Tire sizes
Every size below is one people genuinely buy. There is no page for a size nobody makes.
The catalogue is deliberately bounded. There are thousands of arithmetically valid size codes and a page for each would be a directory nobody reads and Google eventually stops crawling. What is here are the sizes that come off real vehicles and out of real catalogues.
Each page computes its dimensions from the size code rather than storing them, which is why the figures match the calculators exactly. Each also names the nearest genuinely-sold size in the other notation on the same wheel, which is usually the actual question behind the visit.
How the groups below work
Sizes are grouped by the class of tire they are produced as, because that is what determines the load-index band they are sold in — and load index is the constraint people miss. A 265/70R17 built as a passenger tire and a 265/70R17 built as a light-truck tire are the same shape and are not the same tire.
The band shown on each group is what that class is typically produced in. It is not a claim about any particular tire: load index and speed symbol are printed on the sidewall of the one you are holding, and the minimum you need is on the placard of the vehicle you are fitting.
If the size you want is not here
Type it into the comparison tool. The parser reads both notations and any wheel diameter, and the arithmetic is identical whether or not a page exists.
What a size page contains
The computed dimensions first: overall diameter, section width, sidewall height, aspect ratio, circumference, and revolutions per mile in both miles and kilometres. Then the class band, and the reason that class sits where it does. Then the nearest genuinely-sold sizes in the other notation on the same wheel, with the diameter difference of each — which is the question most visits are really about.
Then the platforms recorded with that size, if there are any, and the comparisons involving it. Then prose about that size specifically: where it came from, what it substitutes for, and the particular traps it carries.
Two depths, and why
Some sizes have a great deal that is true of them alone — a history, a substitution they are famous for, a conversion argument that follows them around. Those get a full page.
Others are perfectly real sizes that people genuinely buy and about which there is very little to say beyond the accurate numbers. Those get a shorter page: answer-first prose over the same computed panel, linking to the tool and up to the class.
That split is deliberate. The alternative — writing seven hundred words about every size in the catalogue — produces a hundred pages of the same sentences with the numbers changed, which is worse than a short honest page in every respect that matters.
A note on the numbers
Everything on a size page is computed from the code. Nothing is stored, so nothing can quietly disagree with the calculators. What that also means is that these are geometric figures, and a real tire is not a geometric object: measured diameters vary between manufacturers, and a loaded tire rolls on a smaller radius than its free radius. The methodology page sets out exactly where the arithmetic stops matching the rubber.
Passenger touring
A passenger tire's load index tracks its air volume, and volume tracks section width and sidewall height. Sizes in this class sit in the band that carries a typical two-tonne car with its rated payload across four tires.
- 175/65R14175/65R14 tire size — dimensions and nearest alternativesAt 22.96 in tall, 175/65R14 is the smallest size in this catalogue and turns 878.5 times per mile — more than any other. Computed geometry and the nearest sizes to it.
- 185/65R15185/65R15 — 24.47 in, and its twin on a 16-inch wheel185/65R15 measures 24.47 in with a 4.73 in sidewall and 824.2 revolutions per mile. It lands two hundredths of an inch from 195/55R16, which is the whole story of this size.
- 195/65R15195/65R15 — the default size of the European compact carAt 24.98 in tall and 807.4 revolutions per mile, 195/65R15 sits two hundredths of an inch under 25. Its geometry, its symmetric 10 mm neighbours, and why it outlived the cars it came on.
- 195/60R15195/60R15 — the shortest 15-inch fitment in the catalogue195/60R15 stands 24.21 in tall with a 4.61 in sidewall and 833.0 revolutions per mile. What five points of aspect ratio cost at 195 mm, and the sizes that land closest to it.
- 205/65R15205/65R15 tire size — the tall-sidewall 15-inch fitment205/65R15 stands 25.49 in with 5.25 in of sidewall — more than any other 15-inch passenger size here — and turns 791.2 times per mile. Its geometry and closest alternatives.
