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what is trail

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this definition mainly refers to bicycles but applies the same to moto's:

Trail, or caster, is the horizontal distance from where the steering axis intersects the ground to where the front wheel touches the ground. The measurement is considered positive if the front wheel ground contact point is behind (towards the rear of the bike) the steering axis intersection with the ground. Most bikes have positive trail, though a few, such as the two-mass-skate bicycle and the Python Lowracer have negative trail.[6]

The relationship between head angle, rake and trail in a bicycle

Trail is often cited as an important determinant of bicycle handling characteristics, such as here[7] and here,[8] and is sometimes listed in bicycle manufacturers' geometry data, although Wilson and Papodopoulos argue that mechanical trail may be a more important and informative variable.

Trail is a function of head angle, fork offset or rake, and wheel size. Their relationship can be described by this formula:[9]

where Rw wheel radius, Ah is the head angle measured clock-wise from the horizontal and Of is the fork offset or rake. Trail can be increased by increasing the wheel size, decreasing or slackening the head angle, or decreasing the fork rake or offset. Trail decreases as head angle increases (becomes steeper), as fork offset increases, or as wheel diameter decreases.

Motorcyclists tend to speak of trail in relation to rake angle. The larger the rake angle the larger the trail. Note that, on a bicycle, as rake angle increases, head angle decreases.

Trail can vary as the bike leans or steers. In the case of traditional geometry, trail decreases (and wheelbase increases if measuring distance between ground contact points and not hubs) as the bike leans and steers in the direction of the lean.[10] Trail can also vary as the suspension activates, in response to braking for example. As telescopic forks compress due to load transfer during braking, the trail and the wheelbase both decrease.[11] At least one motorcycle, the MotoCzysz C1, has a fork with adjustable trail, from 89 mm to 101 mm.[12]

[edit]Mechanical trail

Mechanical trail is the perpendicular distance between the steering axis and the point of contact between the front wheel and the ground. It may also be referred to as normal trail.[10]

Although the scientific understanding of bicycle steering remains incomplete,[13] mechanical trail is certainly one of the most important variables in determining the handling characteristics of a bicycle. A higher mechanical trail is known to make a bicycle easier to ride "no hands" and thus more subjectively stable, but skilled and alert riders may have more path control if the mechanical trail is lower.[14]

-wikipedia

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Trail is a measurement. See if you can imagine a line straight through the middle of the steering head of the frame to the ground. Then a vertical line straight through the axle to the ground. The distance between these 2 points on the ground is trail. Trail affects the steering, and therefore, the handling of the bike. The rake of the steering head, and the length of the forks are two of the biggest contributors of trail.

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im try to convert my 80 to a big wheel i checked the specs for the frame and everything is the same except the trail is that because the difference in wheels swingarm and forks, or is the frame different

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