How to safely tighten bolts + Review: Bike Hand YC-617-2S torque wrench

If you like working on your bike, by now you should be used to turning and tightening bolts with a hex key or Allen wrench. Have you ever wondered that perhaps you’ve turned a bolt too tightly though?

WHAT IS TORQUE?

Most bolts on a bicycle actually have a torque specification. If you don’t remember your basic physics, torque is a measure of rotational force applied to an object along an arm of a given length. Torque is usually expressed in newton-meters (Nm) in the metric system, or pounds-feet (lb-ft) in Imperial measurement. In mechanics’ case, this arm is usually a wrench of some sort.

TORQUE SPECIFICATIONS

Normally you can turn a bolt in by hand until its head becomes flush with (and snugs up against) the surface you’re screwing it into. Once finger-tight, further tightening happens with a wrench, where you apply more and more torque to the bolt. As this happens, the tension also builds up along the length of the bolt you’re tightening, due to the interaction of the threads of the bolt and the receiving object. Exceeding the torque specification for that bolt can mean breaking it clean in half, as the material gives out under the tension. These broken bolts are quite hard to extract.

The stem is one place where tightening to proper torque is usually a big deal.

For the most part, metal parts are quite tolerant of a little excess torque. Torque specifications become really important, however, when you’re dealing with carbon fiber parts. Carbon fiber is a wonderful material, but one thing it’s not strong against is crushing force. If, for example, you have a carbon fiber seatpost and exceed the torque spec on its seatpost clamp, you will almost certainly damage the seatpost. Proper torque is also very important for the parts of a folding bike’s hinge and latch mechanisms, even though they’re made of metal.

TORQUE WRENCH TYPES

The dangers of applying excess torque are why a torque wrench is a worthwhile investment for serious mechanics. There are two general types.

A beam-type torque wrench is a socket wrench with a graduated scale, which you use to read the deflection of a freestanding secondary beam. That beam’s deflection off the main wrench arm is the applied torque. Beam-type torque wrenches are simpler and cheaper, and don’t need any maintenance, but require you to keep an eye on the scale. They’re best used for high-torque applications, such as crank arms and lock rings for cassettes or Centerlock brake rotors. These parts see torque loads in the 35-55 Nm range.

A micrometer-type torque wrench is different. Like its namesake, the end of the arm has a rotating collar used for measurement. On a micrometer caliper, this widens or narrows the caliper arms; on a micrometer-type torque wrench, it dials in the desired torque value. Once this value is reached, a clutch mechanism will release and give you both the characteristic “click” sound and slight deflection of the arm. Micrometer-type torque wrenches are more suited for the low-torque applications of most other bolts on a bicycle, but they do need periodic recalibration – and proper storage to reduce the need for recalibration.

Ritchey’s Multi-TorqKey is an example of a torque key. The two wrenches are preset to 4 and 5 Nm. Photo courtesy of BikeRadar.com

A sub-type of micrometer-type torque wrenches is the torque key. These are simpler devices which retain the clicking clutch mechanism, but ditch the adjustability. They are, in essence, made to stop at just one preset torque value, usually the most common 4 or 5 Nm – although Park Tool’s newly released ATD-1 adjustable torque driver has five fixed torque values you can select.

We’ll be looking at Bike Hand’s YC-617-2S micrometer-type torque wrench today. This exact torque wrench can actually be seen sold and rebranded under various names.

FEATURES

  • Micrometer-type construction
  • 1/4″ square drive socket
  • Reversible ratchet head mechanism
  • Included bits: 3mm, 4mm, 5mm, 5mm long, 6mm, 8mm, 10mm, T20 Torx, T25 Torx, T30 Torx
  • Torque rating: 2-24 Nm

IMPRESSIONS AND USE

Bike Hand’s torque wrench comes in a blow-molded black plastic box, made to house the wrench itself and all its bits. A metal double-hinge clasp keeps it shut.

