Quote:
Front end wobble of death
Symptoms -
Around 60-65mph the front end can go into an uncontrollable spasm of vibrations that can frighten the pants of anyone. Usually goes away once you have braked to a speed of about 30mph, regain your pulse and crawl on a bit more
Fix - On both my discoveries (1990 and 1994 models) this has always turned out to be swivel pin pre-load. Fixing is relatively simple and there are posts on this website to help
Believe me, i know the frustration and money that can be spent in fixing this problem. I have been through the whole replace bushes, steering damper, steering box, steering u-joints baloney! If you have this problem it is your swivel pre-load. If any of the other items are shot (a) there are specific symptoms that will prove this and (B) they are probably shot from the death wobble caused by your swivel pre-load.
Explanation. The entire wheel assembly is hinged in the vertical plane on the upper and lower swivel pins. When pre-load is set correctly these pins pinch the swivel bearings such that there is no horizontal play. However over time, the swivel bearings (which take the brunt of the load) obviously wear a little, creating some slack in the horizontal plane. The best way to visualise the effect is to spin a coin on a desk, just before the coin finally comes to rest it has a frantic wobble/vibration just before it comes to rest. At this point the coin is rotating both in the direction you spun it AND horizontally (inline with the desk). If you watch a coin at this point, that is exactly what your front wheel(s) are doing. Im 150% sure of this - this wobble is swivel preload - other suspension/steering faults do not cause this effect (though they will get damaged the longer the pre-load is not set correctly)