Biggest tire on stock 4x4 and speedo recalibration
 

How's it going?

Very new to first gens and first get performance. I picked up an '89 that I am very anxious to get into as a project and a nice daily driver to save the miles on the newer Cummins that I have.

Maybe I'm not the best at hitting the right keywords when I do a search. This has to have been asked before.

The questions are: what is the biggest size tire that I can fit onto my stock '89 4x4, and are there any issues with rubbing?

Do I need any kind of spacers or to buy wheels with certain back spacing?

And, how do I recalibrate the speedometer, and is there some kind of site that sells the gears to do it, and has a reference chart so I get it right?

Also, how would my stock 3.07 gears do with those size tires?

I went to 33" tires and my speedo is closer to accurate than before.

I've been running factory Ford 16x7 steel wheels mostly. 285/75R16 clear without rubbing anything. 315/75R16 rubbed the pitman arm turning right, but no sheetmetal contact. (a wheel spacer would have fixed that I'm sure).

I've also run 9.00R16 michelins and they cleared for the most part. I did roll the front corner of the wheel opening a tiny bit for clearance.

You get too wide of a tire and ittle hit the pitman arm. Depending on how far your front springs have wore down over the years, I'd say 33"-33.5" would be tall as you could go stock height , no rub, but i have heard of people fitting 35's with slight trimming. I guess a lot depends on how wore down your springs are. my 34's rubbed stock height, so i did 2.5in front lift springs

I got 305/70R17 it rubs turning right in the pitman arm and is a pain to reverse out of spaces because it rubs, but i think I'm going to get a 2in lift and throw 35's on there. But add a leaf might stop the rubbing or wheel spacers :humm:

You may get enough spacing with the cheap & easy 5/16" spacer.

I went from 285/75R16 on 16x7 Ford wheels to 295/70R17 on 17x7.5" 3rdgen wheels (+ 2" spacers) and the tires came out about 1" per side. I'm guessing ~1/2" more room on the backside.