I have 19s and planning to install 20s that I have had for sometime now. In order to maintain the same gear ratio I was planning on 225x35x20 on the front and 275x30x20 on the rear. Comments please. While I am at it, my wife has Sumitomo HRT Z III on her Mazda 3 and they drive really nice, anyone has experience with these tires?

 

Those tire sizes will be ok, but how wide is your front wheel? I suggest going a little wider in the front. (245/35)

I'm not huge on sumitomos but they're alright tires.

 

The front rim is 8.5" and the rear 9.5" wide.The only reason for the 225x35 is to maintain as close as possible to the stock wheels. The 225 X 35 is 26.3" and the stock wheel is
26.0". The 245x35 is 26.8 which is almost 1" larger in dia. The 275X30 is 26.5" so both the 225x35 and the 245x35 would work for the VDC. Sumitomo does not carry a 225x30 which would be 25.8". Not sure how the 225 will look or handle & tried Rimtuck but could not get it to work. I do not believe that as I live in Florida where driving is mostly straight roads & I do not road race, the handling differences if any, should not matter.
The Sunitomo's are cheap and got a decent rating from Tirerack. The front is $130 and the rear $186. The Continental Extreme Contact DW was the top rated but almost twice the price and the rear was on back order. If you have any tire suggestions I am ALWAYS willing to learn from others.
I will also be looking for camber adjusters and based on what I have seen on the forum, I probably will go with the SPCs which are a little bit pricy but seems to be the camber adjuster of choice. Thanks for your comments.

 

Both are in your 3% difference so you'll be fine with either.

Sumis are priced pretty well, Falken Ziex and FK452 are priced pretty decently as well.

My favorite tires are Michelin Pilot sports (quiet as hell) and Nitto invos, not loud and great grip.

How low do you plan to go? If you're not going lower than 1.7ish" then I wouldn't worry about the front. The front camber kit price doesn't weigh out how fast it will burn your tires. The rear I would suggest a camber kit though, only because it's cheap and easy.

 

I do not plan to lower the car. The rear 19" wore pretty badly(on the inside) and I assume that when I install the 20" it will cause the front to wear faster as well. Thanks for the tire advice I will check them out.