Lotus Elan

Fact or fiction.? Ttech help needed.........

PostPost by: mark030358 » Sun Feb 26, 2006 12:00 pm

Rang to book an appointment for a laser wheel alignment check yestertday and told the guy what car it was for. "Hmmm..." the guy at the other end of the phone said followed by..."do you have a specification"? To which I replied, "a camber of between 0 to 1 deg negative camber and 3/16 inch total toe in at the front". Answer "Whats that in real money"? To which I replied about 4.5mm for the toe. "No" he said, "what that in degrees/minutes"? To which I replied " Don't know, but I'll find out". End of phone call.

Anyway I know its possible to calculate the toe in degrees but I have never done it. So, could anyone tell me what it is, based on the fact I'm running;-
standard 13" wheels
155x80x13 tyres

thanks in advance
Mark
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PostPost by: M100 » Sun Feb 26, 2006 9:40 pm

Given the totally non adjustable nature of the suspension design on the Elan what precisely are you going to align other than the toe that you can do yourself in 30 mins with a bit of wood and a couple of nails? (I do use a dunlop gauge though)

sin (toe) = toe out/rim diameter (for rim diameter you can substitute measurement distance)

4.5mm total toe on a 13 inch wheel is

arcsin 4.5/(13*25.4) = 0.78 degrees per side = 1.56 degrees total toe
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PostPost by: mark030358 » Mon Feb 27, 2006 7:27 pm

Martin,
Thanks for the reply

Given the totally non adjustable nature of the suspension design on the Elan what precisely are you going to align other than the toe that you can do yourself in 30 mins with a bit of wood and a couple of nails?


Firstly just wanted a general check over to see how it is, both front and rear. I have adjusted the ride height, therefore I presume the camber. And finally didnt know what the equivalent of 3/16" toe would be in degrees.

Final thing, when you say rim diameter do you mean edge to edge of the wheel? I have just measured mine and rim to rim is 14"

thanks
Mark
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PostPost by: M100 » Mon Feb 27, 2006 8:30 pm

The measurement that gets plugged into the equation is the diameter over which you are measuring the toe out.

If you had taken some LSD :roll: and fitted say a 15 inch rim and 205-50x15 tyres giving a similar rolling diameter to the 155-82x13's the toe out measurement in mm/inches would be greater across the rim but the angular measurement would still remain identical.

The 13" size is the diameter at the tyre bead, the rim "edge" is as you found is a bit larger. If you were measuring the toe in mm/inches then ideally you need to measure at 13 inches as that is how the original factory specs are interpreted, or adjust the toe out "distance" to take account of the larger diameter while maintaining the correct angle.

Quote 1.5 degrees total toe in and you'll not be far away, remember that is just a guideline. Move it 0.25 degree either side and on the road you probably won't be able to tell the difference.
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