Newbie question

[DeanB]

Look nice in that dark grey

[Andy wright]

Thank you. RAL 7011 . Satin  A bit different to black .Ised that colour on my previous car ( which was black ) but I think the grey looks ok with the blue( not that any of it will be visible by the time I have finished putting the car back together ) 

[Andy wright]

Episode 27 in this seemingly never- ending saga . Wishbones fitted today ( after a cracker of a ride out on my bike on the road for a couple of hours ) I-thought that fitting them would be a nice easy little job. Well, it was not. The bushes are a ‘close fit’ in the relevant housings ( for close read bloody tight ) . Thank God for a rubber mallet . And shimming up the upper front arms took an age. And why? Because 2x1.5mm shims either side of each bush had absolutely no intention of fitting , nor being persuaded to change their minds. The closest I could get was a total shim stack of 5.5mm for each bush. I think it may be something to do with the Elise parts spherical bearings as the installed total bush width seemed to be higher by about 0.5mm than the o.e ones I took out . 
Anyway, a bit of progress. Photos to follow . 

[Lithopsian]

Not uncommon for the caster shims to need tapping in with a mallet, but obviously not to the point that the thin pickup extrusions would be deformed.  They shouldn't be loose.  After market bushes seem to vary a lot (or just a bit, but 0.5mm is plenty of pain!).  Are you using the original washers, including the snubber?  Is that appropriate for your bushes?  Not all aftermarket bushes, in particular spherical bearings, need the snubber and the thick rubber part of it may be too much for your bushes.

[Andy wright]

Afternoon. Thanks for your comments. No, not using the snubber washer as not required. Fortunately , in addition to the o.e 1.5mm shims, I had a good number of stainless 2mm ones and a few 0.5mm ones , the latter for experimenting. One 2.0mm one one side and a 2 and a 1.5 on the other just fitted with a  light tap using a soft faced drift . This has given my a tiny amount more caster , though given that a 1.5 shim moved from one side of the bush to the other translates to 0.4 deg change in castor, my delta of 1mm is not going to have a dramatic effect.

[Andy wright]

Episode 28( I picked ‘27’ from  thin air but thought I now needed to be consistent) . Front hubs fitted. Easy. Then work out and set where I think the suspension should be to mimic loaded ride height. I did some calcs , then threw in the dampers , loaded up the suspension to check that the centre of the hub was where I thought it should be relative to the garage floor. Within a couple of mm .Now the headache. With the abs shim and four others , on the LHS I got the camber to -0.6 deg. Given that ‘optimum ‘ is -0.1 to -0.3 , another two shims should be needed to get to about -0.3 . I thought I would try the other side to see if it was similar. It wasn’t . With no shim except the ABS shim, I have +0.5 deg. Yes, positive. So, off with the steering arm and tomorrow I will machine 3mm from its mounting face . Slightly worrying that there is such a difference, so I will sleep on this one before firing up the mill. 

[Lithopsian]

Seems odd that it would be off that way, plus one side and minus the other.  Isn't it more likely that something isn't level?  Or a bent chassis; that would be unusual but is fairly easy to check.

[Andy wright]

21 hours ago, Lithopsian said:

Seems odd that it would be off that way, plus one side and minus the other.  Isn't it more likely that something isn't level?  Or a bent chassis; that would be unusual but is fairly easy to check.

Agreed. Chassis is square. Cannot guarantee that the wishbones are all identical. After lots of fiddling about ( and a bit of milling ) I have -0.8 camber on each side , using my bespoke Lotus suspension ( piece of box drilled at 315mm centres)  Camber is 0.5 deg more that o.e but I do want to reduce some of the understeer so more negative camber is worth a try. As for toe, bit of angle iron, spirit level, string and tape measure  and I have 0.2mm toe out . However, my measurement error is at least +- 0.1 mm so the toe is not exact . Interestingly, when I removed the old track rod ends, one was screwed on 19.5 turns, the other 17.5 turns. New ones are at 18.5 turns and that , amazingly , seemed to drop the toe almost dead right. . Dampers in next, then calipers and discs and then to the back to start all over again. 

