What are the largest tyres i can fit?

Does anyone know if i can get some mud terrain tyres sized LT215/75R15 on my stock jimny (no lift yet)? Im looking at getting an 80m lift and getting the flares cut back a bit to fit some larger tyres. but for now the stock tyres arnt cutting it, so im looking for an upgrade.

What is the largest tyre size you can get on the stock jimny??

Depends on a lot of factors, type/use etc. Have a look at the Wikki section at the top of the page (in the black bit)
Be warned, the sizes differ from one manufacturer to another. My Kaimans are 1.5" bigger than normal road 205/70/15
but still sold as this size.

My Kumho MT's are 215/75 but noticabely larger than my GP698 215/75 (copy of Bridgestone Dueler A/T) wich are also larger than friends Toyos 215/75.

Kumhos needed bumper trim to fit with offset wheels.

217/75 BFGoodrich mud terrains will fit if you keep to standard rims and no spacers.

I'm running Insa Turbo Sahara Competicion 195/80 R15's on stock suspension. There was a little bit of rubbing on the front at one particular steering angle initially, but after replacing a missing mudflap screw and cutting a couple of ribs off the inside surface of the mudflaps I can only get it to rub while off road at a very specific steering angle with the suspension heavily compressed.