Bike Parts

34 Factory is the ultimate trail companion. Featuring an EVOL air spring, choice of dampers, and a lightweight yet robust chassis, you can count on 34 to get up and down the mountain, every time. - Genuine Kashima Coating on upper tubes - FLOAT EVOL air spring

Zipp’s Vuka Aero redefines aero handlebar conventions while being compatible with modern-day aero bikes. The current redesigned Vuka Aero builds on the technological foundation of aero excellence set by the original version. Vuka Aero is an integrated aero bar that features market-leading adjustability; it can be used with any stem to help you find your ideal position on the bike. The airfoil used in the Vuka Aero is based on the shape of the SL-70 Aero road bar. The result is an aero bar that’s stiff and streamlined while maintaining the UCI’s 3:1 aspect ratio requirement. - Market-leading adjustability in pad fore-aft, width, height, and angle - Integrated Carbon Aerobar works with any 31.8mm clamp stem - Integrated SRAM eTap AXS Blip box mount in the Center Cap - Rapid Routing cable exits are positioned for easy installation of brake cables - Vuka Aero ships with base bar, extension clamp, and armrest clamp - Extensions sold separately

The Shimano Dura-Ace FC-R9200 crank performs two vital functions; transferring your pedaling effort into the drivetrain and ensuring the fastest, most precise front shifting available. With HOLLOWTECH II crank arms to ensure light weight and Shimano's class-leading chainring designs, the FC-R9200 won't let you down. - Optimal balance of stiffness, strength, weight and rotational performance - HOLLOWGLIDE structure cuts weight yet maintains strength for better power transfer and quicker, more precise front shifting - 148mm Q-factor - 44.5mm chainline

The ergonomics on the Shimano Dura-Ace ST-R9270 dual control levers bring new levels of comfort and control to road cycling. With fast wireless shifting and precise brake modulation, Dura-Ace redefines performance. The Dura-Ace BR-R9270 hydraulic 2-piston calipers are sleek and compact. Mono-body construction ensures light weight and rigidity, proving that good things can come in small packages. - The wireless connection provides a clean cockpit, enhancing the aesthetic of your bike while keeping shifting lightning fast - 1.5 to 2 years of battery life with easy-to-change CR1632 shifter batteries - Wider pad clearance decreases the chance of rotor rub - Raised hood peak improves ergonomics, while a longer hood body increases hand support - Compatible with satellite shifters - Maintenance-friendly bleeding process

The SRAM RED 1 AXS crankset features exceptional 1x drivetrain design. It provides the simplicity and tighter gearing range that is well-suited for road racing and riding in flatter terrain, where a wide range would go unused. The crankset is designed specifically for electronic shifting and can be upgraded to a power meter. - Single-ring drivetrain simplifies functionality and reduces weight - SRAM X-SYNC wide-tooth, narrow-tooth chainring technology provides maximum chain control

The SRAM RED 1 AXS crankset features exceptional 1x drivetrain design. It provides the simplicity and tighter gearing range that is well-suited for road racing and riding in flatter terrain, where a wide range would go unused. The crankset is designed specifically for electronic shifting and can be upgraded to a power meter. - Single-ring drivetrain simplifies functionality and reduces weight - SRAM X-SYNC wide-tooth, narrow-tooth chainring technology provides maximum chain control

The SRAM RED 1 AXS crankset features exceptional 1x drivetrain design. It provides the simplicity and tighter gearing range that is well-suited for road racing and riding in flatter terrain, where a wide range would go unused. The crankset is designed specifically for electronic shifting and can be upgraded to a power meter. - Single-ring drivetrain simplifies functionality and reduces weight - SRAM X-SYNC wide-tooth, narrow-tooth chainring technology provides maximum chain control

The SRAM RED crankset leverages a pivotal design innovation: smaller chainrings and a wider cassette range. This leads to smoother and faster shifting up front and more useful gearing for today's riders. The new configurations improve cadence and efficiency while also delivering shifts that are crisp, clean and quick-every time. Features - X-Range gearing technology gives you more range and a smoother gear progression, so you're always in the right gear - Improved front shifting performance for crisp and accurate front shifts - Unique chainring design results in a lighter weight, stiffer, more durable crankset - DUB bottom bracket adds durability, simplicity and broad compatibility - Power upgradeable Specifications - Speeds: 12 - BB Compatibility: All SRAM Road DUB BBs, GXP/PF GXP 68mm - Chainring Size: 46/33, 48/35, 50/37 - Crank arm length: 165mm, 167.5mm, 170mm, 172.5mm, 175mm - Chainline: 45.0mm - BB Spindle Interface: 24mm, DUB - Chainring material: Aluminum - Guard: No Guard - Bolt Circle Diameter (BCD): Direct Mount (DM) - Crank arm material: Carbon

