What it Takes to Install 42" Tires on 16.5" wheels
Updated January 15, 2022
Finding tires seems to be a difficulty. It looks like that there are only two tires on the market. Either Super Swampers TSL or Irok both around $300 a piece and both bias ply tires.
I have the following:
Two inch suspension lift, requires changing angle of ball joints.
Moved the Arms down on the frame
Two inch body lift
Detroit soft locker front and rear
3.08 ring pinion front and rear
2WD/4WD front drive disconnect.
3/8 spacers between spindle and wheel rim.
3/4 inch longer wheel/spindle bolts (studs).
With 40 inch tires I have just over 20 inch clearance at the cross member.
My speedo is within 1% with the 40 inch tires and 3.08 gears.
I do have clearance for 42 or 44 inch tires
I have noticed no change in the CG or any other problems.
By changing the A arms did the angle of ball joints change?
You went with bigger springs which leads to the change of the ball joints angle (how with shims)?
The next thing I guess by doing this the rim/tire comes a bit closer to the frame for which you compensated with the spacers and due to that longer spindle bolts?
I hope you can post some close ups?
I like idea of a real lift because the frame comes up and really improves the brake over angle (just due to bigger tires)
The 700R4 is weak, the 4L80E is costly and could leave you stranded someday if the computer malfunctions. But there is a solution. Instead of regearing the diffs, I would leave the stock gears in and regear the TH400. the stock first gear of a Th400 is 2.48 and second is 1.48. There are aftermarket gears available, a 2.75 first combined with 1.57 second should do the trick, third will still be 1:1. For gear calculating I use www.4lo.com If you keep the 2.73 gears and regear the transmission, the 42's will lower your highway rpm by about 370 RPM @ 65MPH. So the 42's become your overdrive!! In addition, the lower first and second will still give you the low speed trail gearing you need. It's an alternative to the typical 4L80E conversion that could cost a ton of money, and make the truck more complex than it needs to be. I like simplicity, one of the reasons I won a 93.
As for the 42's I think they will fit, but may rub a little when the wheels are turned all the way while the suspension is stuffed. Others on the list have ran 39.5's with a 2 inch body lift with no rubbing. Now if you surf on over to Interco you will see this:
SAM-71
15/39.5-16.5LT size
10 ply rating
25/32 tread depth
13.0 tread width
39.4 overall diameter
15.0 center section width (width including the sidewall bulge)
16.5x9.75 recommended rim size
60 Max PSI
3860 load rating
SAM-24
15/42-16.5LTsize
6 ply rating
27/32 tread depth
13.0 tread width
42.0 overall diameter
15.1 center section width (width including the sidewall bulge)
16.5x9.75 recommended rim size
30 Max PSI
2685 load rating
This tells me that the 42 is actually a full 42 in height, and the 39.5 is actually a 39.4. subtract the difference and you get 2.6 inches in overall diameter/Height difference. Half of this is 1.3 inches, so the 42 will be 1.3 inches closer to the hood and fender, the other 1.3 inches becomes additional ground clearance. So given that 39.5's fit with a 2 inch body lift and no fender trimming, 42's should fit with a 3 inch lift and some slight trimming.
