Editing Inline skates (section)

=== Wheel diameter and profile ===

[[File:Inline skate wheels-Common profiles and diameters-2025.svg|thumb|right|260px|Common diameters and profiles]]

Inline skate wheels in the 2020s range from as small as 55mm to as large as 125mm in '''diameter'''.<ref name="vegter-everthing-about-wheel-diameter">{{cite web
|url=https://www.thisissoul.com/blogs/hardware-insights/everything-about-wheel-diameter
|first1=Ivo
|last1=Vegter
|title=Everything about wheel diameter
|website=This Is Soul
|others=Also reference the companion video shown in the article
|url-status=live
|archive-url=https://web.archive.org/web/20250404023645/https://www.thisissoul.com/blogs/hardware-insights/everything-about-wheel-diameter
|archive-date=2025-04-04
|access-date=2025-04-04
}}</ref><ref name="powerslide-download-guides-wheels"/> However, their width remains industry-standard at 24mm, regardless of size. Wheel frames are designed for specific setups, accommodating a set number of wheels of particular diameters. Despite these variations, all frames assume a uniform 24mm '''hub width''' and polyurethane tires no wider than 24mm.<ref name="le-roller-en-ligne-on-physics-of-inline-skate-wheel"/><ref name="usenet-chen-FAQ-inline-wheels"/><ref name="liveabout-carlesa-williams-wheels-101">{{cite web
|url=https://www.liveabout.com/inline-skate-wheels-4122926
|first1=Carlesa
|last1=Williams
|title=Inline Skate Wheels 101
|date=2017-10-25
|website=LiveAbout
|url-status=live
|archive-url=https://web.archive.org/web/20250404024354/https://www.liveabout.com/inline-skate-wheels-4122926
|archive-date=2025-04-04
|access-date=2025-04-04
}}</ref>

Wheel '''profile''' refers to the shape of the wheel’s '''contact surface''' when viewed head-on, that is, the portion of the wheel that touches the ground. While any wheel diameter can, in theory, be paired with any profile, certain combinations prove optimal for different skating disciplines.<ref name="liveabout-carlesa-williams-wheels-101"/><ref name="vegter-everthing-about-wheel-profile">{{cite web
|url=https://www.thisissoul.com/blogs/hardware-insights/everything-about-wheel-profile
|first1=Ivo
|last1=Vegter
|title=Everything about wheel profile
|website=This Is Soul
|others=Also reference the companion video shown in the article
|url-status=live
|archive-url=https://web.archive.org/web/20250404030250/https://www.thisissoul.com/blogs/hardware-insights/everything-about-wheel-profile
|archive-date=2025-04-04
|access-date=2025-04-04
}}</ref>

{{multiple image
 | direction = horizontal
 | image1 = Razors Shift Pro Jeph Howard 2 60mm 90A aggressive wheel w bearings-IMG 6607-bg-FRD.png
 | image2 = Razors Shift Pro Jeph Howard 2 60mm 90A aggressive wheel w bearings-IMG 6615-bg-FRD.png
 | total_width = 170
 | footer = Flatish profile (60mm)
}}

Some inline wheels feature a '''flat''' contact profile, resembling car tires with a rounded rectangular shape. This shape provides a stable upright rolling experience with a strong grip on the ground, due to the larger surface area. Flat-profile wheels work well for disciplines that keep skates upright while rolling, such as aggressive skating.<ref name="inlineskates-buying-guide-inline-skate-wheels"/><ref name="usenet-chen-FAQ-inline-wheels"/> Typical '''aggressive wheels''' are relatively '''small''', ranging from 55mm to 64mm in diameter. '''Grindwheels''', installed as middle wheels, are even smaller, typically under 50mm. Made from hard polyurethane or plastic, they have reduced traction to minimize wheel bite during a grind. However, where grip is needed, such as during stair bashing, the flat profile’s large contact surface helps compensate for the grindwheels' inherently low traction.<ref name="skatepro-aggressive-skate-wheels">{{cite web
|url=https://www.skatepro.com/en-us/c44.htm
|title=Aggressive Skate Wheels
|website=SkatePro
|url-status=live
|archive-url=https://web.archive.org/web/20250405010549/https://www.skatepro.com/en-us/c44.htm
|archive-date=2025-04-05
|access-date=2025-04-05
}}</ref><ref name="gorski-skate-o-pedia-aggressive-skates"/><ref name="vegter-everthing-about-wheel-diameter"/><ref name="vegter-everything-about-grindwheels"/> In the 1990s, aggressive wheels and grindwheels trended toward completely flat profiles. However, in the 2020s and beyond, aggressive skaters began favoring wheels with slightly rounder profiles, offering a balance between stability and maneuverability.<ref name="vegter-everthing-about-wheel-profile"/>

