Suspension tune and handling journey

[BDA]

On other threads I've mentioned that I'm not satisfied with the handling of my car. This will be an ongoing (until I'm either satisfied or I give up) thread of my attempts to make it handle the way I think it should.

Mainly, my complaints have been that it feels like will go into severe oversteer going into a turn at speed, fast highway driving (>60mph) requires intense concentration partially because minute steering inputs seem to generate outsized results and also because the car feels a little twitchy.

Here's a bit of what I'm working with. It probably isn't exactly what you have but it might be close enough for you to gain from my experience or I might gain from yours.

What follows is my "starting point." I have a TCS, Richard's twin link rear suspension. Richard's upper front A-arms adjustable for camber. I have SPAX adjustable shocks. SPAX is not sure how many adjustment clicks mine have because they changed the design years ago but it is expected my shocks have 14 clicks.

Tires: Front: 195/50-15, Rear: 205/50-15
Pressure: Front: 15 - 18 psi, Rear: 24 - 26 psi   (Richard's suggestion)
Springs:  Front: 250#, Rear: 130#    (also Richard's suggestion)
Shocks:  Front: 3 clicks, Rear: 3 clicks

Alignment: (D = driver's side, P = passenger side)
Front toe: .20' degrees
Front camber: D: -3/8°, P: -1/4°
Front caster: D: +2 1/2°, P: +1 7/8°
Rear toe: .20' degrees 
Rear camber: D: -1/2°, P: -1/2°


In general, the idea was to have as little rear toe-in as I felt comfortable with to hopefully give my rear tires a few more miles. I also thought that with wide tires, camber maybe should be on the bottom side of the spec.

This is not the beginning of my attempts but this seems like a good time to start. I've decided to put it on a rack to get a good baseline. Also, the shop owner, Gerry, suggested he had some insights into suspension tuning and I was interested in what he had to say. I can also compare what my alignment gear reads and what the big rack reads. To that end, I brought my car to him this morning.

The first thing Gerry told me is that my tire pressure was too low. I have to say that I was a bit surprised by the pressures Richard told me but I figured he knew a lot more about Europas and how to set them up than I. Gerry inflated the tires to 30 psi and that I might want to go to 35 psi in the rear. The next thing he thought was that my camber should be about -1° all around.

The result of Gerry's alignment was:
Front toe: .32' degrees
Front camber: D: -0.9°, P: -0.6°
Front caster: D: 2 .7°, P: 1.5°
Rear toe: .51' degrees
Rear camber: D: -1.0°, P: -0.9°

None of that is particularly noteworthy. Everything is pretty much within specs except for the passenger side front caster. I'm going to try adding a couple of washers to see if I can bring that up. I doubt it will make that much difference though. When Gerry was adjusting the camber on the driver's side front, the passenger front camber was -1.0° so that changed "on it's own". When I got home and checked on my camber gauge, I got about -0.6°.  I will put in a little more negative camber on the passenger side. One thing I note is the rear toe equates to 0.20" which is within specs but on the high side (1/8" to 1/4"). I may try reducing that to aid tire wear.

So what was the result? It was a significant improvement. It's not near to where I want it but it is definitely in the correct direction. Going into a turn, the backend still feels loose but the overall stability is improved. Going near 80 mph did not require nearly the concentration that it used to. The steering was still lighter than I would prefer and I expect the rear toe was probably the biggest contributor to the highway stability and I think the higher tire pressures gave an improvement across the board.

Before I try any alignment changes, I will see if adding 5 psi to the rear tires helps the oversteer situation, then I'll try stiffening up the front shocks a click or two. I think the lightness of the steering on the highway could be adressed by taking a thin shim from under the cap nut on the pinion housing.

Stay tuned...

[Pfreen]

My car has stock alignment.  I found this is best for urban/highway travel. My first “belief” is that zero camber in the front increases stability on the highway by reducing side thrust on the front wheels. The rear camber is -1deg. I have also installed front wheel bearing spacers based upon the recommendation of Richard Hill, who is on the yahoo forum.  I also installed alloy steel front axles

 I also have SJS front and rear springs and Protech dampers.  Finally,  I have a 3/4” rear Addco sway bar with spring links which reduce the bar’s affect.  Without these spring links, the car would oversteer excessively when letting off the throttle.  I also have a 3/4” front Addco front bar.  I have adjustable rear links to set the rear camber.

