PF30 / Frame Stiffness - Fact or Fiction?

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PF30 / Frame Stiffness - Fact or Fiction?

33 posts from 13 voices

Started 1 year ago by Cusco
Latest reply from Pzzamakr1980

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Cusco
Member

Seems to be a lot of contradictory info. out there on frames using a PF30 bottom bracket shells.

From the Kent Eriksen website:

How about BB30?

We do offer a pressfit BB30 shell but we always remind people that it takes away from the overall stiffness of the BB area of the frame. The cranks are a larger diameter, but you don’t increase the stiffness of the frame at all. Also, a threaded BB has more purchase and creates a wider platform for the cranks, not to mention gives you the option of changing systems if you would like to do so in a few years. Remember, the frame will last a lifetime, technology doesn’t.

Moots Mooto X RSL Features:

Oversized Press Fit 30 Bottom Bracket for increased stiffness in the drive line (increases stiffness by 38%)

Who's right? If you do a quick scan of some of the more popular cycling forums there seems to be a debate raging on whether PF30 is mostly hype and will evetually follow in the steps of bio pace chain rings. Seems to also be a lot of complaints regarding creaking issues and higher maintenance for PF30 bottom brackets. I hope I don't regret buying a Moots frame with a PF30 BB shell.

Posted 1 year ago #
tjwall78
Member

I think the wider diameter of the PF BB tube has the potential to make the BB area stiffer espeically on a Metal bike. One it's larger surface area allows for wider diameter seat tubes, down tubes and chain stay, and the wider tube it self should be stiffer. Unlike with carbon bikes wear you can just though more carbon down there i think the tube size does matter some.

The question is weither the stiffness differance is noticable during riding; if it takes 5000 ft-lbs to flex a tradtional BB what the hell do i care since i can only crank out 500 (just made though numbers up as an example).

Kent does have a good point about the larger contanct area of the threaded BB and I like my bikes to be fully servicable for easy overhalling. Rotor (and i think kcnc) has a nice disign for a standard BB30 to BSA conversion that has a spindle that threads together, but i think that is only for the 42MM BB30 and not the 46mm PF30.

I beleive that in a few years there will be a new "Standard" BB, but the market has not figured that out yet. With BB30, PF30, BB86, BB92, BB90, BB95, and the old stand by BSA some thing needs ti get figure out.

Posted 1 year ago #
29ner
Member

Does this site have a spell check? Or maybe a 3rd grade teacher? jeez.

Posted 1 year ago #
johnny5
Member

I've been riding an MX RSL since mid-May and haven't had any bb creak or noise. I worried about the PF30 bb from internet reports but having real world experience with one, I'm happy with it. It's been submerged weekly on our gravel road rides and handles singletrack dust, sand, and mud with aplomb. For what it's worth, I'm using the SRAM steel bearing PF30 BB and Problem Solvers PF30 shims to run a 24mm SLX singlespeed crank.

Having ridden square taper and external bb's in my other bikes (one a Moots Rigormootis) I can say that I'm not really aware of any added stiffness (though the frame isn't flexy feeling at all) but I do notice how smoothly the cranks spin on the bigger bb bearings. I never would have guessed I'd tell a difference, but it's there. Kind of like noticing the instant feeling hub engagement of a king/i9 when you've been riding a shimano hub.

Another nice thing about the PF30 shell, Problem Solvers makes an EBB that fits as well as the shims I'm using. Plus SRAM makes a threaded BB insert for running square taper or external bottom brackets. Which just goes to show you that options exist to handle existing and potentially future bb standards.

I can tell that my MX RSL is a stiffer handling frame than my Rigormoots (Same build on each bike) and I really love the low headtube for dialing in my fit. It really is point and shoot geometry. YMMV.

Posted 1 year ago #
JonC
Administrator

Hmmm, good questions and I'll tell you what I feel/know.

