Tomberlin's Tech Corner by Andy Johnson
Edition: September/October 2011
This is a continuation from the last article. There are numerous factors that affect an electric vehicles range.
First let’s again discuss the mechanical factors involved.
Rolling resistance is one of the biggest factors that influence range and top speed. To insure that you have minimized the rolling resistance be sure that:
- wheel bearings are properly adjusted
- toe in is set correctly
- brakes are not dragging
- Parking brake is properly adjusted
- Tires are properly inflated
We have reviewed in the past two articles the procedures for checking the front wheel bearings, brakes. For this article we will discuss how to adjust the vehicle toe in/out.
First let’s discuss what toe is:
In Vehicle Engineering, toe is the geometric angle that each wheel has as it is related to the center line of the vehicle. Positive toe often referred to as toe in, is the front wheel angle pointing inward toward the centerline of the vehicle. Negative toe often referred to as or toe out, is the front wheel angle pointing outward away from the centerline of the vehicle. Toe can be measured in linear units, at the front of the tire, or as an angular deflection.
In a rear wheel drive vehicles, increasing the front toe in provides greater straight-line stability at the cost of some sluggishness of turning response, as well as a little more tire wear as they are now driving a bit sideways.
Toe is always adjustable in a vehicle although caster and are often not adjustable.
Inspection Procedure of Front Wheel Alignment for Toe in/out.
NOTE: Drive the vehicle well to insure that any settling of the suspension is removed prior to performing the adjustment procedure.
1. Park the vehicle on flat surface. Push the vehicle back about 10 feet
2. Push the vehicle straightly ahead for about 10 feet with the steering and wheel
NOTE: Do not pull back the vehicle or step on the brake pedal, as it will change the angle of the toe.
3. Measure the Toe of the vehicle by measuring the front tires width at the rear and at the front and noting the difference.
Toe in unladed should measure 3 5mm
4. Procedures for the Adjustment of Toe-in:
• Park the vehicle on the flat surface and apply parking brake.
• Loosen the locknut(1) on the ends of the tie rod
• Turn the steering tie rod to adjust the toe-in
o increase rotate the steering tie rod so that
the length between two ball joints increases
o Decrease rotate the steering tie rod so that
the length between two ball joints decreases
(toe-in decrease)
• Tighten the locknut on the drag link ball joints to 40N•m (29.5ft•1b)
5. Test drive the vehicle and then double check the adjustment to insure that adjustments have not changed. If it has, then perform the procedure again to insure accuracy.
As a final “feel check”:
• Place the vehicle on a smooth flat surface
• Check all tires to insure they are inflated to 30 psi
• Wheels point straight ahead
• Push the vehicle forward to see how much effort is required to move it
Just a few other points to remember about EV range:
• Make sure the batteries are in a good condition and specific gravities are in order
• Have been fully charged
• No corrosion is visible on the batteries or cables
• All connections are tight
• The batteries have had a recent “equalization charge.
Insuring all these points are covered in the annual maintenance will insure your customer an enhanced experience.
