Effect of larger tyres

It will make your brakes worse and change the gearing to be taller, but what effect it will have depends on what car they are going on.

In all honesty, going from 31 to 32's won't make a scrap of difference. Unless the tyres you want are only available in that size there really would be no point in changing.

Speedo/odomete - 3% speedo/odo error (97 indicated = 100 actual, that's if your speedo was accurate to begin with - most aren't)

Fuel economy - the same, (generally a product of weight vs speed, although there will be a similar 3% error to the above, in calculations if going by the vehicles odometer)

Braking distance - predominantly determined by the tyre type (Muds - poor through to road terrain - good) Diameter not a factor in actual braking distance, but would theoretically wear the pads out faster and would require more brake pedal effort (3%?? again)

If it is the current Hilux then wouldn't it be more like going from the current 29in tyre to a 32in tyre?

I have a Rodeo with 31s and it has quite noticably affected the gearing however I prefer the higher gearing onroad and put up with it offroad. The added clearance is very welcome offroad.

Going from 31's to 32's will only get you half an inch extra clearance.
What you need is a set of raised springs. 50mm raised springs gets you 50mm more clearance :-) and no adverse effects on brakes or gearing.

Hound

The effect of larger is as follows:

(1) A rotating tyre/wheel has the same effect on the axle as lever and fulcrum.

(2) When designing a vehicle, the brakes, suspension, drive line are engineered to be compatible with the intended tyres within reasonable safety limits.

(3) All things being equal the brakes should stop the said vehicle within specs including load.

Now if you increase the tyre size, it increases the 'lever-fulcrum' effect exponentially exposing the said brakes, suspension to possible failure.

Thats it in hopefully very simplistic terms (Actually very involved when re engineering)

The other effects are:

(1) Increased stress on drive train components

(2) Causes speedo V actual ground speed variances.

(3) If protruding outside of Vehicle side profile - Makes vehicle un roadworthy.

How will the above effect your vehicle, I don't know as the large the tyres you use the larger the effect.