Cyclopedia

The Bike Insights Upright/Aggressive scale is based on analysis of a bike’s proportions relative to similar sized bikes in the same category. All else being equal, a more “upright” bike will position the handlebars closer to a rider, resulting in a more vertical seated position whereas a more “aggressive” bike will position the handlebars farther away from the rider and result in a more horizontal, “leaned-over” position.

Important note: Analysis is category-specific and assumes a convential cockpit setup for its category. Analysis is not applicable when comparing bikes of different categories.

Two distinct methods exist for measuring the length of a bike fork:

Bike companies will often fail to clearly specify the method used to measure a fork in their geometry tables, so it may be necessary to check for an accompanying diagram. If it's unclear which method a bike company uses, select Fork Length: Unknown.

The more common method of specifying fork length on modern bikes, measured in a direct line from the fork crown to the axle. Length-on-Axis is the less common method of specifying fork length on modern bikes, measured from the fork crown to the axle along the steering/head tube axis.

Be aware that bike companies will often fail to clearly specify the method used to measure a fork in their geometry tables, so it may be necessary to check for an accompanying diagram. If it's unclear which method a bike company uses, select Fork Length: Unknown.

The less common method of specifying fork length on modern bikes, measured from the fork crown to the axle along the steering/head tube axis.

Be aware that bike companies will often fail to clearly specify the method used to measure a fork in their geometry tables, so it may be necessary to check for an accompanying diagram. If it's unclear which method a bike company uses, select Fork Length: Unknown.

The maximum length that a suspension fork can shorten by when fully compressed.

Fork travel is often used as shorthand for the overall length of a suspension fork, although the more precise measurement is Axle-to-Crown. Oftentimes mountain bikes can work with a range of fork lengths, but are designed to work best within a smaller range of lengths.

Since a bike's geometry can change dramatically depending on the fork length, it is critical that bike companies specify the Axle-to-Crown or Fork Travel and Fork Sag used when generating the data in their geometry tables. If this is unknown, our ability to assess the design of the bike is severely compromised.

The maximum length that the rear suspension of a full-suspension bike can shorten by when fully compressed.

Rear travel is a measurement just for the rear shock on a full-suspension mountain bike. It often the same as fork travel, but not always.

Stack is the vertical distance from the center of the bottom bracket to the top of the head tube.

Reach is the horizontal distance from the center of the bottom bracket to the top of the head tube.

The ratio of Stack and Reach expressed as Stack ÷ Reach. The larger the value, the more upright a bike is.

However, this ratio is only useful when comparing bikes of similar size since this ratio is expected to change as bikes scale up in size. The ratio tends to increase as road bikes become larger and decrease as mountain bikes become larger.

The amount a suspension fork compresses when a rider is on the bike, expressed as a percentage of the Fork Travel. For example, 20% sag for a 120mm-travel fork means that 24mm of travel is ""used up"" when the rider is sitting on the bike.

Since a bike's geometry can change dramatically depending on the fork length, it is critical that bike companies specify the Fork Sag used when generating the data in their geometry tables. If this is unknown, our ability to assess the design of the bike is severely compromised.

With few exceptions, road bikes have non-suspension corrected forks while mountain bikes have either a rigid suspension-corrected fork, front suspension, or front and rear suspension.

Width of the tire that the bike geometry was calculated using. This can be, in order of preference:

1. A width that is made explicit in the brand's geometry chart.
2. The width of tire that the complete bike ships with.
3. The maximum specified tire width (often this is not in the geometry table but can be found elsewhere in a bike's list of specifications).

This attribute is important because it establishes under what conditions the standover and bottom bracket height were measured. Knowing these conditions allows us to calculate a more precise standover and bottom bracket height for alternate wheel configurations.

The closest distance from the the pedal spindle to the front tire. The closer the distance, the more likely Toe Overlap is to occur.

This value is useful for comparing relative distances between bikes/builds. It does not take into consideration the distance from the pedal spindle to the front end of the shoe or to fenders if they are installed.

The length of the top tube is commonly measured three ways:

The distance between the point where the steering axis of the front wheel intersects the ground and the point where the front tire contacts the ground. In this sense, the contact patch of the tire “trails” behind the steering axis. The greater this distance, the “higher” the trail and the lower the distance the “lower” the trail.

In general, mountain bikes have a higher trail figure (over 75mm) whereas typical road bikes have a trail figure between 55mm and 70mm depending on the expected riding conditions. “Low-trail” bikes, designed to carry cargo on the front of the bike, have a trail figure of less than 45mm.

The distance the front axle lowers towards the ground when the handlebars are turned 90 degrees. This is useful for considering the degree to which the bike will lean into turns and be affected by front-loaded. A larger wheel flop value indicates more front end drop when turning.

For the same trail figure, a steeper head tube angle will result in lower wheel flop than one with a slacker head tube angle.

Select a common wheel size or enter the rim’s Bead Seat Diameter (the measurement of the “shelf” inside the rim that the tire fits around).

For bikes that are designed to accommodate multiple rim diameters (e.g. either 29” with narrower tires or 27.5” with wider tires), please create separate builds for each configuration.