The selection of bits should guarantee that it will work with almost any bolt on your bike. On my Vitesse, 95% of its bolts can be worked on with a 5mm hex key. The larger size hex key bits are for use on kickstand mounting bolts (8mm) and freehub bodies (10mm). The 5mm long hex key bit is particularly useful for tightening the clamp band bolts on my TCX SLR 2‘s STI levers, which are slightly obscured by their brake hoods. The T25 Torx bit should be handy for working on brake rotors, as well.

I like that all the bits themselves have a knurled collar around them. This enables you to turn loose bolts in by hand until finger-tight, before bringing in the torque wrench to tighten to correct torque. You press in the button on the head of the torque wrench to fit the bits onto the 1/4″ square drive socket, where they will stay on very securely.

Turning the collar sets the torque, displayed by a moving red column along a vertical graduated scale. This lets you use Bike Hand’s torque wrench on low torque applications such as stem and seatpost bolts, as well as higher torque uses, such as the 15-18 Nm needed to tighten the TCX SLR 2’s saddle clamp.

I find that for torque loads of less than 4 Nm, extra vigilance is needed as the clutch mechanism clicks very softly and the deflection isn’t very noticeable. At 5 Nm and up, the clutch mechanism works much better and more noticeably.

For more instruction on how to properly use a torque wrench, the boys of GCN have a video on it below.

VERDICT

I’ve had this torque wrench for quite a while now, and it’s a reliable tool to have, especially while working on the TCX SLR 2’s seatpost and stem bolts where setting correct bolt torque is critical. At PhP1,800 to PhP2,000, it’s not exactly cheap, but it’s one important tool to have in your arsenal if you’re serious about wrenching on your own bikes.

This article was originally published on the now-defunct United Folding Bikers blog on July 22, 2015. It has since been slightly updated.

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Making sense of bottom brackets, part 2: Press-fit shells and varying spindle diameters

Previously I covered bottom brackets for frames with threaded shells – right up to where Shimano changed the game with two-piece cranksets. With threaded shells, things remained pretty straightforward…until Cannondale decided to throw a monkey wrench into proceedings.

But first, a recap of some important details.

  • With three-piece cranksets, spindle diameter generally isn’t a big deal.
  • With two-piece cranksets, spindle diameter is a VERY BIG DEAL, especially how it correlates to the inner diameter of bottom brackets.
  • From the threaded shell days, bottom bracket width is 68 mm for road bikes and 73 mm for mountain bikes.
  • With its outboard bearings, Shimano’s Hollowtech II system brought an effective 86.5 mm bottom bracket shell width for road bikes and 91.5 mm for mountain bikes.

I’ll be approaching this installment a little differently from the first one. All press-fit bottom bracket variations are rooted in their almost-universal use of two-piece cranks, which come in different spindle diameters, so I’ll make this the primary consideration. From there, I follow Wheels Manufacturing’s excellent bottom bracket database, which lists the shell width, the shell inside diameter, and the standards’ use or non-use of bearing cups. Finally, in deference to the fact that many, many bikes run Shimano parts, I include any notes for using a Shimano Hollowtech II crankset with each press-fit standard.

NB: Any bottom bracket type that will fit a 24 mm Shimano Hollowtech II crank spindle will also fit SRAM GXP (24 mm/22 mm spindle) cranksets. All you need are the correct bottom bracket bearing parts to properly fit the spindle.

I hope this makes this minefield a little easier to navigate.

CATEGORY 3: BOTTOM BRACKETS WITH PRESS-FIT SHELLS, TWO-PIECE CRANKSETS

TYPE 3.1: CANNONDALE BB30

  • Crank spindle diameter: 30 mm
  • Bottom bracket shell width: 68 mm (road), 73 mm (MTB)
  • Shell inside diameter: 42 mm
  • Bearing cups: None

A cut-away view of a BB30 bottom bracket shell, containing the bearings and the massive crank spindle.

