Tire size help please

2016 SR5 4x4. 3" lift 20" rims. Currently running 285/65r20. Can I go any bigger on the tires without further modifications?

 

Not really.

Unless you are ok with modifying your front plastic, BMC, and/or spacers or new wheels with the proper +20 offset.

I am on 3" lift with 275/65R20 because I also have SPC UCA's and had not enough clearance to the UCA to go wider, so I ended up having to add spacers anyway with these tires just to get a safe gap between tires and UCA.
SPC UCA top ball area sticks out more than stock UCA but I can get a better alignment with my adjustable SPC UCA.

Also try searching and reading the tire/wheel section threads.
This is the general section.

 

what is the offset of your wheel?

 

Offset is -12mm. XD Monsters.

 

i would look at custom offsets.com. they have a huge gallery and you can drill down to tundra 20" etc. thats a lot of poke and i dont want to point you in the wrong direction

 

That was important info you should have started with.

With that much offset your likely to need to cut several things from front wheel well to BMC if you go much bigger tire wise.
But I have never tried to run that sort of combo so I'm not for sure.

Again, the wheel/tire section would give you the answers you seek.

 

https://www.tundras.com/threads/official-tundra-wheel-and-tire-setups-pics-and-info.95/#post-858

 

Welcome from NY.