Okay here it is if someone could help me with this one I would be very greatful. I just finished my first custom built swb bent and on my first test ride I noticed the steering is ultra sensitive. I and using a standard Murray 10 speed road frame, forks off of the same roadie and a 20 rim / tire. I measured the trail and it looks like I have about 1 inch of negative trail, I projected a line from the center of the headtube and a line through the center of the axle and the projected line from the headtube is about 1 inch in front of the projected line of the axle. Correct me if I am wrong but that would be considered negative trail correct? Anyway the steering is really sensitive and seems to be suffering from oversteer. It make the bike almost unridable, Of course some of this could be me not being used to the bike. Most of the custom bikes I have seen have forks that are bent to give more rake, my question is how much trail would be considered normal.
Ken
-- It has yet to be proven that intelligence has any survival value. Arthur C. Clarke English physicist & science fiction author (1917 - )
Somewhere close to 2" of castor / trail (trails behind the steering axis) for a typical swb Think of it like a flag with wind blowing on it. A flag always trails behind the pole. The fork would really like to trail behind the steering axis but you, the rider, is forcing it to stay in front. Turn the fork around and see how it feels. Check frame alignment. Speedy
Ken Marcet said:
Okay here it is if someone could help me with this one I would be very greatful. I just finished my first custom built swb bent and on my first test ride I noticed the steering is ultra sensitive. I and using a standard Murray 10 speed road frame, forks off of the same roadie and a 20 rim / tire. I measured the trail and it looks like I have about 1 inch of negative trail, I projected a line from the center of the headtube and a line through the center of the axle and the projected line from the headtube is about 1 inch in front of the projected line of the axle. Correct me if I am wrong but that would be considered negative trail correct? Anyway the steering is really sensitive and seems to be suffering from oversteer. It make the bike almost unridable, Of course some of this could be me not being used to the bike. Most of the custom bikes I have seen have forks that are bent to give more rake, my question is how much trail would be considered normal.
Ken
-- It has yet to be proven that intelligence has any survival value. Arthur C. Clarke English physicist & science fiction author (1917 - )
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I measured the trail and it looks like I have about 1 inch of
negative
Quoted message said:
trail, I projected a line from the center of the headtube and a line
through
Quoted message said:
the center of the axle and the projected line from the headtube is
about 1
Quoted message said:
inch in front of the projected line of the axle.
I don't think you're measuring trail correctly. Trail is the distance from where the head angle hits the ground to a point directly below the front axle. Here's a good article, picture, and calculation method: http://www.phred.org/~josh/bike/trail.html
Jeff has hit it on the head. AS the bike gets lower and the seat tilts back, we need a little more trail to keep the bike from being twitchy. The problem is that more trail also gives more control force. You can also go to a steel rim on the wheels or add tiller to reduce the twitch.
I would turn the fork around first. It's easy and cheap.
-- Don’t be a 0 to 60 sheep, be a 60 mpg wolf. Yes Miles Per Gallon.
That is how I measured my trail, and the line extended from my forks hits the ground about 1 and 5/16 in front of the line I dropped down from the axle. I was or should I say still am a bit confused about whether this is considered positive or negative trail. I have been emailing back and fourth with A.D. Carson of recycledrecumbents.com and he has told me that it is positive trail, and after sending him a couple of digital photos of my bike he has figured that my headtube angle is really steep at about 81 degrees.. He has also told me that raking my fork further will not help, but suggests that I try a 24 inch tire if it will fit or learn to love my twitchy steering.
Ken
<[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
Ken Marcet said:
I measured the trail and it looks like I have about 1 inch of
negative
Quoted message said:
trail, I projected a line from the center of the headtube and a line
through
Quoted message said:
the center of the axle and the projected line from the headtube is
about 1
Quoted message said:
inch in front of the projected line of the axle.
I don't think you're measuring trail correctly. Trail is the distance from where the head angle hits the ground to a point directly below the front axle. Here's a good article, picture, and calculation method: http://www.phred.org/~josh/bike/trail.html
I have tried like you said to turn the fork around, however due to my design, and lack of experience, I don't have enough clearence with my chain management system pulleys. But after riding it a couple more times I have started to become used to the twitchiness!
Ken
"Bill Patterson" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
[email hidden] wrote:> front axle. Here's a good article, picture, and calculation method:
Jeff has hit it on the head. AS the bike gets lower and the seat tilts back, we need a little more trail to keep the bike from being twitchy. The problem is that more trail also gives more control force. You can also go to a steel rim on the wheels or add tiller to reduce the twitch.
I would turn the fork around first. It's easy and cheap.
-- Don’t be a 0 to 60 sheep, be a 60 mpg wolf. Yes Miles Per Gallon.
