Hi,

What is the tallest 13 inch tire I can find and put on the Brat? preferably an offroad tire.

Pretty sure 185 80 13 is the biggest.

getting much harder to come by, like was said above, 80 series would be the tallest, but be carefull since most 80 series you find are trailer tires. 185 70 r13 are the largest abundant tire, and very few are off road types.

 

if you can find a 185 80 r13 off road tire grab it, but likely you will be stuck with 185 70 r13 winter tires with the studs poped out.

i have a set of 185 80 r13 on my gl, they work good better in the snow than the mud though

Get some ATV/Side-by-side tires. They aren't DOT, but will work just fine for an Offroad/trail tire.

The selection of 13" tires is crap. All i could find was chinese garbage. Tire selection was my main motivation in doing the 6 lug conversion to get a bigger wheel.