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View Full Version : TR6 TR4a vs TR6 fulcrum pins (was TR4a shims)



tdskip
05-26-2011, 07:20 PM
How many shims are you guys running to get the front suspension camber right on your TR4a lower arms?

Darrell_Walker
05-26-2011, 08:44 PM
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
05-26-2011, 08:51 PM
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?

https://mossmotors.com/Graphics/Products/Schematics/TRI-024.gif

tdskip
05-26-2011, 09:14 PM
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
05-26-2011, 09:19 PM
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
05-26-2011, 10:47 PM
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
05-26-2011, 11:00 PM
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
05-26-2011, 11:04 PM
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
05-27-2011, 09:24 AM
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
05-27-2011, 09:30 AM
The "short" side faces out.

https://www.tharkis.com/images/tr6/resto/IMG_0922.JPG

tdskip
05-27-2011, 09:45 AM
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
05-27-2011, 10:10 AM
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
05-28-2011, 03:58 PM
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
05-28-2011, 07:13 PM
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
05-28-2011, 07:49 PM
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
05-28-2011, 08:18 PM
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
05-28-2011, 08:35 PM
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
05-28-2011, 08:59 PM
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
05-28-2011, 10:27 PM
Tom,

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

Scott

PeterK
05-29-2011, 07:43 AM
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.

MDCanaday
05-29-2011, 08:52 AM
this is NOT an area for guess work!! Take the car into a GOOD front end shop and have all the angles read!!!! This is critical in getting the diagnosis right ..
You life depends on good ,safe steering.Damaged vertical links should never be used as they can and do fail.Not to mention tire wear problems.Camber issues of more than a degree or 2 are a major red flag!!!
MD(Mad dog)

tdskip
05-31-2011, 08:16 AM
Hi guys - thanks for the input. It looks like I may have an issue with the passenger side vertical link. Anyone has a known good passenger side vertical link, Moss #661-110, I can buy?

Tonycharente
05-28-2012, 01:31 PM
Hello all,
Just been reading through this excellent topic - as my TR4A has too much negative camber at the front. I'll be checking later to see which way round the fulcrum pins are mounted, but as the camber is greater on the left than on the right I expect I'll need to play with the number of lower wishbone shims too, come what may. Currently there are three shims in each location on both sides. Which leads me to three questions, please. How much, in inches or cms measured at the top of the rim versus the bottom of the rim, does one degree of camber represent? And what is the impact (in degrees - or in distance as measured above) of removing one shim, front and rear? Or putting it another way, if I remove all three shims in one go will this be way too much correction? Finally I know you are supposed to weight the car up, but not having two friends around at present, what, and in which direction, is the effect of weighting the car up? This is just to understand whether my excessive negative camber problem gets worse or diminishes when the car is properly weighted up.
Many thanks,
Tony

Tonycharente
05-28-2012, 04:30 PM
Hello again,
Further to my above three questions, here comes a fourth, please! I have this evening taken the front wheels off to examine the way the fulcrum pins are fitted : they are fitted curve towards the engine. According to the highly detailed (and TR4A specific) diagram and photos in my original (period) workshop manual this is the correct way round for a TR4A, despite some suggestions to the contrary. My fourth question is to ask whether turning them round (curve towards the wheel) increases or decreases negative camber, and by how much. (I've sort of gathered that turning them round would increase the negative camber and make my problem worse, but I'd just like to be sure I've understood.)
Many thanks,
Tony

TR3driver
05-28-2012, 05:08 PM
How badly off is it? I assume you are aware that the TR4A is supposed to be close to zero, not the 2 degrees positive used on earlier cars. (Page 269 in TR4/4A Bentley)

Each degree of camber results in about 1/4" difference (6.6mm) measured between the wheel rims. If you have a nice flat floor, you can make a decent gauge from a carpenter's square with a couple of 6" rulers clamped to it.

I'm not sure about the shims, but I would guess that each shim is somewhere in the region of 1/4 to 1/2 degree.

Another point to check is the crossbrace in front of the engine. If it is missing, damaged or even badly rusted, it can let the frame sag enough to affect the camber. Some racers even modify it deliberately (in classes where suspension changes are not allowed).