The new Reverb AXS XPLR dropper post delivers more control, confidence, and fun on gravel roads everywhere. Getting the saddle out of the way means more room to move, saving you from awkward maneuvering and sketchy descents. We created an all-new design complete with lightweight air-only internals featuring built-in compliance we call ActiveRide. It's like travel for your saddle. Enabled by SRAM AXS technology, Reverb AXS XPLR is part of the ultimate personalized cockpit. - New 27.2mm Reverb AXS XPLR delivers more control, confidence, and fun for gravel - ActiveRide—Air only internals provide a fully rigid top-out position. With the touch of your AXS controller, you've got built-in compliance to ensure comfort and control over the roughest sections of gravel - Two travel options to choose—50mm or 75mm - Saddle clamp options compatible with 7x10 oval carbon rails. - Seat post length includes 400mm and 350mm (50mm drop only) - AXS Technology allows rider customization via the AXS Mobile App - AXS handlebar controls (drop or flat bar) - Shared battery with all other SRAM AXS enabled components - System is completely waterproof and dustproof to IP69K—take it anywhere - SRAM AXS battery and charger included SPECIFICATIONS: - TRAVEL: 50mm, 75mm - POST DIAMETER: 27.2mm - POST LENGTH: 350mm, 400mm - REMOTE: AXS Controller Sold Separately - SADDLE RAIL COMPATIBILITY: Round/Oval (7x9 & 7x10), Round/Oval (7x9) - WEIGHT (G): 562 - WEIGHT BASED ON: 75mm Travel 400mm Length W/O battery - Battery 25g

The XX1 Eagle crankset features a special hollow internal architecture, combined with SRAM's Carbon Tuned technology to provide extreme stiffness and low weight. An X-SYNC 2 chainring offers significantly quieter performance with better mud clearing and extraordinary durability. As a part of the SRAM Eagle ecosystem, this crankset was developed for a superior 1x drivetrain experience. - SRAM DUB technology creates a lighter, stiffer, and stronger crankset - For use with a Cannondale Ai frame interface - Carbon-tuned lay-up crank design provides extreme stiffness and low weight - Included direct mount X-SYNC 2 chainring provides significantly quieter performance with better mud clearing and durability - Chainring is designed specifically for Eagle chains and drivetrains - Use with SRAM Eagle chain for optimum performance

Enjoy the ultimate advantage of freedom and adventure that Eagle provides combined with the Quarq power meter platform that delivers on accuracy and reliability. The SRAM Eagle XX1 power meter is built to pair with the SRAM Eagle drivetrains, providing a significantly quieter performance and extraordinary durability. Take it on the dirtiest, gnarliest trails while maintaining confidence in your cycling components. You came to perform; the Eagle XX1 power meter will perform with you. You are working hard, pushing yourself to new heights in some of the toughest conditions. Ride with confidence knowing that your power meter will not quit when you need it the most. Enjoy up to 200 hours of ride time in any weather or trail condition with its IPX7 waterproof rating and 10k temperature compensation; if harsh environments do not hold you back, then you need a product capable of rising to the occasion. The Eagle XX1 power meter is designed to be rough-and-tumble tough. Train harder, ride faster and unlock your ultimate potential. The Eagle XX1 power meter brings simplicity and ease-of-use to your training. With MagicZero automatic calibration, there is no need to worry about calibrating before you ride; just jump on your bike and go. The Eagle XX1 also features Bluetooth low energy and ANT+ wireless data transfer, delivering power output information directly to your cycling computer. - Speeds: 11/12 - BB Compatibility: DUB:BSA73, PF89.5, PF92, PF30 MTB73, BB30 MTB73, BSA MTB68SP - Bolt Circle Diameter (BCD): 104 BCD - Chainline: 52.0mm - BB Spindle Interface: DUB - Power Meter Type: ANT+ and BLE - Crank Arms/Chainrings not included

