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.

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.

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).

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.

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.
