TR2/3/3A TR3 -->4 Front suspension upgrade questions

[Moseso]

I have been thinking/planning/dreaming about putting the proper TR4 parts on my TR3 to get some caster -- and maybe even go whole-hog, and get the adjustable upper fulcrum kit from Revington to adjust the camber.

I bought a box full of TR4 suspension parts (eBay -- cheap) so I now have the proper upper A-arms.

Question #1: I don't have any TR4 manual or pictures. My assumption has been that the A-arms go on in such a way that the vertical link leans forward, i.e. straighter arm on the front, arm with more offset on the rear. The picture on the Revington site (below) looks like it's the other way around. Which is correct?

Question #2: I will need new trunions. There are two types: fixed pin and bolt-on. Are they interchangeable? Do I need different lower arms to work with either set? Is there any real advantage to the later, bolt-on style?

 

[TR3driver]

The vertical link leans to the rear, so the Revington setup is correct.
https://en.wikipedia.org/wiki/Caster_angle

The bolt-on trunnions require both different lower arms, and a different vertical link IIRC. The fixed pin ones will work with your existing arms & VL.

Along with the change in caster, there is a slightly longer steering arm, to maintain steering geometry.

 

[Moseso]

Cool! Thanks Randall.

The box of parts came with 4 lower arms, still bolted to spring pans, and what looks like the remains of bolt-on trunions. Also, two steering arms. I'll compare 'em to what I've got on the 3. You're saying that if they are slightly longer than the ones I have on the car, they should be substituted?

Sounds like I'll get the fixed pin trunnions and keep my other existing lower parts.

The dang car's still at the body guy. I won't get the chance to do any of this til late-March, at he earliest. So, I have plenty of time to collect parts & wisdom -- and plan this thing out.

 

[TR4nut]

If you went with the bolt on trunnions, you would need the TR6 style vertical link - which would also have the effect of dropping your front suspension by about 1" unless you add spring spacers.

Not sure if the steering arms are longer, but I think they are bent more to accomodate that 3 degree castor tilt. I'm leaning heavily to do this myself on the 3A, but I still need to source the steering arms.

 

[CinneaghTR]

... I still need to source the steering arms.

I am getting ready to do the same thing with the 4A. I called Scott Harper at Team Triumph and he had the used parts in stock and at a great price. NFI, but tired of waiting for eBay auctions...

 

[TR4nut]

Jeremy-

Just curious, but why do you need them for the 4A? What's wrong with your setup now - it should already be setup with the castor and good arms I think.

Randy

 

[CinneaghTR]

You're right, nothing is wrong with the current set up. I am having the parts powdercoated ala Brosky and want to switch them straight out rather than have the car on jack stands for an extended period. I am doing the rebuild as part of a tech session and want to move fast, too.

Thanks for asking for clarification.

 

[vivdownunder]

If ordering from Neil Revington, let him know you have fitted R & P steering, and he will advise which of his products compliment it on a TR3A.

I think Neil's adjustable upper fulcrum still has to be welded in place after it's been set up, which sort of defeats the purpose of having it adjustable. However, he may have introduced updated products since I last checked. Of course the springs have to come out to fit it, as two of the upper bolts are loose rather than welded into the tower.

There's certainly nothing wrong with the original TR3A steering if it's rebuilt to specification. TRF's delrin replacement for the rubber silenbloc bushes makes the steering lighter again.

Viv.