Reversed Forks

[David]

I have noticed that some bent riders reverse the front forks of their machines, what is the reason
for this? I can see how this would increase the trail, but have no idea how the amount of trail
affects the handling. In need of enlightenment, David.

 

[John Foltz]

David wrote:
> I have noticed that some bent riders reverse the front forks of their machines, what is the reason
> for this? I can see how this would increase the trail, but have no idea how the amount of trail
> affects the handling. In need of enlightenment, David.

More trail is supposed to 'slow down' the steering characteristics, that is, make the bike less
twitchy. The part I don't understand is that in most cases, reversing the fork causes, for lack of a
better term, negative fork flop. The head tube should be at its lowest point when the wheel is
pointed forward, and rise somewhat when the front wheel is turned to either side. Gravity then works
to keep the wheel pointed forward, as the head tube seeks its position of lowest potential energy.
Reverse the fork and the head tube will have its lowest point when the wheel is turned backwards(?)
I guess you have to have a *really* vertical head tube for it to work.

--

John Foltz --- O _ Baron --- _O _ V-Rex 24/63 --- _\\/\-%)
_________(_)`=()___________________(_)= (_)_____

 

[Rotofool]

John Foltz <[email protected]> wrote in message news:<[email protected]>...
> David wrote:
> > I have noticed that some bent riders reverse the front forks of their machines, what is the
> > reason for this? I can see how this would increase the trail, but have no idea how the amount of
> > trail affects the handling. In need of enlightenment, David.
>
> More trail is supposed to 'slow down' the steering characteristics, that is, make the bike less
> twitchy. The part I don't understand is that in most cases, reversing the fork causes, for lack of
> a better term, negative fork flop. The head tube should be at its lowest point when the wheel is
> pointed forward, and rise somewhat when the front wheel is turned to either side.

Actually, for "normal" fork flop the head tube should be at its highest point when the wheel is
facing forward. As the wheel is turned the front of the bike lowers. Balancing the right amount of
fork flop with the right amount of trail is one of the most important facets of steering geometry.
The smaller the head tube angle, the more fork flop will be produced for a given amount of fork
offset. To keep fork flop from getting out of hand, fork offset must be increased as head tube angle
is decreased.

The best handling bents seem to have a small but noticable amount of fork flop at lower speeds. As
speed is increased the effect of trail overcomes the effect of fork flop and the wheel tends to stay
straight as the hands are taken off the handlebars. Too little fork flop and the bike doesn't tend
to maneuver as readily at lower speeds.

Len Thunberg

 

[Kelly]

[email protected] (David) wrote in message
news:<[email protected]>...
> I have noticed that some bent riders reverse the front forks of their machines, what is the reason
> for this? I can see how this would increase the trail, but have no idea how the amount of trail
> affects the handling. In need of enlightenment, David.

What type of bikes do they reverse the forks on?

Thanks, Kelly.

 

[John Foltz]

rotofool wrote:
> John Foltz <[email protected]> wrote in message news:<[email protected]>...
>
>> David wrote:
>>
>>> I have noticed that some bent riders reverse the front forks of their machines, what is the
>>> reason for this? I can see how this would increase the trail, but have no idea how the amount
>>> of trail affects the handling. In need of enlightenment, David.
>>
>> More trail is supposed to 'slow down' the steering characteristics, that is, make the bike less
>> twitchy. The part I don't understand is that in most cases, reversing the fork causes, for lack
>> of a better term, negative fork flop. The head tube should be at its lowest point when the wheel
>> is pointed forward, and rise somewhat when the front wheel is turned to either side.
>
>
> Actually, for "normal" fork flop the head tube should be at its highest point when the wheel is
> facing forward. As the wheel is turned the front of the bike lowers. Balancing the right amount
> of fork flop with the right amount of trail is one of the most important facets of steering
> geometry. The smaller the head tube angle, the more fork flop will be produced for a given amount
> of fork offset. To keep fork flop from getting out of hand, fork offset must be increased as head
> tube angle is decreased.
>
This is opposite from what I thought I'd read, so I ran out in the garage and tried to measure it.
The effect is slight, but it seems you're right. I guess I can rationalize why it works that way,
but I'll have to study it more when the weather warms up before I can visualize it better. Thanks
for the correction.
--

John Foltz --- O _ Baron --- _O _ V-Rex 24/63 --- _\\/\-%)
_________(_)`=()___________________(_)= (_)_____