- 205/60R16205/60R16 tire size — a dead heat with 245/45R17205/60R16 measures 25.69 in over the tread, carries 4.84 in of sidewall and turns 785.2 times per mile. It matches a 245/45R17 to within two hundredths of one per cent.
- 205/55R16205/55R16 — the highest-volume replacement size on the shelf205/55R16 measures 24.88 in over the tread with 4.44 in of sidewall and turns 810.7 times per mile. What the 205 mm width does across four aspect ratios, and how the 16-inch wheel became the floor.
- 195/55R16195/55R16 tire size — the narrowest 16-inch fitment here195/55R16 comes out at 24.44 in tall on a 7.68 in section with 825.0 revolutions per mile. Where it sits among the three 195 mm sizes and what a 10 mm step costs on this wheel.
- 215/60R16215/60R16 — the middle rung of the 16-inch 215 ladder215/60R16 is 26.16 in tall with 5.08 in of sidewall and 771.0 revolutions per mile, sitting exactly 0.85 in from the 55-series below it and the 65-series above.
- 215/65R16215/65R16 — a tire that measures exactly 27.00 inches215/65R16 works out at 27.00 in on the nose, with 5.50 in of sidewall and 746.9 revolutions per mile. Three performance sizes on 18, 19 and 20-inch wheels share that rolling diameter.
- 225/60R16225/60R16 — the widest 60-series on a 16-inch wheel225/60R16 stands 26.63 in with 5.31 in of sidewall and 757.3 revolutions per mile. The 16-inch 60-series family moves in 0.47 in steps, and this is the top of it.
- 215/55R17215/55R17 — dimensions, and the codes that match it215/55R17 stands 26.31 in with 4.66 in of sidewall and 766.5 revolutions per mile. Four codes on four different wheels land within 0.3 in of it, which is what this page sets out.
- 225/55R17225/55R17 tire size — and the 20-inch tire that matches it225/55R17 measures 26.74 in with 4.87 in of sidewall and 754.1 revolutions per mile. A 245/35R20 lands 0.01 in away from it, across three wheel sizes.
- 225/65R17225/65R17 — the compact-crossover size, measured225/65R17 works out at 28.52 in tall with a 5.76 in sidewall and 707.3 revolutions per mile. How it compares with the 235/60R17 fitted to the trim above it, and what 225 mm looks like across nine aspect ratios.
- 235/65R17235/65R17 tire size — one rung of a five-step ladder235/65R17 measures 29.03 in with 6.01 in of sidewall and 694.8 revolutions per mile. Five sizes share this wheel at 65-series, each exactly 0.51 in from the next.
- 205/50R17205/50R17 tire size — two hundredths from a 225/40R18205/50R17 measures 25.07 in with a 4.04 in sidewall and 804.4 revolutions per mile. It is the narrow option on a 17-inch wheel, and it sits 0.06% from a size on a completely different rim.
- 215/50R17215/50R17 tire size — geometry and closest equivalents215/50R17 works out at 25.46 in tall with a 4.23 in sidewall and 792.0 revolutions per mile, landing within 0.11% of 205/65R15 — a size two wheel diameters below it.
- 225/50R17225/50R17 tire size — geometry, and the plus-one above it225/50R17 measures 25.86 in with 4.43 in of sidewall and 779.9 revolutions per mile. Its 18-inch counterpart 225/45R18 sits 0.44% away, which is what makes the pair interchangeable in fitment terms.
- 215/45R17215/45R17 — the shortest sidewall on a 17-inch wheel215/45R17 measures 24.62 in with just 3.81 in of sidewall, the least of any 17-inch size in this catalogue, and turns 819.2 times per mile.
- 225/45R17225/45R17 — 3.99 in of sidewall, the sport-compact standardWhy 225/45R17 measures 24.97 in tall on an 8.86 in section, what the four widths at 45-series on a 17-inch wheel do in 0.35 in steps, and the size it shares a diameter with to within a hundredth of an inch.
- 235/45R17235/45R17 — 796.3 revolutions per mile, and what it governs235/45R17 measures 25.33 in with 4.16 in of sidewall. Across the 45-series family on this wheel, revolutions per mile falls by about eleven for every 10 mm of extra width.
