Tire size and re-gearing

[WJAFRICA]

I am looking at fitting an IRO 4" or 6.5" longarm kit, and would like to know from guys with experience what is the biggest tires I can fit before having to re-gear the axles.
Living in South Africa we do not have access to after market parts like you lucky guys in the US, and this means we have to import everything we need at big costs, hence I want to get it right the first time.
What I am looking at getting is:
IRO 6.5" Critical Path Long Arm Lift Kit
ATX AX1812 Artillery Wheel - Chrome
16x9, 5 on 5 Bolt Pattern ,Backspace = 4.53in
Maxxis Mudzillas 31x11.5x16
From doing some research it seams that 31" tires will not be a problem and it seems that it is only once you go to 33" and above that re-gearing needs to be donne - am I correct in this?

Any help and info regarding this set-up is appreciated.
Thanks
Johan

[cheapjeep]

Hey Johan,
I see you did some backspacing homework,thats good because your almost double on your tire width.Also its good to see that this kit has a t-case drop because you're going to need it. Seems everything is good but
if your tires rub at full lock on the inside you might have to invest in a set of wheel spacers. Far as gearing i think you' be alright with 31s The front diff honestly cant handle too much more.Also you'll have to plug the jeep in and recalibrate the computer to your new tire size.
Good luck bud,
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Dave