front suspension

[jean]

Racing geometry has nothing to do on road cars. I had been advised by my good friend Jo from Red Baron, the settings I gave are for driving on a street and not for racing on a circuit

[MadMarx]

Racing geometry has nothing to do on road cars. I had been advised by my good friend Jo from Red Baron, the settings I gave are for driving on a street and not for racing on a circuit

 

 

Seems that I'll meet your good friend at Zandvoort in about 18 days :-)

[Badfrog]

Hi guys,

 

I started to look at my TR4 front suspension and voila: I have a TR4A front assembly.

But I don't know if it's early or late (was changed in the big '76 crash that involved essentially the front right side).

For info, I found these basic values for front susp. TR4A but I don't know if it's early or late 4A:

 

Caster = chasse (fr) = 2 deg. 40' +/- 1/2 deg.

Camber = carrossage (fr) = 0 deg. +/- 1/2 deg.

toe in = Parallel to 1/16"

 

I took the car to a geometry shop and here is the result ( I am not mixing up figures, it's really that bad):

 

left wheel:

1.34° caster

1.03° camber

 

right wheel:

0.12° caster

0.07° camber

 

Looks like I have some work to do.....

 

So what do you suggest: work on the frame for global realignment or compensate with adjustable fulcrums? Can I install Moss's TR4 fixed neg camber link on that TR4A suspension?

Nothing is simple but at least I know where I stand for starts.

 

Cheers,

 

Badfrog

Edited August 23, 2010 by Badfrog

[MadMarx]

.......

Looks like I have some work to do.....

 

So what do you suggest: work on the frame for global realignment or compensate with adjustable fulcrums? Can I install Moss's TR4 fixed neg camber link on that TR4A suspension?

Nothing is simple but at least I know where I stand for starts.

 

 

As you have a TR4a front you have all opportunities to make adjustments.

Shim the lower A-arm outwards to have about - 1.5 degree and add at the rear bracket shims to correct the castor to 3 degree.

Set the toe in as the works manual says.

 

I would say that no bending of parts is needed.

 

Cheers

Chris

[Badfrog]

I would say that no bending of parts is needed.

Cheers

Chris

 

 

 

My saviour.....

 

This being said, nobody here will do this seriously. I have to do it myself. Can you recommend a good tool to measure these various adjustments or a DIY procedure ?

 

Thanks

 

Badfrog

Edited August 23, 2010 by Badfrog

[MadMarx]

Just to make sure:

 

Do you have a FULL TR4a front suspension or only parts of it like wishbones or pivots mounted to a TR4 frame?

 

As you might now - the TR4 has only toe adjustment and the TR4a has a full adjustment.

 

If your frame is a TR4 then it is getting more complicated and you might have to cut or bend things.

[Badfrog]

Just to make sure:

 

Do you have a FULL TR4a front suspension or only parts of it like wishbones or pivots mounted to a TR4 frame?

 

 

All right, I checked : I do I have TR4A stuff on TR4 frame.

If I'm right, the "R" and "L" letters are stamped on the upper side and the longer arm is in front. Suddenly, I wonder whether I have the longer upper arm in the right position.

 

see pics of right side for clarity.

 

 

 

So, what's up, Doc?

 

Badfrog

Edited August 23, 2010 by Badfrog

[MadMarx]

okay, seems that you have a pretty stock TR4 suspension which came on at about production number CT6000 or something in late year 61.

 

The camber difference between left and right is not that bad. The different castor angle might push the car to the right if you take off the hands from the steering.

 

You want to rise the front end grip so you need MORE camber. Not positive, negative camber you need.

I would do a combination of this:

 

Shorten the upper wishbone (or install these fulcrum kits).

That would give you nice negative camber. Go for (-1.5) - (-2.0) degree. As you don't do millions of miles your tire wear will be okay.

 

The castor can be corrected by adding shims in front of the upper pivot joint. I don't have a photo of that but maybe other racers have.

 

Cheers

Chris

[MadMarx]

Have a look here for details:

 

http://www.tr-freun.de/triki/doku.php?id=vorderachse:umbau_tr4_vorderachse

[TR 2100]

Suddenly, I wonder whether I have the longer upper arm in the right position.

 

I think you're OK.

 

AlanR

[Badfrog]

The camber difference between left and right is not that bad. The different castor angle might push the car to the right if you take off the hands from the steering.

 

I would do a combination of this:

Shorten the upper wishbone (or install these fulcrum kits).

The castor can be corrected by adding shims in front of the upper pivot joint.

Cheers

Chris

 

 

Hi again,

 

Yes, the car pushes rightwards on its own.

I will follow your advice for the camber/caster setting.

