Front springs
I took one of my front inner springs out, to soften the front and stop the wheel skipping over bumps when cranked over. (Like the rear, they are Petteford springs, lighter apparently than standard, but to what extent I don't know.) I can do this with next to zero risk of steering malfunction for two reasons. The first is that I have Thornton dampers, much, much superior to anything else commonly available, and as good as the best modern shocks. This combination gives a very comfortable ride, and because the damping really DOES work, the fork neither bottoms nor tops. Or at least if it can, it hasn't yet.
Nor does a bump mid-corner mean an involuntary lane change to the outside of the bend.
Taking the spring out was a Sid Biberman suggestion. It also follows the precepts of Ron Williams (Maxton) that for good roadholding you need not a superstiff frame (the Featherbed Norton isn't particularly stiff, but has very good geometry, which doesn't alter much with suspension movement.) but soft springs and stiff damping. If you have stiff springs and soft damping, the case with virtually every British bike from 1945 onwards, then the wheels bounce off bumps, allowing the bike to crab sideways.
Why are they like that? Well, damping was in its (relative) infancy, and springs had to cope with loads from 8 stone to 20 stone. 8 stone springs would break under 20 stone loads, so they fitted 20 stone ones. Handling might have suffered, but warranty claims were minimised.
The other reason is an hydraulic steering damper. There's never been even a hint that a feared "Vincent tank-slapper" was beginning, not that there's always any warning. However having survived three of them (all on bikes of "legendary handling" and none of them Vincents) I have absolutely NO inclination to risk a fourth. The third one narrowly missed breaking my neck.
There might actually be a third reason. I weigh 12 stone soaking wet, and rarely carry a passenger, so I've set the bike up accordingly. This means I have to take it easy when I do have a passenger (Oh look, daddy! A blue moon!) and I doubt that "fully laden" with camping gear (and tools...) I'm carrying more than 50 lb.
Has anyone tried the latest Thornton "coil-over" shock yet? I know that John Crispin made a coil-over front shock for Bramptons, which he said worked very well.
Tom