and when would you normally consider this type of setup
Good question. I’m intrigued to know the answer.
Id say it doesn’t give huge benefits, but it can be used as “quick fix” for some quircks of the car.
Example 1.
You have car that isn’t quite as responsive as you would like. and it suffers for small understeer, and front tire heat might be bit too high. Knocking wheelsize 1 up on front might reduce this behavior, and as there is less sidewall on the tire there will be less sidewall flex which brings the tire heat down a bit.
Example 2
The car seems to be perfect, but the back end occasionally snaps loose so fast that there isn’t anything you can do to it. Lower rimsize 1 inch on the rear end and it comes slightly looser, giving you more warning that it’s about to go, and if it goes you have more time to react.
Personally I tend to ignore the rimsize and look at the tire profile, as I have found that profile 35-45 leaves me with good responsiveness, while giving myself enough warning that front/rear is about to lose grip, and give me enough time to adjust so it wouldn’t and if I fail at that it doesn’t “snap” away from me.
This might lead to different rimsizes, usually front being +1 compared to rear. if I’m running on wide rear, and not so wide front tires.
^^thank you so much for that explanation. I’m tuning a car and it has wider rears than front to counter some crazy power on oversteer. It actually still suffers mainly from oversteer but funnily enough when it does grip there’s apex to exit understeer that I can feel is going to happen once I’ve fixed the oversteer as well. I’m running larger front rims because I had only an incline that it would help…I just needed to know why that was the case. Thanks again
Bigger rims size is like stiffer suspension, except it affect PI.
I never use that method, but you may want to decrease the PI (Since it add weight) to do another upgrade.
Increasing rim size as ofen as not both adds weight and raises PI. I usually do what Juggs does and opt for around 40mm profile on cars that don’t come stock with less, although older cars and muscle I will often leave at 45-55mm depending on the porfile of the stock tyre. The fact is that increased rim size brings a lower profile, and that also affects the handling by reducing wall flex and sharpening the grip limit. My best guess is that PI rises with rim size because of the marginal increase in top speed. I’m still not convinced that there’s much merit in staggering rim size per se, but I’m happy to be persuaded otherwise if someone else wants to chime in.
Personnally, I just make sure it look good 
That is pretty much what I do. and that leads me to higher profile front tires which isn’t bad. I get some understeer but I usually have enough power to counter it with power oversteer, How ever that is where I’m running a small risk of getting too much power down and spinning. as to get any benefit from that oversteer, it needs to be very subtle.