What tire size should I increase to?

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. For many reasons, it is advisable to stick with the factory equipped tire size. This size is best used to ensure proper transmission operation, anti-lock brake system operation and traction control function - not to mention speedometer accuracy. There is little - if anything - to be gained from changing tire sizes from what Lexus says to something else. If you should choose to do it anyway, a good rule of thumb is to raise the first number (tread width - 235 to 245 as an example) while lowering the second number (aspect ratio, example 50 to 45). This is termed "zero plus sizing" and can get you close to overall tire and wheel diameter to prevent too much variance with the components I mentioned. If you do this, you must be mindful of clearance in the wheel wells, with steering turned lock to lock and with the width of the rims used to ensure they can handle a wider tire. I recommend checking with a tire shop near you for guidance.