Many thanks for your patience,

 

Badfrog

[stuart]

Hi again,

 

Yes, the car pushes rightwards on its own.

I will follow your advice for the camber/caster setting.

Many thanks for your patience,

 

Badfrog

 

Check the inner wishbone mounting tube is straight in the fore and aft plane and that the gap between the end of the rear from one side to the other is the same as the front from one side to the other. This what a bent one looks like.

Stuart

[Badfrog]

Check the inner wishbone mounting tube is straight in the fore and aft plane and that the gap between the end of the rear from one side to the other is the same as the front from one side to the other. Stuart

 

Ouch, bent as they come.

Sure will while I'm down there...

 

BTW, Were you the guy I ran into in 1976? I was too pi***d to remember...

Edited August 23, 2010 by Badfrog

[stuart]

Not a difficult repair but does require engine out. CTM do a complete piece.

Stuart.

 

[Badfrog]

Hi again,

 

I was about to PM Christian about the sequel, but then I felt this story might benefit others so I'll stay public.

I have ordered the adjustable fulcrums so the adjustable camber is a solved thing.

 

Now for caster or castor as also written:

Which part defines the fixed castor angle (0° or 3°) : The upper arms shape or the link/trunnion assembly ?

I have an element of response with the Moss on-line catalogue : The TR4 trunnion assembly is quoted as "0° castor" while the TR4A trunnion assembly is ... undefined. I believe it's a mistake and that it is indeed the trunnion that defines the castor angle. Would you agree on this ?

 

I should have 3° (late TR4 : CT 20649L) and I have 1.34° left and 0.12° right. Two problems: not the right value and asymmetrical.

 

As Christian said:

The castor can be corrected by adding shims in front of the upper pivot joint. I don't have a photo of that but maybe other racers have.

 

The photos below show (I hope) my two upper pivots.

1) It is where I will add shims for caster adjust. Right ? Then, should I also add the same spacer on the upper wishbone axis to avoid twisting the arm ?

 

2) The pivots are not in the same orientation as shown by the ref numbers wich are up front and upside down on the left pivot and back but upright on the right pivot.

 

From the asymmetry stated above, I think I should reorient the pivots so the numbers are similarly presented. Right ? The left being closer to the good values (1.3° for 3°) I should turn the right one so the numbers are also outwards and upside down. Or are these pivots fully symmetrical?

 

Once this done, what shim thickness would bring me from 1.3° to 3° ? This shim I can easily make with all the steel bits lying on my shelves.

 

Cheers,

 

Badfrog

 

 

 

Edited August 24, 2010 by Badfrog

[Kiwifrog]

Dear Badfrog

 

The 3° castor is created by the top arms and the trunions, the uprights are the same on early and Late TR4's then change on the 4A to 6 to include a grease nipple on the upright and the later trunion has a removable lower pivot bolt to make changing trunions easier.

 

If you take the trunions off of the car and place them on a flat surface the 3° angle is quite easy to spot normally if you have the later style upper balljoints you should have the 3° trunions but I have seen a car with 0° trunions and the later style upper arms and ball joints definatly a bad thing. The 3° trunions are also handed unlike the 0° trunions. If you are going to the trouble of rebuilding the suspension I would remove and check the trunnions to make sure they were changed for the correct 3° items after the accident in 76

 

Finally your images show the top ball joints not the Pivots. The top Pivot is the part on top of the suspension tower that houses the front spring. The ball joints have no prefference for installation and can be put in either way as they are symetrical left to right

 

Cheers

 

Alan

Edited August 24, 2010 by Kiwifrog

[Badfrog]

Hi Kiwifrog,

 

Thanks for your input. Things have moved since last my post : I have identified my trunnions as late TR4 (hence 3° castor) due to the additionnal bolt located at the rear.

Which means I have to find where and how my theoretical 3° castor has gone into nothingness ...

 

If I get you right, what I photographed is a top ball joint (I figured that) but not "the" pivot. Ball joints indeed appear symmetrical but have different numbers casted on the body. Is this a problem ? They are in excellent shape (no play) but should I take the short way to safety and change the pair ?

 

Then, what is the pivot?

According to the parts catalog, the horizontal bar with bushes that holds the upper arms on the spring tower is the fulcrum pin. The only pivot mentionned belongs to the lower trunnion assembly.

So, now I have no idea where I should put the shims that Christian mentionned to change the caster. You have to remember that Christian and I live on "borrowed english" and that vocabulary and personal vernacular use may be bigger traps than mechanics.

 

Isn't this fun ?

 

Cheers,

 

Badfrog, is this a dead rat stuck in the lower wishbone? and wait.... my watch ... I found the watch I lost in the crash....

