35 vs 37 tires is the step after 33 vs 35. On flotation stamps it is two inches of overall diameter: 35x12.50 vs 37x12.50. In metric, 315/70R17 is already only 34.4, so a lot of "35s" are not 35s, and a 37 is a real jump. This page puts the slang and the stamps on one table.
The two flotation stamps
| Size | Diameter | Width | Sidewall |
|---|---|---|---|
| 35x12.50R17 | 35.0 in | 12.5 in | 9.0 in |
| 37x12.50R17 | 37.0 in | 12.5 in | 10.0 in |
Diameter grows 5.7%. At 60 indicated on a truck calibrated for the 35, the 37 is doing about 63.4 mph. Width does not change. You are buying an inch of radius: bumper, fender, control arm, and a taller gear. Compare them live: 35x12.50R17 vs 37x12.50R17.
Metric stamps in each band
| Called | Stamp | Actual diameter |
|---|---|---|
| 35 | 315/70R17 | 34.4 in |
| 35 | 315/75R16 | 34.6 in |
| 35 | 35x12.50R17 | 35.0 in |
| 37 | 37x12.50R17 | 37.0 in |
Who this pair is for
F-150 Raptor already offers both: 315/70R17 as the regular Raptor stamp, 37x12.50R17 as the 37-inch package. A Raptor owner stepping to 37s is making a smaller relative change than a stock Lariat owner stepping to 35s, because the Raptor starts tall. A Wrangler Sport stepping to 37s is a different truck. The F-150 and Wrangler pages are the stock heights.
Gearing, weight and mpg all move. The mileage page is the mechanism. A regear restores acceleration. It does not remove the extra rotating mass. Budget both if the truck works for a living.