Keep the same brand and the the same tire. Tires are like shoes, you wouldn't wear a dress shoe and a running shoe and go out jogging would you?

A worn tire will be a little different in size compare with a new tire, but that's what differentials are designed to handle. When you make a turn one wheel is turning faster then the other wheel, but the differential allow one wheel to turn faster then then the other wheel.

If it was me I would just opt to buy 4 new tires, but hey that just me.

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2006 Infiniti G35
2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD
Lotus Europa 1970 Destroyed by fire
Lotus Europa 1970 S2 Renault Powered
Lotus Type 52 1970 Twincam Webers Powered
PORSCHE 911 Targa 1982 The Garage Queen
Audi Avant donated to Kars for Kids
BMW 525IT Sold
Audi 4000CS Quattro Sold
Jensen Healey Lotus Powered Sold
Opel 1900 Sold
Triumph Spitfire 1971 Sold
Triumph Spitfire 1968 Sold
Plymouth "Cuda" 340 Six pack SOLD