So, I did not take a scientific approach and do one thing at a time.  However, the bearing spacer and alloy axles combined with adjustable A arms to allow setting the front camber to zero vastly improved the stability at speed.   Front height is set to 6.5” (measured from the lower a arm pivot bolt) and 7” (measured from the bottom of the transmission lower link mount bracket).

My tires are Achilles 185-70/13 rear and 175-70/13 front.  Pressures are 18 front, 28 rear.

I am very pleased with the stability on on the highway above 90mph ( I don’t have white knuckles afterward) and the cornering is very predictable.  I have not raced it though.

I hope this helps.

[BDA]

Good information, Pfreen!

I'm hoping that beyond my experiences and any suggestions I might receive, that this thread might be a collection of owner's configurations and how they work (or don't) so we can all learn from them.

[jbcollier]

When it was up on the rack, what was the included angle (sometimes called KPI)?

That will tell you if anything is bent up front.

What is your rear thrust angle?

I can't compare my settings to yours as I'm running an S1, narrower tires and stock spring rates though also with the  twin link.  Mine drives very well.  It's a bit nervous at the limit.  By limit I mean when the car is trying to decide which end to let go first.  Up to the limit it likes to be under power through a corner.  Power really settles the car.  Off throttle, the reverse.

To me, your tire pressures sounds too high.  I do run higher than original spec.  I run 20/28 on 175/13s.

Ride height?  Mine is 1/2" lower at the front and a 1/2" higher at the rear.

[EuropaTC]

Hi BDA,
The extra stability could be down to the amount of toe-in you've got there. In the early days of ownership I ran mine with high rear toe-in because I didn't realise/hadn't checked, and that was rock steady at motorway speeds which in those days was 80/90 (before the cops got speed cameras in their cars    ).   Did the set-up give a toe setting per side or the overall toe ? If the latter, and based on my car shims, I'd want to check both sides had equal toe.

Can't comment on the castor because I've never measured mine and the front camber isn't adjustable so that's "stock" 

Those tyre pressures seem high to me. When I had my tyres fitted the guy had pumped them to 35psi because with low profiles that's what he'd done for previously on our modern cars.   I drove the car but didn't like the steering on bumpy roads even at low speeds and as the only thing that had changed was the tyres, I checked the numbers.  Depending on which tyre gauge I use (the foot pump reads higher) I now get 18/20 front and 28/30 rear but I suspect the lower figures are closer to reality. I would have expected 30 psi at the front to make it very light so I'm a bit surprised it feels so much better. Toe in again ?

Finally, the very crude mechanic in me set the dampers to zero for the first "round the block" runs. After a few short runs and the first spanner check I set them to half way which seemed quite firm but better.  I do remember tinkering with front & rear damper settings and I'd need to check notes but IIRC they are within +/- one click from that half way setting now. If yours are the Spax with 14 clicks, I'd try 7 and see what it feels like then alter F/R to see what difference it makes.

Brian

[BDA]

When it was up on the rack, what was the included angle (sometimes called KPI)?

That will tell you if anything is bent up front.

What is your rear thrust angle?

I can't compare my settings to yours as I'm running an S1, narrower tires and stock spring rates though also with the  twin link.  Mine drives very well.  It's a bit nervous at the limit.  By limit I mean when the car is trying to decide which end to let go first.  Up to the limit it likes to be under power through a corner.  Power really settles the car.  Off throttle, the reverse.

To me, your tire pressures sounds too high.  I do run higher than original spec.  I run 20/28 on 175/13s.

Ride height?  Mine is 1/2" lower at the front and a 1/2" higher at the rear.

Thanks for reminding me about my ride height! Measured at the body behind the front wheel, it's 4 1/2" and at the body in front of the rear wheel, it's about 5 3/4". I was looking to get more of the S2 stance. In my notes I have that Richard suggested a difference of 1/2" between front and rear. This is obviously an area that might deserve some attention. This is lower than I've had it in the past. So far speed bumps haven't been a problem. I also seem to remember someone suggesting to me to make the lower rear link and the line between the lower front wishbone pivot and trunnion paralles to the ground. That wasn't really the aim, but that's pretty much how they ended up by my uncalibrated eyeball.