{{multiple image
 | direction = horizontal
 | image1 = Labeda Gripper Asphalt 80mm 85A inline skate wheel-IMG 6707-bg-FRD.png
 | image2 = Round profile and edging angles-Labeda inline skate wheel-80mm 85A-IMG 6359-FRD.png
 | total_width = 310
 | footer = Round profile (80mm) and 3 edging angles
}}

Most inline wheels have a '''round''' profile rather than a flat one. This is because skaters don't always roll with their skates perfectly upright. Much like ice skating with blades, many inline skating techniques involve '''edging''' - that is, skating on the side of the wheels. This requires the skate to tilt at various angles, depending on the move being performed.{{efn-ua|name="outside-inside-edges-terms"|
Inline skating adopts the terms '''outside edge''' and '''inside edge''' from ice skating, even though inline wheels lack the sharp dual edges of ice blades. The outside edge refers to the side of the wheel facing away from the skater's body, while the inside edge is the side facing inward.<ref name="rollerblades-dryland-training-1985"/>{{rp|27–31,41–42,49–52}}
}} A round profile maintains a consistent, usable contact surface across different edging angles, even if that surface is smaller than what a flat-profile wheel provides when fully upright. Disciplines like '''inline hockey''' and '''freestyle slalom''' typically favor round-profile wheels of '''smallish''' to '''medium''' size, with diameters no larger than 80mm.<ref name="liveabout-carlesa-williams-wheels-101"/><ref name="vegter-everthing-about-wheel-profile"/><ref name="powerslide-download-guides-wheels"/>

{{multiple image
 | direction = horizontal
 | image1 = Undercover Team Blank 110mm 86A inline skate wheel with Bones REDS bearings-IMG 4971-bg-FRD.png
 | image2 = Bullet profile-striding and gliding angles-Undercover inline skate wheel-110mm 86A-IMG 6784-FRD.png
 | total_width = 330
 | footer = Bullet profile (110mm) and striding vs gliding
}}

At the opposite end of the spectrum from the flat profile is the '''bullet''' profile, also known as the pointy, thin, narrow, or elliptical profile. This shape is usually found in '''larger''' wheels ranging from 90mm to 125mm in diameter. The combination of a bullet profile and large diameter serves the unique demands of '''speed skating''', where racers aim to satisfy two seemingly conflicting goals.<ref name="miller-get-rolling-2003"/>{{rp|51–52}}<ref name="le-roller-en-ligne-on-inline-wheels"/><ref name="vegter-everthing-about-wheel-profile"/><ref name="welch-demystify-inline-disciplines"/>

The first goal is to maximize [[Friction#Static friction|static friction]] between wheel and ground during the stride phase with a deep edging angle, converting as much energy as possible from a lateral push-off into forward kinetic motion. The bullet profile supports this by offering a generous contact surface when the skate is deeply tilted, effectively extending the power phase of the stride, covering a large striding distance.<ref name="le-roller-en-ligne-on-physics-of-inline-skate-wheel"/><ref name="publow-speed-skating-1999"/>{{rp|316}} The second goal is to minimize rolling friction, more appropriately called [[rolling resistance]], during the glide phase. When the skate returns to an upright position, the bullet profile offers a small point of contact with the ground, reducing rolling resistance and enabling longer, faster glides with minimal energy loss.<ref name="le-roller-en-ligne-on-physics-of-inline-skate-wheel"/><ref name="publow-speed-skating-1999"/>{{rp|316}}

[[File:Bont High Roller G4 110mm 85A and 83A.jpg|thumb|right|220px|Large 110mm racing wheels]]

In addition, '''large''' wheels function like [[flywheel]]s, storing substantial [[rotational energy]], which helps the racer reach and maintain high speeds over long distances. The [[gyroscope|gyroscopic effect]] of these large spinning wheels further enhances efficiency by stabilizing the skate’s direction, promoting straight-line tracking and reducing energy lost to unwanted lateral drift. However, this benefit comes with a trade-off: larger wheels have greater mass, which makes them harder and slower to accelerate.<ref name="le-roller-en-ligne-on-physics-of-inline-skate-wheel"/><ref name="powell-svensson-inline-skating"/>{{rp|24–25}}

In contrast, '''small''' wheels are easier to accelerate due to their lower rotational inertia, enabling faster starts and quicker maneuvers. They also lower a skater's center of gravity, improving control and stability. However, smaller wheels can result in a bumpier ride, as they struggle more over obstacles like bumps, cracks, sticks, and pebbles.<ref name="le-roller-en-ligne-on-inline-wheels"/><ref name="skamidan-inline-skating-in-brief"/><ref name="vegter-everthing-about-wheel-diameter"/>