The foundation of securely locking a bicycle is literally that—a physical foundation that provides an immovable anchor which the user can connect the important parts of their bike to.
What follows is a primer on the bike rack, the most important of all bicycle security technologies, with discussioin on makes an acceptable selection as well as an unacceptable one.
To develop a fuller bike parking area, see this bike rack installation guide.
1. The idea of an “acceptable” bike rack
An acceptable bicycle rack is a high‑security rack that physically supports the bicycle frame (often called a “support‑type” rack). Such a high-security support-type rack or high-security frame-lockable rack is designed so that a user can secure their bicycle frame and at least one wheel to the rack with a personal handheld U-lock while keeping the bike upright and stable.
(Note: A “personal handheld U-lock” is different than an “inverted U” bicycle parking rack, the standard for a bike parking rack that this guide will address. Those two “U-shaped” objects work closely together.)
In practice, manufactured high-security support-type racks generally accomodates two bicycle per rack. An unusual exception to a 2-sided rack a rack is one that is custom-designed, such as a fixture that also works an art installation, provided it meets key criteria.
“High‑security” for a bicycle rack means:
- The rack is made from robust, tamper‑resistant materials (e.g., thick steel) that resist cutting and bending.
- It is permanently and securely anchored to a solid base with tamper‑resistant hardware, so the rack itself is not the weak point.
- Its geometry is compatible with secure locks, so users can realistically use a U‑lock (or equivalent) to secure the frame and at least one wheel.
“Support‑type” for a bicycle rack means:
- The rack physically supports the bicycle frame, not just a wheel.
- It provides two or more points of contact so the bicycle remains upright and does not easily tip, twist, or roll.
- The contact points are located where typical bicycle frames can rest securely, across a wide range of bicycle types.
2. Functional requirements
Acceptable racks meet all the following criteria:
- Enable secure locking of the frame: The rack allows the bicycle frame and at least one wheel to be locked to the rack with a standard U‑lock (or equivalent high‑security lock).
- Provide stable two‑point support: The rack supports the bicycle at two or more points so that it remains upright and does not easily twist, tip, or roll.
- Be durable and securely anchored: The rack is permanently and securely anchored to a hard surface (e.g., concrete) with tamper‑resistant hardware. Materials are strong, weather‑resistant, and vandal‑resistant.
- Avoid damage to bicycles: The rack has no sharp edges, pinch points, or shapes likely to bend wheels or scratch frames with normal use.
- Be accessible to all kinds of users and bicycles: Contact surfaces are smooth and compatible with a wide range of bicycles (including step‑through frames, some cargo bikes, and kids’ bikes).
- Provide realistic capacity: Each usable bicycle space must permit independent locking and removal of that bicycle without moving other bikes.
Any rack or installation of a rack that does not meet these criteria is not acceptable, regardless of manufacturer capacity claims.
3. Acceptable rack designs
The following types of rack designs are acceptable when they meet the functional performance standard above and the dimensional/spacing standards elsewhere in this guide.
3.1. Inverted‑U racks (and equivalent)
Other common names: Inverted‑U rack, staple rack, hoop rack, U‑rack.
Description: A simple upside‑down “U” made of steel tubing, anchored at both ends, generally bolted into concrete. Designed to hold two bicycles, one on each side.
The rack’s width is typically around two feet, and can range from just over a foot (the Reliance Foundry R‑8212 is 14.5 inches wide) to about two and half feet (the Madrax Square “UX” Bike Rack is 31 inches wide). It is typically about three feet tall, or within a couple of inches of that.
Acceptability: Considered the preferred standard rack type. Fully supports all bicycle designs, easily accommodates u‑locks, and is simple and intuitive to use.
Acceptable variations:
- Subtly different shapes: Racks that are similar to an upside-down “U” shape but have rounder or squarer corners, or other slight differences. A couple of those are included in the following entries.
- Inverted‑U with cross member: An additional horizontal bar between the legs to provide another convenient locking point, especially for smaller frames and step‑through bikes. Acceptable so long as it easily accomodates locking locking the frame and wheel for bicycles of all sizes and shapes.
