Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Nero on Saturday,April 27, 2019, 09:30:35 AM
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Hello,
I have a big problem with rattings in the road. The europa want to pull in them. It’s simply dangerous to drive fast then 80kph. The front suspension is original apart from coilovers and a upper arm to give camber adjustment. The car is on 185/60 13 tyres in the front. We already changed for new tyres as we suspected old tyres to contribute to the problem. The suspension settings are as per the workshop manual. From driving I can say that it is definitely from the front. I increased the toe in at the front already with next to no difference.
If somebody with the same or bigger tyres could give me their settings I would really appreciate it.
Thanks
Denis
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Have a computerized, four wheel alignment.
- if the included angle (AKA: kingpin inclination/KPI) then the uprights are bent.
- rear thrust angle also important.
I'm suspicious that something might be bent if you have adjustable front upper arms.
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As John says, the first stage is to get 4 wheel alignment done to get a known baseline before modifying anything.
I have 195/50 & 205/50 tyres on a TC car but with adjustable suspension so perhaps my settings won't translate to your car. Even so, they are broadly in line with the OEM settings and I aim for mid-range on toe settings, low end on rear camber. The ride height is also slightly lower than OEM. Front camber isn't adjustable on my car so I hope it's standard !
The image shows the details recorded almost 4yrs ago and with a mixture of imperial & metric numbers but this was the last time I made any changes. I seem to recall moving the OSR toe closer to the NSR toe after this measurement going on the noted shims, but memory.....
When you say it's unstable at moderate speed, what's the effect ? is it vibration or the car responding violently to bumps, road camber, etc ? If it's definitely the front and your toe is within range then I'd look to see if there's anything wrong with the steering gear, maybe that coupling hidden in the chassis, the track rod ends, bearings, etc.
Brian
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I would also check:-
1) Tyre pressures and uneven tyre wear.
2) The bottom trunnions are working properly.
3) Any movement in the rubber bushes.
4) The top wishbone arms are the correct way around. Thick one at the front.
5) Wheel bearings.
6) Steering rack.
I don't understand "rattings". Do you mean the thick white lines on the tarmac, the camber of the road, the grooves in the slow lane made by heavy lorries, or potholes in the road surface?
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Thank you guys.
For better understanding: groves in the road are problem. Potholes are not more of a problem as with any other car. The car obviously gets pull in them when they are to big.
The car just got completely restored and has about 400km on it. All of the bearing and bushings are new, so I don’t suspect them to be a problem. In the corners the car is absolutely amazing(as a europa should be) so I don’t think there is something totally wrong with the suspension. The steering rack is fine, we just took it out to check. The car is very direct to the steering, actually to direct, but I never expected anything else from this kind of steering geometry.
The tyre pressures are the next thing to check and then the alignment.
Thank you for your input
Denis
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My restored car had all its original front suspension components. They looked great, with no sign of damage. My brand new bushings delaminated within 100 kilometres resulting in the front arms being pushed backwards. After I fixed that -- bushings must have rolled edges -- I had the alignment checked. Both front included angles were off so both seemingly fine uprights were bent. And, the rear thrust angle was off by quite a bit.
Don't rely on "looks" and "feel". Check it out properly!
PS: If your camber is off, don't reach for adjustable arms, find out what is bent or worn.
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The stickier the tyre, the more that lorry grooves pull the car and as the lorry track is wider than cars, that can lead to problems.
Try driving a car on roads with dry racing tyres and the white lines cause a problem.
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The car is running on sticky tyres simply for the reason that it is hard to find tyres in 185 and 205 for 13“ wheels that a road legal in Germany and without paying a fortune. The old ones were pretty much the opposite of sticky but the pulling was the same, that is the reason why the tyres got changed in the first place.
The car popped a heater hose this weekend so there are other things to do before the alignment can take place. I will report back as soon as I have news
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Hopefully in the engine bay and not under the dashboard.
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The car is very direct to the steering, actually to direct, but I never expected anything else from this kind of steering geometry.
The tyre pressures are the next thing to check and then the alignment.
I've had light weight road race and autocross cars and run toe out and they don't feel as twitchy as my Europa at speed. 2 hands over 80 mph.
My specs, I am running super sticky R comp BFG Rival S tires. 205-50-15 in the front, 245 rear. I don't remember what my front camber is (slotted uppers) or caster, I shimmed it to get another half degree but the front is toed in a heavy 1/16". Rear camber - .75* but it is not Europa in the rear, rear toed in is 1/16". I tried an 1/4" toe in on the front and it made it worse. Thrust is perfect. I will increase rear toe in to 1/8" next and see if I can get more caster. I car with too much toe in wants to wander and not return to center very well after turning unless it has a bunch of caster. A toed out car turns in great but will follow cracks, grooves, paint stripes, seams ,ect much worse.
Are you100% you are not toed out or too close to zero?