I've attached the printout of the results from the alignment rack below. Gerry didn't take the starting alignment so I've just posted the "after." Also, the colors are probably wrong because the alignment rack computer didn't have a listing for a Europa so we chose the Elan which was the closest it had.

I don't see anything about KPI or included on the printout. There is something called "Steer Ahead" which is 0. I'm not sure if that's the same.

The thrust angle is listed on the printout at 0.03°.

I recently worried that one of my front wishbone halfs on the passenger side was bent. I took them off and measured them and one was not in spec but it didn't appear to be bent (a straight edge didn't problems and the measurement from the hole for the trunnion to the pivot was correct - see attached measurement dia.) but the tube to accept the lower shock bolt was not in line with the face of the arm that is bolted against the trunnion. They should line up. When I put a washer under the tube, everything measured up correctly. Now obviously it's still not quite right or my caster would be  correct but both lower arms measured (after adding the thickness of the washer) up the best I could tell. In order to get my caster, I added a washer behind the trunnion and under the leading lower wishbone half pivot to move the bottom of the upright forward. My plan is to see if I can get it closer with some more washers.

It's been a LONG time since I drove my car when it was stock but I do remember that driving 90 mph all day was not difficult. I don't remember the finer points of how it felt going into a corner or the reaction to power but it was stable enough that a nutty kid like me didn't get himself into a lot of trouble. As for now, mine seems to react similarly to yours in the turn - though I haven't tried lifting. It does tend to squat down and bite the road when you add power in the turn. Going into the turn quickly feels like it wants to swap ends. I THINK that tire pressures and/or shock adjustments might help here. I found a pretty decent article on adjusting shocks here (https://nasaspeed.news/tech/suspension/damper-tuning/).

As for tire pressures: I will say that I normally add 4 psi the the recommended tire pressures of all my cars and when I raced Showroom Stock (cars with no modifications other than safety equipment), I ran 40+ psi and as I remember it, I liked it so much that I drove the car on the street that way. I never noticed any tire wear anomalies. However, several have suggested that 30 psi is too high so lowering them will be added to future tests.

[EuropaTC]

looking at my conversion chart (I can't think in degrees or minutes !) then I get roughly 1.5-2mm on a 15" wheel, so that doesn't seem too bad when you get the Lotus figures of 3-6mm and the rear camber looks mid range as well. I've no idea what's going on at the front, I think that's "experiment time".

I just checked the manual to see what it says on pressures and basically it's 16/24 normally with 22/32 above 100mph, both measured cold.  There's even a statement about "no other reason to increase pressures" which did make me smile. 16 feels a bit low to me with low profile tyres, I've no logic behind that feeling if I'm honest other than we have potholes over here and I'd be concerned over pinching a low profile wall.

Brian

[Bainford]

Reading with interest...

[BDA]

Brian,

I didn't get a chance to reply to your previous post after I wrote my last post so now I have two of your posts to reply to! 

I think you're right that the toe-in on the rear is a major contributor to the highway stability. As I said, it's on the high side (i.e. more toe-in) of the spec. I may lighten up on the toe-in down the line to get to the least amount of toe-in I'm comfortable with.

As for converting degrees to inches in toe measurements, I use this website (https://robrobinette.com/ConvertToeDegreesToInches.htm).

The tire pressure discussion is interesting. My Honda CR-V tire pressures are 32/30 and Mercedes C230 are 28/32. Admittedly, those cars and their are VERY different from my Europa and its tires, but 30 psi doesn't seem like it would be that much out of line - which is not to say that a bit lower or even higher pressure might not be better. In any case, tire pressures, like everything else are subject to change.

I agree that 16 seems awfully low (which is what my fronts had when I drove to the shop!) and on a modern steel belted radial, where the sidewall stiffness is enhanced by the tire pressure, it would seem low pressure would contribute to "squishy" handling. Of course, lower profile tires would be less susceptible to that than the original 70 series tires.

[BDA]

Next test: I increased the rear tire pressure to 35 psi. This gave a slight improvement but wasn't confidence inspiring enough to increase my speed through a set of twisty roads near my house.

