Biggest width of tire on stock suspension

[benjaminblazer]

I plan on getting 1.25 spacers for 6x5 to 6x5.5 so I can throw on new wheels. Im not sure what the highest width i can use without rub or issues. The biggest rim size would be 20 but not set on that size so could go lower. Is there a guide to follow for this, let's say I get the 20in, would 275 55 20 be too wide? Or if I went with 18s, would 265 60 work? Thanks for reading, any input helps!

 

[Matt]

31.5" is the largest diameter without spacers. Honestly not sure with. The UBJ is the issue and if you can clear that, then go with whatever.

This was mine with no spacers using a 31.5" tyre. No, it didn't rub or touch even over bumps. These were 265/65/17.