Good discussion here, not much to add.
One thing to note that many seem to forget is that a 35" tire rarely measures thirty-five inches, and even if it did, after a season or two it will be closer to 34".
I built a nice Engine RPM and Truck Speed Calculator on our R&P page: https://www.marlincrawler.com/differential/ring-pinion Plug in some numbers, write down the resultants, and then go drive your truck how it sits now and compare. See if the RPMs vs speed is what you're looking for. If the calculator calls for 3,500 RPM for 65 MPH on the freeway then run your truck in 4th gear at 65 MPH to see if those high of RPMs is something you'd want to live with.... etc.
Regards,
BigMike
Correct, most 35's aren't 35" tall when mounted, however, neither are most other tire/wheel combos, most are 1-2 inches shorter than the sidewall size or the metric-to-inch conversion.
6 of my vehicles, all tires at 35psi
225/50R16 24.9", mounted 23.75"
265/75R16 31.6",mounted 29.5"
205/65R15 25.5", mounted 24.5"
205/75R14 26.1", mounted 25.125"
33x12.50 R15 mounted are 32"
35x12.50 R15 mounted are 34"
The calculator shows that there is very little difference when you use stated tire size or actual size providing you use the height discrepancy of the original tires w/the stock gear ratio.
Calculator results,
My '90 w/R150/5th gear/70mph
4.56 w/31's(stated size) 2907rpm's, mounted size 30" 3004rpm's
4.88 w/33's(stated size) 2923rpm's, mounted size 32" 3014rpm's(Confirmed w/Stock tach and gps).
If I ran my 35's BFG MT's
5.29 35's stated size 2987rpm's, mounted size 34" 3075rpm's or 2837rpm's w/4.88's
My '91 '91/W56c 5th gear 70mph
4.56 w/31's(stated size) 2942rpm's, mounted size 30" 3040rpm's
4.88 w/33's(stated size) 2958rpm's, mounted size 32" 3050rpm's.
5.29 w/35's(stated size) 3023rpm's, mounted size 34" 3112rpm's, or 2871rpm's w/4.88's. Stock tach at 70mph(gps) 3250rpms
Could not start with the stock 225/75R15's and w/4.10 gears, the calculator starts at 29", and the 225/75R15's ar.3" unmounted, which would likely be about 27" when mounted.
However, if you use the stated size of the original stock tire w/stock gear ratio and the mounted size of the tire you are now running/plan to, you get false results.
My '90 w/R150
4.56 31's stated size...........2907rpm's
4.88 33's(32" mounted size) 3014rpm's
5.29 35's (34" mounted size) 3075rpm's or 2837rpm's w/4.88's
My '91 w/W56c
4.56 31's stated size....2942rpm's
4.88 33's(32" mounted) 3050rpm's.
5.29 35's(34" mounted) 3112rpm's, or 2871rpm's w/4.88's.
The results make it look like 5.29's would increase the rpm's by 170 at 70/5th gear, when they would actually only be increased by 60-70rpm's, on the other hand it looks like the the 4.88's would only lower the rpm's by about 70, when they actually lower the rpm's by about 170.