Then I increased the stiffness on the front shocks by one click. This was a good improvement. It handled better through the twisties and was very evident by the speed through them. I wasn't able to get a clean run through them but it was much more stable and confidence inspiring. The feeling the car was trying to swap ends was greatly reduced and feel through the curve was more stable.

In spite of the fact (maybe because of it) that I rebuilt my steering rack, the steering is too light.

Next test: tighten the steering by taking out a 0.004" shim from the cap nut on the pinion housing.

[Clifton]

Lotus Owners manual says 18/28 psi.  Generally, lowering pressure increases grip until it rolls over too much (chalk the edge to see), increasing pressure reduces grip.

[EuropaTC]

Hi again....

From what I can see modern cars do have much higher tyre pressures than our old Europas and there's a certain logic in linking the higher pressures with lower profile/smaller sidewall tyres.  I'll preface the next comment by saying "it's vague opinion, no supporting facts", so here goes; 

Modern cars are mostly heavier than virtually any old Lotus from the 60s/early 70s and so when they go for lower profile tyres they need higher pressures to prevent pinch flats on severe bumps or potholed roads, and that's why my tyre guy shoved 35psi or whatever in my Europa wheels.  But because our cars are so light, I've not been convinced that we need such high pressures and that's why I've stuck with close to factory spec. At one time I used to put 30psi in the rears all the time but I can't say I've driven with much more than that.

Before pulling your steering apart, I'd suggest it's easier to put a couple more clicks on those dampers.  If they are ranged to 14 then you've got plenty to go at; try 7 each and see what it feels like 

Brian

ps - you can always click them back down very easily if you don't like it,  but messing with the steering means getting dirty hands !

[BDA]

Lotus Owners manual says 18/28 psi.  Generally, lowering pressure increases grip until it rolls over too much (chalk the edge to see), increasing pressure reduces grip.

Thanks Clifton. So far I haven't used anything more than feel to determine any improvement or lack of improvement. I will be testing lower tire pressures in the future. I haven't worried too much about the original Lotus documentation because I think tire construction is a lot different from when the car was stock (e.g. it didn't come with steel belted radials) and my tires have a much lower profile. My pressures were much lower for many years and I've always had handling issues. Certainly alignment differences could have contributed to them, but I started with a rear alignment done on a rack. This leads me to think that my increased tire pressure is a contributor to my better handling but so many have said 30 psi seemed high that I'm compelled to test lower pressures. When I do, I'll use white shoe polish or chalk to get a measure of it.

[BDA]

...
Modern cars are mostly heavier than virtually any old Lotus from the 60s/early 70s and so when they go for lower profile tyres they need higher pressures to prevent pinch flats on severe bumps or potholed roads, and that's why my tyre guy shoved 35psi or whatever in my Europa wheels.  But because our cars are so light, I've not been convinced that we need such high pressures and that's why I've stuck with close to factory spec. At one time I used to put 30psi in the rears all the time but I can't say I've driven with much more than that.

Before pulling your steering apart, I'd suggest it's easier to put a couple more clicks on those dampers.  If they are ranged to 14 then you've got plenty to go at; try 7 each and see what it feels like 

Brian

ps - you can always click them back down very easily if you don't like it,  but messing with the steering means getting dirty hands !

I think the difference is tire construction and car weights makes comparing tire pressures on modern cars a bit problematic! I think trial and error with the advice of experienced people like those on this forum and local racers makes the most sense. I remind myself and readers of this thread that Richard advised me to use the following pressures F: 15-18, R: 24-26.

As for shock adjustment, so far, it seems to have made the most improvement. At the moment, I'm at 4 clicks on the front and three on the rear. That seems like fertile ground for experimentation.

The steering has very little resistance to it so it requires a lot of concentration to keep from putting more steering input in than I intend. I followed the manual when I rebuilt the rack but there was one place that seemed contradictory and that was the setting of the cap nut. The manual gives a gap between the housing and the cap nut. This impacts the resistance to turning the pinion. It also gives a resistance to turning the pinion. However the proper cap nut/housing gap does not give the proper resistance. I don't remember if I chose the proper gap or the proper resistance - I think I took something in between. I don't think I have to take the rack out to play with the cap nut. It's accessible from under the car (maybe after taking off the chassis to body closing plate).

Stay tuned...

[jbcollier]

Something is bent on the right front.  I suspect the upright itself.