Esprit S1 rear SPAX camber issue.

[jonwat]

On 25/10/2023 at 07:46, tristan reidford said:

If I add shims here to correct the camber, won’t it will push the brake outward meaning the caliper will also have to be offset?

The answer to this question is to place shims between the driveshaft adapter & the UJ housing.

[tristan reidford]

That would certainly push the wheel upright, but doesn’t address what the real cause of this is, I’m still keen on getting to the bottom of that.   Is it common practice to add another shim between the adapter and the u-joint?  Has anyone ever seen this done on a car?

 

[tristan reidford]

Also there is a different lower link for late S2 cars? I wonder what is the diff between the two?

[jonwat]

6 hours ago, tristan reidford said:

I wonder what is the diff between the two?

Give them a call & ask

[EXCEL V8]

If it's anything like the Elite they are the same length but have different bushes - the Elite went from 1/2" to 5/8" stud size.

Pete

[tristan reidford]

I went to see the car today, I looked at the left rear side with a set square and measured and compared. The car is pretty much symmetrical, the left side has exact the same camber as the right.   This probably means this camber was  a choice a previous owner made. Seems unlikely it would be broken exactly the same on each side.   So perhaps the garage was right and these shocks are not going to allow enough adjustment to raise the camber out of those wheels.  I am having a hard time identifying these exact shocks, to see if they are too short.

[EXCEL V8]

Maybe if the previous owner had carefully set the camber to suit the use of the car (track-orientated, for example) the difference in the spring perch height may be from corner weighting, not geometry (assuming the springs are symetrical).  Just a thought.

Pete

[tristan reidford]

I think you are right Pete.  The previous owner did track this car, (I found his YouTube).  It’s a relief that nothing is ‘wrong’ with the setup apart from it can’t be aligned.  I still don’t understand quite how lengthening the shocks would pull out the camber.  I measured the distance from the floor to the wheel arch and it’s about 25 and a half inches. Is that really low?

[EXCEL V8]

Don't forget that there is only one position (height) for the suspension at which the camber will be "correct";  in both compression and droop it will be slightly different.  The manual should show the ride height at which to check the geometry - it's not usually the ride height for normal use - it's when the car is specifically weighted - fuel, passengers etc..  As I mentioned earlier adjusting the toe affects the camber and adjusting the camber affects the toe - you have to creep up on it!  Shimming is the normal (only) way to adjust camber, as it is with toe.  The previous owner may have removed shims to get the increased negative camber or could have machined the components to which the drive shaft bolts, if removing shims was not enough.  You cannot significantly affect camber by altering the ride height (raising spring platforms).

What are you using to measure camber?

I've also made some adjustable upper front suspension arms for my Elite that allow me to adjust camber (and caster using trunnionless uprights and spherical bearings) at the front - in the manner of the last of the Esprits.

Pete

[tristan reidford]

Thanks Pete, I should be able to figure out whether the brake disk adapter has been shortened.  Maybe I should get some adjustable LCAs made (if that is a thing).
My camber measuring is mebutting a set square up to the bottom of the tire, and measuring the distance to the top of the wheel rim.  Not exact, but enough to establish the camber is the approximately the same on each side. 

my ride height (with nobody inside) is 5 inches from ground to the bottom of the crossmember.  I think this is an inch lower than stock.

My LCAs are both approximately 15.25 inches long. (Either total length or measured from each pivot point, I can’t remember). 

[jonwat]

On 29/10/2023 at 18:52, EXCEL V8 said:

adjusting the toe affects the camber and adjusting the camber affects the toe

I must admit I just can't visualise that???

[drdoom]

On 27/10/2023 at 21:14, tristan reidford said:

Also there is a different lower link for late S2 cars? I wonder what is the diff between the two?

 

Just got around to checking this out and it seems these links are both for the Elite/Eclat cars. There is but one specified for the S1/S2 Esprit on the SJ website, as one would expect, and it's neither of these.

[EXCEL V8]

10 hours ago, jonwat said:

I must admit I just can't visualise that???

I had to think about it again!!  It's only a very small effect (and less than the effect on an Elite due to the design difference in the forward mounting point of the trailing arm) and to visualise it you have to imagine gross movements of the components.  Toe affecting camber:  Imagine moving the forward mounting point of the trailing arm two inches outward - it will pivot on the outer bush of the rear lower arm taking the hub carrier with it by a small amount.  However - the drive shaft acts as a tether on the hub carrier only allowing the lower part of it to move - effectively making it twist slightly thereby altering the camber.

Camber affecting toe:  This is a tiny effect and again less so than the Elite.  This arises because the forward mounting of the trailing arm isn't like a spherical bearing - it moves in an arc with the centre in the middle of the rubber bush.  So - altering the camber makes the trailing arm twist on it's forward mount (as it does during any suspension movement), moving it through an arc and effectively moving it in or out very slightly.

As said these are very small effects but none-the-less are worth taking into account if aiming for real accuracy (the later suspension behaves differently, of course).

