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TR2/3/3A 3 degree castor conversion on TR3

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Gordo

Jedi Hopeful
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I've decided to convert to the 3 degree castor on my car. I've got my shopping list together for Moss. I'm pretty sure I've got everything I need to do the conversion but I'm kinda stumped on one piece.

For the 3 degree trunnion, which locking washer would I use: 324-910 or 324-920?

Thanks, Gordo
 
I believe either one will work fine. The difference is that 324-920 has a notch in the edge to accept the 'shim', 661-560. If you plan to use the shims, go with the later washer.
 
I haven't seen a write-up, but from everything I've seen it is no harder than a front end rebuild, you just need to put in the updated parts when putting it back together. Off-hand, I'd say the key parts are trunnions, upper a-arms, and ball joints.

TRF accidently sent me a bushing kit for the older style, the main difference I saw was the seal between the vertical link and the trunnion. I did buy trunnions from TRF, and as an aside I think they worked well.

Randy
 
Yes, it will fit the older frames, even back to the TR2/3.
 
What all do you need to convert? I'm thinking of doing the same thing. I was told all you need is the new TR4 trunnions. Sounds a little more involved then that.
 
Trunnions, upper A-arms, upper ball joints, bolts & nuts to hold upper ball joint to A-arms. Obviously you might as well replace all the bushings, etc. while you're in there, but those are the items that have to change.

Changing the castor means tilting the steering axis. The later trunnions only allow for the tilt, they don't move the lower pivot point. So the upper pivot point has to move. Hence the need to change the upper arms. And since the way the arms mate to the ball joint changed, have to change it too.
 
I'm not sure the extra $$$ of having an extra 3 degrees of caster is going to make much difference...maybe worthwhile if you need a rebuild...
 
Me neither. All it does is increase the "self centering" effect, which means more steering effort. Might make the car more stable under some circumstances (like badly rutted roads or California's infamous rain grooves), tho.
 
I may not have done the conversion if the front end did not require a total rebuild. I'm doing a total resto on the car and I had the upper arms and ball joints from a 6 project I had. The expense will run about the same give or take a couple dollars.

I'm still debating the rack and pinion change, but since reading the recent threads on worm and peg, I may just keep what I have for steering.

Still haven't decided on front brakes yet. I understand the 16PB calipers will work if I change the mounting plate, which I have both calipers and plates.

I ordered a Fast Road kit from Revington TR for the frame and it should be here this week. The exchange rate is killer right now and wish I was on another part of the project and didn't need to buy parts fom across the pond.

Gordo
 
Gordo, I don't see the exchange rate improving anytime soon. I needed some parts for my GT6, and looked them all up when the rate was $1.48. By rhe time I ordered them, it was $1.87. That'll teach me to procrastinate! To the tune of nearly 400 bucks.
Jeff
 
I noticed that the tie rod levers changed numbers with this change too - not sure if this is a critical change though unless there is a bump steer or other interference issue to work out.

Randy
 
Good point, I forgot about the steering lever change. Since the center of the steering axis moves back with the change, the lever needs to be longer to maintain the geometry in turns. But I'm not sure how critical the change is.

Seems to me that keeping the old levers would increase Ackerman, while the modern theory is to decrease it, but I'm guessing here.
 
The book I got the idea from was "How to improve Triumph TR2-4". Roger Williams, the author, makes no mention of changing out the steering lever in the book but I can see the potential for problems.

He recommends trunnions, ball joints, vertical link and upper arms from a 4. I'm not certain why he'd mention the verticals since they are the same for both sides up to the TR4A when they are opposite threads.

It won't be on the road for LONG time, so I'll keep the original on for now.

Gordo
 
I don't know much about steering geometry but if the only advantage is increased 'self centering' couldn't you do the same thing by adding a little toe-in?
 
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