[stuart]

Hi Kiwifrog,

 

Thanks for your input. Things have moved since last my post : I have identified my trunnions as late TR4 (hence 3° castor) due to the additionnal bolt located at the rear.

Which means I have to find where and how my theoretical 3° castor has gone into nothingness ...

 

If I get you right, what I photographed is a top ball joint (I figured that) but not "the" pivot. Ball joints indeed appear symmetrical but have different numbers casted on the body. Is this a problem ? They are in excellent shape (no play) but should I take the short way to safety and change the pair ?

 

Then, what is the pivot?

According to the parts catalog, the horizontal bar with bushes that holds the upper arms on the spring tower is the fulcrum pin. The only pivot mentionned belongs to the lower trunnion assembly.

So, now I have no idea where I should put the shims that Christian mentionned to change the caster. You have to remember that Christian and I live on "borrowed english" and that vocabulary and personal vernacular use may be bigger traps than mechanics.

 

Isn't this fun ?

 

Cheers,

 

Badfrog, is this a dead rat stuck in the lower wishbone? and wait.... my watch ... I found the watch I lost in the crash....

 

The pivot is the bar across the top of the spring tower that your top arms swivel on. The shims go between the outer end of the top arms and the top ball joint. Jaguars used to have that arrangement but you do have to be careful that you dont introduce too much of a twist into the upright as this will cause wear on the trunnion. Looking at your pictures of the turrets it may just be the angle of the picture but the left side looks as if the turret leans rearward more.

Stuart.

[Guest ntc]

Looking at your pictures of the turrets it may just be the angle of the picture but the left side looks as if the turret leans rearward more.

Stuart.

 

 

Hi Badfrog

I thing Stuart may have seen something as I did it may be the pics but I would measure everything two wrongs do not make a right

[Badfrog]

1) The pivot is the bar across the top of the spring tower that your top arms swivel on. The shims go between the outer end of the top arms and the top ball joint.

2) Jaguars used to have that arrangement but you do have to be careful that you dont introduce too much of a twist into the upright as this will cause wear on the trunnion.

3) Looking at your pictures of the turrets it may just be the angle of the picture but the left side looks as if the turret leans rearward more.

Stuart.

 

 

Hi Stuart,

 

1) Ha, we're having an understanding here. So said pivot is the fulcrum pin and I have to put the shims between the front upper arm and the top ball joint. That was my initial idea from Christian's advice and I'm glad this is sorted out.

 

2) I read about this Jaguar story. I'll have to move with caution. I feel that shims between 20-40 thou (0.5-1 mm) should do the trick without causing excessive distorsion.

 

3) You are right. The photos look weird but I was holding the camera with only one hand so it may be a visual trick. Yet, if the turret had been banged rearwards (pardon my french) shouldn't it cause an excessive caster instead of insufficient ? I'll check tomorrow.

 

Cheers,

 

Badfrog

 

PS: NTC, you're right. I'll put on my math brain tomorrow and blueprint the whole area.

Edited August 24, 2010 by Badfrog

[Kiwifrog]

Hi Kiwifrog,

 

Thanks for your input. Things have moved since last my post : I have identified my trunnions as late TR4 (hence 3° castor) due to the additionnal bolt located at the rear.

 

 

 

Hi Badfrog,

 

I am not sure what you mean by the additional bolt located at the rear ?? Both the 0° and 3 ° Trunnions lock stop bolt with excentric spacer parts 97 98 and 99 in the moss catalogue. If I had issues with geometry I would check everything that could affect it and make sure including chassis geometry. As they say assumption is the mother of all foul ups or something simular

 

Cheers

 

Alan

[MadMarx]

offtopic:

 

why does the French nick names do end on "frog"?

[Alec Pringle]

Hi Chris,

 

the good folk of France have a liking for eating the legs of frogs . . . . to them a delicacy, to us Brits a disgusting habit.

 

So we call the French . . . . Frogs !

 

In the same fashion, Germans are Krauts. I guess you might qualify for Madkraut ?

 

Doubtless you have an appropriate nickname for us Brits in exchange ?

 

Cheers,

 

Alec

[MadMarx]

Ahh...I see.

 

A vintage name for the English but still in use is "Tommys".

The name came from the Tommy gun they used during the war.

 

As far I know the French call the Germans "Bosch".

 

I live close to France but I don't know any name we have for French as French. Maybe a lack of fantasia on our side.

 

Cheers

Chris

[Alec Pringle]

Hi Chris,

 

the origins of the nickname Tommy for the British soldier go back long before the Thompson sub-machine gun.

 

http://en.wikipedia.org/wiki/Tommy_Atkins

 

Cheers,

 

Alec