Not always — it depends on your drivetrain and the condition of the other three tires. All-wheel-drive vehicles usually need a matched set, since mismatched tread heights strain the AWD system over time. Front- or rear-wheel-drive vehicles can often get away with one or two, if the rest are close in tread and brand.
Why does all-wheel drive change the answer?
An AWD system constantly compares how fast each wheel is turning, and tire diameter shrinks slightly as tread wears down. Put one new, taller tire next to three worn ones and the system reads that as wheel slip that isn't really happening — over miles, that can wear out the center differential or transfer case rather than just the tire.
What about a front- or rear-wheel-drive car?
Without a system cross-checking wheel speed, a 2WD vehicle is far more forgiving. A new tire paired with three that still have similar tread depth and the same general tread pattern usually rides and handles fine on one axle, without needing to touch the other two. That holds whether the car was driven in from nearby or from one of the shop's 14 service areas.
When would a shop say no to a partial replacement, even on 2WD?
A tread-pattern mismatch that changes how the car grips in rain, or a big gap between how worn the old tires are and how new the replacement is, are the usual reasons. Pairing a tire on the same axle as its closest match — not randomly on any corner — is the other rule of thumb.
Can I just replace the two front tires?
On front-wheel-drive cars the fronts often wear faster and can reasonably be replaced as a pair while the rears stay in service. On rear- or all-wheel-drive vehicles the same logic doesn't automatically hold, so it's worth confirming which axle actually needs it before assuming.
What happens if I only put one new tire on an AWD car?
The mismatch in rolling diameter between the new tire and the three worn ones can put ongoing strain on the drivetrain, not just the tires. Most shops recommend at least a matched axle pair, and often a full set, for that reason.
How do I find out what my car actually needs?
Bring all four tires in and have them checked together rather than guessing from one flat. Atlanta Tire Shop looks at tread depth and pattern across the set before recommending anything, seven days a week.