Diamond frame
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The diamond frame developed by Humber in 1890 is the most common frame shape on bicycles , especially men's bikes. The diamond frame has proven to be the cheapest shape in the course of the history of the bicycle , even if there were numerous alternatives. The basic shape of the diamond frame emerged after 1888 with the advent of low-profile safety wheels and pneumatic tires in Europe. These wheels were originally called "Rover", as bicycles are still called in Polish today.
description
The diamond frame got its name from its shape as a diamond , made of top tube , down tube , seat stay and chain stay . The "Rover", one of the first low wheels to be built in England and produced in large numbers , had this shape. The head tube and seat tube were added later. The correct translation of the appropriate English term diamond frame should have been diamond-shaped frame . In English, the diamond means both diamond and rhombus.
Frame sizes
The frame height is usually measured from the center of the bottom bracket to the top edge of the saddle sleeve. In the case of frames from the Italian manufacturer de Rosa , however, 15 mm must be added to the specified dimension, as these frames are measured differently. To determine the optimal size of a frame for the first time, the inside leg length is decisive, but it may be sufficient to consider the body size instead. Another important factor is the length of the top tube, which has a decisive influence on how stretched the position of the upper body is on the bike. As the frame size increases, the length of the top tube also increases and the handlebars move further away from the saddle. A smaller frame than the inside leg length would allow is then compensated by pulling out the seat post. The usual way of measuring the size of a bike a hundred years ago using the wheels (26 or 28 inches) does not say anything about the size of the bike today. A low frame with 28 tires results in a much smaller bike than a large frame with 26 tires. The size specifications in the table below are approximate values that relate to typical frame geometries with a horizontal top tube; the dimensions are not correct for bikes with a sloping top tube.
| Body size [m] |
Frame height (men) [cm] | |||
|---|---|---|---|---|
| Mountain bike |
Touring bike ATB trekking bike |
Travel bike | Racing bike | |
| 1.65 | 41-44 | 46-48 | 48-50 | 50-52 |
| 1.70 | 44-46 | 48-50 | 50-52 | 53-55 |
| 1.75 | 46-48 | 50-52 | 52-55 | 55-57 |
| 1.80 | 48-50 | 52-55 | 56-58 | 57-59 |
| 1.85 | 50-52 | 56-58 | 59-60 | 59-61 |
| 1.90 and more | 52-54 | 58-61 | 60-64 | 61-64 |
Since women of the same height often have longer legs, they are usually better off with a larger frame. Cheap frames from American manufacturers are often given in clothing sizes (S, M, L, XL). The coarse gradation results in fewer different frame sizes, which lowers manufacturing costs.
Alternatives
Gooseneck frames are often used for women's bikes, with the bike either having a larger down tube or two down tubes, which are curved in the bottom bracket area. Women's frames with two straight down tubes are mainly used for sporty bicycles. A special form is the Pedersen , which has a higher seating comfort with less mass and higher stability. A form of the X-frame can often be found on newer mountain bikes, in particular those with frame springs, as well as Bonanza bikes and folding bikes.
variants
Because of its good properties (high rigidity with low weight), the diamond frame is used with modifications even on extravagant bicycles. Typical modifications are in detail:
- A sloping top tube (sloping frame) is standard on mountain bikes and is also used on racing bikes . The material saved is intended to reduce weight and increase freedom of movement when dismounting. The weight saving is only achieved with expensive bikes, since the heavy seat posts common in the mass market actually increase the overall weight of the bike. Another disadvantage is that smaller frames are less torsion-resistant than large ones.
- , Raised chainstays (Elevated chain stays) allow to place the bottom bracket higher, whereby the danger of touchdown of the pedals is reduced when a steep curve position (see lean angle ). However, with this frame geometry, the driver's feet at the traffic lights are no longer enough to touch the ground, you have to slide off the saddle. In this variant, the chain usually runs completely below the chain stay; in this case it can be exchanged without opening it.
- The diameters of the top and bottom tubes are increased for materials with poor load-bearing capacity such as aluminum (further physical explanation under bicycle frames ). A side effect is the larger surface for striking advertising stickers.