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

Posted 1 year ago #
cincytri
Member

JonC-
I need some selling on the PFBB30. On the PX RSL, I love the shaped top tube, the oversized tubes and the 44mm head tube. I buy into the head tube in large part because Chris King makes a product for that head tube size. I'm a big fan of CK and figure if they are doing it, it must be ok.
I need a bit education on the difference between PF and standard BB30. I also need some selling on the durability of the PF BB30. On a cross bike, are there issues with dirt and mud gumming up the BB? What would be the life expectancy of a PFBB30 on a bike that gets raced every weekend in the fall?
One of the things that really drew me to Moots in the first place was the fact that I felt like I could worry less about my bike and just ride. I love the PX RSL. I want one for next year. Help me get over the PF BB30 concerns.
Also, will a PX RSL head tube, CK headset and Enve tapered fork combo work?

Posted 1 year ago #
29ner
Member

I think Jon answered most of the questions above. Bigger diameter, stiffer, lighter, etc. I, for one, am much less concerned in the Q factor, but others may be. A press fit BB is just that - presses in like a headset. A standard BB30 is a threaded in with outboard bearings (30 indicates the spindles diameter). PFBB's usually are held in with some sort of 'c' clip and there are a few standard PF's on the market (of course!). Why have a 'standard' when you can have 3 or 4 standards?? The point being, is you have to get the 'standard' that fits the frame. I'm sure Moot's literature/web lists this.

The question of dirt and mud gumming up the BB? On a cross bike and in a race, and during a whole season, there are issues with dirt and mud gumming up ANYTHING, let alone the bb. It's the nature of the sport and half the reason the sport is so 'fun' - but, it can be very hard on equiment.

Anyone that has ever raced cross has (or will) ridden in an event where you can hardly pick the bike up it's so heavy with mud, where you can hardly discern where the chain rings/cranks are, where the mud is so thick and heavy, the wheel(s) won't/can't possibly go through the brakes/seat-chain stays/forks. Sounds 'fun' no doubt, but it's why they make pit bikes and spare parts. (any cyclocross racer will/can tell you of some epic mud race - just look at any of the last 8-10 Nationals, just this weekend on Saturday's USGP in Colorado, last weekend's epic in Massachusetts - and sand is usually much worse than mud on equipment). Bottom bracket? I'm sure some of these guys were replacing entire drive systems, cables/housing, and brake pads - after just one race.

No system is going stand up to it entirely, but there are some that have better seals, etc., etc. That said, it's a moving part made of metal/ceramic - whatever - has torque on it, will get contaminates in it, so at some point whether it's season to season, or in 10 years, will need to be replaced - just like a chain, cogs, rings, cables, etc.

Posted 1 year ago #
JonC
Administrator

cincytri,
BB30 vs. PF BB30...the difference between these two: BB30 has a 42mm inside diameter, vs. the PF which has a 46mm inside diameter. In the regular BB30 the bearings press directly into the shell, so you get the outside race contacting the shell material be it carbon, ti, steel or al. The c-clips are put into the shell before the bearings to serve as a "stop" when you press the bearings into the shell.

With the press fit, the bearings are housed in a nylon sleeve that isolates the bearing from the shell. We have found that this is much better to reduce creaking and much better for bearing life. In the case of regular bb30 the bearing, when pressed into the shell could be out of round, thus causing the bearing to wear much faster. (we did proto type our frames with regular BB30 and did not like the bearing interface and bearing wear)

An additional benefit of the Press Fit is the fact the the bearing has another "seal" of nylon on top of the regular seal. Does this hold up? Yes, it's pretty good. Last year I was able to get one season of cross out of the stainless steel PFbb30. I did not treat the bike well....power washers, sand pits, mud ...etc....The stainless steel version of the PFbb30 will run around 40-50 bucks...not too bad....I do think the bearings/seals will get even better as more of the big guys start to use this system.

Check out this link that shows some of the things above: http://www.bikeradar.com/gear/article/workshop-how-to-service-bb30-press-fit-bottom-brackets-29544/

As far as the Enve tapered fork into the Psychlo X RSL....it will work with the 1.5'' lower Chris King cup/bearing, however it will change the geometry of the bike as the stack height gets 1cm higher. We are building the stock Psychlo X RSL's around the non-tapered fork, so to get good geometry you would have to go custom to accomodate the fork change.

