Rear Suspension, ride height

[Gfhug]

Steve, et al, my car on standard springs and Jeremy's on CMC's spring both sit about 8 inch IRS plate to ground and the front and rear wheel arches are the same height and the cars look symmetrical fore/aft. Mine also has renewed front suspension parts and all dimensions were correct.
How does 50EE compare I wonder? And others with their different height IRS compare front to rear?
What is (was back in the day) correct?

Geoff

[mgcjag]

Hi Mark.....any answer to this yet......Steve

[Geoff Green]

Concours with rain today. Judging under cover and I managed to get photos of 6 car rear suspension lower arms. One photo shown as all are about the same. Note the cars were without driver or other items like luggage or passenger and I did not check fuel level.

I extended the photo horizontal and axle lines out to obtain an accurate reading with my angle gauge. All were 4.8 to 5.5 with the average 5.2 degrees with the diff end higher than the hub end.

[PeterCrespin]

All were 4.8 to 5.5 with the average 5.2 degrees with the diff end higher than the hub end.

As per post 42:

"Had that drawing in mind when I posted Stu. Trouble is, I’ve driven too many miles behind many Es and in my mind’s eye I see only wishbones sloping down by varying degrees."

By the time you see one with horizontal wishbones you're usually looking at a heavily laden car, often a V12 2+2, not your average mid-laden day tripper.

[Series1 Stu]

Ah. Did I not say the drive shafts are horizontal so as to reduce wear on the journals? If not then I meant to.

Regards

[mgcjag]

Still no resolution to the original posters problem.....its such a shame when we get no feed back....especially when there has been so much interest..60+ posts.....it just leaves the thread in limbo and dosnt help any other members that may have similar problems when changing shocks/springs.....heres hoping we can get an answer....Steve

[Series1 Stu]

I don't think anybody had forgotten, I just think these things take time. Especially when we are all busy with many other commitments.

I have created a simple 3D CAD model of the rear suspension based on the illustration in the workshop manuals and Peter's measurements along with a few of my own.

Having checked and double-checked everything I think my model is quite credible although if anybody can offer up any precise dimensions from accurate measurement of parts then that would be a great help.

See the 3 illustrations below.







The mid laden image shows the suspension as per the Jaguar illustration. The bump and rebound illustrations show the positions of the suspension at the 3.125" extreme wheel travels.

I haven't bothered to model the damper as this would be pointless for the most part. Instead I have monitored the distances between the damper eyes. Therefore we have:-
Minimum damper length (full bump) = 251 mm between eye centres.
Maximum damper length (full rebound) = 322 mm between eye centres.
Mid Laden damper length = 286 mm between eye centres.

It is encouraging to see that the compression and extension of the damper is exactly equal about the mid laden position, suggesting that we have pretty muich captured design intent.

If anybody has any standard rear dampers (preferably original items removed from their car) hanging around that I could get the measurements from then I can model these up and add them into the assembly. I am particularly keen to find the spring seat positions.

Of note is that this gives us around 4.3° of camber change from full bump to full rebound.

Also, if anyone was wondering, the wheel representation is based on the Jaguar illustration and shows only the tread width.

Regards

[MikeMilton]

Of note is that this gives us around 4.3° of camber change from full bump to full rebound.

Also, if anyone was wondering, the wheel representation is based on the Jaguar illustration and shows only the tread width.

It would be interesting to me if you could update your exercise with the full suspension (really, just both sides) and reflecting camber (and tire patch contact) for a variety of 'solutions'. In this case, the solutions would be various combinations of rim (backspacing would seem to matter, and varies between OEM, MWS, Boranni, etc), tread width, and sidewall ratio (height). There are many discussions about what tires fit but not much about how rims and tires impact suspension geometry. I'm not too sure about how to model tire deformation which would also matter for a discussion of contact patch and would vary significantly between tires.

My impression (completely a guess, really) is that people who like the classic solutions do so (at least in part) because of the way the contact patch behaves during cornering. So one question is: do the traditional solutions give more 'confidence' and then 'give up suddenly' while the wider / flatter solutions provide less confidence but earlier warning and a better opportunity to control slip? Another might be: to what extent do we care about and need to mitigate against body roll for any particular tire solution?

[PeterCrespin]

My impression (completely a guess, really) is that people who like the classic solutions do so (at least in part) because of the way the contact patch behaves during cornering. So one question is: do the traditional solutions give more 'confidence' and then 'give up suddenly' while the wider / flatter solutions provide less confidence but earlier warning and a better opportunity to control slip?

This is the exact opposite of what happens Mike, at least in my experience (unless we mean different things).

[PeterCrespin]

Stuart

What do you use as the horizontal delta between inner fulcrums? Around 100 mm? Looks exaggerated in the diagram, although that may just be an illusion.

An old but I believe original (Armstrong) damper shows these approx distances from the eye centres:

Fully extended 13” (330 mm)
Travel (estimated, metal-to-metal, spring still fitted) 4” (102 mm)
Bottom eye to spring face of lower perch 2” (51 mm)
Upper eye to spring face of upper perch 1 7/16” (40 mm)

[Series1 Stu]

Hey, thanks Pete. I will add the damper dimensions into the model but not for a good week or so due to work and family committments.

I am pretty sure that the relative positions of the inner fulcrums is correct, maybe it's because I've simplified the appearance of the rotational centre of the universal joints.

The full extension length of the damper seems to concur with my estimates. What is the closed length?

Doing some mental arithmetic at the moment.

Regards

[PeterCrespin]

I was hoping you wouldn’t ask...the spring was still on. Fortunately, I found the stripped one ( Girling, incidentally) which had no bump rubber and metal to metal it’s 9”/ 230 mm.

Yes I was assuming the UJ centreline. I checked a diff before posting because the dog bone brackets are ‘outboard’ facing, but despite that the lower fulcrums are still well inboard of the inner halfshaft UJs. ‘Unequal wishbones’ front and rear - gotta love the E-type suspension.