- 245/45R17245/45R17 — the widest tread on a 17-inch performance wheel245/45R17 measures 25.68 in with 4.34 in of sidewall and 785.3 revolutions per mile. At 9.65 in of section on a 17-inch rim, nothing in the passenger part of this catalogue is wider for its wheel.
- 235/55R17235/55R17 tire size — geometry and its 18-inch counterpart235/55R17 stands 27.18 in with 5.09 in of sidewall and 742.1 revolutions per mile, and 235/50R18 sits 0.28% above it — the same width on one more inch of wheel.
- 215/55R16215/55R16 tire size — one inch of wheel, one inch of tire215/55R16 measures 25.31 in with a 4.66 in sidewall and 796.8 revolutions per mile. It sits exactly 1.00 in below 215/55R17 and within 0.06% of 235/45R17.
- 225/60R17225/60R17 — what neighbouring sizes do to the speedometer225/60R17 measures 27.63 in and turns 729.9 times per mile. This page puts the four sizes closest to it on the same wheel into indicated-versus-actual terms.
Performance and ultra-high performance
Low-profile sizes hold less air for their width, so the same vehicle weight needs a higher reference inflation. Extra Load construction is common in this class, and that is what lifts the index band — not any change in the casing size.
- 225/40R18225/40R18 — the shallowest sidewall on an 18-inch wheel225/40R18 measures 25.09 in with just 3.54 in of sidewall — the least of any 18-inch size here — and turns 803.9 times per mile. The 40-series ladder in 0.31 in steps.
- 235/40R18235/40R18 — the shortest 235 mm casing in the catalogue235/40R18 measures 25.40 in with 3.70 in of sidewall and 794.0 revolutions per mile. Five points of aspect ratio at this width and wheel are worth 0.93 in.
- 245/40R18245/40R18 — dimensions, the 18-inch range by sidewall depth245/40R18 measures 25.72 in with a 3.86 in sidewall and 784.2 revolutions per mile. Sorting the 18-inch performance sizes by sidewall rather than diameter puts it third from the bottom.
- 255/40R18255/40R18 tire size — two codes that print the same diameter255/40R18 measures 26.03 in with a 4.02 in sidewall and 774.8 revolutions per mile. So does 255/35R19, to two decimal places, which is a coincidence worth understanding.
- 225/45R18225/45R18 tire size — three codes, one rolling diameter225/45R18 comes out at 25.97 in with a 3.99 in sidewall and 776.5 revolutions per mile, landing 0.06 in from both 255/40R18 and 255/35R19 despite being much the narrower tire.
- 235/45R18235/45R18 tire size — dimensions and odometer consequences235/45R18 works out at 26.33 in with 4.16 in of sidewall and 766.1 revolutions per mile. What each neighbouring size does to a hundred recorded miles.
- 245/45R18245/45R18 — one diameter, three wheel sizes245/45R18 measures 26.68 in tall with a 4.34 in sidewall. Its 19 and 20-inch counterparts land within 0.07 in of it, which makes this the clearest worked example of plus sizing in the catalogue.
- 255/45R18255/45R18 — the widest 45-series on an 18-inch wheel255/45R18 measures 27.04 in with 4.52 in of sidewall and 746.0 revolutions per mile. What the size code fixes, and the several things about a tire that it does not.
- 235/50R18235/50R18 tire size — the same height as a 305-section 20235/50R18 measures 27.25 in with a 4.63 in sidewall and 740.1 revolutions per mile. A 305/30R20 stands 27.20 in, which is the widest tire in this catalogue matching one of the narrowest at that height.
- 245/35R19245/35R19 tire size — the lower of two 245 mm stacks245/35R19 measures 25.75 in with a 3.38 in sidewall and 783.2 revolutions per mile. It is the 19-inch member of a three-size stack that holds 25.7 in across three wheel diameters.
- 255/35R19255/35R19 tire size — a staggered-set rear, measured255/35R19 stands 26.03 in on 10.04 in of section with only 3.51 in of sidewall, turning 774.9 times per mile. What it is usually paired with, and why the pairing matters.
