Suspension 101 questions

[stephen low]

Thanks guys a lot of great info. but now I'm really confused and will have to measure the arms to clarify what I have.

Do the S1 and S2/3 arms look much different?

I ask as the GF manual says the chassis is designed for S2/3 suspension, I have vented front brakes and S2/3 lower arm and am guessing the original constructors would have followed the guidance of GF. They may have unwittingly bought S1 uppers, can this be decided just by visual inspection?

If it proves I have S1 uppers, I gather I can still achieve a suitable set up, is this correct?

Given I will have to look at the rear as well at some time, why do you recomment rear toe in?

What effect does it appear to have/cause to these cars?

How much toe in have you guys used on the rear?

At least I know for sure that my rear brakes are S2/3 I have an old receipt for their repair!

Cheers

[CHANMADD]

Because a Cobra is a short wheelbase car and funny things in the handling department start to happen when the track(width) starts approaching the wheelbase, Imagine driving a square car? With my setup I was always in the top 3 on road race courses in South Africa Cobra Club meetings.(Pissed a lot of guys off)

Well because of this I have found that 1.5 degrees of negative camber on each wheel ,front and back,and 1.5 degrees toe in on each wheel will make the car handle just right. Now of course we need to dial in some castor ,that makes the car self center ,so also I like about 2 degrees of castor on the front wheels. Obviously if you are running a “live” axle at the rear you have no rear adjustments other than to make sure that the triangulation is right ,which of course is important on all cars.If the triangulation is out the car will go down the road like a crab (you know).

[Tenrocca]

Stephen,

Heres a pic of series 1 arms, you can see the difference when the front arm is at the back and back at the front as Ive layed the left hand side on top of the right hand side:



Heres the series 2\3 arms I have:



See how they kink in a bit just after the pivot bolt thingy (technical term). The difference between using series 2\3 arms (which are the same dimensions front and back) and the series 1 arms, is that the series 1 arms will place the upper ball joint 8.5mm further back.

The jury is out on whether series 2\3 arms come in a "straight" design, the place I got mine from said that they had not seen series 2\3 arms straight like series 1.

Cheers.

[Rebel1]

Steve, I have sent the manual pages showing the differences in the arms. ( you may have got it twice )

Together with the above pics from Tenrocca you should be able to identify what you have.

If I remember correctly the problem that Tenrocca was trying to identify was clearance for his springs in the CR. The G-force and RMC don't have the same problem as the spring is mounted under the top pivot bar.

However, Tenrocca's pics show the difference achieved in caster between the two series. This can be used to your advantage. I am positive that series 2/3 did not come in a kinked design.

I would just make sure that the components you have are from the same series and go from there.

Cheers

[justcobra]

Originally Posted by Tenrocca

Stephen,

Heres a pic of series 1 arms, you can see the difference when the front arm is at the back and back at the front as Ive layed the left hand side on top of the right hand side:



Heres the series 2\3 arms I have:



See how they kink in a bit just after the pivot bolt thingy (technical term). The difference between using series 2\3 arms (which are the same dimensions front and back) and the series 1 arms, is that the series 1 arms will place the upper ball joint 8.5mm further back.

The jury is out on whether series 2\3 arms come in a "straight" design, the place I got mine from said that they had not seen series 2\3 arms straight like series 1.

Cheers.

Gentleman! I need more photos of Series 3 RMC front end showing amongst other things how the Jaguar upper and lower wishbones are adapted th the chassis as I am constructing a hybrid chassis.
I got three Jaguars -two with a V12 which have LSD and the third is S2 six cyclinder.

[stephen low]

So are you saying I should run either all S1 top and lower or all S2/3?

Or can I run S1 upper and S2/3 lower if this is what I have, but simply adjust the suspension to suit the different set up achieved by the S1 upper?

[Rebel1]

Originally Posted by stephen low

So are you saying I should run either all S1 top and lower or all S2/3?

Or can I run S1 upper and S2/3 lower if this is what I have, but simply adjust the suspension to suit the different set up achieved by the S1 upper?

I would prefer to run series 2/3 everything.

What can change is the caster with incorrect mix/match of the various series.

