Suspension

A striking balance of low weight and exceptional downhill performance, the SID finds a new level of confidence and defines what modern XC race bikes are capable of. The SID Ultimate is built with more travel, an all-new stiff 35mm chassis that features our lightest damper to date, and the new Charger Race Day. This race-ready package also includes the redesigned DebonAir air spring, tuned specifically for the demands of XC riders. Our friends at SKF and Maxima Plush Fluids come along for the ride, providing long-lasting fork performance and improved overall suspension feel. Lighter and more capable than ever before, SID will get you to the finish line faster. Features - New 35mm chassis is the perfect blend of low weight and stiffness for the modern XC bike - New Charger Race Day Damper - our lightest production damper with rock-solid lockout - New DebonAir air spring is tuned specific to meet the demands of XC and maintains a higher ride height for increased confidence and control - New 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 - Machined/anodized crown - 2-bolt mounts to fit a short fender (RockShox fender sold separately) - Ultimate foil graphics package

With bigger bikes there comes bigger demands. Thankfully, we created the 35 Gold to meet all of them, both in performance and value. Whether you have an E-MTB or MTB, the burly 35 Gold checks the box with our proven DebonAir spring and Motion Control damping. And new this year is an E-MTB-focused option with mounting points for optional full or short fenders. All told, you might wonder how we packed so much quality and performance into such a wallet-friendly package. Features - New E-MTB endorsement options with fender mounts are appropriate for all E-bikes (1.8" taper available) - New graphics are easy to read and make a fresh impact - Motion Control damping featuring low-speed compression adjustment to lockout - Highly tunable DebonAir spring offers a consistent feel throughout the travel - Fits Tires up to 2.8" (without fenders; the use of a full fender will reduce tire clearance) - Fast Black finished 35mm aluminum upper tubes couple stiffness and lightweight with a premium look - Offset: 44mm

Steer Tube: 1" x 18" Long Triple Tree: Aluminum CNC Top Plate: Dipped in Chrome Front Fork Blade: 28" Chromoly Rear Fork Blade: 40" Chromoly Linkage: Aluminum CNC W/ Precision Bearings **Disc Brake Mount Built In **Steer Tube and Fork Blades can all be cut to customize for your bike **MFG in Taiwan Weight: Approx 18lbs **Threadless 1-1/8 Conversion Kit available for an additional $40

The Circus project started as a way to get our slopestyle riders into competition, but it wound up becoming an industry-leading dirt jump fork for riders all over the world. Circus has set the benchmark for everyday riders' jump session requirements and delivered podium results at pro-level competitions for almost a decade. - Coil Spring - ABS+ Compression Damping w/ Jump Stack - Adjustable TPC Rebound Damping - Absolute+ cartridge platform oil damping system: specifically tuned for Dirt Jumping - 20mm hex axle provides superior torsional stiffness - Forged I-beam style crown: bigger, stronger and more durable - 1-1/8" threadless steel steerer and 32mm steel stanchions - Can be reduced to 80mm travel with included spacers

The Machete is purpose-built for slicing trails, with Kwik Toggle compression damping inspired by our renowned Absolute+ technology. Kwik Toggle achieves on/off lockout simplicity in a lightweight, practical package. - TS air spring with in-leg adjustable TPC rebound damping - Kwik-Toggle damper with lockout, adjustable rebound, and high-speed compression - 32mm black anodized stanchions with hollow bore forged aluminum crown - Easily upgradeable to remote using MILO upgrade kit part #314934 - Travel is internally adjustable from 80 to 120mm in 10mm increments - Disc brake only (74mm/6" post-mount) - 27.5x3.0"/29x2.5" maximum tire width

