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All wheel drive tire replacement

One tire on my Mercedes ML430 blew up and I need a new tire. I am buying the same tire as the remaining three. The dealer tells me I need all four replaced. Is he right?

Check your manual, what does it say? For most AWD cars if the tires have worn, then yes, you do need all 4, otherwise the AWD system might be damaged. Other option is to find a tire shop that shaves tires, have the new tire shaved to the same size as the worn ones (google ‘tire shaving yourcity’).

Likely it is required. More specifically all four tyres need to be nearly matched circumference. It does not allow for much wear. Not following those instructions (check your owner’s manual) can cause damage to some expensive parts that will make you wish you did it right.

Unfortunately, it probably is. You may damage the AWD otherwise.

Texases is correct.
Having one new tire “shaved” so that it matches the circumference of the 3 old tires is far cheaper than buying 4 new tires.

If your tire retailer does not offer “tire shaving”, then you need to go to a different, more sophisticated tire shop. Even if their price for one tire is higher than the original shop, even after you add the cost for shaving, you will still save a whole heap of money.

Contact MB for the specifics or possibly your manual. It all depends on many factors. In general many but not all AWD vehicles require all the tires to be close in rolling circumference(distance around tire), the question is how close.