For all the ups, downs and to get you to everything in between. Lyrik Select combines an updated DebonAir air spring with the trusted Charger RC damper for unmatched trail control and precision. Maxima Plush fluid reduces friction, silences noise, and provides all-around lasting performance. Features: - Updated highly tunable DebonAir air spring offers a buttery smooth feel off the top and maintains a higher ride height for increased confidence in steep terrain - Charger RC damper featuring low speed compression adjust - Maxima Plush damping fluid reduces friction and silences damper noise

- 35mm chassis with a focused all-mountain mindset - satisfyingly stiff, efficient and designed to eliminate as much weight as possible. - Charger RC damper featuring Low Speed Compression adjust - DebonAir+ is built to strike the perfect balance of what riders really want: butter-like small bump feel, increased air volume to add support throughout the travel and higher overall ride height for more confidence when things get steep. - RockShox premium short fender included - Maxima Plush damping fluid reduces friction and silences damper noise

Designed not only for the race down but the also ride up. Holding onto every critical line, Lyrik Ultimate features an updated DebonAir air spring paired with our Charger 2.1 damper for unmatched trail control and precision. Ultra-low friction SKF wiper seals and Maxima Plush damping fluid all work overtime to reduce friction, silence noise, and provide unmatched fork performance sunup to sundown. - Updated highly tunable DebonAir air spring offers a buttery smooth feel off the top and maintains a higher ride height for increased confidence in steep terrain - Designed to reduce hand fatigue and fight unwanted friction, the Charger 2.1 damper increases confidence and control over every trail - Charger 2.1 RC2 damper featuring independent high and low-speed compression adjust - Ultra-low friction SKF wiper seals provide long-lasting fork performance and improve overall suspension feel - Maxima Plush damping fluid reduces friction and silences damper noise - Ultimate foil graphics package

This is the Pike DJ. It's a cousin to the award-winning Pike, which makes it look a lot like a trail fork — until you ride it. Pike DJ is built on a stout 35mm chassis and includes a custom-tuned Charger damper and specific Solo Air system designed for more bottom-out progression than you'll ever need because your trails eventually require some landings. - New graphics package for a fresh, premium look - Proven Charger damper with specific Dirt Jumping/Slopestyle tune - Specific Solo Air top cap for extra bottom-out progression - Accepts Bottomless Tokens to easily custom-tune the air spring performance to best match your own riding style and suspension preference

- 35mm chassis at home on the trail - stiff, playful, and light, really light - Charger RC damper featuring Low Speed Compression adjust - DebonAir+ is built to strike the perfect balance of what riders really want: butter-like small bump feel, increased air volume to add support throughout the travel and higher overall ride height for more confidence when things get steep. - RockShox premium short fender included - Maxima Plush damping fluid reduces friction and silences damper noise

Our intention with Reverb AXS was inventive and pure: No hoses. No routing. No energy wasted. Not a single thing in the way of the experience. We created a reliable wireless-electronic dropper post and controller that actuates with drastically less effort and zero distraction. Expanding what's possible on a bike, Reverb AXS is enabled by SRAM AXS technology, a new level of interaction, personalization, and connectivity across all AXS-enabled components. - Effortless Electronic-Wireless actuation and infinite height adjustment with a single touch. - Clean, simple and fast to install. No hoses to route, no fishing required. - Updated internals for faster return speed in all conditions. - New Vent Valve Technology, a simple and reliable built in service solution without disassembly of the seatpost. - SRAM AXS technology, a new level of interaction, personalization, and connectivity across all AXS-enabled components. - Includes RockShox AXS handlebar controller, rechargeable SRAM battery, and charger.

