Q:

What are the largest Technic-compatible tires on the market?

I am looking for the largest LEGO wheels with tires available to build a nice-sized RC LEGO car.
Of course I will start with the simplest prototype, but I would like to achieve a design which will embed an automatic gear box and quite a large propulsion system. So the size of the wheels will be important.

Edit: The "Wheel 81.6x15" 2903 @Pubby8 found seem to be the biggest. But they are thin... Are there any other larger ones? Even 3rd party would be good.
Edit: @Joubarc & @Pubby8 found the biggest wheels but without tires I am still looking for 3rd party solutions before accepting an answer.

A:

The largest wheels I know are these (I measured 110x63 mm, including tyres), but they are quite rare (only available in one single set):
Weels: 22969 "Wheel Technic Racing"
Tyres: 32298 "Tyre Power Puller"
The wheels itself are not that big, but if you include the tyres, they are really huge:

They would probably work really well for an RC car.

A:

The largest wheels I've seen are "Wheel 81.6x15" 2903

To show scale: 

There are larger ones on the Hailfire Droid but these probably aren't good for your needs:

A:

An alternative is the 94.8x44 balloon tires. While they are not as big as the ones elusive suggested, I imagine they are easier to get as they have been in some recent sets.
Comparison:

Left: 81.6x15
Middle: 94.8x44 balloon
Right: 81.6x38 balloon

