Bottom Brackets

- Thread: BC 1.37 x 24T - Caged bearing 1/4" x 9 - Fits most square taper cotterless BB axles - Spindle Type: SQR JIS - Cup Material: Steel

- With plastic washers - Shell: 8mm Allen head axle bolt

- Standard JIS square taper with steel cups, retainers, lockrings, CrMo spindle, shield included - Formerly called CBB-ST, renamed CBBF

Shimano BB-ES300 Octalink V2 Bottom Brackets - Fits Shimano Octalink V2 Spline Cranksets - Crankarm fixing bolts not included

- Simple and reliable square taper bottom bracket - Replaces both BB-UN26 and BB-UN55 - Sealed cartridge bearings - Cr-Mo axle - For bicycles equipped with a chain case, select BB-UN300-K - For E-type front derailleur compatibility, choose BB-UN300-E - Fixing bolts not included; Shimano FC-E6000 bolts suggested

• Lightweight seal structure removes grams • Durable anodized finish • Includes left and right hand cups, spacers, inner cover, and inner o-rings • Easy installation with TL-FC25 tool • Compatible with 24mm crank spindles • English, threaded: 68/73mm bottom bracket • Pressfit: BB86/92 bottom brackets

Shimano Dura-Ace BB92, BB9000 Hollowtech II Bottom Brackets

Pressfit Model: • For use on BB86/92 bottom bracket shells • Compatible with 24mm spindle Hollowtech II cranksets • BB Shell Width (mm): 92 mm • BB/Frame Interface: BB86 , BB92 • Bottom Bracket Shell I.D.: 41 • Defined Color: Black • Spindle Interface Type: Shimano Hollowtech II Threaded Model: • Includes 3 x 2.5mm spacers • Includes TL-FC24 adapter tool • Reduced size for light weight • New seal construction for smoother rotation • Requires TL-FC34 or included TL-FC24 adaptor for installation & removal • BB Shell Width (mm): 68 mm • BB/Frame Interface: English • Defined Color: Black • Spindle Interface Type: Shimano Hollowtech II • Weight: 77 g

Get more distance out of every pedal stroke with SRAM's BB30 Bottom Bracket Assembly. It features sealed bearings for a smooth pedal stroke and impressive reliability. Plus, it presses directly into your frame's BB30 bottom bracket shell for reduced weight and increased longevity.

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—connect your crankarms and protect the smooth, long-lasting application of power to your drivetrain. To allow that singular focus, we've engineered the DUB spindle to be the one true unifying component. One oversized spindle to work across every bottom bracket standard. For better crankarm compatibility. For better protection from the elements. For longer-lasting performance. To be stronger, smoother, simpler. Now, back to the ride. - One oversized spindle to work across every bottom bracket standard - Greater bearing durability

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - For Super Boost+ cranks - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

We've engineered the SRAM DUB crank spindle to be a true unifying component: one oversized spindle to work across every bottom bracket standard. If you only drink cappuccinos before 11, sing Verdi on long climbs, and named your cat Fellini, the SRAM DUB Italian BB is the ticket for getting our lightest and most durable crank system onto your bike. Better crankarm compatibility, better protection from the elements. With style. - One oversized spindle to work across every bottom bracket standard - Gutter Seal Technology drastically improves sealing against the elements - Significantly lighter than GXP system - Sealed cartridge bearings

The new SRAM DUB bottom bracket series has a simple job: connect your crankarms and protect the smooth, long-lasting application of power to your drivetrain. To allow that singular focus, we've engineered the DUB spindle to be the one true unifying component. One oversized spindle to work across every bottom bracket standard. For better crankarm compatibility. For better protection from the elements. For longer-lasting performance. To be stronger, smoother, simpler. Now, back to the ride. - One oversized spindle to work across every bottom bracket standard. - Significantly lighter than PFGXP system - Easier installation by allowing you to press the bearing cups into the frame

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The SRAM DUB bottom bracket series has a simple job—to connect crankarms and protect the smooth, long-lasting application of power to the drivetrain. SRAM engineered the oversized DUB spindle to work across every bottom bracket standard, simplifying crankarm compatibility. - Compatible with Cannondale Ai frames - Gutter Seal Technology drastically improves sealing against the elements - Sealed cartridge bearings - One oversized spindle to work across every bottom bracket standard