- Multiple inverted‑Us on a rail (“racks on rails”): Modules consisting of several inverted‑U racks mounted on a shared base or rail. Acceptable where the module is securely anchored and individual U‑racks maintain required spacing. Can be used for permanent installations or temporary and event use provided they are anchored with secure hardware, such as tamper-resistant screws/nuts to prevent movement or theft.
Bottom line: Inverted‑U racks are the “gold standard” of racks as they provide the simplest, strongest, most accessible options for different sizes and shapes of bicycles and user needs. Most installers should simply select the inverted U.
3.2. Half‑circle / hoop‑style racks
Description: A semi‑circular or arched hoop anchored at both ends, forming a curved support between two bases.
Acceptability: Acceptable where rhe curved portion reaches the main frame area of a bicycle (not just the wheel), and bikes can lean on the hoop and be locked by the frame and wheel to the hoop.
Bottom line: Half‑circle or hoop‑style racks are acceptable where they provide stable support to the bicycle frame and allow secure locking of the frame and at least one wheel. They are essentially a variation of the inverted U.
3.3. Short S‑curve (“swerve”) racks
Description: A short, S‑shaped tube anchored at both ends, forming a gentle curve between two bases. Intended to serve two bicycles, one on each side, similar to an inverted‑U.
Acceptability: Acceptable where each side can be used like an inverted‑U (securely locking the frame and wheel on both sides), and the rack provides two‑point support and does not rely on wheel slots.
Important caveat: This rack is different than the a similarly-sounding rack that is not acceptable–Long multi‑wave “schoolyard” racks that are counted as many spaces but do not provide stable frame support for each bicycle are unacceptable.
Bottom line: Short S‑curve (‘swerve’), like half‑circle / hoop‑style racks, work essentially the same as an inverted‑U rack, allowing secure frame‑and‑wheel locking on both sides and providing two‑point support. Long multi‑wave racks with only single‑point support or wheel‑only locking are not acceptable.
3.4. Post‑and‑ring racks (or ring‑and‑post)
Description: A vertical or leaning post with one or two rings (or other closed shapes, such as a rectangle) at approximately frame height. Bikes lean against the ring and lock the frame and wheel to the ring/post.
Acceptability: Acceptable where the ring is large enough to accept a U‑lock around the frame and wheel (allowing U‑lock attachment around the bicycle frame and wheel and the rack provides stable two‑point support) and the post and ring assembly is robust and permanently anchored.
Important caveat: Post-and-ring racks are prone to having rings that are not large enough to accept all sizes and shapes of bicycles, especially when two are locked on either size.
3.5 Custom racks (sculptural or other artful racks)
Description: Custom-built racks, typically used to present a sculpture or other artful decoration that doubles as useful bicycle rack.
Acceptability: Acceptable where the functional geometry of the design allows U‑locks to secure the frame and at least one wheel, provides two‑point support so the bicycle stands upright, and is constructed and anchored to the same standards as a conventional rack.
Pitfall to avoid: Racks that are primarily sculpture and only offer wheel‑only locking or single contact points are not acceptable, regardless of artistic merit.
Bottom line: Artistic or custom racks are acceptable when they meet the same functional criteria as standard high‑security, support‑type racks: frame‑and‑wheel lockability, two‑point support, durable construction, and permanent anchoring.
3.6. Other support‑type racks
Other support‑type forms (for example, A‑frame or triangle racks that operate like wide inverted‑U’s) may be acceptable if they clearly meet all functional criteria in Section 1. These should be evaluated explicitly against those criteria, with an emphasis on high‑security construction and U‑lock‑compatible geometry.
4. Unacceptable rack types (do not use)
The following rack types are not acceptable according to the conesus of bicycle security professionals. They should generally be avoided and retired in favor of acceptable designs.
4.1. Wheel‑slot (“comb” or “toaster”) racks: Do not use
Description: Racks with parallel slots or thin hoops into which only the front wheel (or sometimes the rear wheel) is intended to be inserted.
Why they are unacceptable:
- Typically allow wheel‑only locking; the frame cannot easily be secured with a U‑lock.
- Provide poor support; bikes are easily knocked over.
