TR6 TR4a vs TR6 fulcrum pins [was TR4a shims]

[tdskip]

How many shims are you guys running to get the front suspension camber right on your TR4a lower arms?

 

[Darrell_Walker]

Re: How many shims on your TR4a

I have a couple on one side, not to get it correct, but just to get it even between the two side. I'd need negative thickness shims to get it right (or try to shim out the cross tube, I guess).

 

[tdskip]

Re: How many shims on your TR4a

Hi Darrell - thanks for the response.

So you are neutral to negative chamber even without shims? Huh. I'm pretty positive with two shims still.

The ball joint #10 is centered / that is not direction installation sensitive, correct?

If I managed to reserve the upper arms #2 and #3 would that result in the positive camber?

And #1 would also have an impact if I mounted it "backwards", correct?

 

[tdskip]

Re: How many shims on your TR4a

Actually - #2 and #3 would just mess up vertical alignment of the suspension/shock etc so I think I may have put #1 in backwards.

 

[Darrell_Walker]

Re: How many shims on your TR4a

So you are neutral to negative chamber even without shims? Huh. I'm pretty positive with two shims still.

Yes, the bottom of my tires are about 1/4" wider than the top. Actually one side it like that without shims, the other is vertical, but I shim it out to match (figuring that matching side to side is more important).

The ball joint #10 is centered / that is not direction installation sensitive, correct?

I believe that is true.

If I managed to reserve the upper arms #2 and #3 would that result in the positive camber?

I don't think so, at least not directly. It would cant the link forward (and might be hard to do, since the lower trunnion is canted).

And #1 would also have an impact if I mounted it "backwards", correct?

Yes, though I'm not sure you can, I think it would partially block the top shock mount.

I should also add that most of my lower brackets have been replaced, so there position may not be exactly as they left the factory.

 

[justin_mercier]

Re: How many shims on your TR4a

Actually - #2 and #3 would just mess up vertical alignment of the suspension/shock etc so I think I may have put #1 in backwards.

You can put it in backwards, and it will mess your alignment up a lot =D

 

[tdskip]

Re: How many shims on your TR4a

So it would seem Justin! What a chuckle head I am.

I'll check it in the AM, pretty sure that is what I did.

Trying to think how much of this needs to be disassembled to turn it around the right way.

 

[Darrell_Walker]

Re: How many shims on your TR4a

Trying to think how much of this needs to be disassembled to turn it around the right way.

If you support the lower link (jack or stand), you should be able to undo the two bolts through the top ball joint, and the bolts holding #1 down. Do both sides, and you can flip the upper arms over and swap sides, so you don't have to remove the arms from #1.

 

[tdskip]

Re: How many shims on your TR4a

OK guys - double check me here. Which way does the fulcrum pin curve face - towards the engine or towards the outside of the car? The curved section currently faces the engine now.

 

[justin_mercier]

Re: How many shims on your TR4a

The "short" side faces out.

 

[tdskip]

Re: How many shims on your TR4a

Hi guys - so I think I may have found something here.

Justin - I believe that is correct for the TR6 but NOT for the TR4a. I believe that the curved side faces out on the TR4a.

There is a large difference in offset in the fulcrum pin, and having the curve face out would adjust out my too positive camber.

As installed on the car - which I did not remove or even check since I assumed it was right and matched by TR6 - my fulcrum pins had the curve towards the engine. Hence my inability to get the camber correct.

 

[tdskip]

Re: How many shims on your TR4a

Yep - just finished switch the orientation on the driver's side and I have correct camber on that side now.

Someone please double check me here but there are two good reminders here;

1) Don't assume that anything from the PO was done correctly.

2) Don't assume that the suspension detailed between the TR3, TR4, TR4a and TR6 are all identical.

 

[HerronScott]

Re: How many shims on your TR4a

Tom,

2 out of 3 TR4A front suspensions prefer curved side facing the engine and those are the 2 that I'm pretty sure have not been touched. Of course the one that I restored has it the other way with curved side facing the wheel which might explain why I had issues getting the darn thing aligned! At the time I chalked it up to some issues I had with the crossbrace bar and the frame but now I'm thinking that I assembled it incorrectly.

Don't you have 2 TR4A's also?

Scott

 

[tdskip]

Re: How many shims on your TR4a

Hi Scott - I'll have to check the earlier TR4a and report back, but there is a chance that it has been messed with as well.

 

[HerronScott]

Tom,

Trying to find other references to this and found the following quote from a post on the TR Register forum.

"In my TR4A it was mounted in the way TR6 does (fulcrum pin DOES NOT follows the natural curve of the top of the turret) . When it was assembled again (after my frame off restoration) it was mistakenlly made like the older version (TR4). Since I got problems with camber (too negative) I am assuming the former position is correct and so I am changing it back during the next weekend."

There are some more posts there as well about this which all seem to indicate that that TR4A-TR6 are all the same.

Is there anything else that could be causing the postive camber?

Scott

 

[tdskip]

Hi Scott. Funny - my Googling supported the opposite conclusion. People said it changed on the TR5/250/6 due to the extra weight of the engine (which kind of makes sense).

In any case the only way I could get close to neutral camber was the have the curve facing outwards. Could just be this car but now I'm really curious!

 

[TR4nut]

Well, now this thread is making me question the whole thing even on my TR4. According to Roger Williams the 4A had it with the curve towards the engine, and kept that way through the TR6. The TR3 had it outward towards the wheel. And Roger notes than on the TR4, it might be either way - his writing style isn't very direct, but it appears the change in pivot orientation may be when they went with the TR6 style upper ball joint. Confusing.

 

[tdskip]

Hi Randy - some pegged the cut over at the TR4 not TR4A, others at the TR5/250/6. I'd be willing to believe that the extra weight of the six cylinder engine could prompt a change.

I think the whole thing may be further thrown off by ball joint changes, and of course this will be car specific.

All I can say is that on my particular TR4a there is no way that I could get to a proper camber angle with the curve facing inwards.

I'll check the other TR4a tonight and report back, but as mentioned above who know if that car is correct.

 

[HerronScott]

Tom,

I didn't think there was that much weight difference between the 4-cylinder and the 6-cylinder?

Scott

 

[PeterK]

It was common to flip the upper fulcrum around to decrease camber (increase negative camber) in race cars. But AFAIK (which isn't much), the 6 and 4A (not TR4) have identical front suspensions except for the two pin lower inner fulcrum brackets used in the 6. The only difference there is the extra mounting pin for strength. Same rack, arms, ball joint, tie rods, et c.