Mazda Repair: tires, wheel drive cars, miata mx5


Question
Hi, in a previous post you said not to go with the set up of a oem tire size tire in front and half set bigger in rear because it affects handling. i have a 2007 miata sv and yesterday put on 215 50 16 dunlop dz 101 in rear and left the front alone just to see how it feels. i didnt notice any adverse effects. so now i want to put those in front and go with 225 50 16 in rear. corvetts do it porsches do it i know other cars do it. why not the miata? granted my car is not a high end sports car but im failing to see the reason behind why i cant do it.

Answer
Miata's are rear wheel drive cars with front wheel drive offset hub measurements.  It is perfectly balanced by design and engineered to have each corner support handling equally.

I'm not going to tell you that you can't do it.  Just like I tell people who want to install 20" plus rims that they can't, it's your ride - I'll say that it was not engineered to be outfitted that way.

I can advise that in 20 years of this you are not the first person to want this look nor the first person to make the switch in sizes regardless of advice.  I can tell you that mixing wheel and tire sizes on a MIata will induce over steer and will create an instability issue that can effect handling and safety.

If you make the switch you will need the front tire alignment to be as neutral as possible in toe and camber.  You will have to also reduce rear toe.  

Corvette 0-60 in 4.4 sec
Porsche 911 0-60 in 4.7 sec
Miata MX5 0-60 in 7.0 sec

The Miata is a roadster built to handle corners not a straight line car.  Vettes don't handle corners well, a 911, well that is what you get with deep pockets and German engineering, the ultimate mix of both worlds.

Find someone who road races or solo's a Miata they will share face to face insight to support the reasons to stay 50/50.