Trail or not
Posted: Mon Aug 17, 2009 4:52 pmIn the past year or two I have become aware of several P2 sidecars with positive trail, sometimes as much as 1”. IMO these are not just hard to steer but dangerous to the other teams on the track
The argument is often positive trail is “good trail”, the answer is a definite no.
If you take your hands off the handlebars when the bike is rolling and the front wheel wants to turn, you should check the trail.
Find a flat area and chalk a couple of lines 6-8 ft long, a wood T&G floor works well. Place the bike over them in line with the bike, determine the ground clearance front and back with both team members on the bike, drop the front wheel out and you may need to drop one shock off back and front to maintain the same height. If you have a hollow steering head bolt shine a light down it, mark that point on the ground. Take a square and using the lines or floor as one side draw a line 6-8” at 90/o from the steering head point (neutral point). Put the axle back in place and drop a vertical down from the center and allowing for ½ the diameter, you now know exactly what your stationary trail is.
If the centerline of the axle is forward of the neutral point, it will want to castor back around and you will be fighting it all the time.
If it is too far to the rear, it will want to go straight and you will be fighting it on the corners.
IMO the best setting is about ¼”-1/2” of negative (rear of the neutral point) trail.
If the lines come together (zero trail) you will have little feeling for how much contact you have with the road, so some trail is needed. A new driver may want to start with ¾” if you have that option, and reduce it as confidence builds. .
The argument is often positive trail is “good trail”, the answer is a definite no.
If you take your hands off the handlebars when the bike is rolling and the front wheel wants to turn, you should check the trail.
Find a flat area and chalk a couple of lines 6-8 ft long, a wood T&G floor works well. Place the bike over them in line with the bike, determine the ground clearance front and back with both team members on the bike, drop the front wheel out and you may need to drop one shock off back and front to maintain the same height. If you have a hollow steering head bolt shine a light down it, mark that point on the ground. Take a square and using the lines or floor as one side draw a line 6-8” at 90/o from the steering head point (neutral point). Put the axle back in place and drop a vertical down from the center and allowing for ½ the diameter, you now know exactly what your stationary trail is.
If the centerline of the axle is forward of the neutral point, it will want to castor back around and you will be fighting it all the time.
If it is too far to the rear, it will want to go straight and you will be fighting it on the corners.
IMO the best setting is about ¼”-1/2” of negative (rear of the neutral point) trail.
If the lines come together (zero trail) you will have little feeling for how much contact you have with the road, so some trail is needed. A new driver may want to start with ¾” if you have that option, and reduce it as confidence builds. .