Why can't I have bigger wheels?
Well you can sir, but they must meet the modification guidelines (VSI No 8).
But it will handle better with big wheels!!
Well it might, but it might be worse.
Rubbish, with all that extra rubber it must stop and steer better!
Actually if the wheels are taller than standard, the brakes will have to work harder to stop the vehicle.
Why is that?
Its all about leverage. The brakes are trying to stop the wheel from turning. The amount of energy they can dissipate is related to how big the brakes are, how hard they are applied and how well they get rid of the heat. How hard they have to work depends on the how much force in the form of the road pushing the wheel around they have to resist.
What difference does a taller wheel make?
A taller wheel gives the road more leverage to fight against the brakes.
So all I have to do is press harder on the brakes?
That's OK for normal driving if the change is very small. However, in some cases you might not be able press the brake pedal hard enough to stop the vehicle fast enough in an emergency.
What about my 4WD, I need big wheels to get through the ruts?
If you put the taller wheels on then you have effectively done a brake modification. In that case you will need an engineer's report. The engineer will tell you what other changes need to be made so the brakes will work properly again.
At least the big wheels will make it handle better!!
Perhaps! But only if you consider.......and the story goes on and on.