and con's.

We speak the same language. Good stuff and thanks for contributing your expertise.
With our background we also share the same disdain for BB30 because we see the tradeoffs.

I honestly admit to being slightly astounded that BB30 came into being. Not so much that a poor or challenged design is born...perhaps even with good intention...of stiffness and weight...but a design so flawed fundamentally and yet most top frame manufacturers have embraced it. Telling though isn't it?...that both Shimano and Campag never produced BB30 cranksets? They know.

Don't forget, guys...we're talking "mass-produced" here- which means it has to be done fast & easy....i.e. NOT by precision craftsmen hand-measuring and touching up every bore and clearance and installation carefully and by hand. We're talking automated machines stamping stuff out and pressing things in...which is probably ultimately the reason BB30 was invented. In the instances where it is done with more care and precision, on hand-made, hand-assembled high quality bikes, maybe it can be done with better results [MAYBE...]- but then, using BB30 under such circumstances is pointless, isn't it?

Question: Does one actually have to use a press to disassemble a BB30? Somehow, I don't see presses and carbon frames being very good friends....

No, a bushing is paced on the bearing, and its tapped out.