Lotus Elan

My take on the "old geezer's method" for steering alignment

PostPost by: Andy8421 » Sat Apr 07, 2018 7:32 am

john.p.clegg wrote:Mark
So what degrees did you end up with ?

It's all very confusing...inches/mm's/degrees/radians/per side/overall....

John :wink:


John, I spent quite a bit of time trying to figure this out when I started racing - I could never get a straight answer (if you will excuse the pun).

Clearly by adjusting toe, you are adjusting the angle of the wheels relative to each other. Angle is independent of wheel size, and would be the obvious measure for everyone to standardise on.

I can only assume that this was problematic for an average workshop to measure in the 60s unless they had fancy tracking gauges. Most places did however have a tape measure laying around so toe was also quoted as a distance. The challenge here is distance of what?

While I can't comment on American practice, the convention in the UK seems to be to quote difference in distance between the front wheels measured at the front and back of the rim of a standard size wheel.
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PostPost by: john.p.clegg » Sat Apr 07, 2018 7:52 am

I think for the Plus2 I'd settle for 0.3 degrees all round...

John :wink:

I think even Prince Charles would back me on that one....

Edit..Thanks Mark..
Last edited by john.p.clegg on Sat Apr 07, 2018 10:08 am, edited 1 time in total.
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PostPost by: MarkDa » Sat Apr 07, 2018 8:07 am

I thought it was Prince Charles!?
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PostPost by: 69S4 » Sat Apr 07, 2018 8:12 am

nmauduit wrote:
69S4 wrote:If I move the string to equalise the gaps I'll have a rectangular car set within a trapezoid string frame which surely can't be right. It would probably do to get the toe within what is a fairly wide spec but part of it now is trying to work out how I've cocked it up.


no, you use your setup making sure that the strings are parallel, and center the car within so that they both share an identical "symetry" axis by equalizing independantly
1) the rear wheel gaps (same distance A between left rear nut and string, as the right rear nut and other side of the string rectangle)
2) the front wheel gaps (same distance B between left frontnut and string, as the right front nut and other side of the string rectangle)

Make sure the steering is centered, and do not touch it while doing adjustments

Then say you check toe in for front left wheel by measuring A-a between the string and the rim at front near the bumper at nut height, and A+a between string and rim at the rear near the door - same nut height, then work out the math

Same for the other side. Do it several times, average out and get a feel for where the imprecision comes, do some adjustments ....



Ok, so it looks like I've been doing this backwards. I tried to set up a string + plank box where the strings had to be parallel because the locating cut-outs in the planks were exactly the same distance apart. The hard part with that is making sure the planks are parallel to each other as if they're not I'll get a trapezoid shape and, with fixed string points, the error I originally described.

Instead I should ensure the strings are parallel by referencing them to the wheel nuts (and allowing for the 1mm difference in front / rear track). That way it doesn't matter if the planks are not quite parallel to each other.

Getting the steering centred is another issue. I remember reading somewhere about putting a couple of grease lubricated plastic bags under the front wheels so they'll turn easily. I'll try that and see if it works.

As soon as the rain eases off I'll pull the car out and try again. Pity I couldn't do it in yesterday's sunshine but darling daughter needed all her stuff bringing back from university so the day vanished into a 250 mile drive and hours stuck on the M25.
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PostPost by: 69S4 » Sun Apr 08, 2018 10:36 am

Ok, tried again yesterday and got it set up with the strings parallel to the wheel hubs. Probably took me about half an hour to check and recheck that everything was as accurate as I could get it. Because I have to do this outside and it was a breezy day the biggest problem was the wind moving the strings around so measurements had to wait until the gap between gusts.

Results for the front were massive toe in - 9.0mm is what I measured. That's not surprising as both track rod end ball joints had been replaced and they looked visibly shorter than the ones that came off. As soon as the rain stops and I can get under the car again it shouldn't take long to get it reduced to something more reasonable.

At the rear the near side came in at 0.5mm toe in but the off side was 1.5 mm toe out. That one's going to need looking at a bit more closely to see if I can identify where the measurement came from. First job will be to string it again to see if it's real or a measurement error. With the wind moving the string around it's hard to be certain that there's not a wind blown element to what the ruler says. If it turns out to be accurate presumably my next port of call would be to check the A arm bushes. That side's not been apart in some time so there may be some deterioration. I have a set of turnbuckles that Alex Black kindly produced for me some years ago but they'll need welding in so that'll be my last port of call.
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PostPost by: Bigbaldybloke » Sun Apr 08, 2018 10:50 am

For me, checking with bits of string is fine to see if you have a problem, but I?d want it adjusted and set up on a decent laser alignment system that had a reputation locally for knowing what they are doing.
I?m doing a rough set up with tape measures and string just enough to drive it to my local garage once I?ve completed the restoration, so I know there is no major problem, but that?s all.
It?s fun playing around, but I want an accurate measurement of my suspension angles to know if I need to go to the expense of adjustable suspension arms etc.
Change is inevitable, except from a vending machine!
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PostPost by: Foxie » Sun Apr 08, 2018 1:39 pm

JonB wrote:Ok. I have measured the wheels at 355mm (14?) across the rim and 560mm (22?) across the tyre which gave me a conversion factor of 1.577. With measured toe in at the tyre of 3mm, I calculate that is 1.9mm at the rim which seems to be in tolerance. Should I increase it?

Meanwhile the rear wheels have 7mm toe in at the tyre (4.43 mm at the rim). Perhaps front and rear toe in should be the same?


Jon, I'd say your settings are within the ballpark, but read below !

The basic requirement for toe, as has often been stated here, is to ensure that when the car is being driven forward, the wheels move towards a zero toe due to suspension compliance, to minimise tyre wear and give a neutral steering effect.

However, zero toe does not give best steering feel, and so normal adjustment is made to give some extra toe.
In fact, setting up a rear wheel drive car with static toe-in will result in increased toe-in when under power due to suspension compliance. This is an important factor in vehicle straight line stability.

Lotus do not specify a definite figure for toe, instead they give a range within which settings may be made. This is very probably that settings outside this range will result in instability (too little) or excessive tyre wear (too much )

I don't think there is much advantage in using one method, string/optic line-up or direct measurement over the other (I prefer to use a 2" x 1" batten with 1" x 1" uprights, with butterfly clamping screws, see pic) as long as the method gives a repeatable result with your initial setting.

The main thing is to use the initial setting (pick 4.76mm/ 3/8") is just a base-line or datum. Once you have set that up, the next thing is to give a car a good test drive. Then reduce the setting to say 3mm/1/8" and see if it is better or worse. Test drive again. Then increase the setting to 6mm/1/4" and test that. This will give you a very good idea of what is right for you/your car.

The foregoing applies to the front wheels.

For me the Lotus rear suspension was another story. I have the car now for 33 years. Many years ago I checked the rear toe, and it appeared within limits. The suspension being non-adjustable, I thought no more about it.

However, two years ago I took the car to a laser alignment shop and was horrified to find that although the wheel to wheel toe was ok, one wheel had massive toe-out and the other had equally massive toe-in. (The cambers were also way off, one in and one out :shock: )

They only solution was a set of Spyder adjustable rear wishbones, not cheap, but when I finally set them up after several trial variations they completely transformed the car's handling.

I think with the Lotus it's important to check the rear toe relative to the car centre line, and not just wheel-to-wheel.

:)
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