PS, here's a diagram from the TR4A page in the workshop manual

Foura
05-28-2012, 07:33 PM
A couple of the TR restoration books point out that the diagram shown in the Workshop manual is wrong and that the "bulge" in the fulcrum pin should be mounted towards the spring tower, even though that looks incorrect. My car had them mounted the wrong way around (probably by me!) after the rebuild and had excessive negative camber. Swapping the top wishbones complete with pins from one side to the other cured the problem. Neil Revington has the full picture here:-

www.revingtontr.com/TR4A-6%20Upper%20Fulcrums.doc (https://www.revingtontr.com/TR4A-6%20Upper%20Fulcrums.doc)

It is not a big job to swap them. Support the lower wishbones on stands and undo 6 bolts per side - 4 on the fulcrum and 2 on the upper ball joint - and change them over. You don't have to disturb springs or brakes etc. Just make sure that you get the 2 bolts holding the ball joint correct. There is a difference. One faces forward and the other backwards.

Tonycharente
05-29-2012, 12:28 AM
Thank you both for your replies,

The diagram attached by Randall is the one I was talking about - it could hardly be more clear, and it is definitely for a TR4A. Obviously it could have been drawn wrongly, BUT the PHOTOS in the manual also show this same mounting (curve towards the engine). So did Triumph change their minds???

Either way, having spent all night thinking about it (!!! how sad is that? !!!) I realised that turning the fulcrum pins round (moving the curve to be towards the wheel) would in fact decrease the negative camber and so improve my position, thank you.

What is the impact of weighting the car up - what impact on the measured camber? I imagine it will further increase my excessively negative camber? Is that right?

Thanks again,
Tony

Tonycharente
06-26-2012, 02:56 PM
Just make sure that you get the 2 bolts holding the ball joint correct. There is a difference. One faces forward and the other backwards.



Well after spending a while "in denial" I finally got round to removing the fulcrum pins in order to turn them round - it stripped down VERY easily - just waiting for new wishbone bushes to arrive before putting everything back together - and reporting back to the forum.

So one last question, please... ...what difference does it make which way round the 2 bolts holding the ball joint are mounted? (Looks like either way would be the same to me - I must be missing something?

Thanks,
Tony

martx-5
06-27-2012, 06:31 AM
Just make sure that you get the 2 bolts holding the ball joint correct. There is a difference. One faces forward and the other backwards.

...

So one last question, please... ...what difference does it make which way round the 2 bolts holding the ball joint are mounted? (Looks like either way would be the same to me - I must be missing something?

Thanks,
Tony

And make sure that the inner bolt points toward the front and the outer bolt points toward the rear as shown in all the parts breakdowns. :whistle: WHY?? I ain't gotta clue! :crazy:

So, is there anyone out there that can come up with a logical reason why Triumph put the bolts in that way? Sure doesn't seem like it should make any difference which way they go. Good thing I have a TR3 and don't have to worry about that issue. :laugh:

PeterK
06-27-2012, 07:08 AM
The reason might be that at full lock the inner wheel rim surface can interfere with the excess threads of the bolt if they are inserted F to R. And R to F only leaves the bolt head and no threads sticking out.

On my 4A with alloys, I had to grind a bit of the upper rear arm to clear the wheels.

or not ...

JerryVV
06-27-2012, 11:49 AM
Agree, I think that is the reason.

martx-5
06-27-2012, 12:04 PM
I could see that there might be an issue with outer bolt hitting the rim at full lock in one direction or the other, but the inner bolt wouldn't be anywhere near the rim, so why do they reverse the direction? Besides, I can't tell you how many front ends we've taken apart at out Triumph tech sessions, and no one has ever paid attention to which way the bolts were inserted, and as far as I know, never have we run into a problem with any wheels hitting. Of course, there may well be some after market wheels that may hit to due their offset or other issues. Also, don't forget about the adjustable lock stops. I've seen those adjusted incorrectly and the wheels had problems at full lock. Offhand, I don't remember what they were.