Picked up my 09 Mazda5 last week.
It is sitting on 2 - Michelin Pilot Sport A/S in front & 2 Toyo Proxes A18 in the rear.
Tread on both are 70% or close to that.
Ride is good....

Should I be concerned about mixed sets of tires on my M5 ? What might the issues be?
This is first use of low profiles ... so that the experience here might help...
thanks - B

 

It shouldn't cause a problem as they're roughly worn the same and you have the same brand on each axle.

 

a lot of people just run mixed tire combos anyways. on my rx7, the fronts are nexen and I have ordered a set of hoosiers for the rear. in the past, I have run bf goodrich in the rear and whatever is cheap on the front. for ride quality, you will want to keep the matching pairs on each axle as previously stated. if not, you could experience some steering issues at high speeds.

 

I once went to buy two snowtires for my old 86 Golf (don't miss that car) Anyways, I went to Sears, and they REFUSED to sell me just two tires, saying I needed 4 tires or the car would be unsafe. I called a bunch of other places and NOBODY else told me the same thing (Canadian Tire, Walmart, Kal Tire, OK Tire, & Costco) ALL said they would do 2 tires.

So IMO, as long as the fronts are the same, and the rears are the same, It is probably perfectly safe.

 

The only "potential" problem I can see, and I am playing the devil's advocate here, is if one set were more grippy than the other. That could cause uneven braking and handling.

 

For a 24 hour period I once had different rubber front/rear (I had to leave the shop due to an "emergency" at work). IIRC, the new Michelins were on the front and the factory Goodyears were on the back; the combination made the car extremely squirrelly to drive in anything other than a straight line. This is not to say that all tire combinations will do this, but be forewarned.

 

There's no problem with fitting two tyres at a time. However, as I recall, on a front wheel drive vehicle, the two new tyres are supposed to go on the back with the two older tyres moved to the front.

Back when I was still a student, I put new tyres on my front and kept the old ones on the back. My reasoning was that new tyres=more grip therefore go on the front. I won't be doing that again

 

The "new tires go on the rear" thing only applies to situations where the demands of maneuvering can overcome the available adhesion (i.e. winter weather or when "tracking" the car in wet weather), other than that it makes no difference. What I was talking about wasn't so much the condition of the tread but the handling characteristics of different tire models (i.e. Michelin's on the front, Goodyears on the rear).