free hit
counters
Castor shims on Turbo SE 1990. - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums #ForTheOwners Jump to content


Castor shims on Turbo SE 1990.


Recommended Posts

HI all,

Since I renewed the suspension on the 1990 Turbo SE, I thought why not do the rest? so fast forward to today. I have just begun reassembling the front suspension, wishbones etc. So, when I took the upper front wishbones apart, I noticed the following:

* there are one 3mm castor shim on each side (right and left side of car), placed just in front of the rear most upper wishbone, (parts manual says min 1,5mm for clearance under extreme movement).

* there are on the left side of the car, front, one 1,5mm shimplate and one 3,0 shimplate on the rear pointing side of the upper ball joint, so it's opposite the parts manual, and opposite the service notes' standard setup.

* there are on the right side of the car, front, one 1,5mm shimplate on the rear pointing side of the upper ball joint, so that is opposite the parts manual and opposite the service notes' standard setup. And it's not equal to the other side of the car.

So, my questions are these, from looking at things:

1/ I realise that adjusting the castor on the front wheels, shim plates can vary but can they also be installed on the opposite side than described in manuals?

2/ Are they allowed to be unequal between left and right side of car?

3/ As my car is a 1990, it's the old setup with similar arms front and rear of upper ball joints, etc. So to what angle can the upright be installed and correctly function? Castor seems to be described for my car being min. 1 degree 45 minutes to max. 3 degrees, within 0 degrees 30 minutes side to side.

4/ having installed Lotac poly bushings all over, save the radius arms rear, torqued things up tp spec as per service notes (I know, only once car is balasted with half tank, 2 persons), but as a test, I can only move the upper front wishbones in a fairly stiff spongly manner, which seems to be the red poly bushings twisting by their shore. Is that correct, or should the upper wishbones, ones installed, be moving up and down more freely? How does that work with the suspension? Does it counteract the suspension?

And in this setup, what's does the snubberwashers inserted do?

I should note, that Lotac red poly bushings once installed, protrude slightly on each side of each top wishbone arms, and that washers only touch this protruding point. Are the upper wishbones supposed to move freely, or by certain strengh, determined by the bushing ahrdness? Or something else?

5/ Are shimplates for the upper ball joint allowed to sit behind that, instead of in front as per manual?

6/ The parts manual and the picture on page 2 in section CD in Service Notes, show a 1,5 mm castor washer both show the upper wishbone shims to chassis as being behing right in front of the rear upper wishbone, not behind the front upper wishbone as described in text on page 3, section CD, Service Notes. Now I am confused???

7/ If I install the present shimplates in front of the upper ball joint as shown in drawings, the upright REALLY tilts. If they are placed behind the upper ball joint, the upright seems more like normal and like it was... Strange...

Can anyone help with these points. And what is the correct starting point when assembling the car, before a full geo?

What have I misunderstood?

Any other tips and need to know stuff?

Any help is greatly appreciated.

Kind regards,

Jacques

 

 

 

 

 

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites


Upgrade today to remove Google ads and support TLF.

1 & 2)

The idea with the shims is, you have shims at the front of the top balljoint, and that same thickness of shim (basically a big washer) between the rear arm and the car, so that the upper arm bushes are kept aligned.  That's the important bit to keep equal. Left Vs right, doesn't matter whether they are the same or not, it's just about getting the correct angle on each wheel.

That 1.5mm shim for the front of the balljoint, is a minimum, so you can swap it to a thicker one, but not less than 1.5mm.

 

3) you have just stated what the specification is, so don't understand the question. It tells you the acceptable range for each, and says that the two should be pretty much equal (within 30 mins of the other side).

 

4) Lotus suspension uses the bushes almost as a spring, so what you describe sounds right. That's why there is fuss about tightening up the bolts when the car is at the correct height.

 

Link to comment
Share on other sites

The minimum total thickness of the castor shim washers is 6 mm and at this minimum thickness no castor shim plates are used.  At all times a castor shim washer with a minimum of 1.5 mm thickness is to be placed between the front wishbone arm and the chassis. This gives possible front : rear combinations of 1.5 : 4.5,  3 : 3,  4.5 : 1.5  and  6 : 0.

If you need to add castor shim washers in excess of the 6 mm thickness then you must add castor shim plates equal to the thickness of the additional shims to the opposite wishbone arm. e.g. if you have castor shim washers totalling 7.5 mm between the front wishbone arm and the chassis then you would also fit a castor shim plate of 1.5 mm thickness between the rear wishbone arm and the ball joint.

By applying these rules the wishbone arms are kept parallel.

From your description of the shim washers and shim plates fitted it appears that whoever did the alignment is not aware of the correct procedure and the wishbone arms will be unnecessarily skewing the pivot bushes.

