Jag front suspension / steering geometries

[Rebel1]

Originally Posted by Aussie Mike

The word tampon actually developed from the word "Tampion" which is a plug for the end of a naval gun to stop the ingress of water.

Check it out: Tampion

Cheers

Ohhhh..OK...so if I want to go shooting guns underwater then I need some tampons.

Silly me....but then I have led a very sheltered childhood.

[Ant]

Phil,

What size rotors are you running under the big AP Racing calipers?

I am looking at AP caliper 6pots road version with large pad, but not sure whether to go 1.10" width X 13" rotor or 1.25" wide X 13" rotor. This car would be lucky to more than 950 - 1000kg kerb weight when finished - hopefully!

[Philm]

HI Ant,
The fronts are 365mm x 32 rotors.

at 1000kgs that is light, my car is about 1200kgs.

Phil

[David Hodgson]

Slowy,

I wouldn't have any pic's as I built mine pre digital and wasn't so snap happy with film. I could try and sketch something for you soon.

I like CHANMADD's arms that project rearward. There has been some talk on this set up before, but I don't recall what the concensus was. The arms would be under tension rather than compression when accelerating.

One thing in favour, it keeps the area under the seat clear for best seat positioning.

[stephen low]

David

Any type of pic would be good for me so yes please.

Re-reading your post, please correct me if I have pictured the wrong items!

The pinion flange I presume is the face to which the tailshaft is bolted to? If so then the string line would be run parallel to the chassis rails, assuming the chassis is square in construction, or averaging the distance to the rails each side if not.

The hub flanges are the faces against which the wheel rims bolt? But here with pivoting arms, the pivot bushings have the potential to cause excess lateral movement if worn?

Cheers

[CHANMADD]

These arms have never given an ounce of problem and like you say under tension whilst accelerating(very little stress),and so easy to install,and they are long so very little effect when traversing through the arc with suspension travel.

[David Hodgson]

Originally Posted by stephen low

David

Any type of pic would be good for me so yes please.

Re-reading your post, please correct me if I have pictured the wrong items!

The pinion flange I presume is the face to which the tailshaft is bolted to? If so then the string line would be run parallel to the chassis rails, assuming the chassis is square in construction, or averaging the distance to the rails each side if not.

The hub flanges are the faces against which the wheel rims bolt? But here with pivoting arms, the pivot bushings have the potential to cause excess lateral movement if worn?

Cheers

Spot on Slowy. I used a right angle square and string line to project perpendicular to the pinion flange.

[stephen low]

Thanks David.

I am presuming that it is ok to leave the diff alignment for now and tackle this later when the body comes off again? And I suppose the same question for all other rear tyre settings, toe in etc can I leave alone until after engineering?

I will be tackling the front shortly so that the bugger can just be driven, let alone safely driven. I will need to get to a few venues to finish it off and will be doing this via the 28 day Vicroads freedom ticket!!

Cheers

[David Hodgson]

If the diff alignment is not spot on, an alignment shop can still set up the rear wheels with the Jag adjustments.

It is best practise to have the extended axis of the pinion and crankshaft in the same planes for the uni's to function correctly. So it is not critical if you are not spot on now.

Having said that, as the suspension raises and lowers, the angle of the of the hub's change in relation to the diff axle flanges, though this is only momentry.

A quick way of checking your rear alignment is way out(this works best with solid rear axles) is to roll the car straigh through wet pavement on to dry and check the tracking of the rear in relation to the fronts.

[stephen low]

Thanks David I will get to that in stage two after rego.

But it does lead me to another question I know I asked through the forum in the early days, and that was why the diff. pinnion flange is not centrally located down this car's centreline.

I noticed this soon after getting the car and again when I was fitting the tailshaft. The flange is definitely off centre left to right, to teh driver's side, by I guessing 10 plus millimetres, ie enough to visually detect.

Do you know why this is so? Is it std GF practice or have the initial builders of my kit got it horribly wrong? I bought the kit as a roller from previous owners.

Certainly from a rear wheel location, nothing seems untoward so I'm guessing each side has been shortened appropriately, but it still worries me that I have another problem to sort. Or at the worst my uni joints are always going to have a short life!

How was your diff set up?

Cheers

Steve

[Rebel1]

Stephen, I know you directed your question to David but the offset pinion is normal so stop worrying.

Mine is offset 25mm. (If I remember correctly)

The main thing is to get the three flanges square in the car as David suggests. That is the pinion and the two drive shaft flanges.

In my RMC the top mount plate was off square so that when I bolted the diff in with the tapered Jag bolts it would pull the diff out of square. ie. Looking down on the top of the diff in plan view, it ended up rotated slightly anti clockwise.

Now....it wasn't much but when you extend that inaccuracy out to the wheels it ends up quite considerable.

Cheers

[David Hodgson]

Steve,

As Les says, if the pinion is offset lateraly it does not matter, it will most likely be offset verticaly as well. The alignment does not need to be in the "same axis", but the two axis should be in the "same plane" to look after the uni's and vibration.

I have another jag diff at home, I'll measure if the pinion is in the centre. My guess is not.

[NASSTY]

To concur with Les,

The whole point/simplicity of the Jag IRS is that as the half shafts also double up as the top arm of the suspension. Therefore the driveshafts must be equal in length for the IRS to work properly/evenly on both sides. As a result the pinion must be offset so that the crown wheel is in the middle of the axle in order for the half shafts to be equal in length.

This offset doesn't matter as you want the uni's on the drive shaft to rotate or else they will not be lubricated properly.

What does matter is that the horizontal and the vertical plains of the pinion to the tail housing of the tranny are the same.

[stephen low]

Thanks Les & David

I don't care who gives me the info. just so long as it is accurate, so many thanks for straightening out my worries.

I'll definitely have a good look later down the track.

The radius arms obviously locate the drive hubs during fore/aft movement so I presume they are not the means to ensure the hub flanges are parallel to the chassis. If these hubs need to be adjusted, how is that achieved?

[David Hodgson]

just to expand on Nassty's reply, the crown wheel can be offset within the diff housing, so too the pinion, the axle stubs will be varying lenghts depends where the carrier ends up. Most live axles do this. External IRS arms and drive shafts will be equal.

The hub alignment (toe in) is adjusted at the diff housing by shims where the lower pivot bracket is attached. I suppose Jag figure the is enough give in their trailing arm rubber bush.

My G-Force bent trailing arm has an adjustable rose joint to allow for the control arm adjustment.

Camber is adjusted again at the diff axle flanges, by shims, where the drive shaft uni bolts up.

[BJ's Snake]

Dave,

Is the "other jag diff at home" a LSD version?

Cheers

Brett

[David Hodgson]

Slowy,
The spare diff is spare diff is stored in a hard to get ot place, but best I could reach in and measure, the pinion centre line is about 45mm off centre to the drivers side.

Hi Brett,
No it's an open wheeler 3.31?

Chris G has a 3.54 LSD I've been eyeing off for a while, but like I said, I got no drive to do the swap.

[stephen low]

David

Thanks again

If you look at my thread signature, you will notice mine too is a 3.54 Powerloc diff just itching to lay twin black lines - not to mention the driver!!

[Rebel1]

PL 3.31 here.

Hope that it gives me a better first gear and minimize wheel spin with the huggggeeeeeee torque.

[stephen low]

Les

Mine was part of the deal when I bought the kit so didn't have any choice and it will be something I'll review and consider down the track.

Can jag diff centres be changed to get closer to the ratio desired?