I don't think it's a big deal to get matching tires for a normal car/truck. If you were talking about a high power sports car where you try to extract every ounce of performance and take the car to it's handling limits then it's a different story. I'm not gonna ever lose traction or push into a corner too hard, the car is not really meant for that. Even in spirited driving I bet you will not be able to tell the difference. I'm not telling you to get the cheapest tires out there but you can save some money on getting a different brand.

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03 M5
05 X5
01 RX300