Jeep Wrangler (JL): from the factory 33 upward

This is the rare platform where the factory already took the first step, and the size you start from decides how large the second one is.

Jeep Wrangler · JL · 2018 onward

Factory tire sizes: 245/75R17 · 255/75R17 · 255/70R18 · LT285/70R17
Factory wheel diameters: 17 in · 18 in
Factory axle ratios: 3.45:1 · 3.73:1 · 4.10:1 · 4.56:1
Aftermarket sizes covered here (untraced): 35x12.50R17 · 37x12.50R17 · LT315/70R17 · LT295/70R17; Sizes this site works the arithmetic for on this platform, so that the comparison exists when someone looks for it. The arithmetic is derived and checkable, like every figure here. The list is not: it is not drawn from a survey, a registration dataset or the manufacturer’s specifications, and the source line at the foot of this page does not cover it. Nothing here says these are popular, recommended, or fitted to your vehicle.

Transmission gear ratios are not recorded for this platform. A figure that could not be confirmed against a source is left out rather than printed: an invented ratio yields engine-speed arithmetic that looks exactly as authoritative as a measured one. How these numbers are calculated sets out the rule.

The arithmetic of the aftermarket sizes covered here, measured from 245/75R17

Size	Diameter	Change	Speedometer	Ratio restoring original rpm
35x12.50R17	35.00 in	+3.53 in	+11.22%	5.07:1 (nearest sold 5.13:1)
37x12.50R17	37.00 in	+5.53 in	+17.58%	5.36:1 (nearest sold 5.38:1)
LT315/70R17	34.36 in	+2.89 in	+9.20%	4.98:1 (nearest sold 4.88:1)
LT295/70R17	33.26 in	+1.79 in	+5.69%	4.82:1 (nearest sold 4.88:1)

Ratio column computed from the tallest factory axle ratio recorded for this platform (4.56:1). Change any input in the gear ratio calculator.

Four factory sizes and a 1.24 in spread

The recorded factory fitments run from 245/75R17 at 31.47 in to LT285/70R17 at 32.71 in. That top size is a genuine 33 — an LT-construction tire on a 17-inch wheel, fitted to the Rubicon — and it means the highest trim arrives having already made the change most owners of other platforms pay for.

Two of the four are the same height to within a hundredth of an inch. 255/75R17 and 255/70R18 both compute to 32.06 in: one holds height with sidewall on a 17-inch wheel, the other with less sidewall on an 18. Identical rolling diameter, identical speedometer, entirely different appearance.

The spread across all four is 3.94%, which is unusually wide for one model year's range and is why "what size does a Wrangler come with" has four answers.

Where you start decides what 35s cost you

35x12.50R17 is the size this platform is most often stepped to, and the arithmetic depends entirely on which JL you have.

From the Rubicon's 33: +2.29 in, a 7.01% change, and an indicated 70 mph becomes 74.9.
From 255/75R17 or 255/70R18: +2.94 in, 9.17%.
From the base 245/75R17: +3.53 in, 11.22% — an indicated 70 is really 77.9, and the odometer under-counts by better than a mile in ten.

Same tire, three different consequences, because the platform's own range is wide.

The gearing question is sharper here than the clearance one

Recorded factory axle ratios span 3.45:1 to 4.56:1. That range exists because Jeep geared the platform around very different tire diameters and very different intended use, and it is why the same tire change lands differently across the range.

Restoring engine speed after fitting 35s from the base size on a 3.45 axle asks for 3.84:1, with 3.91:1 the nearest set sold. From the Rubicon's factory 33 on a 4.10 axle, the arithmetic asks for 4.39:1 and the nearest catalogue neighbour is 4.30:1 — a smaller correction because the starting tire was already large.

The 37-inch step is where the numbers stop being subtle. 37x12.50R17 from the factory 33 is +4.29 in and 13.12%: an indicated 70 mph is 79.2 mph, and 100 miles on the odometer is 113.1 covered.

The narrow alternative

LT315/70R17 computes to 34.36 in — call it a 34.5 — and sits between the 33 and the 35 at +1.65 in from the Rubicon's size. LT295/70R17 is smaller again at 33.26 in, a +0.55 in change that is barely more than the difference between a new tire and a half-worn one.

Both exist because the jump from 33 to 35 is larger than many owners want, and because width at the inner fender is a separate constraint from height at the arch.

Why the 18-inch trim usually changes wheels too

Owners starting from 255/70R18 almost always end up on 17-inch wheels, and the reason is supply rather than geometry. The flotation sizes this platform is stepped into are produced overwhelmingly in 17-inch fitments, so the tire decision drags the wheel decision behind it. Since the two 32.06 in factory sizes are the same height anyway, nothing is lost in the swap except the cost of four wheels.

What this page is not telling you

That any of these fit. A JL's clearance depends on its suspension, its bumpers, its steering components and how far you turn the wheel, and none of those are readable from a size code. The arithmetic above is exact; whether a given tire clears your Wrangler is a question for your Wrangler.

Community practice on this platform is well documented and widely shared, and it is community practice — not a fitment finding from this site.

Where these figures come from

The factory sizes, wheel diameters and any axle or transmission ratios above: manufacturer's published specifications for the model year range shown, cross-checked against the size printed on the vehicle's tire and loading information placard.

Last checked 2026-08-10.

The aftermarket sizes above are not covered by that source and are not traced to one. The arithmetic derived from them is computed the same way as everything else on this site; the choice of which sizes to work through is this site’s own.

Your vehicle's own tire and loading information placard — the sticker on the driver's door jamb — is the authoritative record of what left the factory on your specific vehicle, including the inflation pressures its speedometer and load ratings were set against. Read that before you trust any table, including this one.