Let me know if you have any other questions.

Thanks,

Jon@Moots

Posted 1 year ago #
29ner
Member

Oops, my bad, thought you meant the threaded vs non. But, everything he said. Nothing much mechanical lasts long in a cross season though - certainly not in the sandy and/or muddy ones.

Posted 1 year ago #
cincytri
Member

JonC-
Thanks for the response. It is a bit comforting knowing that the PF BB30 are relatively inexpensive and, therefore, not a huge budget-breaker when they give out. How much trouble are they to remove and install? Worth doing yourself or better to leave something like that to the pros?
Also, help me understand the 44mm head tube. I gather by your explanations that the head tube itself is wider and, therefore, stiffer. Can you provide the specs on the Moots PX fork that comes with the PX RSL? Is it a 1 1/8 or 1.5? Perhaps the tapered fork is unnecessary with the configuration that you guys are selling? If so, why? How about this combo: PX RSL + RSL fork + King Inset headset?
Thanks again for your insight. I'm starting my "Next Moots Bike" fund and want to know everything I can about this frame. I have a few months to deliberate, but the 29 and 26 Divides have complicated things a bit...good problems to have.

Posted 1 year ago #
JonC
Administrator

cincytri,
The install is very easy with the PF BB30. A standard head set press does a perfect job. It takes me back to my BMX days and doing a similar move to put the cups in my Mongoose....sorry, I digress.......

The removal can be done with a stantard headset remover as well, however tool companines are now making specific tools for the job and those work nicely as well.

As for the 44mm head tube.....the outside diameter itself is about 2 inches or 51mm, the inside diameter is 44mm. The Chris King inset basically takes an outie and turns it into an innie. The bearings sit inside the head tube....except if using the 1.5 lower (for tapered) the bearing sits outside the headtube.

I have been riding the PX RSL with our new fork as a 1 1/8'' straight steerer tube and find it to be amazing in the stiffness catagory....Adding the 1.5 lower might be a bit much for smaller riders, however with disc coming to cross the 1.5 will help keep things happy under the disc power and forces the fork will see vs. good old cantis.

The spec on our fork is a industry standard of 395mm axle to crown, 47mm offset, 1 1/8'' steerer (all carbon). The fork weighs in at one pound even. At the moment we are only selling the fork with new frame orders, but after the first of the year will be able to offer the fork to exsiting Moots Psychlo X owners in order to upgrade/freshen up your rig.

I better go now....I could talk cross all day.

Let me know if you have any other questions.

Thanks,

Jon@Moots

Posted 1 year ago #
Mikej
Member

To JonC, about the PF30 having more real estate to accomodate larger diameter tubes-I have seen both Eriksen and Steve Potts frames with 1" chain stays, 2" downtubes and a 1 3/8" seat tube on a 73mm and a 68mm threaded bb shell. I would be on an RSL VaMoots if it were not for the PF30. I was told the threaded bb is not an option on the RSL. Also Firefly will accomodate the same diameter tubes on an English threaded bb. As for a 44 mm head tube with a standard 1 1/8" hs, I do not believe it could be compared since the RSL PX has a different tubeset all around as opposed to the std PX. I want - an RSL VM with a threaded bb and less tt slope. Great looking bikes though, and also top notch craftsmanship.

Posted 1 year ago #
JonC
Administrator

Mikej,
We now offer the Vamoots RSL with a threaded shell as an option. As far as the slope of the tt goes, we can do less if you like, however at that point it is a full custom build....but we can handle that.

Let me know if you have any other questions.

Thanks,

Jon@Moots

Posted 1 year ago #
cincytri
Member

JonC-
Can you do a PX RSL with a 68mm standard BB and the rest of the new features like shaped TT, bigger tubes and 44mm HT? Just curious. I'm still several months from pulling the trigger, so mostly just doing research. Thanks.