The new SRAM DUB bottom bracket series has a simple job: connect your crankarms and protect the smooth, long-lasting application of power to your drivetrain. To allow that singular focus, we've engineered the DUB spindle to be the one true unifying component. One oversized spindle to work across every bottom bracket standard. For better crankarm compatibility. For better protection from the elements. For longer-lasting performance. To be stronger, smoother, simpler. Now, back to the ride. - One oversized spindle to work across every bottom bracket standard. - Greater bearing durability - Easy installation - PressFit cups for lighter weight

The new SRAM DUB bottom bracket series has a simple job—connect your crankarms and protect the smooth, long-lasting application of power to your drivetrain. To allow that singular focus, we’ve engineered the DUB spindle to be the one true unifying component. One oversized spindle to work across every bottom bracket standard. For better crankarm compatibility. For better protection from the elements. For longer-lasting performance. To be stronger, smoother, simpler. Now, back to the ride. - One oversized spindle to work across every bottom bracket standard. - Significantly lighter than PFGXP system - Easier installation by allowing you to press the bearing cups into the frame - Easy installation - Two fully sealed cartridge bearings - ISO 4210 compliant. See Declaration of Conformity for details. - BB-frame interface PressFit (MTB: 89/92mm) - Crank-BB interface DUB - Bearing type Standard - Spindle diameter DUB - Cup material Steel

The new SRAM DUB bottom bracket series has a simple job—connect your crankarms and protect the smooth, long-lasting application of power to your drivetrain. To allow that singular focus, we’ve engineered the DUB spindle to be the one true unifying component. One oversized spindle to work across every bottom bracket standard. For better crankarm compatibility. For better protection from the elements. For longer-lasting performance. To be stronger, smoother, simpler. Now, back to the ride. - One oversized spindle to work across every bottom bracket standard. - Significantly lighter than PFGXP system - Easier installation by allowing you to press the bearing cups into the frame - Easy installation - Two fully sealed cartridge bearings - ISO 4210 compliant. See Declaration of Conformity for details. - BB-frame interface PressFit (Road: 86.5mm) - Crank-BB interface DUB - Bearing type Standard - Spindle diameter DUB - Cup material Steel

SRAM's GXP PressFit Road Bottom Bracket Cups are the premium choice for getting the most out of every pedal stroke. They feature smooth bearings that keep drag to a minimum and seals that keep debris out. Plus, these BB cups press directly into the frame without having to be threaded in for reduced weight and enhanced durability.

Get the most out of SRAM's high-tech cranksets with the GXP Team Bottom Bracket. Built to last, this super-smooth bottom bracket lets your SRAM GXP crankset (sold separately) spin effortlessly without weighing you down.

SRAM's GXP Team PressFit MTB Bottom Bracket Cups are the premium choice for getting the most out of every pedal stroke. They feature smooth bearings that keep drag to a minimum and seals that keep debris out. Plus, these BB cups press directly into the frame without having to be threaded in for reduced weight and enhanced durability.

Get the most out of SRAM's high-tech cranksets with the GXP Team Bottom Bracket. Built to last, this super-smooth bottom bracket lets your SRAM GXP crankset (sold separately) spin effortlessly without weighing you down. This GXP100 bottom bracket matches SRAM's Fat Bike cranks.

A tough bottom bracket that will go as hard as you. The PowerSpline has a heat-treated chromoly 12 spline spindle to make sure it can go the distance with even the most demanding riders. SPECIFICATIONS: - BB-FRAME INTERFACE: English/BSA 68E/73mm, English/BSA 68mm, English/BSA 73mm - CHAINLINE: 46.0mm, 48.5mm, 51.0mm, n/a - SPINDLE LENGTH: 108mm Spindle, 113mm Spindle, 118mm Spindle - SUPPORT E-TYPE FD: n/a, Yes - CRANK-BB INTERFACE: Power Spline - BEARING TYPE: n/a - SPINDLE DIAMETER: n/a - CUP MATERIAL: n/a - WEIGHT (G): 363 - WEIGHT BASED ON: BSA 73mm, 113mm spindle

SRAM saw the opportunity to make a better press fit system where all the best from BB30 and PressFit bottom brackets would be combined into one captivating package. Pressfit 30 will feature an integrated seal, pre-assembled into the cups, to further prolong bearing life. The key difference with Pressfit 30 is how the bearings are fitted into the frame. Bearings are housed in nylon cups which will be pressed into the frames bottom bracket shell. This bottom bracket is designed for 30mm spindle cranksets. Frames will need a 46mm inner-diameter bottom bracket shell to accommodate this system. Pressfit 30 for road will require a 68mm wide shell while Pressfit 30 for MTB will require a 73mm wide shell. - Easy installation - PressFit cups for lighter weight - Narrow Q-factor and more ankle clearance - Integrated gutter seal to prolong life - Integrated adjuster - 30mm spindle diameter

