Lotus Exige (Wheel Alignment)

A wheel alignment is recommended after upgrading the suspension dampers in the Lotus. After spending some time searching through the resources available on the Lotus Talk internet forum I’ve decided to tackle this project in the “L” Shaped Garage. The Nitron shock absorbers have adjustable spring perches that allow the ride height and corner weights to be set independently. Of the various methods described in detail on the forums a couple of different approaches seem appropriate for a home alignment system.

First a few general thoughts on the topic of wheel alignment…

• The lotus suspension allows for independent adjustment of Caster, Camber, Toe, and Thrust Angle. The Nitron Dampers provide for ride height adjustment.
• A system for measuring the physical position of the wheels to a fraction of 1mm (.039”) is required.
• Any system used to align the Lotus has to facilitate measurement and adjustment of Ride height, Toe, and Thrust Angle all at the same time. That is… these three elements of the suspension are interdependent.
• An alignment system requires a reasonably level working surface and the facility to add the weight of the occupants to the vehicle.

Commercial alignment systems from manufactures like Hunter Engineering have advanced to amazing degrees. Their HawkEye Elite system is an engineering marvel I would love to own. Unfortunately their new alignment system costs $15,000 and at that does not include a drive on alignment rack with the necessary accessories like turntables.

Fortunately putting together a simple system to directly measure wheel alignment is not all that difficult. As a matter of fact some simple “old school” techniques and equipment provide precision and accuracy that easily equals the capabilities of these new systems. All that is required is a complete understanding of the task at hand and some simple tools. I've already spent some time in the garage setting up to perform a wheel alignment and plan to summarize those efforts in a few posting following this introduction.

So a few definitions and descriptions to start off with...

Caster...
Caster is the angle of the steering pivot, measured in degrees.

Camber...
Camber is the angle of the wheel, measured in degrees, if the top of the wheel is tilted out then the camber is positive, if it's tilted in, then the camber is negative.

Toe...
The toe angle identifies the direction of the tires compared to the centerline of the vehicle.

Thrust Angle...
Thrust angle is the direction that the rear wheels are pointing in relation to the centerline of the vehicle.

Steering Center...
Steering center is the steering wheel angle when the vehicle is traveling down a straight and level road.

Because all these elements work together as the car rolls down the road it is important to perform an alignment with the weight of the vehicle and its occupants loaded on the suspension. It is also important to provide a low friction connection (slip plates) where the rubber meets the road.

Finally a quick diagram that helps shed light on the subject of Caster in suspension systems. Most vehicles allow only very small (if any) adjustments to caster. It is usually a design feature of the suspension and dealt with only in the event of an accident. Changing caster on the Lotus is much more difficult than Toe or thrust angle.