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Hopefully in the engine bay and not under the dashboard.
Luckily in the engine bay. My father made a crossover pipe because we didn’t want the hoses laying on the engine.The hose slipped of that pipe.(see picture below)
Are you100% you are not toed out or too close to zero?
We initially set the toe in to the lowest within the factory spec. So it is toe in but not that much.
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Nice looking engine.
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My father had the alignment done last Friday. The king pin inclination is perfect in spec. The toe in on the front is 1.3 degrees to each wheel(2.6 in total) which is actually good. The caster in the front is only .5 degree. Camber is good. On the rear the toe is just slightly towards toe in(.5 degree).
First I want to get the caster within spec as it affects straight line stability a lot.
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That is not enough toe at the rear. Europas are quite twitchy with minimal rear toe. The rear toe setting in the manual is per side, not total as in the front.
If your castor is off, something is bent.
What was your rear thrust angle?
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We already adjusted the toe on the rear as the car runs with a 47 replica chassis, which means the adjustment is towards the rear of the wheel and that makes adjustment a fast and easy process. My father made the jig for the adjustable upper arms over 15 years ago, which means I need to look at the drawings to compare them to the factory ones.
I need to have a close look at all the parts because there are too much variables within the front suspension right now.
I will look at the rear thrust angle tomorrow as it is late in the evening right now in Germany.
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Nero, what alignment specs are you using? The S2 spec for rear toe is 3/16" in. to 0. The TC spec is 1/4" to 1/8" in. Using this site (https://robrobinette.com/ConvertToeInchesToDegrees.htm) and a tire diameter of 23.1" which should be close to the diameter of a 185/70-13 tire, I find that 3/16" toe in is equivalent to .466 degrees. Unless I made a mistake (or the calculations this website makes is seriously flawed), your .5 degrees toe in is actually a little more than specified. Maybe somebody can check me on this.
Do you have a fully adjustable front suspension (i.e. spherical rod ends on the inboard side), you would need to adjust them for more caster. Otherwise, JB is right. Something is bent. Since the stock front A-arm pieces are designed to bend and absorb energy in the even of an accident, finding one that is bent is not that unusual.
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Kevin W sent me this info a few years ago, taken from the Lotus 47 Spec and Maintenance notes:
W base 91”
F track 53"
R track 48.5"
Height 40"
G clearance under front box 4.75"
Under rear hoop 5.25"
All with driver and ½ fuel load
F toe in 1/16"
Rear 1/8"
F Castor 3 deg
F camber 0
Rear ½ deg neg
Wheels 7.5F, and 10 rear
Anti rolls bars F5/8”
Rear 11/16”
Front springs 188lb
Rear 218 lbs
It may be of some help in setting up the replica 47 chassis. Definitely take John C's advice and check the rear thrust. Mine was out by quite a bit which caused some interesting handling.
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It seems strange the caster is so low, on both sides. I was complaining about 2.5 degrees.
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Ah, now I understand your readiness to adjust the castor. It’s because it is adjustable on your set up. 47 suspension, especially at the rear, bears little resemblance to a stock Europa.
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Nero, what alignment specs are you using? The S2 spec for rear toe is 3/16" in. to 0. The TC spec is 1/4" to 1/8" in. Using this site (https://robrobinette.com/ConvertToeInchesToDegrees.htm) and a tire diameter of 23.1" which should be close to the diameter of a 185/70-13 tire, I find that 3/16" toe in is equivalent to .466 degrees. Unless I made a mistake (or the calculations this website makes is seriously flawed), your .5 degrees toe in is actually a little more than specified. Maybe somebody can check me on this.
I got something similar by a different reference - included as an attachment here. The chart is intended to convert mm to degrees but you can obviously get an idea working it backwards. The rear doesn't look wildly out of range to me.
What did surprise me was the front toe at 1.3deg/wheel, 2.6 deg total. At first I thought I'd read mm and passed on, but after BDA's post I re-read it and using this chart on 2.6deg it comes out as approx 15mm. Huh ? Am I reading this wrong or did you mean mm not degrees ?
Without checking my latest notes I can't be certain but I seem to think mine is set around 1/16", (approx 1.5mm) at the front. I have run the car parallel in the past without undue problems on our motorways but have settled back on the factor ranges for a while now.
Brian
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We increased the toe just to see what difference it makes. As it did not had a big impact we will reduce the toe again.
We use S2 data for reference. I would consider a fault with the lower arms when one side would be off and the other is fine but both are equal. The front has standard bushings but we can move the arms, so caster is adjustable.
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It looks like we found the reason for the none existing caster yesterday. The upper arms assembly on the front of an europa is asymmetrical by 7mm. It took me about 10 minutes to find the jig for the adjustable ones that are on the car. The jig has the same 7mm offset. After taking off a wheel we found the arms to be mounted upside down. So we will take the upper arms out in the weekend and that will hopefully solve the problem.
