Friction anti-sway device use in rain or wet roads
So; when trailering in the rain while using the friction anti-sway device, should I loosen or tighten this thing?
Forum Discussion
It is correct that the friction sway control (FC) bar will resist allowing the trailer to return to normal.
However, I believe many people over estimate the magnitude of the effect.
The most commonly sold FSC is factory-set to produce a yaw-axis torque of about 500 lb-ft.
If the 500 lb-ft of torque is applied to a TV with a 130" (10.8') wheelbase, the front tires must generate a lateral force of 46# to counteract the torque.
If the front axle is carrying 3000#, typical tires must be turned about 0.14 degrees on dry pavement to generate a lateral force of 46#.
Required increases in steering angle for other surface contitions might be: wet pavement = 0.2 degrees, packed snow and dry ice = 0.3 degrees, glare ice = 0.55 degrees.
So, yes, a FSC can induce some "understeer".
However, the added steering angle required to overcome the "understeer" is relatively small compared to the maximum tire slip-angle of 5-6 degrees at which the lateral force begins to plateau.
The required added angle might be so small as to be undetected by the driver.
The "stiffening" effect of the FSC might be noticed when coming out of a curve.
When not towing, the the camber and toe in of the TV's front suspension will tend to straighten the steering tires.
When towing with a friction-based SC, the FSC torque will tend to oppose the camber and toe in effects and reduce the TV's self-straightening.
It might or might not be possible for the TV to self straighten.
However, as long as the driver is aware that it might be necessary to provide some assistance in the straightening process, the FSC yaw-axis torque should not cause problems.
Ron
However, I believe many people over estimate the magnitude of the effect.
The most commonly sold FSC is factory-set to produce a yaw-axis torque of about 500 lb-ft.
If the 500 lb-ft of torque is applied to a TV with a 130" (10.8') wheelbase, the front tires must generate a lateral force of 46# to counteract the torque.
If the front axle is carrying 3000#, typical tires must be turned about 0.14 degrees on dry pavement to generate a lateral force of 46#.
Required increases in steering angle for other surface contitions might be: wet pavement = 0.2 degrees, packed snow and dry ice = 0.3 degrees, glare ice = 0.55 degrees.
So, yes, a FSC can induce some "understeer".
However, the added steering angle required to overcome the "understeer" is relatively small compared to the maximum tire slip-angle of 5-6 degrees at which the lateral force begins to plateau.
The required added angle might be so small as to be undetected by the driver.
The "stiffening" effect of the FSC might be noticed when coming out of a curve.
When not towing, the the camber and toe in of the TV's front suspension will tend to straighten the steering tires.
When towing with a friction-based SC, the FSC torque will tend to oppose the camber and toe in effects and reduce the TV's self-straightening.
It might or might not be possible for the TV to self straighten.
However, as long as the driver is aware that it might be necessary to provide some assistance in the straightening process, the FSC yaw-axis torque should not cause problems.
Ron