Posted 1 year ago #
tjwall78
Member

MikeJ
Thanks for the post, we want the same thing, you saved me the question.

Would going with a tapered stear tube make it a full custom build as well, do to having to change the head tube angle?

Posted 1 year ago #
Mikej
Member

Wow, I wish I new that was an option, is the threaded BB RSL listed somewhere?

Posted 1 year ago #
JonC
Administrator

cincytri--yes, we can do the Psychlo X RSL with a threaded shell if you wish.

tjwall78--going with the tapered fork would be full custom. The build height of the fork changes and impacts the top tube, down tube location.

Mikej--the options are not yet listed as it is a new program for 2012. We'll have those up soon and will let you know when and where.

Many thanks,

Jon@Moots

Posted 1 year ago #
cincytri
Member

JonC-
Thanks for answering my questions. I'm not sure which BB I prefer. As the time to order draws closer, I'll talk to my dealer and maybe give you a call for a bit of guidance? Again, I do appreciate your presence on the forum and willingness to answer my questions.

Posted 1 year ago #
JonC
Administrator

Update on my latest PF BB30 encounters...

So after last years cross season and this past Saturday at the USGP in Fort Collins (mudpocalypse), my first PF BB30 had to be replaced. Bearings toast....So a season plus in the cross world to me is pretty good and very acceptable.....I run the cheaper stainless version.

That one bb had seen power washers, my own at-home-washing and riding in the rain. Not too bad. The great thing is that it easy to replace. Seriously, my 5 year old daughter helped press the new on in with the old Park HS press.

The old bb is now an experiment destined for roll of back up in a pinch style ....I pulled the seals (the outer PF and the bearing seal itself). Cleaned with WD-40 and packed with fresh grease. For the most part the old bb won't be of much use, but in a back up setting it should do the trick.

Thanks,

Jon@Moots

Posted 1 year ago #
cincytri
Member

Well, that certainly affects the decision making process. If the SRAM PFBB30 runs about $40.00 and lasts a solid year in abusive riding/washing conditions, then the benefits of stiffness and welding contact area would seem to outweigh the downside of BB replacement. I really like my PX and this PX RSL is something I can't seem to get out of my head. Of course the Divides are doing the same thing to me as well!!

Posted 1 year ago #
tjwall78
Member

My M760 BB has lasted 7 year of mountain bike riding, and my King is on 2. Both with little to no service and both are still in working order, so I guess I’m less impress with one season of use as the life span. Is it just me, but are bike parts (and most bikes) becoming more disposable. Sure they are lighter but they don't last as long and most of the times don’t even work as well. The open bearing hubs on my 1980's towny road bike are way smoother then my mavic ksyrium sl. That’s why I’m a moots fan. They make a product that just plan works well and for a long time. They don't rely on their product failing in 1-2 years to get more customers; they believe making a good product will keep people coming back. How many people here have more than one Moots or plan on getting more than one Moots.

Posted 1 year ago #
cincytri
Member

@tjwall78-
Well, I certainly understand your concerns and comments. The beauty of ti is that you expect to have less concern about durability and maintaining your frame. I think Moots does a good job of providing plenty of options for those who want things simple and "old school." The standard MX YBB, Psychlo-X, Vamoots, etc. seem to fit that bill pretty well. One of the things that I really like about Moots is their ability to push the envelope a little and offer some of the more cutting edge products. The PFBB30, 44mm headtube and shaped tubes are all things that the industry seems to be adopting or at least testing out. I think that it is great for Moots to be taking the lead when it comes to boutique ti builders and technology. They have to produce what the market wants and the market seems strong for ti builders with a bit of technology.

Based on the postings by JonC here, it would seem that you can pretty much have it your way. You can get the 68mm BB, shaped Psychlo-X RSL top tube, over size tubes, 44mm headtube, disc compatible, and geometry for a tapered 1.5 Enve disc fork. I am positive I won't like the price tag, however, and may spring for a standard PX RSL. Or another "plain" PX. If you have the cash, Moots seems like they are willing to do it. Either way, you're getting a sweet ride.

