BBinfinite-one-piece-pressfit-GXP-bottom-bracket

Look around and you might notice that more and more bikes are using the BB86 and BB92 bottom bracket shell. That’s a boon for Shimano since they’ve resisted going to a 30mm spindle, and it makes using that larger spindle that SRAM, FSA and others love more difficult to use.

BBinfinite founder Wes Wolfenbarger noticed that trend and saw another issue – bearing placement. Fortunately for him, his one-piece design solved that issue if you were running a straight 24mm spindle. But if you had a GXP crankset, which steps down to 22mm on the non-drive side, you’d have to stick with a traditional two-piece, pressfit bottom bracket. And that simply wouldn’t do.

So, not only did Wes create a complete line of GXP BB’s, increasing his SKU count by a full third, he wrote one heck of a story about how bottom bracket shells, bearings and spindles work together. Or don’t…

bbinfinite-bottom-bracket-tech-explanation

BBinfinite’s design philosophy is simple: Take the frame out of the equation. Frames, particularly carbon fiber ones, can have varying tolerances that don’t always line the bearings up perfectly. That puts a torsional load on the spindle, which creates drag. That’s the first problem.

The second is the cheap composite cups that the bearings sit in. These cups are pressed into a frame that may be too tight, which ends up putting radial pressure on the bearings. Drag and reduced lifespan are the result.

Their one-piece BB shell solves both problems. It provides a stiff, perfectly aligned platform for the bearings to rest in, and the firm metal shell won’t allow radial deformation of the bearings.

With those two issues solved, the final piece of the puzzle in reducing drag was to eliminate pressure coming from the crank arm’s installation. To remove lateral play from the spindle, we typically use a wave washer or tighten the bolt inside the spindle to pull both arms snugly against the BB. This can load the inner bearing race, causing it to shift out of radial alignment with the outer race. Once again, drag and reduced lifespan are the result. BBinfinite’s solution is a solid sleeve supporting the inner races, keeping them perfectly aligned with the outer races so the bearings roll as smooth as can be. Video above shows how it works.

BBinfinite-one-piece-pressfit-GXP-bottom-bracket

That was great news for anyone with a BB30 frame or, as long as you were running Shimano or FSA MegaExo 24mm spindle cranks, a BB86/92 frame. If you had GXP cranks, BBinfinite couldn’t help. Until now. Over the next eight weeks, they’ll roll out GXP compatible BB’s for:

  • BB30A Campagnolo
  • BB30A Shimano
  • BB30A GXP
  • BB30 GXP
  • BB386EVO GXP
  • BB86 GXP
  • PRESSFIT 30 GXP
  • BBRIGHT GXP
  • OSBB GXP
  • OSBB MTB GXP
  • PRESSFIT 30 MTB GXP
  • BB92 MTB GXP
  • BB30 MTB Shimano
  • BB30 MTB GXP

They do offer a bottom bracket that’ll fit a 30mm spindle into a BB86 frame, but Wes says the bearings have to be so small that they’re easier to damage when inserting or removing the cranks, particularly FSA cranks whose spindles tend to be slightly larger in diameter than normal.

BBinfinite-one-piece-pressfit-GXP-bottom-bracket

Each model is made specifically for each application, which includes the particular frame type as well as the particular crank spindle, so there are no adapters or spacers needed other than an occasional wave washer. That said, what separates the GXP models from the 24mm ID models is the use of an alloy reducer on the non-drive side. This keeps the bearing as large as possible while stepping down the inside diameter to GXP’s 22mm spec. The side benefit of this is it serves as a stop for the spindle’s step, which is sized such that the spindle will pull perfectly snug against it so there’s no lateral play.

BBinfinite-one-piece-pressfit-GXP-bottom-bracket

The drive side uses a Shimano-style top hat so there’s no steel on steel (spindle on bearing), helping everything last a good long time.

Whether you’re running GXP or not, Wes says their design allows for the most freedom of crank fitment since there’s no flange on the driveside. That makes more room for power meters and ensures the driveside stays well within the chainline guidelines for optimum shifting.

Look for all of the GXP models to be shipping in early 2016, before the road racing season starts. Check out their tech page for a graphical illustration of all the ways two-piece PFBB’s suck (starts about 1/4 of the way down the page).