Pete

[peteyg]

I had this very problem when I installed new adjustable Protechs on my S2 years ago. Took it to a Lotus 'Specialist' who it turns out didn't have a clue about older cars and it came back with the rear wheels like this / \ . Turns out the springs needed cranking up way more than they had been which pulled the bottom of the wheels inwards and created the correct camber. Nothing more complicated than that. Worth a try before you start messing about with shims etc.

Pete

[JLP]

Hi Tristan,

Jeff here.  Not much to add as the topic has been well documented, but since my car (139H) is very similar to yours I thought I'd add a few measurements and comments.

My car rests (unloaded) 5" between the rear lower frame (where the LCA attaches) to the floor.  It also rests at 5" at hub connection.  So basically, the LCA is parallel to the floor and at a similar height to yours.  Distance to the top of the fender flare is 26".  Yours was 25.  Not sure what to make of that (you might have different springs).  My springs are not stock.  Our wheels are the same.

I measured camber the same way you did (1.5"). Mine measured 1.25".   The measurement from lower wheel rim flange to upper rim flange is a negative camber of  3/8".  Please note that all rear suspension, transmission, and engine rubber joints/bushings were replaced two years ago.  The 3/8" negative camber is approx -1.5 degrees. Factory spec is 0 to -.5.  My toe-in meets factory  spec.

The distance between the LCA bolts  (center to center) is 379mm, see pic.  I have no shims (aside from those centering the brake rotor to caliper) in the driveline.

LCA measurement (379mm):

 

Before replacing all rubber suspension joints/bushings/mounts, I had shims all over the place.  Example follows.  All were removed.

My front springs (Federal) and shocks are original to the car.  I purchased replacement springs (Euro) for front and rear from SJ along with all the bushings/joints etc to redo the front suspension this Winter.  After installing the new bits, I will revisit the out-of-spec rear camber issue.

Let me know if you need any additional measurements.

Jeff

Esprit 139H

 

[tristan reidford]

Thanks Pete, It’s definitely worth trying to get the most out of these shocks, before I try anything else. The alignment place said their was not enough adjustment in the current shocks, but I can’t see beyond the springs how much thread is available.

hey Jeff thanks for taking those measurements, I’m encouraged that my car isn’t that far off yours.  Maybe if I replace the radius bushings and correct the toe the geometry will pull the camber in a bit too as Peter suggests.
 

It’s interesting to see the shimming of the intermediate shaft there.  I will update this thread after I find the alignment report that I lost.

[drdoom]

Hi Jeff. Thanks for your info, glad you chucked those dodgey shims. Not sure why the calipers would want shimming anywhere as they are slider type, inherently self-centering right? I'll look forward to your further postings once the new suspension bits are installed. 👍

[tristan reidford]

Hey,  a small update on this now the car is up in the air.  See how the trailing arms are right up against that frame.  My favorite theory now is that someone had these made.  Although, if you are going to that much trouble why wouldn’t you make adjustable ones?

[rgh0]

First thing I would do is replace those inner bushes as they look badly distorted.  The arms themselves look standard to me. The outer bushes are probably also needing replacement. 

 

cheers

Rohan

[drdoom]

Tristan, you ask a valid question when wondering why someone would have fabricated those transverse ( not trailing ) arms. You're nearly there in thinking why not adjustable and, like Rohan, I'd regard them as standard. Clearly the bushed ends should be clear of conflict with the crossbeam and, again as suggested by Rohan, the bushes themselves are surely shot. Lotus are not particularly hard on their bushings but they will not handle properly at all unless the bushings are in good shape. That's an old car by now, still fabulous to drive by any standards if in good condition. You'll find the solutions are straightforward, rather than obscure or exotic.

Cheers

[Fridge]

Just gone through this thread. Most of it is correct, but there some misdirects.

First of all, did you sort this problem?

The camber will be effected by the coil over (lower) cup position. The higher it is camber is decreased ie. wheel is more upright and the rear of the car will sit high. Lowering the cup increases camber and lowers the rear of the car.

No doubt there will be an effect on the camber when adjusting the radius arm, but nothing to concern yourself with. The radius arm bush affects the rear wheel toe-in via shims. This is very unlikely to be a source of your camber problem. Saying that, the radius bush shown looks worn out and misshapen.

The lower control arms do fit snuggly in the channel of the lower beam beneath the transaxel.

My suggestion if you haven't already sorted this problem is:

1) rebush the radius arms, not difficult or expensive. Fit new locking nuts when doing so.

2) ideally rebush the lower links

3) Only fit single shims to the transaxel output side of the drive chain, not directly behind the UJ. They won't fit anyway as their diameter is greater.

4) ideally renew those shock absorbers if unequal heights/camber persists as I think those are the main source of your problem, and are an unknown. Unless of course you've since found out that there's something more serious going on post accident of course.

AND

5) fit some lock tabs to those UJs!! They're available from SJ Sportcars.

Then get the geometry setup done by a reputable outfit that preferably understand race cars of that period. Get it corner weighted to obtain a level ride height, and aligned according to the specifications in the WSM. The lower sill of the S1 sits flat to the road, the ride height is in the WSM. Saying that, if done well the car should have a "forward" stance.

Do that and that car will corner like its on rails!

Edited June 26 by Fridge