- 275/35R19275/35R19 — an upgrade that lowers the carThe Mustang S550 leaves the factory on 275/40R19 and lists 275/35R19 as a step up. It is 1.08 in shorter. Everything about the change is width and sidewall, and the speedometer moves the wrong way.
- 245/40R19245/40R19 tire size — and the whole 19-inch range, measured245/40R19 measures 26.72 in with a 3.86 in sidewall and 754.9 revolutions per mile. The eight 19-inch sizes in this catalogue span more than six inches of diameter.
- 255/40R19255/40R19 — what a wheel size costs when diameter is held255/40R19 measures 27.03 in with a 4.02 in sidewall and 746.1 revolutions per mile. Against its 18 and 20-inch counterparts, only the sidewall and the wheel change.
- 275/40R19275/40R19 — the factory rear on an S550 MustangAt 27.66 in, 275/40R19 is the tallest performance size on a 19-inch wheel in this catalogue and the last rung before the wheel diameter changes market entirely.
- 245/35R20245/35R20 — the narrowest 35-series on a 20-inch wheel245/35R20 stands 26.75 in with 3.38 in of sidewall and 753.9 revolutions per mile. At 35-series, each 10 mm of section width is worth only 0.28 in of height.
- 255/35R20255/35R20 — 20-inch wheel matching a 16-inch crossover tire255/35R20 measures 27.03 in with a 3.51 in sidewall and 746.2 revolutions per mile — within 0.09% of 215/65R16, four wheel diameters away.
- 275/35R20275/35R20 — a 20-inch wheel and 3.79 in of tireNo vehicle in this catalogue ships 275/35R20 or lists it as an upgrade. It stands 27.58 in, and three codes on three other wheel diameters land within a tenth of an inch of it.
- 285/35R20285/35R20 — the top of a very short ladder285/35R20 is the tallest and widest of the five 20-inch performance sizes catalogued here, at 27.85 in. Above it the wheel diameter stops serving cars altogether.
- 305/30R20305/30R20 — the lowest aspect ratio in this catalogueThirty is the smallest middle number anywhere on this site, and 305/30R20 is the only size that uses it. The result is 12.01 in of casing width and 3.60 in of casing depth.
Crossover and SUV
Crossovers are heavier than the cars they share size families with, so the same nominal size is produced at a higher index for SUV fitment than for passenger fitment. Two tires wearing the same size code can carry materially different loads.
- 235/60R17235/60R17 — four single edits and what each one costs235/60R17 measures 28.10 in with a 5.55 in sidewall and 717.7 revolutions per mile. Changing one element of the code at a time moves the diameter by between 0.47 in and 1.00 in.
- 245/65R17245/65R17 — where crossover fitments start being rated like truck tires245/65R17 measures 29.54 in with a 6.27 in sidewall and 682.8 revolutions per mile. Its immediate neighbours on this wheel sit on both sides of the passenger and crossover classification.
- 255/65R17255/65R17 tire size — what each step costs at the fender255/65R17 measures 30.05 in with 6.53 in of sidewall and 671.1 revolutions per mile. Ride height moves by half of any diameter change, and this page puts numbers on that.
- 265/65R17265/65R17 — the mid-size truck's common denominatorThree manufacturers put 265/65R17 under five different mid-size pickups. It measures 30.56 in, and it belongs to a family of 265-section sizes that hold the same rolling height across 16, 17, 18 and 20-inch wheels.
- 265/70R17265/70R17 — stock on a half-ton, an upgrade on a mid-sizeTen platforms in this catalogue leave the factory on 265/70R17 and three more list it as a step up. At 31.61 in it is the busiest crossing point in North American truck fitment, which makes it the size most comparisons start from.
- 245/70R17245/70R17 tire size — five codes inside a tenth of an inch245/70R17 measures 30.50 in with a 6.75 in sidewall and 661.2 revolutions per mile. Five other sizes, on wheels from 16 to 20 inches, land within 0.10 in of it.
