A step-through frame is a type of bicycle frame

Bicycle frame

A bicycle frame is the main component of a bicycle, on to which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles, a main triangle and a paired rear triangle...

, often used for utility bicycle

Utility bicycle

A utility bicycle is a bicycle designed for practical transportation, as opposed to bicycles which are primarily designed for recreation and competition, such as touring bicycles, racing bicycles, sport/training bicycles, and mountain bicycles. The vast majority of bicycles can be found in the...

s, with a low or absent top tube or cross-bar

Crossbar

- Structural engineering :* A primitive latch consisting of a post barring a door* The top tube of a bicycle frame* The horizontal member of many sports goals including those for hockey, association football, rugby league, rugby union and American football...

.

Traditionally, bicycles with a step-through frame were known as "Ladies, "Women's", or "Girls, mainly for their advantage to riders wearing skirt

Skirt

A skirt is a tube- or cone-shaped garment that hangs from the waist and covers all or part of the legs.In the western world, skirts are usually considered women's clothing. However, there are exceptions...

s or dress

Dress

A dress is a garment consisting of a skirt with an attached bodice or with a matching bodice giving the effect of a one-piece garment.Dress may also refer to:*Clothing in general*Costume, fancy dress...

es. Bicycles with a high top tube (cross-bar), known as a diamond frame, were known as "Men's", "Gents, or "Boys. As a result of changing clothing styles since the late 20th century, descriptions that describe the frame style, rather than the presumed gender of the rider, are becoming increasingly common.

Advantages

• less risk of stretching or ripping clothes when mounting the saddle
• the rider can wear a skirt (also requires a skirt guard
  Skirt guard
  A skirt guard or coatguard is a device fitted over the rear wheel of a bicycle to prevent a long skirt, coat or other trailing clothes or luggage catching in the wheel, or in the gap between the rim and the brakes....
  
   and possibly a chain guard)
• very quick to mount and dismount, so is suitable for delivery bicycles, or any journey with many stops
• suitable for elderly and others with restricted agility
• potentially safer than a high crossbar; a rider who loses balance can step through the bicycle without becoming entangled
• compactness provides a popular starting point for folding bicycle
  Folding bicycle
  A folding bicycle is a bicycle designed to fold into a compact form, facilitating transport and storage. When folded, the bikes can be more easily carried into buildings and workplaces or onto public transportation or more easily stored in compact living quarters or aboard a car, boat or plane...
  
  s.

Disadvantages

• Heavier, and therefore slower. Compared to a traditional diamond frame consisting of two near-triangles, alternative open or step-through frame designs of equivalent construction have been shown to be demonstrably less strong using finite element structural analysis
  Finite element method
  The finite element method is a numerical technique for finding approximate solutions of partial differential equations as well as integral equations...
  
  . Consequently step-through frames must be made substantially stronger, accomplished by thicker gauge tubing, the use of additional gusseting members, and/or monocoque
  Monocoque
  Monocoque is a construction technique that supports structural load by using an object's external skin, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork...
  
   frame construction, all of which add weight over a traditional diamond design.
• Reduced rigidity and frame life, unless reinforced. While a certain amount of vertical frame flexibility is desirable for a compliant ride on a bicycle with an unsuspended rear wheel, any lateral flexing or excessive vertical flex due to loss of the primary triangle can result in reduced frame life and a loss in pedaling efficiency.

• Fewer places to mount accessories, e.g. an air pump or water-bottle.

Mixte

One particular type of step-through frame is called a mixte. In a mixte frame, the top tube of the traditional diamond frame is replaced with a pair of smaller tubes (lateral tubes, or lats) running from the top of the head tube

Head tube

Most bicycles, tricycles and motorcycles have a tubular frame. The front fork pivots within the head tube . On a motorcycle, the "head tube" is normally called the steering head...

 all the way back to the rear axle, connecting at the seat tube on the way. The normal seat stays and chain stays are retained. This provides the lower standover height of a step-through frame bicycle while avoiding some of the additional stresses the step-through frame bicycle places on the seat tube.

"Mixte" is a direct appropriation of the French word meaning "mixed" or "unisex". The usual North American bicycle industry

Bicycle Industry

The Bicycle Industry or Cycling Industry can broadly be defined as the industry concerned with bicycles and cycling. It includes at least bicycle manufacturers, part or component manufacturers, and accessory manufacturers...

 pronunciation of this loan word is ˈmɪkstiː.

Cross

Another type of step-through frame is called a cross. The cross frame consists mainly to two tubes that form a cross: a seat tube from the bottom bracket to the saddle, and a backbone from the head tube to the rear hub. and