I have had 22" wheels with 305/40/22 tyres on my H3 for over 6 years and 70,000km, apart from a slight difference in ride quality they have been fine. I got 60,000 km out of the 1st set of tyres and replaced the disc rotors and pads at 70,000 km with cross drilled and slotted ones for looks.
I have no intension of taking my Hummer off road, it's just a great car to travel long distance in, we have pretty poor roads here in Australia and I have never damaged a rim due to the low profile tyres.
I have never had a problem stopping from speed and trust me here in western NSW I have to dodge Roos on a daily basis, wet weather grip has never been a problem either.
Cheers Stubbsy

 

Stubbsy, this is a refreshing post...when you put the new wheels on did you do any modifications at the same time?

Thanks

 

I don't like wheel spacers. I feel they are not safe.
I don't like large diameter wheels because I don't like the look.
But larger wheels are not a problem. If the OP had bought the wheels with the correct backspace, we would not be having this conversation. If the OP had posted the TIRE size we could have easily determined potential rubbing or fitting problems.
HappyThree is correct, we need to know the tire size and type that he is running.
Stubbsy above is running a 31" diameter. No wonder he has no problems. It's probabally lighter than OEM. It's just not a look I care for.
Lastly, the tire TYPE has more influence on handling than anything else on wet conditions. Most low profile tires are designed for speed, and a tire meant for speed is not a good tire for rain.

 

Yeah, I can confirm that I have 305/40/22 tires.

So can I assume no modifications are needed with this size. Just out of interest, the tires will need changing soon, so what could I possibly go up to on the 22" rims without damaging the car?

Thanks

 

I actually lowered mine 3" and fitted shorter shocks, my wife and young son were having trouble getting into the H3 being so high.
My H3 now handles sweet wet or dry.

 

That sweet!
Got some pic's to share?
Chris