As for the multiple Moots, check out the thread on this forum where posters are asked to list their Moots collections. It does happen...a lot. I basically sold all of my Litespeeds, Treks and Cervelo's to round out my Moots fleet. I'm not done yet...not by a far piece...

Posted 1 year ago #
tjwall78
Member

cincyti

I could not agree with you more. I love how moots is at the leading edge of what is being done with a ti bike, but you can still get it old school if you like (or any type of mix). I too am in the process of mootsen out my quiver.

Posted 1 year ago #
Bob G
Member

IMO PF30 has 3 advantages: a slightly larger area to weld larger diameter downtube and seatubes to the BB without tapering them, with PF30 nylon cups there is no metal on metal contact so in theory you should get less creaking , and it permits a lower Q factor.

That said, it does not seem to likely create a big advantage in desireable drivetrain stiffness. Much drivetrain stiffness comes from your chainstays and even massive 1 inch diameter chanstays can be welded to a standard threaded 68 bb with no issue. Also, even large oversized downtubes or seatubes tapered to fit a threaded bb are tapered perpendicular to the bikes long axis, or along the long axis of a 68 threaded bb shell. This directional tapering actually improves drivetrain stiffness in the exact direction that you want from the DT and ST - increasing resistance to left to right swaying of the bb area during pedaling so tapering the tubes in that direction is actually a good thing for drivetrain stiffness. Last, IMO, Eriksen is correct when he contends that a standard threaded bb creates a wider platform for the cranks. Just MO.

Posted 1 year ago #
Mojo Man
Member

Bob
If one would analyze it like you did, it makes no engineering sense what so ever. Other than maybe getting more resale value on your bike because most have drank the PF30 Kool-Aid. I’ll even admit I almost did too, until my engineering background persuaded me to stick to what makes more sense.
I came across this from the people at Santa Cruz

It is true that there are some slight weight savings available with the various pressfit bb designs (exact weight savings obviously vary depending on system, frame manufacturing techniques, and crank model), but we don't feel this small savings make up for the inconveniences. We are still able to make a frame that is lighter than most of our competitors (5.1 lbs), while still using a heavier bb system. There are a number of disadvantages that exist with press fit systems:

1) Special installation and removal tools are required for these parts, including a headset press. This is not convenient for most home mechanics, and they are quite expensive. Traditional external BB's can be installed or removed with a simple $10 hand tool.
2) "Permanently installed cups". Shimano doesn't recommend removing and re-installing their press in bb cups (as they may become damaged), so moving parts from bike to bike is no longer an option. http://techdocs.shimano.com/media/te...9830625426.pdf
3) Creaking or shifting bb's can be common with these systems. Since the bearing is pressed into a cup, which is then pressed into the frame- it can be hard to get all of the press fits snug- without being too tight on the bearing or too loose in the frame.
4) Reasonable tube sizes. One of the most commonly claimed advantages of a larger bb shell is the larger diameter downtube that goes with it. This may be an advantage on road bikes, where tubes can be increadibly thin and large for optimal stiffness. On a mountain bike, this area of the frame sees a lot of abuse from rocks and crashing, and needs to have a certain amount of wall thickness to survive actual use. Using what we consider a "safe" wall thickness and carbon layup, and a fairly typical tube diameter, we get an exceedingly stiff, light, durable product. If we used a larger downtube, we would either have a heavier frame (same wall thickness but larger diameter), or a less durable product (thinner walls and larger diameter).
5) Chain clearance. Take a look at some of our competitors frames with press in bb shells. The down tube comes so close to the chainrings that many frames have chainsuck guards on the downtube! In our mind, the chain should be able to fall off on a mountain bike and not get jammed between your crank and thin-walled carbon downtube.
6) Backwards compatibility: Many of our customers purchase a frame and build it up with their choice of parts, or parts from an old bike. By using a standard bb, we are compatible with everything without requiring confusing adaptors.
7) Chainguide compatibility: While it may seem strange to talk about putting chainguides on a 100mm bike, it is becoming more common now with 10 speed drivetrains. Thread in bb's mean the frame is compatible with bb mount chainguides. We like versatility....