Historically speaking, Cannondale and aluminum go hand-in-hand. The firm is a pioneer with its advanced use of this material in bicycle frames. While only a third of the density of steel, two of the keys to making aluminum strong are using oversize diameter tubing and the strategic butting (narrowing of wall thickness) of tubes.

A Park Tool HHP-1 headset bearing press being used with suitable drifts to press in bearings into an unthreaded bottom bracket shell.

In 2000, Cannondale decided to apply the same concept to the crankset. Instead of following Shimano’s lead with a 24 mm steel spindle, they substituted a beefy 30 mm aluminum unit – and created a bottom bracket standard to suit. Instead of relying on threads, they decided to use the interference fit concept of literally smooshing bearings into the shell. Thus, BB30 was born.

Contents of a typical BB30 kit: (L-R) Two circlips, the bearings themselves, and external dust seals. The wavy washer’s use depends on the crank being used.

As one of the first major press-fit standards, BB30 makes use of bare cartridge bearings that are directly pressed into the frame – no cups. Two circlips are inserted prior, to prevent the bearings going deeper into the shell than they’re supposed to. Cannondale later made BB30 an open standard so that anybody could make use of it.

The whole point of BB30 was to stiffen the crank with that enormous spindle diameter so that more of the rider’s pedaling power went into propulsion instead of crank and spindle flex. At the same time, the narrow shell width meant a lower Q-factor (distance between pedal attachment points), which is a better ergonomic fit for some riders. When BB30 works, it supposedly works great. When it doesn’t…you get creaking at the bottom bracket. Sloppy tolerances at the bottom bracket by less-than-industrious frame makers meant that sometimes generous helpings of Loctite 242 or grease were needed to take up the slop between shell and bearings.

The great thing about BB30 though is that since its opening to third parties in 2006, it’s really well supported: SRAM, FSA, Rotor, Praxis and other firms make compatible cranksets. To install a Shimano Hollowtech II crank into a BB30 frame, you’ll need adapters to reduce the shell’s 30 mm inside diameter to 24 mm.

TYPE 3.2: CANNONDALE BB30A

  • Crank spindle diameter: 30 mm
  • Bottom bracket shell width: 73 mm (5 mm wider on non-drive side)
  • Shell inside diameter: 42 mm
  • Bearing cups: None

As of this writing, BB30 has given birth to a new standard, BB30A – the “A” standing for “asymmetric.” This adds 5 mm to the non-drive side of the shell.

To my knowledge, there are only a few bikes that make use of BB30A: the 2015-2016 Synapse and 2016 Slate are prime examples. All of them so far are nominally road bikes, although with its Lefty Oliver suspension fork, the Slate definitely pushes the boundaries. BB30A is currently too new to be properly supported with compatible cranks. The same rules for BB30 apply to using Shimano Hollowtech II cranks on BB30A frames.

TYPE 3.3: SRAM PRESSFIT 30 (PF30)

  • Crank spindle diameter: 30 mm
  • Bottom bracket shell width: 68 mm (road), 73 mm (MTB)
  • Shell inside diameter: 46 mm
  • Bearing cups: Yes, composite

A PF30 bottom bracket kit. Note the use of bearing cups and a center sleeve connecting them.

Introduced by SRAM in 2009, PF30 takes the basic BB30 concept and tries to improve it by making the bearings ride on plastic cups. When pressed in, the lip of the bearing cup becomes flush with the outside lip of the bottom bracket shell and stops the bearing from sinking farther inward. Theoretically, this should let the bike frames do away with circlips and improve the tolerances of the interference fit, as the plastic cup essentially sacrifices itself to conform to any irregularities on the bottom bracket shell.

In practice, though, based from what I’ve been reading, this seems to be just as problematic as BB30 is, or maybe even worse – again due to poor, sloppy manufacturing tolerances. It reportedly got so bad that a handful of artisan American frame builders created a new bottom bracket standard, T47, out of the foundation of PF30. T47 is basically a threaded version of PF30, with a specific thread pitch.

The same rules for using a Shimano crank in a BB30 frame apply for PF30.