Link to comment
Share on other sites

Thanks for the replies. I am not sure though, that I understood it.

a/ So, I understand that a minimum of 1,5 mm shim washer should always be between the front wishbone and the chassis. I don't have that. I have 0 washers in that point on both left and right side of car.

b/ I understand that shims in total inner and outer - stud axles and upper ball joint respectively, should be the same, to align the upper wishbones - parallel. I have that on both left side of car and on right side of car. They are jsut not places as in the text or pictures of manual.

c/ Let's take the left side of car. I have 1 of 1,5mm shimplate and one of 3,0 mm shim plate (and corresponding shim washers at thre inner stud axles). I f I place the outer shim plates for the upper ball joint in front of the ball joint as per drawing in book, the upright will tilt quite extremely. That would correspond to a seriously high castor angle, right? So why place them there? My shim plates were behind, not in front, of the upper ball joint. Is that allowed?

d/ Because of the book describing that there must always be a 1,5 mm shim because of extreme condition clearance between chassis and front upper wishbone arm, why are there none on my car, and none on the drawing on page 2 in section CD in the books?

e/ The same goes for the right hand side of the car. Only difference is, that there are only one shimplate and one shim washer.

f/ I understand that it doesn't matter if left side and right side of car is different, as the chassis will not be totally straight, and possible other variances. So that's okay now.

Sorry, I don't understand any of this. There must be clear errors in the text and the drawing in the Service Notes. I mean: something doesn't add up??? Could it be, that the drawing and the text is not clear on that there must be shims on both side of the ball joint and the chassis to wishbone arms?

Kind regards,

jacques

 

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites

a/ Yes, you are missing the essential 1.5 mm thick castor shim washer from between the front wishbone arm and chassis.

b/ The combined thickness of the castor shim washers and the combined thickness of the castor shim plates should not be the same.  The minimum total thickness of the castor shim washers is 6 mm and only when the combined thickness of the castor shim washers is increased beyond 6 mm then castor shim plates are required. The diagram on page 2 of Service Notes Section CD does not show how the shim washers and shim plates are to be arranged; it is just a copy of the parts manual diagram with labels instead of part number references. The description in Service Notes Section CD is not giving a specific arrangement applicable to all vehicles.

c/ On the left side you do not have castor shim washers giving the minimum total thickness of 6 mm. Having castor shim plates either side of the ball joint shows whoever did the alignment did not know what they are doing as you only need shim plates to one side of the ball joint. The castor shim plates can be fitted on either side of the ball joint. Which side is dependant on whether more or less castor is required to bring the alignment into the specified range.

d/ You are missing the essential 1.5 mm thick castor shim washer from between the front wishbone arm and chassis because someone who obviously does not know what they are doing has removed them. See my comment on 'a/' regarding the diagram.

I am sure that once it 'clicks' with you the simplicity of how the castor adjustment works will be obvious.

  • Like 1
Link to comment
Share on other sites

Perfect Derek. Thanks a TON! I'll see then, what gives meaning on my car as a setup. I'll make a normal correctly setup then, and suppose as you say, that my car was done by someone who did not know what they were doing, so I therefor ignore all things on the car itself, and follow standard procedures. Good that I bought a cariety of shimwashers and shimplates to have on the shelf.

Maybe that is why my car always felt a bit "nervous" in keeping straight when doing an obscene amount of miles per hour? Not correct castor?

Once this is done, and everything else is ready on the car, including all rear wheel setup etc, I'll do a full geo.

Kind regards,

Jacques

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites

Glad to see the useful information coming forth. I had made a study of castor when sorting out my Elan after fitting a replacement Spydersport chassis and finding the steering feel not up to par. Alignment check determined the castor to be quite low, something in the 1 - 2 degree region IIRC. Once corrected to something like 3 degree I found the car more calm at speed and also that I could better feel the front tyre loading as the traction limits were approached. It was a successful exercise and one I believe to be quite applicable to an Esprit. The new SE I track tested when introduced in late '89 felt lacking in that sense of tyre load feedback, though a very quick and capable car otherwise. The literature reports substantially reduced castor spec with introduction of the Eagle chassis as opposed to the earlier Esprit, while later series brought the castor back into line with what seems normal.

Cheers

Link to comment
Share on other sites

So, I'll go for those later values ;) And a limited understeer to neutral, please.

The Service notes states in section CD, page 3:

Before vin 3582, 1 degree, 45 minutes, max 3 degrees.

From vin 3582, +1 degree, 0,5 degree, -0.

Would that later be sufficient (my frame relates to the 3582 onwards, or should it be more radical?

Kind regards,

jacques

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites

Let's hope the later Esprit lads check in with their views, especially if familiar with on-track behaviour. Absent any expert opinion I'd go for 3 degrees, rather than 1+. Another interesting, less well known aspect of castor is that it contributes increased camber ( that is "negative" ) on the loaded side as steering angle increases. Can't speak to whether of benefit on the Esprit, as that camber curve is not familiar, but the Elan's on limit behaviour was superlative on 60 series, R spec tyres.

Link to comment
Share on other sites

Those later cars have power assisted steering, helpful as low speed steering effort will increase somewhat with increased castor. Worst case is parallel parking. No other drawbacks as far as I know.

