TR2/3/3A Has anyone put late TR4/4A upper A-arms and ball joints on TR3?

[TuffTR250]

I'm experimenting with putting some late TR4/4A upper A-arms and ball joints on the front suspension of my TR3A. Has anyone done that, and how did it work out? Are there any problems with doing this?

I put them on one side of the car today. I have taken the jack out from under the bottom pan and let the suspension go down against the new rubber stops. It appears that the center of the TR4 ball joint (using the grease fitting hole as reference) is about 1/2 (plus) inch in front of the center point of the spring housing. The TR3 ball joint sets right in the middle of the spring housing where there is a V-shaped cut out in the center of the spring housing. Will this 1/2 inch forward position of the late TR4 ball joint cause any problems?

When I measured the distance from the shock absorber top bolt to the center of the ball joint grease fitting hole, both TR3 and the TR4 ball joints were right at 6-1/8 inch, so it does not seem to affect the camber. However, I have not put the car down on the wheels yet so I may be premature in saying camber is the same for both TR3 and TR4 A-arms. Does anyone have experience with this?
Thanks and Regards,
Bob

 

[TR3driver]

I think you're installing the arms backwards; the front arm should be the one with the deeper offset so the upper pivot moves to the rear to provide positive castor. (Positive is when the steering axis meets the road in front of the tire.)

To do it right, you also need to change the lower trunnion to the later ones with the 3 degrees of castor built into them; and then to keep the steering geometry install the longer steering arms.

In theory at least, you can slot the holes in the A-arms to allow some camber adjustment.

The extra castor will give you more centering, which is a big advantage especially on rutted roads with wide tires. The penalty is more steering effort.

 

[TuffTR250]

Thanks Randall!! You're right, I put them on backwards. The way I put them on would give me negative castor which would cause steering problems. I will reinstall them the correct way around. What kind of problems will I have if I leave the original "0" castor trunnions and steering arms on and use the TR4/4A upper A-arms? Will it be safe?

BTW, I got these TR4/4A upper A-arms I'm using from a fellow Triumph Club member who welded a piece onto them on the back part of where the ball joint attaches, and then the ball joint mounting holes of the A-arms have been slotted toward the inside of the car so that the camber can be adjusted somewhat. He was planning to use them on a TR4 race car, but then did not build the race car. I have attached pictures of one set of the upper A-arms to show how they have been altered.
Regards,
Bob

 

[TuffTR250]

I installed the TR4/4A upper A-arms the right way around. It was somewhat difficult to get the ball joint to line up with the back A-arm. I had to pull it back with the ball joint bolts. For some reason when I installed them backwards I did not have any problem lining up the ball joint with the A-arms. Once I got it together I realized some of the problems resulting from not using a turnnion with the 3 degree castor. The back A-arm was getting a lot of twisting in order to get it to fit and then I could see the inside mounting rubbers were getting very twisted as well,in fact the A-arm was starting to go over the top of the inside rubber and rub against the metal of the mount due to the force requiring the top of the trunnion to lean toward the back of the car. As a result, I have decided it is not a good idea to install these A-arms with the zero degree castor trunnion, which was not really a surprize, but I just needed to try it myself to see what would happen. So I reinstalled the original TR3 A-arms and ball joint.
Regards,
Bob