Still confused on backspace and offset.

First my apologies for asking this. Have been searching this stuff for weeks. There is tons of info on here regarding this but some of it seems dependent on certain setups. Just about when I think I understand there is some type of variable that makes me second guess myself.

I have a 17' Or 4wd.

Ordered an OME 888/Dakar kit and will be needing tires/wheels once it gets installed.

Still trying to decide on 17x9 and 18x9. Trying to stay around 32's or 33's on the tire. Seems the most popular backspace numbers are 4.5" which I believe is around -12 and 5.0"/+1. Will either one push out past my fender? Would like to avoid that.

Which one is ideal for larger tires? I have read opinions both ways, confusion seems to be when getting up to 285 and larger. I am just trying to make sure I get the right specs the first time.

Thank you in advance!

 

I answered a similar question in the link below.
You can use the calculator I link there, to see what different combos will do.
Tires have a "measured width". This is the rim width used to calculate the other specs listed; such as tread width, section width, and load psi.
285s for example, have a measured width of 8".
Tires also have a "rim width range"; 285s are 7.5"-9".

A stock offroad wheel is 16x7, +25 offset(5" bs).
17x9, +1(5" bs) will stick out 2" further than stock.
17x9, -12(4.5" bs) will stick out 2.5" further than stock.
9s push them out a lot.

17x8, 0 offset(4.5" bs) will stick out 1.5" further than stock.
17x8, -12 offset(4.25" bs) will stick out 2" further than stock.

https://www.tacomaworld.com/threads/wheel-backspacing-and-offset-info.102992/page-37#post-13441531

 

Thank you!

 

Does running spc UCA's help with the clearance issue?

 

Their purpose is to regain lost caster due to lift and/or add caster when larger tires are fitted.
If anything, it will move closer to interference at the cab mount.

FWIW, the toku58 school of thought, says to run 2.4 degrees of caster, with 33" tires.

 

I'm looking specifically at 18x9. After reading it seems like 4.5" backspace is what most go with.

Seems to me since it sticks out further it would hit the body mount first. In this case would the 5" backspace not tuck it in more. Don't see many cases of 5" bs with 33's mentioning contacting the UCA's.

Not sure if I'm missing something here.