Coil Fans Rejoice! Once again, the Dorado is available with a coil option. The new Dorado Comp features the same 37mm chassis as the Expert but with a more set-it-and-forget-it vibe. The coil spring provides a smooth consistent feel 100% of the time with 0% of any hassle. On the damping side of things, our ABS+ Damper offers a great adjustment range, terrific reliability, and easy serviceability. The Dorado Comp is built for riders who just want to ride and not sweat any of the small stuff. Key Features: - New 37mm chassis results in a massive increase in stiffness and ride quality. The new chassis is 20% stiffer compared to our former 36mm version. - Inverted Design provides an incredibly smooth and consistent feel due to constant lubrication of the bushings and seals. The inverted design also provides a major increase in fore-aft stiffness compared to traditional forks while maintaining torsional compliance which provides more control to the rider over rough terrain. - Coil Spring provides maximum bump sensitivity and simple service procedures. The standard spring rate provided in the fork is a medium rate of 35lb/in. For tuning, there are six spring rates available for this fork; 25lb/in, 30lb/in, 35lb/in, 40lb/in, 45lb/in, and 50lb/in. - ABS+ damper is known for its incredible reliability and easy tunability. Adjustments include a low-speed compression adjustment and a low-speed rebound adjustment. - Fits both 29" and 27.5" wheels. Markings on the outer legs indicate the proper clamping point for the ideal axle to crown measurements depending on wheel size. The fork legs can be used with both wheel sizes. - Two Crown Options are available with this fork. The 47 offset is designed to work with 27.5" wheels and intended axle to crown. The 57 offset crown is designed for 29" wheels and axle to crown. For those looking to run the lower offset crown with 29" wheels please reference our fit document to see if your headtube length is compatible. - TSR Bleed Screws allow you to release excess pressures built up in the outer legs of your fork while riding keeping your fork smooth and supple all day long. Product Details: - 37mm 6000 Series Aluminum stanchions with carbon fiber legs - Externally Adjustable: high-speed compression, low-speed compression, and rebound - Dorado air spring with IRT (Infinite Rate Tune) volume adjuster allows the rider to adjust mid-stroke support and bottom-out progressivity independent of initial spring rate - TPC+ Damper with HBO (Hydraulic Bottom Out) - TSR Bleeders - Includes removable bolt-on fender

The award-winning 36 with FIT GRIP2 4-way adjustable damper features patent-pending Variable Valve Control (VVC) high- and low-speed rebound adjuster, improved compression damping, and less friction overall. With all this and the legendary Fox feel, the 36 offers a level of performance and adjustability sought by today's riders. "Factory" says it all. The best-of-the-best technology we have to offer is available in our Factory Series models with our buttery smooth and ultra durable Genuine Kashima Coat. These products are World Cup proven. Buttery smooth Kashima's distinctive gold color is backed by its high performance attributes—properties that provide an exceptionally smooth feel and extreme durability. GRIP2 — Next-Generation Sealed Cartridge FIT Damper GRIP2 is our next-evolution sealed cartridge FIT system, our highest performing gravity-focused damper. The new damper shares its roots with the original GRIP architecture, but has been seriously enhanced with all-new technology: 4-way adjustability, VVC high-speed rebound circuit, high-performance mid-valve, and overall friction-reducing treatments. EVOL — Air Transfer Port System Our EVOL linear spring curve gives forks and shocks plushness off the top, extra mid-stroke support, and more tunable bottom-out progression, allowing riders to tap into the ideal pairing of front and rear-end feel. FLOAT EVOL Air Spring EVOL technology from rear shocks is integrated into all FOX forks. EVOL increases negative air spring volume, specifically positioned and sized for optimum small bump sensitivity.

The award-winning 36 with FIT4 adjustable damper features patent-pending Variable Valve Control (VVC) high- and low-speed rebound adjuster, improved compression damping, and less friction overall. With all this and the legendary Fox feel, the 36 offers a level of performance and adjustability sought by today's riders. "Factory" says it all. The best-of-the-best technology we have to offer is available in our Factory Series models with our buttery smooth and ultra durable Genuine Kashima Coat. These products are World Cup proven. Buttery smooth Kashima's distinctive gold color is backed by its high performance attributes—properties that provide an exceptionally smooth feel and extreme durability. EVOL — Air Transfer Port System Our EVOL linear spring curve gives forks and shocks plushness off the top, extra mid-stroke support, and more tunable bottom-out progression, allowing riders to tap into the ideal pairing of front and rear-end feel. FLOAT EVOL Air Spring EVOL technology from rear shocks is integrated into all FOX forks. EVOL increases negative air spring volume, specifically positioned and sized for optimum small bump sensitivity.