Race Face bottom brackets for use with 30mm spindle cranksets in the Race Face CINCH crank family. - Compatible with standard threaded BSA shells - Standard 6806 retainer bearings - Includes inner plastic sleeve and spacer; additional BB fitments can be accommodated with CINCH spacer kits - Inner sleeve protects against water - Rubber seal located on the bearing's external side helps to reduce the risk of water penetration

Spinning and Grinning This rock-solid, durable performer is everything you need in a press-fit 24mm bottom bracket and nothing more. Roll on...and on...and on. Greased Lightning This 24mm BB uses quality retainer bearings sealed with waterproof grease and wiper seals for durability and worry-free cranking mile after mile. Taking A Pass On Plastic This BB uses lightweight 24mm coated steel cups that are precision CNC-machined for a solid fit and are far superior to molded plastic cups. Weather, Or Not All RF bottom brackets come with an inner plastic sleeve to keep the elements out and the appropriate spacers to ensure a perfect fit.

As The Wheel Turns This trusty 30mm workhorse of a bottom bracket is built with custom RF double row cartridge bearings for trouble-free, long haul rolling for you PF41 frame. In A Sea Of Bearings These little buggers can make a huge difference, so we've made sure our double row custom retainer bearings are super durable and up for the long run. Close Enough Won't Cut It These precision steel cup are coated for corrosion resistance, and CNC-ground surfaces of this bottom bracket provide an exact, perfectly quiet fit in your frame. Weather, Or Not All RF bottom brackets come with an inner plastic sleeve to keep the elements out and include all appropriate spacers to ensure a versatile fit.

Designed to be used with X-Type or EXI cranksets. Manufactured from high strength aluminum & featuring custom retainer bearings. Features • BB Cups are forged & CNC machined from 6066 aluminum. • Tapering wall construction to minimize weight. • Custom 6805 16 ball retainer bearing • Bearings feature our custom triple wiper seal to better retain grease & keep contaminants out. • Bearings are factory filled with Phil Wood waterproof grease — tested & proven to extend bearing life.

Origin-8's BB30 Adapters allow you to convert your bicycle so that you can install a SRAM GXP or Shimano Hollowtech II BB30 crankset with a 24mm-diameter spindle. These Adapters include machined-aluminum cups, super-smooth and durable sealed bearings, shims and C clips.

Aluminum cups - Fits BB86 and BB92 - Includes shims for GXP - SHIMANO Equivalent SMBB-72-41B / SMBB-71-41A - Shell: 86mm - Spindle Type: HT2/GXP - Weight: 103g

Origin-8's ISIS Bottom Bracket is everything you need to get your wheels rolling. It features a steel body and hollow-chromoly spindle that adds stiffness and cuts down on weight. The sealed bearings are super smooth and durable, and this fine BB is available in 3 sizes with a 68mm shell.

Origin8's Revolvr thread-together bottom brackets provide a secure and stable shell interface for smoother operation and extended bearing life. Their hybrid AL6061/Nylon fiber cups deliver a superior fit and noise-free operation. Low-friction dual seals protect the bearings from harmful contaminants, while sealed premium bearings are both serviceable and replaceable. - Designed for installing Shimano HTII 24mm or SRAM GXP 22/24mm spindle cranks into BB30 frames without the need for adapters - Shell: 68-73mm x 42mm - Interface: BB30 - Material: AL6061/Nylon Fiber - Weight: 123g

- Thread-together bottom brackets provide a secure and stable shell interface for smoother operation and extended bearing life - Hybrid AL6061/Nylon fiber cups for a superior fit and noise-free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed premium bearings are both serviceable and replaceable - Designed for installing SRAM DUB 28.99mm spindle cranks into BB30 frames - Shell: 68/73mm x 42mm - Interface: BB30 - Spindle Type: SRAM DUB 28.99mm - Cup Material: AL6061/Nylon Fiber - Weight: 120g