TYPE 3.4: SHIMANO PRESS-FIT (BB86 ROAD / BB92 MTB)

  • Crank spindle diameter: 24 mm
  • Bottom bracket shell width: 86.5 mm (road), 91.5 mm (MTB)
  • Shell inside diameter: 41 mm
  • Bearing cups: Yes, composite

A BB92 bottom bracket. The only real difference between BB86 and BB92 parts is the length of the center sleeve.

All of the BB30 press-fit derivatives make use of the classic 68 mm and 73 mm bottom bracket shell widths. This is different: it sought to expand the width of the bottom bracket shell itself in order to allow larger diameter tubing and give the frame more lateral stiffness.

In 2006, Shimano teamed up with Scott Bicycles to create its own take on the press-fit bottom bracket. You’ll notice the bottom bracket shell widths (86.5 mm road, 91.5 mm MTB) are exactly the same as they were for a threaded bottom bracket shell with the Hollowtech II bearing cups screwed in. They basically translated threaded Hollowtech II into a press-fit application; i.e. what was once outboard is now inboard again! In this case, the numbers after “BB” refer to the bottom bracket shell widths. Confusing eh?

The funny thing about “Shimano Press-Fit” is you never hear people refer to it by this name. BB86 and BB92 are much more commonly used, as is the identical PF86 and PF92.

Shimano’s naming convention for its press-fit bottom bracket parts is confusing, to say the least.

Another funny thing about BB86/BB92: the bottom bracket parts themselves have ridiculous Shimano nomenclature. When I installed my 105 crank, I got a SM-BB91-41B bottom bracket – nowhere on the box does it say that it’s BB86, but it is. The letters and numbers in the name mean:

  • BB = bottom bracket
  • 91 = model tier (i.e. this is a Dura-Ace level part)
  • 41 = internal diameter in millimeters (Specialized bikes use “42”)
  • B = road use/BB86 (“A” is for MTB use/BB92)

Ridiculous naming aside, this is by far the press-fit standard I read and hear the least problems with. I can back this up with personal experience. I was half-expecting creaks to drive me nuts when I got my TCX. Almost two years later, it’s been creak-free, with no need for stuff like anti-seize, Loctite or grease between bearing cup and frame.

By the way, the whole method of installing reducer adapters to fit a Shimano crank into a BB30/BB30A/PF30 frame? In effect, you’re actually just converting that frame into BB86 – or BB92, as the case may be.

I’ve seen some companies try the reverse: fit a 30 mm spindle crank into a BB86 shell. This is not without its potential drawbacks, though. By smooshing a 30 mm spindle in there, the bearings may be too small to do their job properly – like what happened with most bottom brackets of the splined ISIS standard.

TYPE 3.5: TREK BB90/BB95

  • Crank spindle diameter: 24 mm
  • Bottom bracket shell width: 90 mm (road), 95 mm (MTB)
  • Shell inside diameter: 37 mm
  • Bearing cups: None (cups molded directly into frame)

BB90 in action. The bare cartridge bearing is pressed directly into the frame, which already contains pre-molded cups.

BB90 and its mud-plugging BB95 cousin are the exclusive domain of Trek bicycles. It’s essentially a defacto hybrid of BB86/BB92 and BB30: the cartridge bearings go into frame-molded cups, while the whole system is expressly designed to take 24 mm spindles – meaning Shimano cranks will fit right in. Any cranks with oversize spindles are out, though.

While the system is very similar to BB86/BB92, the different bearings mean that supply might be a problem outside of the official Trek dealerships. BB90/BB95 does have good support from companies like Wheels Manufacturing and Enduro Bearings, though.

TYPE 3.6: WILIER/FSA BB386EVO (BB392EVO MTB)

  • Crank spindle diameter: 30 mm
  • Bottom bracket shell width: 86.5 mm (road) / 92 mm (MTB)
  • Shell inside diameter: 46 mm
  • Bearing cups: Yes, composite

A BB386EVO crank inside a BB30 shell. Adapters mean the system plays nice.

