17-05-2022, 12:32 PM
Hi Mike
This sounds like a case of a resonant system with little or no damping. In the case of front wheels it used to be called "shimmy", presumably after the dance from the 1920's. Once energy is put in by the bump in the road, it sets the whole thing off. I suggest the two most important things to check are the castor angle and the toe-in. I guess you will already have checked for any suspension and steering linkage slackness anywhere that shouldn't be present, including the radius arm ball joint and the drag link ends. Finally, tyre pressures too high can reduce the damping. Sevens don't seem to be particularly prone to this, judging from this forum over the years.
I'm doubtful if the friction damper will have much effect on side to side movement, but it needs to be doing its job.
I once saw a Land Rover coming towards me with the front wheels leading an alarming dance. On signalling to the driver, he gave me the thumbs up - presumably he was well aware and had just got used to it !
This sounds like a case of a resonant system with little or no damping. In the case of front wheels it used to be called "shimmy", presumably after the dance from the 1920's. Once energy is put in by the bump in the road, it sets the whole thing off. I suggest the two most important things to check are the castor angle and the toe-in. I guess you will already have checked for any suspension and steering linkage slackness anywhere that shouldn't be present, including the radius arm ball joint and the drag link ends. Finally, tyre pressures too high can reduce the damping. Sevens don't seem to be particularly prone to this, judging from this forum over the years.
I'm doubtful if the friction damper will have much effect on side to side movement, but it needs to be doing its job.
I once saw a Land Rover coming towards me with the front wheels leading an alarming dance. On signalling to the driver, he gave me the thumbs up - presumably he was well aware and had just got used to it !