- 255/70R17255/70R17 — the mid-size truck size, and a very exact one255/70R17 stands 31.06 in with 7.03 in of sidewall and 649.4 revolutions per mile. Five points of aspect ratio move it exactly one inch at this width, which makes the 255 mm family the most legible in the catalogue.
- 235/60R18235/60R18 — 1990s truck tread on three inches more wheel235/60R18 comes out at 29.10 in with 5.55 in of sidewall and 693.0 revolutions per mile — 0.77% from 235/75R15, which shares its exact section width and almost nothing else.
- 235/65R18235/65R18 tire size — six codes at thirty inches235/65R18 measures 30.03 in and turns 671.7 times per mile. Five other sizes in this catalogue, on wheels from 15 to 19 inches, stand within three hundredths of an inch of it.
- 245/60R18245/60R18 tire size — the 18-inch 60-series family, measured245/60R18 measures 29.57 in with a 5.79 in sidewall and 681.9 revolutions per mile. Five widths share this wheel at 60-series, and the steps between them are not all equal.
- 255/60R18255/60R18 — indicated speed against actual, for nearby sizes255/60R18 measures 30.05 in and turns 671.2 times per mile. Four sizes on the same wheel put an indicated 70 mph anywhere between 67.8 and 72.3.
- 255/65R18255/65R18 tire size — 31.05 in, against two tires marked 31255/65R18 stands 31.05 in with 6.53 in of sidewall and 649.5 revolutions per mile. Two flotation sizes printed as 31 measure 31.00 in exactly, and this metric size overshoots them by 0.05 in.
- 265/60R18265/60R18 — five factory fitments and no flotation neighbour265/60R18 measures 30.52 in and appears on four mid-size pickups plus a Grand Cherokee. On an 18-inch wheel the nearest flotation size is 2.48 in taller, because 18-inch flotation sizes start at 33.
- 265/65R18265/65R18 — General Motors' half-ton 18, and the Tacoma's265/65R18 measures 31.56 in, which puts it 0.04 in from 265/70R17. Both are factory sizes on Chevrolet and GMC half-tons, and the pair is a worked example of what changing wheel diameter does to a size code.
- 265/70R18265/70R18 — the metric size closest to a 33 from belowOn an 18-inch wheel, 265/70R18 at 32.61 in is the nearest factory metric size underneath a flotation 33. It appears on a Toyota Tundra and, in LT form, on a Chevrolet Silverado 2500HD.
- 255/55R19255/55R19 — half an inch of sidewall per inch of wheel255/55R19 measures 30.04 in with a 5.52 in sidewall and 671.3 revolutions per mile. It is the 19-inch member of a four-wheel stack in which the sidewall falls by half an inch at every step.
- 255/65R19255/65R19 tire size — a 32 that measures 32.05255/65R19 works out at 32.05 in with 6.53 in of sidewall and 629.2 revolutions per mile. Two flotation sizes marked 32 come in at 32.00 in exactly, and three metric codes overshoot them together.
- 245/60R20245/60R20 — the narrow 20 on full-size trucks and SUVs245/60R20 stands 31.57 in with 5.79 in of sidewall and 638.7 revolutions per mile. It matches 265/65R18 and 265/70R17 — the same vehicles' smaller wheel options — to within 0.03 in.
- 245/50R20245/50R20 — a 20-inch wheel doing a crossover's job245/50R20 measures 29.65 in with a 4.82 in sidewall and 680.3 revolutions per mile. It completes a three-wheel stack with 245/65R17 and 245/60R18 that holds 29.6 in.
- 265/50R20265/50R20 — the Grand Cherokee's 20-inch fitment265/50R20 stands 30.43 in on 5.22 in of sidewall. It is one of four factory sizes on the WK2 Grand Cherokee, and all four are within a tenth of an inch of each other in height.
- 275/55R20275/55R20 — a 20-inch wheel with 5.95 in of tire above itFive half-ton pickups leave the factory on 275/55R20. It stands 31.91 in, which means the wheel accounts for two-thirds of the tire's height and the sidewall for less than six inches.