In a sense, the names BB386EVO and BB392EVO almost give away that this is another hybrid of BB86/BB92 and PF30, taking the former’s wider bottom bracket shell and plastic bearing cups, and retaining the larger spindle and shell diameters and longer spindle length. Created in 2011, it’s the newest of the bottom bracket standards, and from a production and tooling perspective, it has the most to offer in terms of commonality.

A comparison of two same-model FSA cranks. Above is the BB386EVO version; below is the BB30 counterpart.

As per BikeRadar’s comprehensive guide to bottom brackets, BB386EVO cranks themselves can be used in a very wide variety of frames; you could put them in almost all the bottom bracket standards mentioned in this post. Due to the wider shell, the spindle is longer and the crank arms are straighter, making for less overall weight but also a slight decrease in crank stiffness compared to a BB30/PF30 crank.

FSA even makes an adapter to use these cranks in a BSA threaded shell.

As with PF30, reducer adapters are needed in a BB386EVO shell to make use of a 24 mm Shimano Hollowtech II crank.

TYPE 3.7: CERVELO BBRIGHT

  • Crank spindle diameter: 30 mm
  • Bottom bracket shell width: 79 mm (road)
  • Shell inside diameter: 46 mm
  • Bearing cups: Yes, composite

Where BB386EVO sought to play nice with almost everybody, BBright goes in the other direction. Dimensionally, it’s very similar to PF30, but it takes the 68 mm road bottom bracket shell and adds 11 mm on the non-drive side to give frame designers leeway for bigger frame tubes.

As far as frame makers go, as of this writing BBright is the exclusive domain of Cervelo. Parts, meanwhile, make for fairly good support. I know Rotor makes BBright-compatible bottom brackets and cranks, and SRAM has a particular model of PF30 bottom bracket that is meant to fit into BBright frames.

TYPE 3.8: PRAXIS M30

  • Crank spindle diameter: 30 mm + 28 mm on non-drive side
  • Bottom bracket shell width: See BB30/A, PF30, BB86, BB386EVO
  • Shell inside diameter: See BB30/A, PF30, BB86, BB386EVO
  • Bearing cups: Yes except for BB86

Praxis Works is a company based in California that started life making some highly lauded, cold-forged aftermarket chainrings, sporting shift quality and longevity that rivaled previous generations of Shimano’s Dura-Ace groupset. They later renamed themselves Praxis Cycles and diversified into other products, including their own cranksets and matching bottom brackets.

Their cranks make use of their own take on the 30 mm crank spindle called “M30.” In principle, it’s basically a mix of traits from BB30 and SRAM’s GXP: the crank spindle steps down to 28 mm on the non-drive side to lock the bearings in.

As of this writing, Praxis does not create bike frames, so it sells bottom brackets that allow the use of its M30 cranks in the formats mentioned above, as well as the BSA English threaded and T47 shells. I’m not entirely sure how they do it, but apparently they can make an M30 crank work in a BB86 shell, which conventional wisdom says shouldn’t work because there will not be enough space left for good-sized bearings to fit.

 

This is by no means a definitive guide and it’s entirely possible I’ve gotten a few things wrong. I hope, though, that this helps you make more sense out of the dense fog of press-fit bottom bracket standards. If the new T47 standard of 2015 is any indication, we’re likely not done with the bicycle industry introducing more confusion with this very important component.

RESOURCES

This article was last updated September 5, 2017.

Making sense of bottom brackets, part 1: Introduction and threaded types

If there’s a bicycle component that has the most potential for aggravation, it has to be the bottom bracket.

As I’ve mentioned before, the bottom bracket is one of the four main sets of bearings a bicycle relies on for its function. Its purpose is to allow the cranks and their connecting spindle to spin freely, in order to accept the rider’s pedaling power.

So why the potential for aggravation? It’s primarily because bicycle parts manufacturers can’t seem to stick with a tried and true concept, proliferating new bottom bracket standards and frame interfaces in the name of increased frame stiffness and pedaling stiffness. The plethora of standards can be an overwhelming minefield for those not in the know, which is why I’ve decided to help out.