- Double air spring system with independent positive and negative chambers - Adjustable from 130 to 160mm of travel internally - Redesigned air spring with threadless air seal head for service and travel change ease - Damper: Low speed rebound in addition to high and low speed compression adjustable; with 2.5wt damper oil and 11% lighter viscosity - Air volume adjustment with internal indexed system - Threadless aluminum steerer - 35mm low friction anodized upper tubes with SKF wiper seals - Post mount brake: minimum 180mm rotor with 210mm maximum rotor size - Boost 110: allows for a hub with a wider hub flange that provides the rider with a stiffer wheel for more precise steering - D-Loc 15mm bolt-on thru-axle - 27.5"+: 75mm wide by 739mm tall maximum tire size - 29": 64mm wide by 749mm tall maximum tire size

Yari shares the stiff, hard-hitting chassis as the Lyrik and combines it with the updated DebonAir air spring and proven Motion Control damper. The Yari fork is designed to inspire confidence for those hard-hitting enduro and E-MTB riders alike. - 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 - New graphics package for a fresh, premium look - Motion Control damping featuring low-speed compression adjustment

With bigger bikes come bigger demands. The new Domain takes cues from ZEB, our enduro specialist fork with serious credentials. Domain offers a new burly 38mm chassis, short fender compatibility, and a confidence-inspiring DebonAir air spring matched with a reliable Motion Control RC damper. We even brought the performance of Maxima Plush damping fluid along for the ride. Nothing goes as big as Domain does in value and performance. - 38mm chassis for increased stiffness and rider confidence - Motion Control RC damper featuring low speed compression adjust with externally adjustable dual-flow rebound - Highly tunable DebonAir air spring offers a consistent feel throughout the travel - Maxima Plush damping fluid reduces friction and quiets damper noise - Short fender compatible. RockShox premium fender sold separately. AM Variants include RockShox zip-tie fender - Fits tires up to 2.8" without fenders—use of any fender may reduce tire clearance

One of the most successful and hard-working RockShox forks of all time capitalizes on the innovations born from SID. It features a chassis that combines classic XC performance with light trail duties, while a Motion Control damper completes the package, making Reba more capable than ever before. Features - New graphics package for a fresh, premium look - Highly tunable Solo Air spring - TwistLoc and OneLoc remote compatible

- 38mm chassis for increased stiffness and rider confidence - ButterCups block 20% of high frequency "trail chatter". Limiting these vibrations massively reduces hand and arm fatigue leaving you feeling fresh with more control. - Charger 3 features a completely new Internal Floating Piston (IFP) design with better fidelity, performance and truly independent adjustments without any "cross talk". - DebonAir+ is built to strike the perfect balance of what riders really want: butter-like small bump feel, increased air volume, and higher overall ride height. - Ultimate Bushing Package maximizes the fork's bushing overlap, reducing friction and creating the smoothest ride possible - Pressure Relief Valves eliminate unwanted air pressure build up in the lower leg caused by variations in altitude or temperature - Includes premium short fender

- 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

- 35mm chassis with a focused all-mountain mindset - satisfyingly stiff, efficient and designed to eliminate as much weight as possible. - ButterCups block 20% of high frequency "trail chatter". Limiting these vibrations massively reduces hand and arm fatigue leaving you feeling fresh with more control. - Charger 3 features a new Internal Floating Piston (IFP) design with better fidelity, performance and truly independent adjustments without any "cross talk". - DebonAir+ is built to balance butter-like small bump feel, increased air volume, and higher overall ride height - Ultimate Bushing Package maximizes the fork's bushing overlap, reducing friction and creating the smoothest ride possible - Pressure Relief Valves eliminate unwanted air pressure build up in the lower leg caused by variations in altitude or temperature. - RockShox premium short fender included