BBinfinite.com

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Callum
Callum
6 years ago

Super cool stuff but really messes with a couple forms of internal cable management,

Eric Hansen
Eric Hansen
6 years ago

The entire reason GXP exists at all is a tl;dr kind of thing… in short, it’s because SRAM had to play catch-up with Shimano in the early ’00s, but didn’t want to spend ANY money doing so.

In the beginning… there was the square taper spindle. Ok, not actually the beginning. I’m just glossing over the stone ages that no one really cares about anymore. So there was the square taper. It was OK, it did the job. Economies of manufacturing scale created the cartridge BB using sealed bearings. This was a great thing for 99% of cyclists, as it simplified maintenance.

People eventually said “it would be great if we could get some more stiffness!”, so Shimano designed Octalink. Octalink was a 22mm spindle crammed into the BSA shell, reducing the size of the bearings, but it was stiffer and lighter. Shimano offered to license the interface to crank manufacturers, but declined to allow anyone to make Octalink BBs. They had standards to uphold, and would later be proven right in their assertion that it was difficult to make a 22mm spindled cartridge BSA BB.

King, Truvativ, and others said “SHIT! We’re gonna get locked out of the lucrative business of selling people a new BB every few years! We’re gonna make our OWN BB standard with booze and hookers!” They designed ISIS to be a copy of Octalink without infringing on patents. 22mm spindle, same as Octalink, but with a different splined interface. ISIS BBs pretty much universally sucked shit, and roached themselves in short order.

SRAM bought Truvativ, and Shimano invented HT2, which moved the bearings outside. SRAM said “well SHIT! Now we’re totally screwed!” SRAM took the interface from ISIS, and grafted it onto a 24mm steel spindle, so their cranks could be as stiff as Shimano’s at the same weight. This let other manufacturers continue to use their old tooling to make crank arms.

GXP results in ALL the sideload being concentrated on one bearing, while the other floats on the spindle. HT2 has sideloads going in one direction handled by one bearing, and the opposite on the other side. GXP has the trouble with the ISIS spline being a slight taper fit, and capable of being wallowed out.

It’s just a bad system that’s stuck around because SRAM didn’t want to spend any money in the first place.

greg
greg
6 years ago

Disagree with your assessment. In many ways, GXP is actually better. First, at least on actual GXP cups, the left bearing uses bigger balls. Second, that bearing only sees side loads as they are applied by the rider. on Shimano HT2 and most certainly FSA’s first Mega Exo for carbon, the side load is first introduced by the installation. That side load could be a little, could be a lot.
That’s not to say that GXP doesn’t have problems. It’s just that they aren’t the ones you mentioned.
Regarding this bb in the article, I have mixed feelings about the aluminum cup somehow being superior. The aluminum cup slightly reduces radial compression relative to a plastic cup, it does not eliminate it. If anything should be able to resist the compression, it ought to be the STEEL outer race of the bearing itself, but it doesn’t. Plastic has the benefit of being able to deform and displace its outer circumference, essentially sacrificing itself to save the bearing. Unfortunately, there’s very little place for the deformation to go. If there were lateral or circumferential grooves in the mating area, then it might have worked. Alas, nope.
People aren’t talking about one huge benefit of threaded interfaces. The compressive forces of the install are low and much more controlled. There’s actual space between threads and only gets some compressive force from the angular translation of the loaded thread itself. This force is also very even. Not that threads don’t have problems…
The one benefits I see to this bb above are that both bearings are in one housing, and the addition of the center sleeve. Hopefully all that is assembled perfectly to begin with. My one worry with the bb above is I don’t see what keeps the entire sleeve from walking out the left side of the frame.

shemp
shemp
6 years ago

Have OSBB on Crux frame, it was nightmare. I got the treaded insert and pressed it in with 609 or 640 loctite (I forgot which one), it’s been problem free since. My next frame will have a 68 mm BSA.

Bob
Bob
6 years ago

Can anyone with experience comment on the loading a frame may be under when a one piece aluminium bb that compresses less is pressfit in the frame. Ie in particular if the frame shell ID is undersize. Are frame manufacturers designing for this? I guess ideally the ID of a threadless bb shell should be reamed much like a headtube. Afterall we all know that frame tolerances are not always correct from the factory.