The new Rudy is a perfect match for your gravel bike. It's energy-efficient for straightaways and offers enough travel to keep you comfortably in control when things get rough. Featuring all-new 30mm upper tubes built around the Charger Race Day damper (our lightest damper ever) and our proven SoloAir spring. Rudy offers precise steering, full or short fender compatibility, and the looks to make your road bike proud. Everything designed with the needs of gravel riders in mind. - Purpose-built and laser-focused on gravel and e-gravel bikes - 30mm upper tubes are light and look the part - 30mm and 40mm travel options - Charger Race Day damper tuned for gravel needs with rock-solid lockout and a full range of rebound adjust - Solo Air spring perfectly tuned for shorter travel and efficiency over bumps - Short fender compatibility with a 3-bolt system - Full fender compatibility with custom stealth stay bosses - Lightweight machined and anodized crown offers a premium and durable finish - Maxima Plush damping fluid reduces friction and silences damper noise - Up to 700x50 tire clearance - Available in new Kwiqsand Signature colorway or Gloss Black - E-bike approved

Cross-country purists… we see you. You’re why SID SL Ultimate is the lightest XC fork on the trail. But weight is meaningless without world-class performance and durability. SID SL features a new Charger Race Day 2 Damper with three-position (3P) compression damping—rigid Lock, plush Open, and efficient Pedal positions, on demand for every inch of the race course. FEATURES - Our lightest 32mm chassis ever. World Cup-proven performance, built for your next podium result. - Longer-travel 110mm option, in case you’re feeling extra. - Charger Race Day 2 damper is the lightest damper on the market. This 3P damper features three compression positions: Open, Pedal, or a rock-solid Lock. - Machined crown for lighter weight and greater strength. - Covetable “Blue Crush” signature colorway and Ultimate High Gloss Black, featuring the new lustrous Pearl White graphics package. - Maxima Plush Dynamic Suspension Lube reduces friction, lasts longer, and enhances suspension performance ride after ride. -DebonAir air spring is tuned specifically to meet the demands of XC and maintains a higher ride height for increased confidence and control.

The ZEB Select is packed with performance in a stout 38mm chassis and features the updated DebonAir air spring with the trusted Charger RC damper. SKF wiper seals and Maxima Plush fluid reduce friction, silence noise, and provide all-around lasting performance anywhere you need it to be. - New, 38mm chassis for increased stiffness and rider confidence - Updated, highly tunable DebonAir spring offers a buttery-smooth feel off the top and maintains a higher ride height for increased confidence in steep terrain - Charger RC damper features low-speed compression adjustment - Dual Position Air adjustment option to change the geometry of the bike for climbs and descents - Ultra-low-friction SKF wiper seals provide long-lasting fork performance and improve overall suspension feel - Maxima Plush damping fluid reduces friction and silences damper noise

- Performance-packed, featuring an updated 38mm chassis, now compatible with new Pressure Relief Valves. - 38mm chassis for increased stiffness and rider confidence - Charger RC damper featuring Low Speed Compression adjust - DebonAir+ is built to strike the perfect balance of what riders really want: butter-like small bump feel, increased air volume to add support throughout the travel and higher overall ride height for more confidence when things get steep. - Compatible with new Pressure Relief Valves - Maxima Plush Dynamic Suspension Lube reduces friction and enhances fork performance ride after ride - Bolt-in torque cap adapters now included for the use with standard hub end caps

Notched binder bolts for frames with integrated seat collars. Details: CroMoly steel bolts Three lengths available: 16, 19 and 21mm 8mm diameter

Riders have been asking for it, and Marzocchi heard the call and has proudly delivered. The new Z1 Coil builds on the legacy of the single-crown fork that started the revolution way back in the '90s – the O.G. Bomber Z1 Coil. Starting with the stout and proven 36mm chassis of the modern day Bomber Z1, the new Z1 Coil retains the renowned Grip damper but swaps out the air spring assembly for the most advanced coil spring system Marzocchi has ever made. At the heart of this new coil system is an ultra-lightweight tempered silicon-chromium steel spring (available in 4 spring rates to suit a wide range of riders) coupled with a noise management system for near silent performance, an integrated air assist for progressivity and bottom-out control, and an external preload adjuster to dial in sag and firmness off the top. Travel can easily be changed in 10mm increments from 150-180mm (depending on wheel size) via included reconfigurable internal spacers. - Ultra-lightweight tempered silicon-chromium steel spring (Medium Spring included) - Noise management system for near silent performance - Integrated air assist for progressivity and bottom-out control - External preload adjuster to dial-in sag and firmness off the top - Travel can easily be changed in 10mm increments from 150-180mm (depending on wheel size) via included reconfigurable internal spacers - Additional springs sold separately to fine-tune and adjust for rider preference - Rake: 44mm

