Until the 2000s the shape of the frames of all the bikes were the same. After this date have been placed on the market other forms, mostly similar to that shown in figure 2 on the left .

Initially the new forms were produced as part of the walking bike / city bike where the cyclist ride for a short distance and then everything is fine but the surprising thing is that within a few years the slope are also entered in cycling where the amateur cyclist using the bike as professional.


What are the advantages of the slope?

For manufacturers have been at least two advantages because being able to create a fashion they could sell a very large number of new bikes that have replaced the traditional models and reduced distribution costs as these frames are smaller than those traditional and are produced in a smaller number of measurements than the traditional bike with horizontal pipe parallel to the road surface.

Cyclists have advantages with the slope?

the opinion of the writer Cyclists have had no benefit from these new forms, those who want to discover the reason being read on this page.

Have altered the shape of the frame, even in the days of Coppi and Bartali had assumed its final shape, has created some problems for those who would like to continue to ride in a professional manner with the slope.

The slope frames are smaller than traditional frame and their measures shall be established by the manufacturer that ranks them in sizes, using the same symbols used in clothing: S (small), M (Medium). L (Large) etc..

The classification of the measurements of the slope frames no longer based on the length of the crotch used in traditional frames was an obligatory choice as the length of the column is no longer representative of the frame frame size.

The above has practical consequences which we will examine now.


The choice of frame size suitable for each individual cyclist and become more approximate

With slope frames, rather than have about 12 measurements for each type of bicycle, as is the case for traditional frames professional only 4 with, at most 5 for which the choice of the measure of the frame suitable for each individual become more summary because there unless measures are available to choose from.

The method of calculation based on the length of the crotch related to the length of the cseat tube, which since the 90s was used throughout the world as a criterion for the calculation of the traditional frame, with inclined frames no longer good but its place is not revealed anything easily manageable by End User.

Result of this innovation countdown is that in the moment in which the Cyclists were learning to calculate the frame individually were repulsed back 50 years for the primary choice of the size of the frame slope is made ​​according to the stature of the cyclist and no longer in reference to the length of his crotch which, as described in the page on the calculation of the traditional frame, is a more rigorous method.


The seatpost should protrude more than the traditional bikes

Since the slope frames are smaller than traditional frames, and that the height of the human species is not decreased in the meantime, for pedaling efficiently even on inclined frames the saddle is more protruding than protrudes in traditional frames because part of it is as if it belonged to the frame.

The distance saddle pedal is in fact independent of the length of the column and by the extent of the frame and depends exclusively on the length of the crotch of the rider.

The increased prominence of the seat tube, from a theoretical point of view, gives less security and stability than the traditional frame in which the saddle is less prominent. A saddle most protruding creates a bending moment in the engagement point with the column greater than the saddle less projecting the traditional frame and this in the course of time may break the tube of the steering column in the area of ​​the graft due to greater stress.

Some sellers to justify the deployment of inclined frames would like to switch the tale, which is a non-mechanical sense, arguing that a smaller frame (Slope) by a saddle protruding surrogate is better than a larger frame with a saddle less protruding.

Even during a fall in the bike seat tube is thicker than the frame tilted could not escape even if they move from home with greater ease than less protruding tube of the bike with the traditional form.

The advent of inclined frames, also induces many Cyclists common, perhaps the majority, those who do not go to look for the measurements of the frames to ride with a saddle-pedal distance, away from that fateful 0.88 x inseam measurement which is the value for pedaling efficiently.

The cycling of these inefficient Cyclists is why they continue to adjust the seat tube with the same boss who observed in the traditional bikes where, excluding BDC, usually protrudes about 6/8 Inches.

Raising the saddle so little, these people, it is as pedaled with a traditional bike with the seat lowered all on the seat tube so that when the pedal is at the top of the thigh does not have the agility to push on the pedal with the right angle and a component of the force that the cyclist has the legs is wasted.

In the inclined frames the seat tube must instead file a long time to finish in the efficient pedaling, the more the tube is inclined more the saddle needs to be raised because a portion of the sleeve is visible because protruding from the steering column but in fact it is as if it belonged to it .

It is therefore not uncommon to see that on bikes Cyclists slope pedaling with the saddle even below the height of the handlebar.





The figure on the left shows that the traditional frame continues to exist even in the bike with inclined frame, but in a virtual way.

If you pull a line parallel to the road that starts from the steering head and intersects the seat tube is seen that the seat tube, even though not structurally belongs to the frame, as it is a mobile tube, helps to reconstruct the shape of the traditional frame for the purple shown in the figure.

In the inclined frames, therefore, the seat tube performs the dual function of supporting the saddle, as it has always done in the traditional bikes, but also allows you recompose the frame by linking the classical form.

The distance H , which represents the lenght of the steering column in the traditional bicycle, thus continues to exist also in the bike with inclined frame but with the contribution of the seat tube for the stretch colored in purple.

This image shows even when already said above about the overhang of the seat tube that if it is adjusted according to the formula ralativa the distance saddle pedals Hs should protrude from the frame in a consistent way as a part of the protrusion (purple stretch) serves only to provide the missing cm to reassemble the steering column: the purple stretch physically belongs to the seat tube, but it's like it column.



Slope frame measurement table

Bike frame calculators with non-traditional shape