- 275/60R20275/60R20 — a 33-inch tire that does not say so275/60R20 computes to 32.99 in and carries 6.50 in of sidewall. A 33x12.50R20 computes to 33.00 in and carries 6.50 in of sidewall. The two differ in one dimension only, and it is not height.
- 275/45R21275/45R21 — the only 21-inch size in this catalogueThe sixth-generation Explorer offers 21-inch wheels, and 275/45R21 is what goes on them. It is the shortest of that vehicle's three factory tires and the widest, which is not the combination the wheel size suggests.
- 275/50R22275/50R22 — one of two sizes on a 22-inch wheel275/50R22 stands 32.83 in and shares its wheel diameter with exactly one other catalogued code. Both are full-size SUV and half-ton fitments, and they are 0.73 in apart.
- 285/45R22285/45R22 — three half-tons on the biggest factory wheel285/45R22 measures 32.10 in on 5.05 in of sidewall. Three full-size trucks ship it, and every one of them also offers the same rolling height on a much smaller wheel.
Light truck (LT-metric)
LT-metric tires use a stiffer casing at a much higher reference inflation — Load Range C, D or E, meaning 50, 65 or 80 psi. The index band reflects the pressure the casing is rated to hold, not a larger tire.
- 235/75R15235/75R15 — a 28.88 in tire that everyone calls a 29The last 15-inch light-truck size still stocked in volume. 235/75R15 measures 28.88 in with 6.94 in of sidewall, sits 1.12 in below a 30x9.50R15, and carries a second life as a trailer size.
- 225/75R16225/75R16 — where the light-truck range begins on a 16225/75R16 measures 29.29 in and turns 688.6 times per mile, the shortest light-truck fitment on a 16-inch wheel here. Its nearest neighbours are all crossover sizes.
- 235/85R16235/85R16 — the tall, narrow oneAn 85-series casing that stands 31.73 in on 9.25 in of section width — taller than a 265/75R16 while being 1.18 in narrower. The geometry behind the ambulance and expedition size.
- 245/75R16245/75R16 — the three-quarter-ton workhorse size245/75R16 comes out at 30.47 in tall on a 9.65 in section, 0.14 in shy of a 265/70R16. The 16-inch light-truck ladder, the spare-tire connection, and what 7.23 in of sidewall buys.
- 265/70R16265/70R16 — 30.61 in, and exactly an inch under its 17-inch namesakeThe size Toyota and Nissan kept on mid-size trucks while everything else moved to 17s and 18s. 265/70R16 measures 30.61 in — one inch, precisely, below 265/70R17, and that precision is the whole point.
- 265/75R16265/75R16 — what one aspect-ratio step actually buysAt 31.65 in, 265/75R16 is five aspect points above 265/70R16 and exactly 1.04 in taller for it. That figure is fixed by the section width alone, which makes this size a clean worked example of how the code behaves.
- 285/75R16285/75R16 — the 16-inch size no truck comes withFour Toyota and Nissan platforms list 285/75R16 as an upgrade and none ship it. At 32.83 in it is the only catalogued size on a 16-inch wheel between 31.73 in and a real 33.
- 245/75R17245/75R17 — the same height as a 285/60R18, 1.57 in narrower245/75R17 stands 31.47 in with 7.23 in of sidewall and 640.9 revolutions per mile. A 285/60R18 measures 31.46 in, which makes the pair the widest-versus-narrowest match in the catalogue at this height.
- 255/75R17255/75R17 — the narrow 32Jeep and Ford both chose 255/75R17 over a wider tire of the same height. It stands 32.06 in on 10.04 in of section width, against 11.50 in for the flotation size it matches almost exactly in diameter.
- 255/80R17255/80R17 — an 80-series metric size on a 17-inch wheel255/80R17 reaches 33.06 in on only 10.04 in of section width, using an aspect ratio almost nothing else on a 17-inch wheel still uses. Computed dimensions and its place among the 33s.
- 265/75R17265/75R17 — 32.65 in, no vehicle in this catalogue wears it265/75R17 is a genuinely produced size with no factory fitment and no listed upgrade on any platform here. It measures 32.65 in, six hundredths of an inch from 285/70R17 and 0.79 in narrower.