- 35mm chassis at home on the trail - stiff, playful and light, really light - ButterCups block 20% of high frequency “trail chatter”. Limiting these vibrations massively reduces hand and arm fatigue leaving you feeling fresh with more control. - Charger 3 features a new Internal Floating Piston (IFP) design with better fidelity, performance and truly independent adjustments without any "cross talk". - DebonAir+ is built to balance butter-like small bump feel, increased air volume, and higher overall ride height - Ultimate Bushing Package maximizes the fork’s bushing overlap, reducing friction and creating the smoothest ride possible - Pressure Relief Valves eliminate unwanted air pressure build up in the lower leg caused by variations in altitude or temperature. - RockShox premium short fender included

The Z1 is freedom from the status quo. Step outside enduro's obsession with counting seconds and go have some fun in the woods. The Z1 is an aggressive all-mountain and enduro fork with a different viewpoint for riders' priorities. Everyone wants suspension performance that's smooth as butter with great traction and control, and that's where the Z1 shines. After that, the Z1 departs from industry norms. More time fiddling with adjustments means less time shredding the trails. The Z1 keeps it simple with intuitive compression sweep adjustment, from locked out to full open. Simple rebound adjustment covers the range from fast to slow rebound for a full range of rider weights and preferences without overcomplicating things. Plus, it's biased towards stiffness, ride performance, and durability, so while it's carrying a few extra grams, you probably won't notice because you're having too much fun. - 36mm stanchions - Enhanced lower leg stiffness with "M" arch design for maximum tire clearance - 15 QR x 110mm Boost axle - FIT GRIP damper with adjustable compression and rebound - FLOAT EVOL air spring

Legends Never Die Back in a big way, the all-new Dorado Pro is ready to turn the suspension world upside down. Featuring an inverted design, carbon upper structure, 37mm stanchions, and refreshed internals the new Dorado Pro is the pinnacle of suspension technology. The new stiffer chassis is paired with an all-new sealed version of our TPC+ damper and improved Dorado Air Spring with an IRT volume adjuster. These technologies combined into one ultimate platform provide more than enough tunability to satisfy any savvy suspension tuner while being so easy to adjust that every rider can dial in their fork with ease. Key Features: - Carbon Fiber Legs and the 37mm chassis result in the stiffest and lightest Dorado to date. The carbon pro chassis is 27% stiffer than the previous 36mm version and 238g lighter than the new 37mm Expert version. They also have looks that can kill. - Inverted Design provides an incredibly smooth and consistent feel due to constant lubrication of the bushings and seals. The inverted design also provides a major increase in fore-aft stiffness compared to traditional forks while maintaining torsional compliance which provides more control to the rider over rough terrain. - Dorado Air Spring system contains a unique balancing valve that equalizes the positive and negative air chambers during the air-fill process resulting in a consistent feel without any flat or dead spots. It also allows easy Travel Adjustability from 180 to 190 and 203mm without the need for any spare parts. - IRT (Infinite Rate Tune) allows for advanced spring tuning by independently adjusting air pressures in the beginning and end stroke. IRT technology creates a secondary positive air spring that affects only the middle-to-end stroke of the fork. This allows the main air spring to be set to lower pressures for improved small bump sensitivity while maintaining mid-stroke support and moderate to aggressive end-stroke ramp-up. - Sealed TPC+ is a velocity and position-dependent damping circuit that maintains light damping through small bumps when the fork is high in its travel. As the fork compresses deeper in the travel the secondary TPC+ circuit engages and increases the damping force for added support and bottom-out prevention. Additionally, an independent Hydraulic Bottom-out circuit further increases the damping force in the final 30mm of travel to soften deep travel events and prevent hard bottom-out. The new cartridge design with spring-backed IFP fully seals damper oil for the most consistent damping on long demanding DH runs. Spring-backed IFP has improved performance during extreme riding, unlike a bladder an IFP pressurizes the oil at the initial stroke eliminating any cavitation for the most consistent damping. - Fits both 29" and 27.5" wheels. Markings on the outer legs indicate the proper clamping point for the ideal axle to crown measurements depending on wheel size. The fork legs can be used with both wheel sizes. - Two Crown Options are available with this fork. The 47 offset is designed to work with 27.5" wheels and intended axle to crown. The 57 offset crown is designed for 29" wheels and axle to crown. For those looking to run the lower offset crown with 29" wheels please reference our fit document to see if your headtube length is compatible. - TSR Bleed buttons allow you to release excess pressures built up in the outer legs of your fork with a simple tap of the button. This keeps your fork smooth and supple all day long. Product Details: - 37mm 6000 Series Aluminum stanchions with carbon fiber legs - Externally Adjustable: high-speed compression, low-speed compression, and rebound - Dorado air spring with IRT (Infinite Rate Tune) volume adjuster allows the rider to adjust mid-stroke support and bottom-out progressivity independent of initial spring rate - TPC+ Damper with HBO (Hydraulic Bottom Out) - TSR Bleeders - Includes removable bolt-on fender