We’ll begin with what I consider the elder statesman of the standards: bottom brackets for frames with threaded shells and three-piece cranks.

CATEGORY 1: BOTTOM BRACKETS FOR THREADED SHELLS AND THREE-PIECE CRANKSETS

A bottom bracket shell with threads being tapped into it.

Once upon a time, all bicycle frames had bottom bracket shells with threads tapped into them. After the French retired their idiosyncratic screw thread standards and got along with the rest of the world sometime in 1985, two major standards were left: English (also called “BSA”) and Italian (or “ITA”).

Both standards refer to a bottom bracket shell that is 68 mm wide. The only real difference between BSA and ITA is the threading of the non-drive side. Frames made to fit ITA bottom brackets are right-hand-threaded (turn clockwise to tighten) on the non-drive side. For BSA bottom brackets, the non-drive side is left-hand-threaded (turn counter-clockwise to tighten). It could be argued that BSA is the more common threading of the two, these days.

A Shimano Hollowtech I three-piece crankset. The Octalink-spindled bottom bracket serves as the third piece.

Many bikes of old also used three-piece cranksets. These consist of:

  • The drive side crank arm with the chainring(s)
  • The non-drive side crank arm
  • A separate spindle inside the bottom bracket connecting the two crank arms

On a three-piece crank, the spindle and bottom bracket are a single unit. There are variations of these, but they tend to differ only on how the crank arms attach to the bottom bracket spindle.

TYPE 1.1: SQUARE-TAPER 

A Shimano UN55 square taper bottom bracket. The “113” refers to the total spindle length from end to end, in millimeters.

These are so called because of the shape of the spindle. The spindle has a square end which tapers (narrows) as it extends from the bottom bracket. The crank arms attach purely by friction due to the tapering of the spindle. A square-taper bottom bracket usually has a spindle with a 17 mm nominal diameter – at least in the center where it’s actually round.

Square-taper cranks and bottom brackets are remarkably long-lived. They’re still around today, serving duty in lower-cost parts and applications, such as fixed-gear and track bikes. Bino’s stock crank is based on a square-taper bottom bracket. Many square-taper bottom brackets these days use cartridge bearings and aren’t really designed to be serviceable. Once it goes bad, it’s usually cheaper to replace with a new one instead of having a mechanic dismantle it.

TYPE 1.2: SPLINED – SHIMANO OCTALINK

A Shimano ES25 Octalink bottom bracket. Note that this is “Version 2” with the spline teeth cut deeper into the ends of the spindle.

Shimano introduced Octalink with its Dura-Ace 7700 groupset. Splines are basically gear teeth cut on a cylinder or the end of a shaft, instead of on a flat wheel like a normal gear, cog or chainring. In the case of Octalink, there are eight splines on the end of the bottom bracket spindle. The thinking went that a splined interface between crank arm and spindle would improve power transfer compared to a square-taper system.

Octalink still exists today, mainly in the form of Shimano’s entry-level Claris 2400 eight-speed groupset and its Dura-Ace 7710 cranks for velodrome track racing. They are nowhere near as populous as square-taper parts though.

TYPE 1.3: SPLINED – ISIS

An ISIS splined bottom bracket sold by Nashbar.

Shimano kept its Octalink system proprietary. In response, an alternative, open standard called ISIS (International Splined Interface Standard) was born, used by companies such as FSA and Truvativ.

ISIS made use of ten splines on the spindle, as well as adopting the tapering spindle concept of the square taper bottom bracket. In theory it should have been sound, but problems in the design meant that in most ISIS bottom brackets, the bearings themselves were too small to be reliable. Here’s a good read on the subject.

Anatomy of an ISIS splined bottom bracket.

For the most part, ISIS is an orphaned standard now, one that stopped making sense because Shimano decided to fuse the spindle with the drive side crank arm – creating the two-piece crankset. When other manufacturers followed this design, it effectively meant that Octalink got “discontinued” as well, too.