- Frequently bend or damage wheels when bikes are pushed or fall.
4.2. Long multi‑wave (“schoolyard”) racks counted by crest: Do not use
Description: Continuous wave‑shaped racks marketed as multi‑bike racks, often counted as one space per crest or valley of the wave.
Why they are unacceptable:
- Typically do not allow independent, secure frame‑and‑wheel U‑locking for each “advertised” space.
- In practice, bikes usually contact the rack at a single point, leading to instability.
- The practical capacity is much lower than the nominal capacity.
- Are generally not of high-security construction; furthermore, are prone to one point of failure exposing many bicycles to theft.
4.3. Coathanger racks: Do not use
Description: Racks that resemble a “coat hanger” bar with multiple angled arms or short protrusions intended to hold bikes by the top tube or to hang them partially off the ground.
Why they are unacceptable:
- Typically not allow easy frame‑and‑wheel U‑locking to a robust, continuous element.
- Typically support the bike at a single point, often only by the top tube.
- Create usability and accessibility issues for many riders: They can be difficult or impossible for many people to lift bikes into position; incompatible with many frame types (step‑through, some e‑bikes, cargo bikes, kids’ bikes, some adaptive cycles), and cause bikes to swing into each other, increasing the risk of damage.
4.4. Single posts or bollards without rings: Do not use
Description: Simple posts or bollards without any ring, hoop, or extended element to stabilize and secure the bicycle.
Why they are unacceptable:
- Rarely allow secure U‑lock attachment to the frame and wheel in a stable position.
- Offer very limited support; bikes are prone to tipping and twisting.
4.5. Low wheel stands: Do not use
Description: Very low hoops, spring‑loaded wheel clamps, or short fixtures that contact only the lower wheel and do not extend up to the frame triangle.
Why they are unacceptable:
- Do not reach the frame triangle and therefore do not support frame‑and‑wheel U‑locking.
- Provide minimal stability and can damage wheels.
5. Potential specification language
For use in codes, standards, RFPs, and drawings, the following language can be used summarize these requirements:
Racks allow users to lock the bicycle frame and at least one wheel with a standard U‑lock or equivalent (NACTO, 2014; Boulder, B.R.C. §9‑9‑6(e) 2025).
Inverted‑U (“staple”) racks are intended to serve bikes on both sides of the rack. Layouts provide space for that two‑sided use.
Racks support the bicycle in at least two points of contact so it does not tip over or twist (NACTO, 2014).
Rack placement and spacing avoids interference between adjacent bikes: handlebars, pedals, baskets, and trailers do not routinely collide if users park normally (Boulder, B.R.C. §9‑9‑6(e) 2025).
Racks are designed and finished to avoid damage to bicycless—no sharp edges, rough welds, or abrasive contact surfaces (Boulder, B.R.C. §9‑9‑6(e) 2025).
Clearances prevent frequent scraping of bikes against walls, posts, or other racks (NACTO, 2014).
Racks are securely anchored to concrete or similarly durable paving with tamper‑resistant anchors, so racks cannot be easily removed (Boulder, B.R.C. §9‑9‑6(e) 2025).
Racks are of solid, vandal‑resistant construction, resistant to rust, corrosion, and cutting or prying with common tools (Boulder, B.R.C. §9‑9‑6(e) 2025; NACTO, 2014).
As an alternative, here is a summary statement that combines all those items: “Bicycle parking shall be provided using high‑security, support‑type, U‑lock‑compatible racks that allow the bicycle frame and at least one wheel to be locked with a standard U‑lock, provide at least two points of support to prevent the bicycle from tipping, and are constructed of durable materials and permanently anchored. Acceptable rack types include inverted‑U racks and their variations, post‑and‑ring racks, short S‑curve (‘swerve’) racks that function equivalently to inverted‑U racks, half‑circle/hoop racks, and art racks whose functional geometry meets these criteria. Wheel‑slot (‘comb’/‘toaster’) racks, long multi‑wave racks that permit only wheel‑locking or single‑point support, coathanger‑type racks, single‑post stands without rings, and low wheel‑only stands are not permitted as compliant bicycle parking.”
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