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It looks like we found the reason for the none existing caster yesterday. The upper arms assembly on the front of an europa is asymmetrical by 7mm. It took me about 10 minutes to find the jig for the adjustable ones that are on the car. The jig has the same 7mm offset. After taking off a wheel we found the arms to be mounted upside down. So we will take the upper arms out in the weekend and that will hopefully solve the problem.
:) now that's a good answer to find, and in one way a confirmation of Chapman's original theme of not wanting adjustable suspension components on his road cars
Make the suspension adjustable and they will adjust it wrong -- look what they can do to a Weber carburetor in just a few moments of stupidity with a screwdriver.
I don't know if he actually said that, but it wouldn't surprise me. I've got adjustable lower links and know only too well how I can mess it up !
Good to know you've got a potential solution, let's know how it all works out now.
Brian
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It´s been a while now but I was able to get the castor to 3 degrees with some adjustment. I knew that castor has a big impact on a car but the difference is actually huge. I also found a good shop for the alignment with a young guy that really knows his stuff. As for now the toe is 1/16“ toe in at the front and the rear(both wheels, not to each wheel). First I was not sure about the straight line stability with such low toe, but it’s actually very good. There will be some more testing with the toe but for now it’s going to stay like that.
Thank you for all you help I really appreciate it.
Denis
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Hi Denis,
Good to know you've made progress and are happy with the results. It's always worth a final post to let everyone else know what you've learnt because it all adds to the general pool of knowledge.
Cheers
Brian
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Nero, is your caster actually adjustable or did you adjust it with washers? I suspect that increasing front caster would compensate for minimal front toe in since it also enhances stability (though I think I've heard of others using 1/16" toe in so that doesn't surprise me that much). Your rear toe seems really little for good stability so that is interesting. What is your rear camber?
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Nero, is your caster actually adjustable or did you adjust it with washers? I suspect that increasing front caster would compensate for minimal front toe in since it also enhances stability (though I think I've heard of others using 1/16" toe in so that doesn't surprise me that much). Your rear toe seems really little for good stability so that is interesting. What is your rear camber?
The adjustment is done with washers, but the chassis is made with that in mind and you need to put washers in with the assembly, it’s just a question if you shift the control arm towards the front or the back. The upper control arm is fixed(same as a 47) just with chamber adjustment. The camber in the rear is for now .75 degrees.
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I have another question for you guys. Can somebody please measure how much droop the front wheel has from ride height? I measured mine and it’s just 3cm(1.2inches). On some occasions the feels like it’s just falling into holes or if you drive over a lower curb stone it just falls down. I have played with the dampers which had no change what so ever. The damper is an AVO unit and also lowered. I have attached a picture. The car goes lower about one cm as soon as you get in.
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I'm not sure you can tell much from how much the front suspension droops when you jack it up. Usually, the front springs are preloaded so the rate of the springs and the amount of preload would greatly impact the amount of droop. The same goes for how much the car lowers when you get in. That ie more correlated to your spring rates and your weight. IIRC you have the stock front suspension except for adjustable (for camber) upper arms and using the stock rubber bushes. A reminder: using stock rubber bushes means you need to tighten the fulcrum nuts at ride height.
I've never measured the droop on my front suspension, but 1.2" does not seem out of line to me.
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Sounds like you are running springs that are too stiff. I have a lot more sag than that.
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The springs are 225lbs/inch. The car lowers another 2cm with the weight of the driver
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I'm not sure I understand what you mean by falling into a hole but I'm running 250lb on the front. Mine's fine unless the road is old, bumpy and rough. A lot of suspension programs and suspension experts recommend around 33% droop. Your 1.2" sounds about right given your spring rate. I don't see you using much more than 2.5" on bump.
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Try backing your shocks back to "0" and going up one click at a time until it's just "right". If your shocks are set too stiff, the wheel won't be able to follow the road.
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How much movement is there in your front axle taper roller bearings?
The manual states a method for arriving at the correct bearing end float to allow for build tolerances and thermal expansion.
This results in wheel that can move a small amount in response to road imperfections, this occurs randomly according to where the tyre contact patch load is highest. On a car with the precise steering of a Europa, this can cause wandering at speed, especially if the nose of the car is high, as yours appears to be from the photograph you posted. Air gets forced under the nose and reduces load on the front suspension and at the same time resistance to wandering reduces as speed increases.
In a corner the bearings are loaded laterally and the movement from the clearance is held consistently in one direction, it therefore steers precisely in the direction the driver is telling it to via the steering wheel.
Check how much bearing clearance you have by jacking the front of the car and trying to move the road wheels against the bearings by grasping the tyre at the top and bottom.
I made spacers to go between my bearings such that the castellated nut could be tightened onto the inner races whilst still maintaining the correct bearing clearance. It made a massive difference to straight line stability and resistance to road imperfections.