I'm thinking about going staggered too. Purely for the aesthetics. Seems like I could fit some 10s or 10.5s in the back, which would look great from behind. I've been thinking as long as the overall diameters are the same, the computer will read the front/rear speeds the same, and I won't have any AWD problems.
To my mind, different grip characteristics on each wheel are just as important as diameter. If your front wheels are constantly slipping differently to the back wheels, the AWD system is not going to be particularly happy with you.
Are you sure though that they will be constantly slipping differently? In my amateur understanding, a tire with twice as much grip can withstand twice as much shear force in it's contact patch before it starts to lose traction. I thought below the traction limit (transition zone) the slip in both tires would be negligible.
Thinking about straight line driving, under acceleration or braking, in dry or slippery conditions, I don't yet see the downside of increased rear grip.
If you LOOOOVVVEEE understeer, go with staggered wider rear tires with a CX-5 (with or without AWD).
I'm trying to understand if this would be an issue for me. I enjoy spirited driving, but I don't really push my car to the limit through turns. Increasing rear grip will exacerbate, but won't cause, front grip issues, right? Like, if I'm going through a turn and my front wheels are starting to lose traction, it can be better if my rear wheels are also starting to lose traction, making turning more neutral. But, if I don't track my car, and am not planning to approach the traction limit of my front tires, would it matter if my rear tires had infinite grip? And in wet conditions, where I do risk losing traction, couldn't a wider rear tire reduce oversteer?
I appreciate any insights more experienced folks have to improve my understanding of the handling and reliability issues I could expect running 9s in the front, 10s in back. I do see a couple other issues giving me pause:
1) no more rotating wheels. So I won't be replacing all 4 tires at the same time. No 4-tire discounts, and double the trips to the tire shop.
2) I still have 3 years of powertrain warranty. Detrimental or not, this would probably void that on a lot of those components.