View Full Version : TR4/4A Using TR4 upper wishbones & balljoints on a "3"

06-26-2008, 05:47 PM
I'm still rebuilding my front end.Apparently this gives 3 degrees more castor if you use the 4 trunnion. Does anything else on the front end need to be modified when doing this? Is there any appreciable difference in doing this mod if I'm going to a wider wheel. Might consider doing it seeing as how everything is apart. Karl

06-26-2008, 05:56 PM
Karl, This is the same upgrade i have been considering for my TR3. I like the way the ball joint is mounted in the "4", but I have not done it yet.

06-26-2008, 06:18 PM
Yes, if you change to the 3 degree trunnions, you also need to change the upper A-arms and ball joint; otherwise the trunnion will bind (and not give you the caster). The steering arms also changed at the same time, but I think not changing them just screws up the Ackerman angle so maybe that's not essential.

You can find this info in the Moss catalog, just look for everything that changed at CT6344 (wire wheels) and CT6391 (disc wheels).

Personally, I don't see the need for stronger "return to center", but that's a matter of opinion. I was running 205/55-15 tires on 5.5" wide wheels, and had no trouble with wander at speed unless the road surface was rutted. But the wide tires did want to climb the ruts, and maybe some castor would have helped that.