Lotus Elan

Wheel alignment.

PostPost by: dougal9887 » Wed May 03, 2017 6:32 pm

I went for an alignment check on one of these sophisticated four wheel alignment setups that give you caster camber and toe readings.
My 2 pieces of mdf and a measuring tape got the front toe VERY close. However I was surprised that the rear wheel toe was well out on one side, +1deg7sec and -9sec on the other; total toe 57sec, thrust angle -37sec. The chassis has never been damaged. The A frames are newish Spyder oval tube.
Should I be bothered? Do I need to consider adjustable A frames?
I haven't noticed any untoward handling issues.
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PostPost by: Chancer » Wed May 03, 2017 6:39 pm

+ 1? toe out on one wheel?

Not desirable, will create snap oversteer on turn in at the limit.
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PostPost by: dougal9887 » Wed May 03, 2017 7:52 pm

Presumably the cause of this is the A frame?
And I assume that there is the potential for an alignment problem with any A frame one buys so the only way forward is adjustable?
Recommendations?
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PostPost by: vincereynard » Wed May 03, 2017 10:19 pm

dougal9887 wrote:Presumably the cause of this is the A frame?
And I assume that there is the potential for an alignment problem with any A frame one buys so the only way forward is adjustable?
Recommendations?
Dougal.


A frames / chassis build tolerances / a combination of all of the small differences added together.
You would probably find a difference swapping the A frames side to side - but it could be worse!

I am going for adjustables as there is no other adjustment so no alternative.
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PostPost by: Quart Meg Miles » Thu May 04, 2017 9:30 pm

Chancer wrote:+ 1? toe out on one wheel?

Not desirable, will create snap oversteer on turn in at the limit.

Are we using the car on the track or on the road?
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PostPost by: gjz30075 » Thu May 04, 2017 10:51 pm

Could be worn bushings. How recent are those?
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PostPost by: dougal9887 » Sun May 07, 2017 6:08 pm

Thanks for the replies.
I've now fitted adjustable rear wishbones and am heading back to the alignment place tomorrow.
The car is just for the road, however toe in on one wheel and toe out on the other can't be good.
The bushes were new polybushes and I've swapped these to the new wishbones.
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PostPost by: rgh0 » Mon May 08, 2017 9:37 am

Personally I would never trust an alignment place no matter how fancy the equipment unless i knew the owner and he did the work and he understood the geometry challenges of an Elan and the mathematics on how his equipment operated. Without that I would just use the old Parallel string method.

As Chapman is reputed to have said about adjustable suspensions - "make it adjustable and they will stuff it up like they do with Weber's" or something similar

cheers
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PostPost by: dougal9887 » Tue May 09, 2017 7:18 am

Well I went back to the alignment place yesterday and as Rohan expected it was total confusion!!
The machine's data for the Elan, year range but not model specific, stated total toe in front and rear of 0*00' - 0*50'.
My rim measures 366mm, so I calculate that max toe in of 4.76mm (3/16") equates to .745deg or 0*45'. That pretty much matches up with the machine data.
However the ongoing confusion over whether this figure is total or for each wheel at the rear remains.
When we started doing adjustments there was much confusion over what the screen pointers were telling us! The technician maintained that when the pointer was at the centre of the display block, the wheels were straight ahead. I read it to indicate that the reading was mid-point of the specification. In the heat of the moment we were also struggling with the conversion of inches/mm/degrees.
We ended up with a compromise of 0*26' total toe front and rear ie mid spec for the machine.
On reflection, it would probably be better to set the rear to 0*45' (3/16") total toe which would be nearest to satisfying both schools of thought.
Opinions welcomed!!!
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PostPost by: vincereynard » Tue May 09, 2017 9:00 am

I understood that the figure was for both wheels at the front as they are linked. Individually at the rear.

Assuming your car is a +2, John Clegg has an interesting system based on the fact that the rear track is 1 inch wider that the front.

He has a sight tube that he connects to the rear spinner and adjusts the toe in so it is pointing at the front spinner. In effect the 4 wheels form a trapezium (or trapezoid for some).
trapezium.png and

a - front track / b - rear track / h - wheel base.
You could make a posh version with a laser shining down the sight tube!

It was discussed a few months back so a search should bring results.
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PostPost by: mark030358 » Tue May 09, 2017 7:31 pm

Hi,
Here is a post I uploaded sometime ago. Car is just perfect, no angles, just measurements, really simple.

lotus-suspension-f42/stability-speed-t25650.html?hilit=Mark030358#p167784

Cheers

Mark
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PostPost by: dougal9887 » Fri May 12, 2017 6:54 pm

I finally settled on 1/8" or 0*15' toe in for each front wheel and 3/16" total, 0*22' each rear wheel.
The handling feels good.
Regards the question of whether the rear toe in stated in the manual is total or per wheel, I am in the total camp. The manual states the information in exactly the same way front and rear so I feel it should be interpreted the same way. Spyder recommend a rear toe in of 3/16" total.
The alignment place took the trouble to get in touch with Hunter, the manufacturer, over the question of toe in stated in mm. It turned out that this option was selectable! The data held for the Elan was 0 - 2.4mm, 0 - 0*25' toe in each wheel all round.
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