- 275/70R17275/70R17 — the middle rung nobody asks for275/70R17 measures 32.16 in, exactly midway between 265/70R17 and 285/70R17 at 0.55 in from each. Two Toyota platforms list it as an upgrade, and almost nothing else does.
- 285/70R17285/70R17 — the metric size everybody calls a 33285/70R17 measures 32.71 in tall and 11.22 in wide, turns 616.6 times per mile, and is 0.29 in shorter than a real 33x12.50R17. Full computed geometry.
- 295/70R17295/70R17 — a 33 that measures 33.26 inTwo off-road platforms list 295/70R17. It stands a quarter of an inch over a flotation 33 on the same wheel, on a casing 0.89 in narrower, and it is one of the few metric sizes that overshoots rather than falls short.
- 305/70R17305/70R17 — 33.81 in, in the band nobody countsOff-road tire sizes are talked about in twos: 31, 33, 35, 37. 305/70R17 lands at 33.81 in, in the middle of a gap the vocabulary skips, and no vehicle in this catalogue lists it either way.
- 315/70R17315/70R17 — 0.10 in narrower than a 35, and 0.64 in shorterThis size gets called a 35 constantly. It measures 34.36 in, so the name is wrong — but its 12.40 in of section width is within a tenth of an inch of a real 35x12.50R17, which is why the impression sticks.
- 255/70R18255/70R18 — what the step up from 255/65R18 does to gearing255/70R18 measures 32.06 in and turns 629.2 times per mile. Coming from 255/65R18 it lengthens the gearing 3.23%, and the axle ratio that would undo that is not one anybody sells.
- 275/65R18275/65R18 — the same numbers on a half-ton and a Super DutyEight platforms in this catalogue ship 275/65R18, from an F-150 to an F-250. It measures 32.07 in on every one of them, and what separates the fitments is printed after the size, not in it.
- 275/70R18275/70R18 — the three-quarter-ton size nobody calls a 33Ford, Ram and Chevrolet all ship their 2500-class pickups on 275/70R18. It measures 33.16 in, which puts it 0.16 in above the flotation 33 that owners of lighter trucks spend money reaching.
- 285/65R18285/65R18 — the middle of a three-rung 285 towerOn an 18-inch wheel the 285 casing is catalogued at 60, 65 and 75 aspect. 285/65R18 stands 32.59 in, exactly 1.12 in above the 60 and 1.12 in below the 70.
- 285/70R18285/70R18 — past the 33 without changing notation285/70R18 stands 33.71 in, which is 0.71 in taller than the flotation 33 that shares its wheel. It is a metric route to a size the aftermarket usually reaches with an imperial code.
- 285/75R18285/75R18 — the closest a metric code gets to a real 35Every flotation 35 in this catalogue measures 35.00 in. 285/75R18 measures 34.83 in — 0.17 in short, or 0.49%, which is nearer than any other metric size on any wheel manages.
- 265/60R20265/60R20 — the Tundra's 20-inch tire, half an inch under 33At 32.52 in, 265/60R20 sits 0.48 in below a flotation 33 on the same wheel and 2.07 in narrower than one. It is the third-generation Toyota Tundra's factory 20-inch size.
- 275/65R20275/65R20 — the rung the flotation ladder skipsAt 34.07 in, 275/65R20 sits almost exactly between a 33x12.50R20 and a 35x12.50R20 on the same wheel. It is a factory heavy-duty fitment, and it is the only catalogued way to stand there.
- 285/60R20285/60R20 — what a three-quarter-ton leaves the factory onBoth a Ford F-250 and a Ram 2500 are recorded with 285/60R20 as original equipment. At 33.46 in it is a heavy-duty fitment that lands within half an inch of the aftermarket's favourite 20-inch tire.
- 285/65R20285/65R20 — 0.41 in short of a 35, 1.28 in narrower than oneSix platforms list 285/65R20 as an upgrade and not one ships it. At 34.59 in it is the top of the 285-wide family on a 20-inch wheel, reached by aspect ratio rather than by changing notation.