Lighter, stiffer, and more tunable than its competitors, the Mattoc is the desired componentry for all bikes. The Mattoc Expert should be on your bike not just because it can address all needs, but because it can improve the riding experience in a meaningful way. The Expert version of #thepeoplesfork tips the scales at a scant 1770 grams yet is stiffer than nearly anything else available in its travel range. Translation: an extremely lightweight and efficient build whose industry-leading stiffness ensures precise and reactive handling ready to outperform any other product it is compared to. The Manitou Expert boasts an Expert Air spring with IVA, compression damping via the VTT-6P system, and rebound damping via an open cartridge with adjustable TPC. True to Manitou’s industry-leading tuning capabilities, the Expert allows adjustments via Air, Air Volume, Rebound, and 3-position Compression (Open, Trail, Lock) With Open Mode Low-Speed Compression Adjustment. Perhaps the most versatile fork available not only in terms of travel but also application and customization of performance. Such amazing performance, tailor-tuned to your needs, arises from Manitou’s never-ending search for a smoother and better, best ride. KEY FEATURES - 27.5” is 20g less than the previous model. - Over 19% stiffness increase from the current 27.5" 160mm to the new 27.5" 150mm. 29" Stiffness increases are higher. - Expert air allows for internal travel adjustments with no added parts. New travel spacers account for negative air volume change, so the 110mm fork has the same initial stroke feel as the 150mm - Expert Air spring systems contain a unique balancing valve that equalizes the positive and negative air chambers during the air fill process. This gives the spring rate a consistent feel without any flat or dead spots in the stroke, along with giving riders of different weights the same initial stroke feel. Expert Air has identical performance to DoradoTM Air in a more cost-effective package. - Incremental Volume Adjust (IVA) modifies the volume in the positive air chamber with self contained spacers dictating the position of the IVA piston. This allows the main air spring ramp-up to be tuned to the rider's weight, style, and conditions without the need for additional parts. - A single external compression adjuster that simultaneously adjusts HS and LS damping characteristics. It features a fixed shim stack and a secondary shim stack that is preloaded by the external adjuster. The resulting wide tuning range combines the benefits of a low-speed platform and high-speed progressive tune can suit any terrain. - Trail Side Relief casting bleed screws allow users to release casting pressure from the fork. Casting pressure increase is normal, and extreme riding can increase the pressure at a fast rate. Temperature and elevation changes can also cause increased casting pressure. Releasing casting pressure can improve overall fork feel and small bump compliance.

Featuring 37mm stanchions, home mechanic-approved travel adjustability from 180mm to 140mm, and our easy-to-use VTT-6P damper, the Mezzer Expert is the smart choice for anyone looking to dive into the Enduro Fork market. Should you later decide you would like more adjustability from your fork, factory upgrades such as IRT and MC2 are available and can be easily installed in your own garage. At 2030g this fork is the second lightest option available within the Enduro fork market, second only to the Mezzer Pro of course. - Expert Air offers ultimate sensitivity featuring a self-equalizing negative air spring. - IVA (Incremental Volume Adjuster) allows you to modify your positive air chamber volume by rearranging self-contained spacers. You'll never lose a volume spacer again. - Integrated fender can be installed/removed by three small screws threaded into the arch of the fork. - VTT-6P damper provides 6 clicks to tune damping for all types of terrain - 37mm stanchions, Reverse-Arch design, and Hexlock SL2 axle for the ultimate stiffness - TSR, Trail Side Relief valves on the back of the lower legs allow air to be bled off if it builds up within the lower legs to keep things butter smooth between service intervals - Internally adjustable travel from 180mm to 140mm in 10mm increments with included spacers - 2.6" maximum tire width