[Lithopsian]

-0.8 degrees on the front is pretty aggressive.  Are you going racing?  Good for really hard cornering, but I'm not sure it will be so good on the road.  Might be worse in most situations.  A good solution for the road is to fit wider front tyres and use a more moderate geo.  The S1 only came with a tiny amount of negative camber on the front and most people didn't think it has too much understeer (not enough grip at the back is a more common complaint!).  Tweaking the toe slightly out can be a part of that, but setting it DIY is a pain, with tiny tiny increments, backlash in the threads, etc.  Do you still have the stock ARB and ride heights?  Dropping the front slightly can help.

[Andy wright]

2 hours ago, Lithopsian said:

-0.8 degrees on the front is pretty aggressive.  Are you going racing?  Good for really hard cornering, but I'm not sure it will be so good on the road.  Might be worse in most situations.  A good solution for the road is to fit wider front tyres and use a more moderate geo.  The S1 only came with a tiny amount of negative camber on the front and most people didn't think it has too much understeer (not enough grip at the back is a more common complaint!).  Tweaking the toe slightly out can be a part of that, but setting it DIY is a pain, with tiny tiny increments, backlash in the threads, etc.  Do you still have the stock ARB and ride heights?  Dropping the front slightly can help.

It will go to the track on occasion. The S2 has a decent dose of understeer. I agree that some good, slightly wider tyres will help.I suppose that I am used to running cars with much more negative camber than the Lotus has . I am using standard ride height and standard arb for the moment . The dampers are Bilsteins with 47.5N/mm at the front and 65N/mm at the rear. ( multiply by 55 to get to lb/in ) This is a standard S2 Bilstein set which I bought second hand recently. Oh. Discovered my camber disparity. Schoolboy error confession time . When I put the car up on axle stands I took car to make sure it was level. Since that I have moved the car up and down a number of times and, foolishly , assumed that it was still level. I came to do the rear camber this afternoon and discovered that , like the front, the RHS had too little and the LHS too much . Yep. Car not level but tipped slightly towards the RHS . Bugger. Levelled the car and now shims more or less in equal numbers side to side( save for the 3 extra  on the RHS steering arm as I machined 3mm from its face . ) 

Toe to do next but I will save that until Friday. 

[Lithopsian]

Oh, and don't ignore caster, he says after you've managed to get all the shims in!  If you can get any more, you probably should.  Apart from the obvious effects on straight-line stability and self-centering, it is like having more (negative) camber when you're cornering, but without having so much camber when you're not cornering.  Not easy to measure at home, but you're unlikely to add too much with the Elise suspension setup.  Unless maybe you increase the caster and have a lot of negative camber - that could be really bad, but I'd argue you'd normally want to reduce the camber.  Or you could drive it first and see how it feels.

I was going to ask if the steering arms looked any different side by side, but it sounds like they didn't.  But now they do!  I'm paranoid about butchering components until I'm convinced I haven't messed up.

[Andy wright]

I did check the Castor ( camber gauge does caster, camber and KPI . ) The steering arm just had a 3 mm shave , so easy to reinstate with shims. Now I have fixed my cock-up , everything is much more symmetric. Having reflected on your observations, I have the rear camber at -2.0 which is just 0.2 more than spec, so I will drop the front down to the same 0.2 more than the o.e value and then see how it feels on the road when the alignment is checked. ( though I plan to string it first anyway. 

[Andy wright]

The photographs tell today’s story. Just about ready now to put the brakes on. 

[DeanB]

I don't claim to be a suspension geometry expert but from experience I will say that too much negative camber on an Elise affects braking performance - not as good a tyre footprint so more lock up (on my non-Abs car) or earlier Abs application. Not ideal on a car with a very light nose that is therefore prone to locking fronts anyway.

I just fitted wider tyres on the front. I can also soften my Nitrons slightly on the front if I want it more pointy but if I do a lot of that it scares the shit out of me on fast corners.

I measured tyre temp across the width of the (wider) fronts on a track day once and the outside edge was still cooler than the middle. I'm not Ayrton Senna so others may have a different result but plainly adding more negative camber was not necessary for me.

[duncx]

15 hours ago, DeanB said:

I don't claim to be a suspension geometry expert .....etc

Listen to Dean, he is a driving God and my personal hero