Tire replacement
 

I recently experienced a blowout on one of my tires. The tires are OEM Michelin on an RX350 AWD. The tires had 25,000 miles with 6/32 tread remaining. Do I have to replace all four tires or can I replace just one with an exact match to the original but with a full 10/32 tread?

In vehicles with all-wheel-drive systems, the differential and the computer work together to send the right amount of torque to each wheel to minimize slippage and maximize control. If one of the tires is a different size than the others -- because three tires are worn and one is brand new -- the computer will take an incorrect reading and the differential will work too hard. Drive this way long enough and you'll burn out the drivetrain. With that said we recommend you replace all 4 tires to avoid adverse affects. You can consult with the technicians at your local Lexus dealer for additional information.

That response is a straight cut and paste from the web, provided without attribution from: http://auto.howstuffworks.com/replac...htmInteresting,

Be aware that some Lexus dealers apparently have another opinion on the subject:
https://www.clublexus.com/forums/rx-...ml#post6321386

Frankly, I'm confused. It seems to me that tires are always rotating at different speeds (for example, every time you enter a curve or turn a corner). Rarely does a vehicle go exactly in a straight line on a perfectly level road.

Just replace them as a pair. No need to replace all four.

You can always order a single tire from Tire Rack and ask them to shave the tire to the depth you ned to match the other tires. You do waste milage on the new tire but it would then be the same size as the other tires.

What does the Owners Manual say?
 

I continue to be amazed by the question about replacing a single tire. For the 2014 RX 350, here's what the Owners Manual says:

Replacing tires
Make sure that all tires are of the same size, brand, tread pattern and total load capacity. In addition, make sure that the tires are inflated to the recommended tire inflation pressure level.

NOTE THAT THE MANUAL DOES NOT MENTION TREAD DEPTH OR WEAR LEVEL.

In fact, the manual goes on to say that it is OK to put snow chains on the front wheels. Now, wouldn't you think that chains would make a bigger difference in tire diameter than a bit of tread wear?