CATEGORY 2: BOTTOM BRACKETS FOR THREADED SHELLS AND TWO-PIECE CRANKSETS

TYPE 2.1: SHIMANO HOLLOWTECH II

A Shimano Hollowtech II bottom bracket installed on a bike, characterized by the notched outboard (external) bearing cups

As Shimano fused the spindle with the drive-side crank, it also learned from the difficulties ISIS had and thought of thinking outside the BSA/ITA bottom bracket shell width (68 mm for road bikes and 73 mm for mountain bikes). By moving the bottom bracket bearings outside the bottom bracket shell, it could use larger, more efficient bearings while effectively widening the shell at the same time.

The Shimano Hollowtech II system was born. It has many defining characteristics:

  • The bottom bracket bearings are mounted in outboard cups that screw into the bottom bracket shell’s threads. Once the cups are mounted, the shell effectively widens from 68 mm to 86.5 mm for road bikes, and from 73 mm to 91.5 mm for mountain bikes.
  • All Shimano Hollowtech II cranks have a hollow 24 mm steel spindle fused to the drive-side crank arm. With two-piece cranks, this spindle diameter now becomes a very important detail.
  • The spindle is splined to accept the non-drive side crank arm.
  • The non-drive side crank arm is the “compression slotted” type, according to Park Tool’s classification. It has a slot and a compression cap that pre-loads the bearings by squeezing the crank arms together, and is tightened with a proprietary eight-point star tool (Shimano’s TL-FC16). Once that is set, two opposing pinch bolts secure the non-drive side crank to the spindle.

Drive side crank of a Shimano 105 FC-5800 two-piece crankset. Note how the spindle is permanently fused to the crank arm and is now independent of the bottom bracket.

Chances are, if you have a Shimano crank, you use at least part of Hollowtech II. If your frame has threaded-in bottom bracket cups, you have the full system.

The Hollowtech II design proved so successful that many other manufacturers provided their own versions on the formula – which are generally very similar. I’ll mention a few standouts.

TYPE 2.2: SRAM GXP

The main difference of GXP compared to Hollowtech II is the “stepped” spindle diameter. The drive side is 24 mm as before, but this tapers down to 22 mm on the non-drive side. This supposedly allows for larger bearings to be installed on the non-drive side, and it is also inherited from the ISIS design.

A Truvativ GXP crank. Note the ISIS-like splines on the spindle, and “step-down” in spindle diameter on the non-drive side.

GXP is still around. If you have a SRAM crank, you’re on GXP unless your frame requires a BB30 or PF30 bottom bracket. SRAM makes specific versions of its cranks for those, which have straight spindles (no taper).

TYPE 2.3: CAMPAGNOLO ULTRA-TORQUE

A Campagnolo Ultra Torque crank. Note that both crank arms have half the spindle. Also note the bottom bracket bearings which are threaded onto both arms.

While Hollowtech II cranks fuse the whole length of the spindle onto one crank arm, Ultra-Torque splits this straight in the middle. Both arms have half the total spindle length fused to them. They meet halfway and mesh in the middle of the bottom bracket shell via a Hirth joint made up by meshing teeth on each half, then a bolt joins the two crank arms in the middle of the spindle.

While Ultra-Torque uses external bearing cups, the bearings themselves aren’t integral to the cups as they are on Hollowtech II. They just slide onto each crank arm.

TYPE 2.4: FSA OMEGA (NON-BB30)

Hyro came stock with an Omega crank. These also use outboard “MegaExo” bearing cups, similar to Hollowtech II and GXP in general design, but the cranks have a strange 19 mm spindle diameter which is hard to get replacement bottom bracket bearings for. The non-drive side crank arm is the “self-extracting” type, as well.

This takes care of bottom brackets for frames with threaded shells. In the next installment I’ll discuss the messy minefield that is the bottom bracket situation for frames with press-fit shells.