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Geometry Concept

In 2014 we introduced a new Stack-to-Reach based geometry concept across our whole road range. Using three different geometries (Sport, Sport Pro and Pro), we have been able to create bikes that fit perfectly to the demands of our customers and professionals across all scenarios.

The Stack-to-Reach Quotient, upon which our concept is based, can be applied across a range of frames. This figure determines the frame’s geometry by looking at its effect on seat position. In order to explain our three geometries, we would like to go over some basic principles and highlight how they affect seat position.

Stack-to-Reach from 1.55

More comfort for more performance. An upright riding position reduces the load placed on the back and shoulders to provide the ideal geometry for endurance riding.

Bike Series

Stack-to-Reach between 1.45 and 1.55

A balanced geometry for enthusiasts. The Sport Pro Geometry lays emphasis on performance while maintaining rider comfort.

Bike Series

Stack-to-Reach under 1.45

Designed for racers and triathletes. The Pro Geometry provides a low and aggressive riding position for better aerodynamics and maximum speed.

Bike Series

What is actually meant when we say stack?

Stack (E) is a measurement taken from the bottom bracket, the only contact point a rider has with the bike that cannot be adjusted. It is measured vertically to determine the difference in height between this point and the top of the head tube.

What advantages does stack measurement have over head tube measurement when comparing two different road frames?

Using head tube length to determine a frame’s cockpit height only works when comparing two frame sizes belonging to the same model. Furthermore, fork length and bottom bracket depth in relation to wheel axles has to remain constant across all frame sizes. Stack measurement is affected by neither of these and determines the precise height difference between the top of the head tube in relation to the bottom bracket, which can then be applied across different frame models.

What does reach mean?

Reach (F) is the length measured from the centre of the head tube to the bottom bracket along a horizontal plane.

How do we work out the Stack-to-Reach Quotient?

When we divide stack measurement by reach measurement, we get the Stack-to-Reach Quotient. This value usually lies somewhere between 1.35 and 1.65.

What advantages does reach measurement have over top tube length when comparing two different road frames?

Using the top tube length to determine the length of a frame makes sense only if the seat tube angle remains constant. For example, combine a slack seat tube angle with a straight seatpost and you can achieve the same saddle position as when you combine a steep seat tube angle with a setback seatpost. Even if head tubes are identically placed on two frames in relation to the bottom bracket, top tube length can still differ. Reach measurement functions independently to seat tube angle and therefore provides a more accurate reading of frame length.

What does the Stack-to-Reach Quotient show us?

The higher the stack value, the higher the Stack-to-Reach Quotient. The same is also the case when the reach value is lower. With this in mind, a Stack-to-Reach value in the upper region between 1.55 and 1.65 would result in a comfortable, in other words short and upright, seating position. We class this in our Sport category.

The opposite is the case for sportier frames. The lower the stack value or the longer the reach, the smaller the Stack-to-Reach Quotient. Values in the region of 1.35 and 1.45 result in a long and low position. We class this in our Pro category, in which we include the Aeroad CF. If a frame’s Stack-to-Reach value lies between 1.45 and 1.55, we often refer to it as having a ‘balanced’ geometry. We class these frames in the Sport Pro category.

  • a Seat tube length
  • b Top tube length
  • c Head tube length
  • d Fork installation length
  • e stack
  • f reach

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