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A Cannondale without LEFTY: driving sensations?

Today 2 topics in one: we will talk about the rake value in a fork, tests with different rake and in the end we have also answered the question: how is it to use a CANNONDALE without its LEFTY?

cannondale fox rake

Today 2 topics in one: we will talk about the rake value in a fork, tests with different rake and in the end we have also answered the question: how is it to use a CANNONDALE without its LEFTY? [see video]

Video featured in episode # 16 of PULITI dentro BIKER fuori:

To talk about rake you have to start from the basics, that is, talk about the 3 elements that are at stake: namely steering angle, rake (or offset) and trail (or trail).

The relationship between steering angle and rake is very important because it modifies the trail (or trail), a value that changes the handling of the vehicle.

- Steering angle: inclination of the head tube with respect to the ground: downhill bikes have a more open angle (greater degrees), vice versa cross country (minus degrees). Normally enduro/dh bikes vary from 60 to 65° while trail/all-mountain bikes from 65° to 70°.
- Rake (or offset): distance between the axis of the head tube and the axis of the front hub. Values ​​usually range from 37mm to 55mm.
- Trail (or trail): distance between the extension on the ground of the steering axis and that of the front wheel axis.

steering angle
The 2020 Cannondale F-SI World Cup steering angle: 69 °

trail OR TRAIL

WHAT WILL CHANGE IF THE RAKE IS CHANGED?

On a theoretical level, with the same steering angle, with a lower rake value you get a greater trail (therefore more stability). While if you increase the rake, the trail decreases (more handling).

WHAT IF I CHANGE THE STEERING ANGLE?

The more the steering angle is closed, the shorter the trail becomes, vice versa if I open the steering angle. Easily noticeable sensation on the field: a DH bike is more stable than a CROSS COUNTRY bike.

AND DOES THE WHEEL DIAMETER CHANGE THE TRAIL?

Yes, with a bigger wheel the trail increases. Here, too, it can be easily found using a 26 "or a 29": with large wheels the stability is greater.

trail trail
From this image it is easy to understand how changes in the steering angle or rake affect the TRAIL / FORWARD value (projection on the ground of the 2 axles: hub and steering)

ONLY BENEFITS BY SHORTENING THE RAKE?

No, there are always strengths and weaknesses: with the shorter rake stability increases but the distance of the contact point of the front wheel with the ground decreases (wheel closest to us). This leads to a shorter bike and easier loading of the front.
However, the greater stability clashes with the fact that a wheel closer to us increases the tendency to overturn. Another negative aspect is the fact that the fork works more vertically and therefore absorbs less horizontal forces.

So there are those who seek stability by opening the steering and those who shorten the rake… and those who do everything and 2 things together! (Speed ​​Balance Geometry by Transition).

supercaliber trek

VARIOUS GEOMETRIC APPROACHES

THEORETICAL GEOMETRY

One of the pioneers of MTB was also one of the pioneers of innovative geometries, namely Gary Fisher with his G2 Geometry, later taken over by other brands such as Cannondale with his Lefty.

Gary says that in order to have a manageable and stable bike at the same time, you have to open the head angle (higher value) and increase the fork rake. So the less maneuverability of the open head angle compensates for this by the higher rake.

Precisely for this reason, Gary Fisher and Trek (who included this geometry in his models), had the suspension companies make specific forks with increased rake (51mm) when the standard was on 42mm.

MODERN GEOMETRY

The forerunner of such geometry is Transition with its Speed ​​Balance Geometry. The handling is also given by the wheelbase of the bike and the high rake values ​​certainly did not help to keep this value contained. Here is that Transition has decided to have specific forks produced with 37mm rake! Since the handling, in the downhill field, is also given by the stability, Transition (in contrast) has decided to open the steering angle as well, creating a slightly twisted geometry that clashes a little with the theory but seems to be winning and gives the bikes of the American brand have their own style.

Speed ​​Balance Geometry by Transition
Speed ​​Balance Geometry by Transition

We close by saying that each geometry has its strengths and weaknesses and as usual we should be the ones to understand what we want from our bike.



Written by

[email protected] I am passionate about everything that has 2 wheels: in my youth I practiced competitive cycling on the road and on the track with good results. At the age of 18 I moved to cross country competing at national/international level as U23. Once I passed Elite, I made the choice to take things easier from the training point of view, and that's how my love for gravity disciplines was born, training as an FCI MTB instructor and guide. Now I have made my passion my profession by managing 3 MTB centers on the island of Elba (Elba MTB), creating the FANTAmtb and telling in an ironic but professional way, everything that revolves around MTB thanks to 365mountainbike and 365TV (YouTube 'PULITI dentro BIKER fuori').

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