Rebirth of an Icon. The R7 has a vast history of combining a lightweight chassis with performance and reliability. And this latest incarnation of the icon is no different. The new R7 expert pairs superior damping thanks to our 3-position dual piston VTT damper with a lightweight and stiff 32mm chassis. - VTT damper with compression open mode and rebound adjustability - 32mm black anodized 6000 series aluminum stanchions with Reverse-Arch design - Internally adjustable from 120 to 80mm in 10mm increments - Available in two different offsets 44 or 51mm

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

FOX 38 Factory Series Suspension Fork is the long-travel enduro specialist. It redefines what you think a long travel single crown fork is capable of, and sets a new benchmark for confidence, performance, and durability. - The floating axle offers a distinct performance advantage due to its unique ability to match the exact width of the fork’s wheel mounting surface precisely to the front hub flange spacing, thus creating perfect chassis alignment and eliminating unwanted friction between the upper and lower fork legs - Floating axles provide much smoother suspension movement throughout the entire range of the fork’s travel, notably improving sensitivity and overall ride quality - The 38 Fork comes equipped with a quick-release lever operated patent-pending floating axle system, combining the benefit of a floating axle with the ease of a tool-free quick-release - Lower leg bypass channels alleviates air pressure by dramatically increasing air volume within the lower legs and thereby reducing the amount of additional unintended pressure ramping - Lower leg bleeders allow for atmospheric pressure equalization at the simple press of a button - The 38's lower leg arch design pulls out all the stops, shaving every possible gram while making sure not to compromise stiffness or strength requirements of modern enduro and gravity style riding

Premium performance at down-to-earth prices. Judy now includes all of the 30mm MTB and E-MTB forks, with axle and steerer options to match any spec. Gold level gives you aluminum upper tubes and Motion Control damping. Features - New graphics package with E-MTB endorsement option (15x110mm) - Motion Control damping featuring low-speed compression adjustment to lockout - Fits Tires up to 2.8" - Fast Black finished 30mm aluminum upper tubes couple stiffness and lightweight with a premium look - Highly tunable Solo Air spring

Revelation is all grown up and ready to explore, wherever the trail may turn. Value-packed, the Revelation features an updated DebonAir spring paired with a Motion Control damper and 35mm Fast Black upper tubes. - 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 - Motion Control damping featuring low-speed compression adjustment to firm - Chassis is derived from the renowned Pike fork - New graphics package for a fresh, premium look

An entry level fork with the latest features and performance; Judy Silver is built around a brand new chassis derived from the Pike, works with Plus tires up to 2.8 in both the 27.5" and 29" models. Judy Silver features the Motion Control RL damper and is compatible with OneLoc remotes and has Fast Black upper tubes for an all-black look and low friction performance. - 80-120mm travel - External rebound - TurnKey lockout controls - Fast Black upper tubes - Motion Control RL damper - Compatible with OneLoc remote - Solo Air spring

