What does positive caster do for the vehicle?
- Reduces wear on the inside shoulders of the tires
- Helps straight-line stability and steering wheel return
- Lowers the steering effort needed when parking
- Keeps the rear wheels in line with the front wheels
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B. Helps straight-line stability and steering wheel return
With positive caster the steering axis meets the road ahead of the tire's contact patch, so the wheels trail like a caster and tend to self-centre. More positive caster actually raises steering effort slightly, which is why that choice is wrong.
Reference: Wheel alignment angles; caster
A front tire is worn smooth on its inside shoulder only. Which alignment fault is the most likely cause?
- Too much positive camber
- Too much positive caster
- Too much inflation pressure
- Too much negative camber
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D. Too much negative camber
Negative camber leans the top of the wheel inward, so the inside shoulder carries more of the load and wears first. Positive camber wears the outside shoulder, and caster by itself is not a tire-wearing angle.
Reference: Tire wear pattern diagnosis; camber
A tire has cupped (scalloped) dips worn around its tread. What is the most likely cause?
- Too much negative camber
- Too much inflation pressure
- Worn shock absorbers or struts
- Too much positive caster
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C. Worn shock absorbers or struts
With weak damping the tire bounces and repeatedly slaps the road, scooping out patches of tread. Wheel imbalance can add to it. Camber wears one shoulder evenly instead of in dips around the tread.
Reference: Tire wear pattern diagnosis; cupping