Featuring 37mm stanchions, home mechanic-approved travel adjustability from 180mm to 140mm, and our easy-to-use VTT-6P damper, the Mezzer Expert is the smart choice for anyone looking to dive into the Enduro Fork market. Should you later decide you would like more adjustability from your fork, factory upgrades such as IRT and MC2 are available and can be easily installed in your own garage. At 2030g this fork is the second lightest option available within the Enduro fork market, second only to the Mezzer Pro of course. Key Features: - 37mm stanchions, Reverse Arch design, and Hexlock SL2 axle combined together result in ultimate stiffness - Expert Air offers ultimate sensitivity featuring a self-equalizing negative air spring. - IVA (Incremental Volume Adjuster) allows you to modify your positive air chamber volume by rearranging self-contained spacers. You'll never lose a volume spacer again. - VTT-6P damper provides 6 easy clicks to dial in your damping for all types of terrain. - Integrated fender can be installed/removed by three small screws threaded into the arch of the fork. - TSR (Trail Side Relief) valves on the back of the lower legs allow you to bleed off built-up air within the lower legs to keep things butter smooth between service intervals Product Details: - VTT-6P damper provides 6 clicks to tune damping for all types of terrain - 37mm stanchions, Reverse-Arch design, and Hexlock SL2 axle for the ultimate stiffness - IVA, Air Volume Adjustability by rearranging self-contained spacers - TSR, Trail Side Relief valves on the back of the lower legs allow air to be bled off if it builds up within the lower legs to keep things butter smooth between service intervals - Internally adjustable travel from 180mm to 140mm in 10mm increments with included spacers - 2.6" maximum tire width

Competition drives innovation, and as cross-country athletes and course designers push the boundaries of lightweight components, 32 Step-Cast Factory rises to meet the demand. A redesigned crown for 2020 increases stiffness to the same level as the trail-proven 34. The distinct shape of the Step-Cast chassis uses a narrow stance to save weight and the step design makes room for the spokes and brake rotor. - Genuine Kashima Coating on upper tubes - 32 mm upper tubes and ample bushing overlap for a quality ride - Hollowed out lower legs provide even more weight savings - FIT4 damper and FLOAT air spring

Competition drives innovation, and as cross-country athletes and course designers push the boundaries of lightweight components, 32 Step-Cast Performance rises to meet the demand. A redesigned crown for 2020 increases stiffness to the same level as the trail-proven 34. The distinct shape of the Step-Cast chassis uses a narrow stance to save weight and the step design makes room for the spokes and brake rotor. - Black anodized upper tubes - 32 mm upper tubes and ample bushing overlap for a quality ride - Hollowed out lower legs provide even more weight savings - FIT GRIP damper and FLOAT air spring - Performance Series black-on-black graphics package

Competition drives innovation, and as cross-country athletes and course designers push the boundaries of lightweight components, 32 Step-Cast Performance rises to meet the demand. A redesigned crown for 2020 increases stiffness to the same level as the trail-proven 34. The distinct shape of the Step-Cast chassis uses a narrow stance to save weight and the step design makes room for the spokes and brake rotor. - Black anodized upper tubes - 32 mm upper tubes and ample bushing overlap for a quality ride - Hollowed out lower legs provide even more weight savings - FIT GRIP damper and FLOAT air spring - Performance Series black-on-black graphics package

THE HARD CHARGING DO IT ALL TRAIL FORK Smoother, lighter, more tunable, and more capable than ever before; when it comes to a do-it-all trail fork the 34 is in a class of its own. - LOWER LEG BYPASS CHANNELS As a fork compresses, the air volume within the lower legs decreases, increasing air pressure. The more the fork compresses, the more pressure increases. This effect can have the unintended consequence of preventing full travel from being achieved. Our lower leg channels help alleviate this issue by dramatically increasing air volume within the lower legs and thereby reducing the amount of additional unintended pressure ramping. - LOWER LEG ARCH Stiffness-to-weight is the ultimate metric for bicycle design. Engineers invest countless hours poring over every ounce of material in an effort to optimize this critical ratio. The all-new 34 pulls out all the stops, shaving every possible gram while making sure not to compromise the stiffness or strength requirements of modern trail riding. - GRIP2 Our GRIP2 damper is the benchmark for unparalleled ride quality and ultra-precise adjustability. GRIP2 includes our patented Variable Valve Control (VVC) technology which allows for external fine-tuning of suspension performance. GRIP2 achieves with the twist of a knob what typically requires the time consuming and complicated task of completely disassembling and reassembling the fork. -FLOAT EVOL Returning with the same legendary suppleness and longevity, the EVOL air spring in 34’s now has an enlarged negative air spring to assist with mid-stroke support. - Performance-Elite series with black anodized stanchions - Step Cast (SC) legs with narrow stance and stepped design to saves weight, decrease frontal area, and provide clearance for the spokes and brake rotor - FIT4 damper with 3-position damper control - 160mm to 203mm rotor compatible post mount - Lightweight Kabolt thru-axle - Tapered threadless steerer