Origin8's BB386 Thread-Together Bottom Bracket provides a secure and stable shell interface for smoother operation and extended bearing life. Its hybrid AL6061/Nylon fiber cups offer a superior fit and noise-free operation. Low-friction dual seals protect the bearings from harmful contaminants, while sealed premium bearings are both serviceable and replaceable. - Designed for installing Shimano HollowTechII 24mm or SRAM GXP 22/24mm spindle cranks into BB386 frames without the need for adapters - Shell: 86.5mm x 46mm - Interface: BB386 - Cup Material: AL6061/Nylon Fiber - Weight: 135g

- Thread-together bottom brackets provide a secure and stable shell interface for smoother operation and extended bearing life - Hybrid AL6061/Nylon fiber cups for a superior fit and noise-free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed premium bearings are both serviceable and replaceable - Designed for installing Shimano HTII 24mm, SRAM GXP 22/24mm, or DUB spindle cranks into BB386 frames without the need for adapters - Origin8 Nylon composite BB tools are recommended to avoid the possibility of damaging the cups - Shell: 86.5/92mm x 46mm - Interface: BB386/BB392 - Spindle Type: SRAM DUB 28.99mm - Cup Material: AL6061/Nylon Fiber - Weight: 135g

- Thread-together bottom brackets provide a secure and stable shell interface for smoother operation and extended bearing life - OS versions are designed for use in frames with worn-out, oversized bottom bracket shells - Hybrid AL6061/Nylon fiber cups for a superior fit and noise free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed premium bearings are both serviceable and replaceable - Models available for both Shimano HTII 24mm and SRAM GXP 22/24mm spindles - Replaces all standard BB86/92 press-fit bottom brackets - Origin8 Nylon composite BB tools are recommended to avoid the possibility of damaging the cups

- Precision machined AL6061 cups for a superior fit and noise-free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed dual-row premium flanged bearings - Designed for installing SRAM DUB 28.99mm spindle cranks into BB86/92 frames - Shell: 86-92mm x 41mm - Interface: BB86/BB92 - Spindle Type: SRAM DUB 28.99mm - Cup Material: AL6061 - Weight: 90g

Origin8's Revolvr BB86/92 Thread-Together Bottom Bracket provides a secure and stable shell interface for smoother operation and extended bearing life. Hybrid AL6061/Nylon fiber cups offer a superior fit and noise-free operation. Low-friction dual seals protect the bearings from harmful contaminants, while sealed premium bearings are both serviceable and replaceable. Models are available for both Shimano HTII 24mm and SRAM GXP 22/24mm spindles. - Replaces all standard BB86/92 press-fit bottom brackets - Shell: 86-92mm x 41mm - Interface: BB86/BB92 - Cup Material: AL6061/Nylon Fiber - Weight: 103g

- Forged and CNC machined AL6061 thread-in cups for a superior fit and noise-free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed premium bearings are serviceable - Designed for installing SRAM DUB 28.99mm spindle cranks into BSA threaded frames - Shell: 68/73mm - Interface: ENG - Spindle Type: DUB - Cup Material: AL6061 - Weight: 100g

Forged and CNC machined AL6061 cups - Double sealed replaceable bearings - Fits 68mm and 73mm shell widths - 1.37" x 24T English thread - Alloy spacers included for chainline adjustment - Anodized and laser etched finish

Origin8's Revolvr PF30 Outboard Thread-Together Bottom Bracket provides a secure and stable shell interface for smoother operation and extended bearing life. Hybrid AL6061/Nylon fiber cups provide a superior fit and noise-free operation. Low-friction dual seals protect the bearings from harmful contaminants, while sealed premium bearings are both serviceable and replaceable. - Designed for installing Shimano HollowTechII 24mm or SRAM GXP 22/24mm spindle cranks into PF30 frames without the need for adapters - Shell: 68-73mm x 46mm - Interface: PF30 - Cup Material: AL6061/Nylon Fiber - Weight: 138g

- Thread-together bottom brackets provide a secure and stable shell interface for smoother operation and extended bearing life - Hybrid AL6061/Nylon fiber cups for a superior fit and noise-free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed premium bearings are both serviceable and replaceable - Designed for installing SRAM DUB 28.99mm spindle cranks into PF30 frames - Shell: 68/73mm x 46mm - Interface: PF30 - Spindle Type: SRAM DUB 28.99mm - Cup Material: AL6061/Nylon Fiber - Weight: 125g

