Suspension 101 questions

[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.

[Tenrocca]

Originally Posted by Rebel1

Small observation of Tenrocca pics.

The outside bolt attaching the top ball joint (round head) should have the head to the front of the ball joint for clearance with the tyre at full lock

Cheers.

Thanks Uncle Les - will do

[Aussie Mike]

I've got those straight series 1 upper arms and when I went to get my wheel alignment done I had about 8 degrees of positive castor. I flipped them left for right and that brought it back to a more respectable 6 degrees.

Cheers

[Rebel1]

Originally Posted by Aussie Mike

I've got those straight series 1 upper arms and when I went to get my wheel alignment done I had about 8 degrees of positive castor. I flipped them left for right and that brought it back to a more respectable 6 degrees.

Cheers

Once upon a time lots of folks thought the jag front suspension was fixed and unadjustable and lots of money was spent on fabricating arms to get the adjustments.

This exercise indicates how adjustable it really is. One has only to become familiar with all the various series.

As mike indicated....swopping series one arms front to back changes the caster. Series 11 are neutral and is between the two extremes of the series one.

When you consider this range of adjustment and then remember the top three ball joint shims can also be moved about, it makes for considerable range of adjustment to the caster.

Camber is just as adjustable with various thickness shims between the top mount and the pivot bar. Maybe one set for the street and another for the track.

It's certainly not perfect...but it isn't the un-adjustable beast many thought.

Cheers

[Rebel1]

Originally Posted by Tenrocca

Thanks Uncle Les - will do

Ya welcome ole buddy.

Now can I also tell ya you're only sposed to have a total of three shims on the sides of the top ball joint...you have four.

[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]

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

[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?

[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

[stephen low]

G'day guys

Had a good go at settings and found some strange results.

Bolted uppers direct to chassis and had neutral camber one side and reasonable negative the other. Set everything else up and after a short burst down the court found both sides have negative camber. Clearly my springs have to settle heaps.

Steering is tough at park speeds so may have too much castor but will sort this later.

Also lowered body using spacers under the lower wishbones and figured out why I have so much room above tyres to mudguards - 50 series tyres. Hadn't even twigged to this one.

Only query I have is whether the steering tie rods should be bolted in from the top or bottom?

As I've said previously, the previous owners of this kit really had no knowledge, and I suspect that their attachment of the tie rods from the top is wrong. Is this suspicion correct?

Both the angle the rods make with the stub axle units and particularly the wheel movement when the car is raised and dropped tells me all isn't right.

Look forward to more info.

Cheers

[stephen low]

Don't need advice on the tie rod ends guys, but learnt a lot tonight swapping attachment and seeing what it did.

Comments and advice I previously recall all fell into place when I changed the tie rods around. I noted how the steeing rack was level with the lower wishbone pivot and how the tie rods located correctly, replicate the angle made by the lower wishbone.

Once done properly, any lift or compression of the front suspension didn't cause the wheels to toe in or out.

Clearly I had bump steer extreme until this correction.

Strange how the builder's manual doesn't say a word about such an important issue.

Anyway all sorted - for now - and many thanks to those that contributed to my learning curve on front suspension.

Cheers