Link to comment
Share on other sites

Thanks guys.
So, I am making up a paper template or scheme to fill out for saving the adjsutments I end up with in the cars papers.
Anyway, I have the bare setup now, no washers or shims installed. So, reading the manual, section CD, page 3, it clearly says that at all times, for clearance, there must be a 1,5mm washer inserted between the front upper wishbone arm and the chassis.
My question is this: Does that mean that I should also in the same time, insert a 1,5mm shimplate between the upper ball joint and the rear upper wishbone arm, according to the text's description? Please see picture. The front of car is to the left.

My reason for asking this is, that I want to find out what is the bare 0, the basepoint, before adding or moving shims (and plates).

As I read the manual, a required min. 1,5mm washer is ALWAYS needed for clearance front inner.

But do I therefore also need a 1,5mm plate outer rear?


Cheers,

Jacques

 

needed minimum shim.JPG

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites

Ah, okay, I re-read your earlier comments. In fact mine was done all wrong on all accounts. Not 6mm total inner left, and right hand side, of car; no 1,5mm thereof inner front, and no angle correction by moving fore and aft the chassis, plus the eventual shimplates outer...

Sigh...

For me, the slow one...:

I need min. a total of 6mm inner each side of car.

I need min. 1,5mm inner front each side of car.

Now I just need to find a suitable way of measuring it, so I can insert the shims and eventual plates if going over 6mm shims.

I think I got it now.

Geez, it begins to dawn on me why the car was a bit nervous at very high speed.

I have encountered another problem: The stud axle (inner) I took off the car is not long enough to carry a total of min. 6mm shims.

The new stud axles I bought is the same length, so not long enough... I bought new ½" unf nyloc nuts for everything, but discovered that they are all the very long type, taking up even more space. The original slimmer ones, doesn't solve the problem though. And I had the new ones milled down, but also didn't help.

How to solve that?

Kind regards, and thanks for your patience.

Jacques

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites

Would a pair of non-locking, slim nuts ( i.e. jam nuts ) work to secure the upper wishbones? Maybe not if a slim Nyloc won't get it done. Longer pivot studs seem likely, as you must keep that minimum distance between wishbone and chassis to cover off deflection in hard use and we know you'll be doing that!

Link to comment
Share on other sites

On alignment specs, the following from the final compilation of Lotus Esprit Service Notes:

Castor (F)  -  3.2 degrees, +/- 0.2 . For S4, S4S and Sport 300;

Toe (F)  -  1.0mm Toe OUT (!!), +/- 0.5mm. For S4, S4S and Sport 300;

Toe (R)  -  1.5mm Toe IN, +/- 0.5mm, EACH SIDE, For S4 and S4S;

Toe (R)  -  1.0mm Toe IN, +/- 0.3mm, EACH SIDE, for Sport 300.

Cheers

Link to comment
Share on other sites

Great thread.

Checked my front suspension, with this new knowledge in hand, it looks well messed up too.

My right side front has a 1.5mm shim washer between the rear wishbone arm and the chassis and no shim washers between the front wishbone arm and the chassis.

The ball joint has a 3mm shim plate to the rear and a 1.5mm shim plate to the front.

I checked the castor on this side and it appears to be +0.4 deg.

Some interesting correction work ahead.😬

Andy.

Link to comment
Share on other sites

On 11/04/2020 at 19:29, Jacques said:

How thick are the correct nyloc nuts supposed to be, and the same for the contranut at the rear end?

Hi Jacques,

The std nylocs are 7/16" thick and the half nut is 5/16" thick.

Andy.

Link to comment
Share on other sites

Thanks, that would be something like 11,11mm and 7,94mm. Something to work with. I'll go measure all the different ones that I have currently. The problem is, that I cannot really get these in my country, as we are metric (fortunately), and every time I order something from abroad, they send me the thicker ones, which doesn't fit. So I had some milled down by 4mm.

But as one sets up the car, more is needed, also for other places on the car. So it would be good to just get the propper ones from a reliable source, in a stream, so to speak. Anyway, I have currently set up the left front side, and I have a lot of space between the upper wishbones and the upper balljoint, using only the collective 6mm shim washers, as required minimum. I set up 1 of 1,5mm front and 1 of 1,5mm + 1 of 3mm rear. Everything else is not together yet, so cannot measure on the wheels.

I have a thought, looking at the chassis and upper wishbone arms, that possibly the later part of the LOTAC bush programme was not intended for the earlier Stevens cars, but more for the later cars with revised front arms, or they should be used only in connection with these later arms. My thought was to go measure the old original rubber bush in metal sleeve and the ne Lotac bush. I might be wrong though. I'll report back.

Kind regards,

Jacques

Nobody does it better - than Lotus ;)

Link to comment
Share on other sites

The locknut used on the top wishbone pivot stud is half nut width too; 5/16".

The Lotac bush having a wider inner sleeve than the OE rubber bush is a possible reason for the gap between the wishbone arm and the ball joint but I think it is unlikely as the same bush is used on all models from the S3 onwards. Another possibility is that the rubber has developed a 'memory' from having the wishbone arms splayed due to the incorrect combination of castor shim washers and plates being fitted.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...