Editing Inline skates (section)

=== Wheel structure ===

{{multiple image
 | direction = horizontal
 | total_width = 260
 | image1 = Gordon K Ware-US3287023A-1966-Roller skate-Adjustable rockered frame-Patent Drawing-FIG 3 Wheel.png
 | image2 = Chicago Roller Blade-inline skate from ca 1965-patented by Gordon Ware-pic by Ojibwa-P1360137.jpg
 | footer = Rubber wheel & press-fit bearing
}}

{{multiple image
 | direction = horizontal
 | total_width = 260
 | image1 = Morris L Maury Silver-US3880441A-1975-Tandem roller hockey skate-Patent Drawing-FIG 2 Wheel.png
 | image2 = Scott Olson-Early Rollerblade Prototype-CCM Super Tacks with Super Street Skate-2010-02-11.jpg
 | footer = bearings enclosed by metal discs
}}

From the 1910s to the 1970s, many wheeled skates served as precursors to modern inline skates. Most of these early skates featured small wheels made of rubber or rubber reinforced with fibers, often with relatively simple constructions. In many cases, the wheel was merely a rubber ring shaped like a donut, with a bearing cylinder press-fit into its hollow center – an example of which can be seen in the 1966 Chicago Roller-Blade.<ref name="Gordon-Ware-patent-US3287023A"/> Other designs incorporated two metal discs to enclose the bearing cylinder more securely within the rubber wheel, as seen in the 1975 Super Sport Skate.<ref name="maury-silver-tandem-skate-1975"/>

These early rubber wheels were designed to flex under load, providing grip on road surfaces. Nevertheless, the same elasticity that enhanced their performance also made them increasingly unsuitable for securely housing precision ball bearings, which inline skates began adopting from roller skates in the 1980s. A misaligned bearing could cause the wheel to tilt, resulting in constant dragging against the frame. This friction not only impaired performance but also generated heat, which could soften the wheel and further compound the misalignment issue.<ref name="hirschmugl-august-skate-wheel-plastic-hub-patent-1954">{{Cite patent
|country=US
|number=2697010
|fdate=1951-07-13
|pubdate=1954-12-14
|gdate=1954-12-14
|title=Roller skate wheel
|inventor1-first=Hirschmugl Robert
|inventor1-last=August
}}</ref><ref name="usenet-chen-FAQ-inline-wheels">{{cite newsgroup
 | title = Skate FAQs: Wheels and Hop-up Kits
 | author = Anthony D. Chen
 | date = 1992-05-17
 | newsgroup = rec.skate
 | url = http://skatefaq.adchen.com/wheels.html
 | url-status=live
 | access-date = 2025-03-29
 | archive-url = https://archive.today/20250329231124/http://skatefaq.adchen.com/wheels.html
 | archive-date = 2025-03-29
}}</ref>

[[File:Hirschmugl Robert August-US2697010A-1954-Roller skate wheel-Patent Drawings-Rearranged.png|thumb|right|260px|First plastic hub (roller skates)]]

To address this in roller skates, metal bushings were introduced to hold two ball bearings and a spacer in precise alignment at a 90° angle to the wheel axle. While effective, these bushings added weight and introduced new issues such as metal grinding noises. As plastic became more common, metal bushings were replaced by injection-molded plastic hubs. These single-piece hubs not only securely encased the bearing assembly but also interlocked with the elastic wheel without additional hardware. Furthermore, plastic hubs reduced overall wheel weight, unlike metal bushings, which increased it.<ref name="hirschmugl-august-skate-wheel-plastic-hub-patent-1954"/>

{{multiple image
 | direction = horizontal
 | total_width = 380
 | image1 = Brennan J Olson-US4909523A-1990-Inline roller skate-Patent Drawing-FIG 5 6-urethane tire interlocked with plastic hub.png
 | image2 = Rollerblade-Lightning TRS-Team Rollerblade Series-1988-IMG 5722-bottom view-FRD.png
 | footer = Polyurethane tire molded over a plastic hub - 1988 Rollerblade Lightning patent (left) and skate (right)
}}

In the 1980s, Rollerblade collaborated with Kryptonics to develop polyurethane wheels for inline skates. The inline industry adapted hub innovations from roller skates, integrating them into inline wheels. These wheels were manufactured by placing a plastic hub at the center of a mold and then pouring molten polyurethane around it. The liquid polyurethane flowed into cavities and holes in the hub before settling. As it cooled and solidified, it formed a secure interlock with the hub.{{efn-ua|name=notes-on-brennan-olson-1987-lightning-patent}}<ref name="brennan-olson-1987-patent-modern-inline-skates"/>{{efn-ua|name=ricardo-lino-with-tony-gabriel-tour-wheel-factory-notes}}{{efn-ua|name=kryptonic-rollerblade-wheel-collab-1980s|
Page 79 of Skaters magazine from 1990 features a Kryptonics ad showing the cross section of a Kryptonics wheel with polyurethane molded over a hub through holes in its interlock rim. Page 77 of the same 1990 Skaters magazine features a Rollerblade ad stating that Kryptonics is the official wheel supplier for rollerblade skates.<ref name=Shevelson-golden-days-of-skating/>}}

[[File:Wheel assembly cross section-Bearings Spacer installed into hub with axle-Inline skates-Side view-Bearings Not Preloaded-IMG 7773-bg-FRD.png|thumb|right|180px|Wheel cross section]]

Modern inline wheels consist of two main components: an outer '''polyurethane tire''', shaped like a donut, and an inner '''plastic hub''', also known as a '''core'''. The hub features a hollow center designed to accommodate a spacer and two ISO 608 ball bearings. Made of hard plastic, the hub securely holds the bearings in place through a friction fit - something the softer polyurethane tire cannot achieve. On the other hand, the soft polyurethane tire is able to deform upon ground contact, cushioning the landing and gripping the ground.<ref name="brennan-olson-1987-patent-modern-inline-skates"/>{{efn-ua|name=ricardo-lino-with-tony-gabriel-tour-wheel-factory-notes}}<ref name="le-roller-en-ligne-on-physics-of-inline-skate-wheel">{{cite web
|url=https://www.rollerenligne.com/materiel/physics-of-the-inline-skate-wheel/
|title=Physics of the inline skate wheel
|website=Le Roller en Ligne
|url-status=live
|archive-url=https://web.archive.org/web/20250322134824/https://www.rollerenligne.com/materiel/physics-of-the-inline-skate-wheel/
|archive-date=2025-03-22
|access-date=2025-03-27
}}</ref>