Why did Shimano go with their current system (over say a BB30)?

When Shimano originally released the external bearing two piece crankset back in '02 they determined that a 24mm diameter axle was the optimal for strength to weight ratio, stiffness and also minimising friction from the rotating BB bearings. It also allows them to use steel as an axle material without a weight penalty. A BB30 system requires an oversize axle to give stiffness but axle made of steel would be bring a weight penalty as it wouldn't be possible to make the steel thin enough to keep the weight down for this application. Shimano feels aluminium is an inferior BB axle material compared to steel. Shimano chooses to use steel on all its high end axles for durability and peace of mind.

Posted 1 year ago #
Butch
Member

I thought I would chime in and let you know some of the thought process regarding the use of the PF-30 on the RSL line of bikes. Our goal with the design of these bikes was to find ways to increase stiffness while reducing weight. Each tube and assembly was looked at to try and do this. Keep in mind we have to think ti.
Our standard bb shell and the press fit shell weigh the same once vent holes are drilled and the piece goes on the bike. Here we increased the diameter by 20% with no increase in weight = stiffer. A Sram Red crank with PF 30 is 52 grams lighter than their standard crank even though the spindle is 20% larger in diameter = stiffer. The PF 30 BB bearing system weighs 25 grams less than standard as well.
The other aspects of the design we focussed on was to increase certain tube diameters while maintaining or decreasing the weight of these tubes. The seat tube, down tube and chainstays were all increased in diameter. The contact patch we have on a standard bb shell (1.563") effectively forces us to "bunch" these tubes together, using large counter miters so the downtube has a much smaller % welded to the bb shell because the miter cut into the downtube for the seat tube to fit. With the larger shell (1.975") we can offset cuts to produce a much larger footprint and a much smaller counter miter into the downtube.
I don't know if this qualifies as "it makes no engineering sense what so ever", but there was one other very important element to our decision. When we first built prototypes we built two identical bikes; one used a standard bb and one used PF 30. Then we rode them, many of us rode them. The conclusion was surprising to all of us, the PF 30 bike felt stiffer. As one rider said " I was running one gear higher on each climb". We have always been believers in "build it and ride it" engineering. As we have always approached changes to the bikes, we were not really looking for koolaid, just results.

In response to bb 88 etc again our goal was to decrease weight where possible. As we make our standard bb shells as thin as we feel comfortable, the notion of increasing the width of the shell by 30% seemed to be headed in the wrong direction for weight savings.

butch@moots

Posted 1 year ago #
29ner
Member

If you all don't know Butch....you should. A good man. Throw Butch some love.

Posted 1 year ago #
PhotosByChris
Member

G'Day All,

Looking for an optimal solution, I am riding a new Moot-X RSL and have opted to run the new 2012 XTR group set, and am having issues with the bottom bracket adapters pulling out of the frame when riding. The adapters have been pressed into the frame with a headset press, and the cranks pulled up tight.

Currently I'm looking additional spacers to try and hold it all together. I'm hoping someone else has a good solution that is working for them on this.

Posted 1 year ago #
JonC
Administrator

Chris,
What adapters are you using? Very strange to hear they are "pulling" out. We've got miles and a couple of seasons on bikes with the same adaptor/shimano XTR set up. Does the crank also come loose on the spindle?

Let me know....

Jon@Moots

Posted 1 year ago #
PhotosByChris
Member

G'Day Jon,

It has the Parlee adapters in place, the crank isn't moving on the spindle, the crank bolt and allen bolts are still tight. There is a wavy washer on the drive side, my guess is it may be compressing and allowing the adapters to move out???

The bike was silent when I got it, but now it creeks as the cups/adapters slip. Should I try a different adapter, or washer setup to space out the crank??

This is the only issue with the bike, otherwise it far exceeds my expectations.

Cheers
Chris

Posted 1 year ago #

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