Both RMC and g-force originally suffered from light, vague steering and would not self center. The solution was to move the top control arms back to increase the caster. Note how your top arm is bolted behind the centerline of the chassis cross tube. Originally the arms were in line with that cross tube. ( leastwise it was with the RMC.)

Caster is not a critical issue when compared with other front end settings. In fact caster in modern cars has increased progressively as power steering has become standard fitment. My fairlane on full lock would almost lay the front tyres on their side.

Your G-force has heaps of caster and it is for that reason I'd prefer the series 2/3 components. But.....the series 1 components could be used if you found the steering heavy as they are offset so could reduce caster by moving the arms front to back.

Confused yet?

[RoyTheBoy]

Stephen, What are the part numbers on your upper control arms?

Roy

[CHANMADD]

I would definately brace the bottom arm as well.

[stephen low]

So I am now guessing but will confirm that I have S1 uppers but have S2/3 lowers.

Les

You said first, stick with all the same series, but your last post talks on how adjustable it can all be, so does it really matter if I am happy to shim etc?

Only advantage I see is that GF guidance to set up is for all S2/3 components hence I'll need to find my own way if it is mixed componentry.

Is there enough adjustability to get to 3- 4 degrees positive caster?

And then to get to that sort of caster range, which S1 arm is fitted to front and which to rear? That is, am I trying to move the upper ball joint forward or rearward, compared to what a S2/3 arm set would achieve?

Tenrocca's pic of the S1 arms shows fore / aft variation perfectly, the trouble is I don't know which way it needs to be on the GF chassis.

Tenrocca

Did you change to S2/3 uppers as the 2nd pic. shows? Why?

Mike

You are running S1 upper arms? Did you stay at 6 degrees caster and how has this felt in terms of wheel turning effort at slow turning speeds?

Additionally, to my mind the offset S1 arms then also need the spacers at the top behind the upper wishbone pivot arm, as my picture shows, to achieve the same degree of camber as a S2/3 set of arms directly bolted against the chassis, as the GF manual suggests.

Is my logic right here?

[Tony Cram]

Stephen,

I would suggest you came and look at my setup on the RMC. It will be very similar to the G Force. The car is currently up on stilts while I work on the radiator but wont be there much longer. You can get a good look at everything while it's there.

I have series 1 uppers and Series 2 lower arms and I can get enough adjustment for both track and road. If I put the series two upper arms my front wheel would sit too far forward in the wheel arch (ie I start to get - ve caster). I would have to do some surgury to get the wheel to sit correclty. You dont need/want a lot of caster especially if you are not going to have power steering. I have 3 degrees + castor and it is plenty. The car pulls up straight all the time and feels very firm on the road.

Give me a call.

Cheers

Tony

[PCC]

Les,

Are you a Jag Designer from a past life????

Very informative - You'll be saying that you have 51% pome in you

Is it right that with the Jag shims, you can only alter the alignment by reversing the shims from one side to another?

I was told this when getting the new tyres on. Like most things I just nodded and asked if they had a VB in the fridge

[Rebel1]

Originally Posted by PCC

Les,

Are you a Jag Designer from a past life????

Very informative - You'll be saying that you have 51% pome in you

Is it right that with the Jag shims, you can only alter the alignment by reversing the shims from one side to another?

I was told this when getting the new tyres on. Like most things I just nodded and asked if they had a VB in the fridge

Pete, I guess you are talking about the caster shims on either side of the top ball joint.

It is somewhat true that is the only adjustment but only with the top arms you have.

To try to explain.... The series 11 top arms each have an offset of 2.1" (5.3cm). if you drew a line thru the center of the ball joint to the inner pivot shaft at 90 degrees to the pivot shaft you would have an equal amount of pivot shaft to the front of that line as there is to the rear of the pivot arm. However, moving the shims allows a variation of that point.

However, the series one upper arms are handed. The rear one has an offset of 1.75" whilst the front one has an offset of 2.38" so a similar line drawn thru the ball joint would be offset on the pivot shaft by the difference of .35" or .28" depending on what arm is installed where.

Now, if you swop out your series 11 arms for series 1 then you have a much larger range of caster angle because of that offset and you still have the shims. Note, you cannot use a series1 and a series 11 arm together....that's a no no for sure.

Is that clear Pete?

[Rebel1]

Steve, I think you are worrying about bugga all. Just put on what you have but do identify what you have from the manual pages I sent you.