Tim
Tim
6 years ago

English threaded bottom brackets were not perfect, but when used with a cartridge bottom bracket, they were pretty awesome just in terms of bearing life and not creaking. Stiffness was an issue, but was anyone really complaining about the external Shimano bearings with a 24mm axle?
Eric Hansen’s account may have some flaws in it (and I am not knowledgeable enough to say which ones there are, or indeed if there are any), but the general arc of what he says- individual companies making it up as they go along, with quite bad results for end users, is pretty much indisputable.

gringo
gringo
6 years ago

As Eric and Tim have both pointed out, there are indeed a few engineers in this business who most certainly have something to be ashamed of.

Can you imagine if you were applying for a job at Bike Company X and you had ‘design lead, ISIS BB system’ on your resume!?? NO chance!

English threaded BB’s may not have been perfect, but it’s been pretty funny to see them outlive all the would be replacements over the years.

MaraudingWalrus
MaraudingWalrus
6 years ago

Every time I see these, I don’t understand what makes this better for the same application than a PraxisWorks conversion BB. Let’s say it’s to put the same cranks (Sram Red, GXP) on the same bike (PF30 frame), why is this better than a PraxisWorks?

baaa
baaa
6 years ago

@Walrus, this isn’t for PF30 frames… It’s not equivalent to the Praxis BBs (which are in fact really good).

Cheese
Cheese
6 years ago

“sized such that the spindle will pull perfectly snug against it so there’s no lateral play.”. The problem here is that nothing is sized perfectly with no tolerance. The solution to dimensional tolerances is to add a small and consistent preload (with wave washers, for example) and use the angular contact bearings appropriate for this application.

Trail Dog
Trail Dog
6 years ago

@Eric Hansen, you’re leaving out the fact that GXP bb’s use an angular contact bearing on the left side so it’s not as disastrously lopsided as you indicate. Also, GXP crank arms don’t fall off anywhere near the rate that their ISIS counterparts did. It’s a tolerable system.

Don’t get me wrong, I love Octalink and rode it until 2012 and I’m considering going back again. One LX-level 68×113 V2 bb lasted me a 4,000 mile cross country tour plus 5 years of mountain biking. Also the heel clearance was better than anything other than true BB30, which of course was bastardized in short order by SRAM et al and now often has terrible heel clearance despite that being one of the main goals and benefits of the original design.

Looks like here BBinfinite has used the center sleeve to replace the need for a left side angular contact bearing. I was just thinking yesterday about how suspension and hub bearings generally have inner race spacers but BB’s do not. Of course the shell tolerance issue prevents the use of an inner race spacer with independent cups so BBinfinite has a pretty clever solution by combining the unified shell with an inner spacer. Hopefully isn’t right and it won’t walk out, though I might be inclined to try some sleeve retainer (not that that stops independent cups from walking out).

duder
duder
6 years ago

IMO the plastic Shimano pressfits are less likely to creak than the other brands who use metal shells.

anonymous
anonymous
6 years ago


Same thoughts about aluminum and deformation. The primary advantage I see is that the bearings are held by a single shell that isn’t the frame, and can be in relatively perfect alignment without needing the frame and the person pressing in the BB to be perfect.

wuffles
wuffles
6 years ago

And none of this is an issue if frame manufacturers don’t cheap out, and just install a proper threaded BB. It’s gotten so bad that my next road bike will have to be a custom frame, simply because I refuse to ever buy anything with a pressfit bb ever again.

“But shows why pressfits are better!”

Wrong. It’s lazy engineering. Santa Cruz, to name one example, can make some of the lightest and strongest carbon mtb frames around, and they use threaded bb’s exclusively.

eric
eric
6 years ago

GXP does not use an angular contact bearing on the locating left side. Angular contact bearings only allow side force from one side. You need two, opposing, to handle side forces from both sides.

Since the left side does all the locating, from both sides, it has to handle forces from both sides. So they use a deep groove ball bearing, which is the standard cartridge ball bearing used in BBs. The side forces from a rider are low so one bearing can take them with no problem.

The big advantage of GXP is that there’s no bearing preload to set (and screw up). Excess preload does put a lot of side force on deep groove ball bearings and will wear them out quickly. With GXP you just slap the crank in there and torque the left crank arm. Done.

Angular contact bearings are awesome and I use them in my BB30 bike. But they’re not needed for GXP.

matt m
matt m
6 years ago

running two bbinfinites. THEY WORK. The praxis i had worked as well, but with noticeably more drag.

BDT
BDT
6 years ago

+1 for bbinfinite. I’ve got a year and 5k miles on mine without issue.