Pull and Vibration after a Pothole Impact
A 2020 petrol hatchback has covered 34,000 km. Its front tyres have about 6 mm of tread and the rear tyres about 4 mm. After the owner hit a deep pothole at 50 km/h, the steering pulls to the left, the steering-wheel spokes sit at about 11 and 5 o'clock when driving straight, and there is a vibration at 70–90 km/h. A faint clunk is heard over speed breakers. A tyre shop recommends wheel balancing and four-wheel alignment. On the lift, the left front tyre's outer shoulder is worn more than its inner shoulder, and the left front rim has a slight dent on the inner lip but no visible crack or tyre bulge. The tie-rod-end boot is intact and no free play is felt by hand. The brake pedal is firm and the car does not pull when braking. The owner plans a 200 km highway trip in two days.
1. Is alignment and balancing alone an acceptable repair? List the inspections you would complete before approving alignment.
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No. Alignment and balancing assume the steering and suspension geometry is intact and the wheel and tyre are round and true. Before approving alignment I would check and set tyre pressures; inspect both front tyres for bulges, cuts, tread separation and uneven wear; measure rim runout and check the inner-lip dent for cracks or buckling; check wheel bearings for play and noise; check ball joints, tie-rod ends, track-rod adjustment sleeves, control-arm bushes, strut mounts and anti-roll-bar links for play; check for a bent strut or control arm; check brake drag and wheel rotation; and road-test to confirm the pull direction.
Only after those checks pass would I balance the wheels and set alignment. The pothole impact makes a bent rim or suspension component a real possibility, and alignment alone cannot correct a bent component.
2. Map each symptom to a probable cause and explain which faults could be hidden by simply adjusting the alignment.
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The pull to the left after a pothole suggests a camber or caster change, a bent left-front suspension component, a dragging left brake or tyre conicity. The off-centre steering wheel means the front wheels are not pointing straight ahead relative to the rack; that is an alignment symptom, but it can also follow a bent tie rod or steering rack. The 70–90 km/h vibration is most likely wheel imbalance or a bent rim, less likely a worn CV joint or wheel bearing. The clunk over speed breakers suggests a worn strut mount, ball joint or control-arm bush.
Simply adjusting the alignment could hide a bent strut or worn ball joint. The car may drive straight on the alignment machine but still be unsafe, and the tyre may continue to wear. The inner-lip dent is also a red flag for runout and possible air loss.
3. Give the repair order and decide whether the car is safe for the 200 km trip if only balancing and alignment are done.
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Repair order: first replace or repair the damaged left-front rim if runout exceeds specification, and replace any tyre with a bulge or crack. Then inspect and replace worn suspension parts. Then balance the wheels, set tyre pressures and perform four-wheel alignment with the steering wheel centred. Finally road-test.
If the owner refuses the rim and suspension checks and accepts only balancing and alignment, I would not certify the car for a 200 km highway trip. A vibration at highway speed can indicate a failing wheel or tyre, and a bent rim can crack or lose pressure. The car may be usable for low-speed local trips after balancing, but the safe decision is to complete the inspection first.