The Circus project started as a way to get our slopestyle riders into competition, but it wound up becoming an industry-leading dirt jump fork for riders all over the world. Circus has set the benchmark for everyday riders' jump session requirements and delivered podium results at pro-level competitions for almost a decade. - Air Spring - ABS+ Compression Damping w/ Jump Stack - Adjustable TPC Rebound Damping - 130mm travel models can be reduced to 120mm and 100mm models can be reduced to 80mm travel using included spacers - 20mm hex axle provides superior torsional stiffness - Absolute+ cartridge platform oil damping system: specifically tuned for Dirt Jumping - Forged I-beam style crown: bigger, stronger, and more durable - Alloy steerer, and 32mm aluminum stanchions

Service kits include dust seals, foam rings, oil seals, air and damper o-rings needed for basic service.

• High-tensile steel construction • Threadless

Own the mountain with the award-winning 36 Factory, featuring high- and low-speed rebound adjuster, improved compression damping and reduced friction for unmatched performance and adjustability. - Genuine Kashima Coating on upper tubes - FIT damper and FLOAT EVOL air spring - Low friction seals for improved performance - Lower Leg Bleeders and Bypass Channels - Floating axles for perfect alignment - Updated Crown Design saves up to 20 grams, and offers significant structural improvements

FOX 38 Factory Series Suspension Fork is the long-travel enduro specialist. It redefines what you think a long travel single crown fork is capable of, and sets a new benchmark for confidence, performance, and durability. - The floating axle offers a distinct performance advantage due to its unique ability to match the exact width of the fork’s wheel mounting surface precisely to the front hub flange spacing, thus creating perfect chassis alignment and eliminating unwanted friction between the upper and lower fork legs - Floating axles provide much smoother suspension movement throughout the entire range of the fork’s travel, notably improving sensitivity and overall ride quality - The 38 Fork comes equipped with a quick-release lever operated patent-pending floating axle system, combining the benefit of a floating axle with the ease of a tool-free quick-release - Lower leg bypass channels alleviates air pressure by dramatically increasing air volume within the lower legs and thereby reducing the amount of additional unintended pressure ramping - Lower leg bleeders allow for atmospheric pressure equalization at the simple press of a button - The 38's lower leg arch design pulls out all the stops, shaving every possible gram while making sure not to compromise stiffness or strength requirements of modern enduro and gravity style riding

FOX 38 Factory Series Suspension Fork is the long-travel enduro specialist. It redefines what you think a long travel single crown fork is capable of, and sets a new benchmark for confidence, performance, and durability. - The floating axle offers a distinct performance advantage due to its unique ability to match the exact width of the fork’s wheel mounting surface precisely to the front hub flange spacing, thus creating perfect chassis alignment and eliminating unwanted friction between the upper and lower fork legs - Floating axles provide much smoother suspension movement throughout the entire range of the fork’s travel, notably improving sensitivity and overall ride quality - The 38 Fork comes equipped with a quick-release lever operated patent-pending floating axle system, combining the benefit of a floating axle with the ease of a tool-free quick-release - Lower leg bypass channels alleviates air pressure by dramatically increasing air volume within the lower legs and thereby reducing the amount of additional unintended pressure ramping - Lower leg bleeders allow for atmospheric pressure equalization at the simple press of a button - The 38's lower leg arch design pulls out all the stops, shaving every possible gram while making sure not to compromise stiffness or strength requirements of modern enduro and gravity style riding - GRIP2 damper includes Fox's patented Variable Valve Control (VVC) technology which allows for external fine-tuning of suspension performance - FLOAT EVOL air spring technology increases negative air spring volume, optimizing small bump sensitivity - Direct mud guard mount - Genuine Kashima Coating on upper tubes - 27.5: 723mm peak tire diameter