Origin8's Revolvr PF30/BB386 Thread-Together Bottom Bracket provides a secure and stable shell interface for smoother operation and extended bearing life. Hybrid AL6061/Nylon fiber cups for a superior fit and noise-free operation. Low-friction dual seals protect the bearings from harmful contaminants, while sealed premium bearings are both serviceable and replaceable. - Designed for installing BB30 or BB386 30mm spindle cranks into PF30 or BB386 frames without the need for adapters - Shell: 68-86.5mm x 46mm - Interface: PF30/BB386 - Spindle Type: BB30/BB386 30mm - Cup Material: AL6061/Nylon Fiber - Weight: 120g

- Thread-together bottom brackets provide a secure and stable shell interface for smoother operation and extended bearing life - OS versions are designed for use in frames with worn-out, oversized bottom bracket shells - Hybrid AL6061/Nylon fiber cups for a superior fit and noise free operation - Low-friction dual seals protect the bearings from harmful contaminants - Sealed premium bearings are both serviceable and replaceable - Designed for installing BB30 Wide or BB386/BB392 30mm spindle cranks into PF30 or BB386/BB392 frames - Note: Spindle length must be 104mm or longer when used in a 68mm wide shell, 108mm or longer when used in a 73mm wide shell - Origin8 Nylon composite BB tools are recommended to avoid the possibility of damaging the cups - Shell: 68-92mm x 46~46.1mm - Interface: PF30/BB386/BB392 - Spindle Type: BB30 Wide/BB386/BB392 30mm - Cup Material: AL6061/Nylon Fiber - Weight: 120g

Maximize your pedaling efficiency with Origin-8's Torq Lite Outboard Ceramic Bottom Bracket. It features CNC'd 6061-aluminum cups with super-smooth and durable double-sealed ceramic bearings and stainless-steel races. It is made for 68mm, 70mm or 73mm bottom brackets and can be used in road or mountain bikes. It comes with spacers and has an anodized and laser-etched finish, too.

Pedal smoothly and steadily with Origin-8's Torqlite Square-Taper Bottom Bracket. The forged aluminum body and cups are light and tough, the CNC'd hollow-chromoly spindle is stiff and shaves more grams, and the sealed bearings are super smooth and durable.

The FSA Alloy Cup JIS bottom bracket is suitable for Italian threaded interfaces. - Alloy cups - Double "snap" seals for water and dirt protection - Spindle Interface Type: Square Taper JIS

- Road sets include bearings, shields, c-clips and wavy washer for bearing retention/tension - Mountain sets include bearings, shields, c-clips and spacer - Choose ceramic or stainless steel options

Running a conventional threaded bottom bracket on your BB30 or PF30 frame doesn't have to be complicated. This press-fit adapter from FSA goes in snug and opens up a lot of crankset possibilities for your BB30/PF30 frame. - Aluminum - Allows conventional threaded bottom brackets to be installed in a BB30 or PF30 frame - Install with headset press (not included) and green Loctite (included)

Run your 386EVO crank with your frame that is designed for BB86 Shimano Pressfit bottom brackets with this FSA bottom bracket. - 2 lines of bearings on each side

- Enables the use of a BB386EVO (30mm spindle) crankset on a 68mm English threaded frame

This FSA MegaExo bottom bracket is for use MTB MegaExo cranksets with 24mm spindles. - Sealed bearings - Die-cast then CNC machined alloy bearing cups - Composite Di2-compatible adjustable center sleeve

- Left and right bottom bracket cups with standard bearings for FSA MegaExo cranks - BB-9050 is for 24mm spindle 68/73mm MTB K-Force and Team Issue cranks - BB-8681 for K-Force Light (a non-ceramic option) and SLK Light Road MegaExo cranks (BB-8681 bearing covers have been redesigned so that the spindle now rides directly on the bearing itself) - BB-7000 is for 24mm spindle 68/73mm shell MTB Gravity Lite, Moto X and Afterburner cranks - BB-7000 is for 24mm spindle 83mm shell MTB Gravity Lite cranks - BB-6200 is for 24mm spindle 68mm shell Energy, Gossamer and Omega No Bolt Design cranks - BB-6000 is for 24mm spindle 68mm shell Energy, Gossamer and Omega cranks - BB-4000 is for 19mm spindle 69mm shell Omega cranks - BB-1000 is for 19mm spindle 68/73mm MTB Gamma cranks - 1.37" x 24tpi (English threads) or M36 x 24tpi (Italian threads)

ISIS revolutionized bottom bracket spindles. Keep yours spinning smoothly with this Platinum ISIS Bottom Bracket from FSA. - Forged, hollow chromoly spindle with titanium nitride coating - Integrated, large ball bearing design - Cold-forged aluminum cups - Includes crank bolts