The reason for that knowledge is that you know from what point you are starting when you do get a final alignment.

I just advised the series 11 because that's what G-force say for the car. The series two top arms are not handed and can be put to the front or back and your caster will remain as G-force set up in their jig.

Looking at the second pic you posted I'd say you have heaps of caster if fitting the series two. However, you can fit the series 1 but may end up with little caster or too much caster depending on where you place the series 1 arms. Again tho, it is obvious the top mount is set for a series 11.

The reason for that is the if you consult the manual pages it shows that the rear arm has 1.75" offset and the front 2.38". Note that is over .5", a hell of a lot if you get them wrong.

Look at those pages I sent...identify what you have. Identify the three different top arms and the two bottom control arms.

If you have series 1.....I'd go buy a set of series 11 from a wrecker. They are cheap and plentiful.

Cheers

[stephen low]

Thanks Les

Will be going home shortly to consult your manual.

Have a conversation with TC who raised one valid point from his RMC. He found that using a S2 upper pushed his overall wheel location too far one way within the wheel arch, to the extent it was noticeably closer to one edge and not so visually appealling. It may also have raised issues of rubbing but that wasn't mentioned.

I'll go with my arms if S1 and endeavour to set up as needed.

Many thanks for the comments though, it's all valuable knowledge.

Cheers

ps I'll let you know what I do have when I find out - just for the record!!

[Rebel1]

Steve, that's because of the 1/4" difference in the lower control arms.

Cheers

[Rebel1]

I have posted pages showing the difference between series 1 and 2 in my gallery for those interested.

EDIT: The shape of the top arms does not necessarily define the series.

Cheers

[stephen low]

Les et al

I have S1 upper wishbones!!!!

Thanks for the diagrams Les, infact only measured to see if the arms were bent, as I compared front and back to each other and the difference was obvious.

However per my discussion with Tony, and his lowers are S2 with S1 uppers, I will continue with the mixed arms and see how close I can get the settings to my preferred targets.

Can I do any simple measurements to try and ascertain what settings I might be close to without first visiting an alignment shop? I know how to go about checking camber and toe in, what about caster assessment - how can this be done?

Also why the shim limits either side of the top ball joint?

And what is it about the car's narrower track width and lighter weigh that makes the suggestion of rear toe in a more successful option?

Cheers

If I can set up myself to something sensible I will road test to see how good, bad or indifferent the car is prior to getting professional alignment.

[Rebel1]

Ok Steve, least you know.

Caster can be roughly checked with a plumb bob and protractor. hang the plumb bob so it intersects the center of the lower ball joint. Use a projector ( I have a marine version) to measure the caster angle. ( ie a line thru the bottom and top ball joints from the perpendicular). You can buy a tool but it will get little use.

Shims either side of the top ball joint total three. The width of the top ball joint body, plus 3 shims plus the offset of the arms equal the length of the inner pivot shaft. more shims and you'll be inducing stress to the top arms.

Rear toe.....a debatable subject and a bit involved for this short space. My rear will be set with 1/8" of toe.

It's a topical discussion because the jag is so difficult to change rear toe as it's done with shims under the control arm inner brackets. If it was an easy adjustment folks would try it and test the results.

Cheers

[AC-460]

Originally Posted by Rebel1

Ok Steve, least you know.

Caster can be roughly checked with a plumb bob and protractor. hang the plumb bob so it intersects the center of the lower ball joint. Use a projector ( I have a marine version) to measure the caster angle. ( ie a line thru the bottom and top ball joints from the perpendicular). You can buy a tool but it will get little use.

Shims either side of the top ball joint total three. The width of the top ball joint body, plus 3 shims plus the offset of the arms equal the length of the inner pivot shaft. more shims and you'll be inducing stress to the top arms.

Rear toe.....a debatable subject and a bit involved for this short space. My rear will be set with 1/8" of toe.

It's a topical discussion because the jag is so difficult to change rear toe as it's done with shims under the control arm inner brackets. If it was an easy adjustment folks would try it and test the results.

Cheers

Can you give me a bit of an idea with measurements...ie if you were to place a spirit level centre to the bottom ball joint what is an ideal measurement to have the centre of the top ball joint back from the centreline.