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
)
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.