- 295/65R20295/65R20 — an odd width on a heavy-duty wheel295 mm is a section width the market barely uses, and 295/65R20 is the only place it appears on a 20-inch wheel here. Five heavy-duty and full-size platforms list it as an upgrade.
- 305/55R20305/55R20 — width without height on a 20-inch wheel305/55R20 stands 33.21 in on 12.01 in of section. It is a fifth of an inch taller than a flotation 33 on the same wheel and only half an inch narrower, which makes it the closest metric approach to that tire anywhere.
- 325/60R20325/60R20 — the widest metric casing in this catalogueAt 12.80 in of section, 325/60R20 is wider than any other metric code here and wider than a 12.50 flotation tire. It stands 35.35 in, which puts it past a 35 as well.
- 215/75R15215/75R15 — light-truck geometry on a 15-inch wheel215/75R15 measures 27.70 in with 6.35 in of sidewall and 728.2 revolutions per mile. The narrowest of the three 75-series 15-inch sizes, and a common trailer fitment.
- 225/75R15225/75R15 tire size — and the modern size that replaced it225/75R15 measures 28.29 in with a 6.64 in sidewall and 713.0 revolutions per mile. Its closest match in the catalogue is 225/65R17, the size the same vehicles wear two generations later.
- 255/70R16255/70R16 — the deepest sidewall in the 255 mm family255/70R16 measures 30.06 in with 7.03 in of sidewall and 671.0 revolutions per mile. On a 16-inch wheel it carries more casing than any other 255 mm size in this catalogue.
- 285/60R18285/60R18 — a dead heat with a light-truck 17285/60R18 computes to 31.46 in. So does 245/75R17, to within a hundredth of an inch, on a casing 1.57 in narrower. One is a Land Cruiser's factory tire and the other belongs on a work truck.
Flotation (imperial)
Flotation sizes are almost always LT construction, so they share the light-truck band. Speed symbols run low because the aggressive tread patterns these sizes are sold in are rated against heat build-up, not against sustained high speed.
- 30x9.50R1530x9.50R15 — the narrowest flotation size hereAt 9.50 in of section, 30x9.50R15 is the slimmest imperial-notation tire in this catalogue. It stands 30.00 in, and five modern metric codes on larger wheels stand within a sixteenth of an inch of it.
- 31x10.50R1531x10.50R15 — the size with an aspect ratio nobody printsA flotation code states diameter and width and stays silent about shape. Derive it for 31x10.50R15 and the aspect ratio is 76, with 8.00 in of sidewall on a 15-inch wheel.
- 32x11.50R1532x11.50R15 — one of only two sizes called a 32The catalogue holds exactly two 32-inch flotation codes, and both are 32x11.50. This is the 15-inch one, with 8.50 in of sidewall. No metric size on a 15-inch wheel comes near it.
- 33x12.50R1533x12.50R15 — nine inches of sidewallPut a 33-inch tire on a 15-inch wheel and 9.00 in of the result is sidewall on each side. That gives a derived aspect ratio of 72 — the same shape as a 35x12.50R17, two inches larger in every direction.
- 35x12.50R1535x12.50R15 — ten inches of sidewallA 35-inch tire on a 15-inch wheel leaves 10.00 in of casing above the rim on each side. Only one size in this catalogue carries more, and it is a 40.
- 31x10.50R1631x10.50R16 — the same 31, half an inch less casing31x10.50R16 and 31x10.50R15 both stand 31.00 in on 10.50 in of section. The 16-inch version carries 7.50 in of sidewall against the 15-inch version's 8.00 in, and that is the entire difference.
- 33x12.50R1633x12.50R16 — the widest thing a 16-inch wheel takesOn a 16-inch wheel this catalogue runs from a 24.44 in supermini tire to a 35.00 in off-road one. 33x12.50R16 sits near the top of that range and is 3.25 in wider than the narrowest tire of comparable height.
- 35x12.50R1635x12.50R16 — the top of a wheel nobody upgrades any more35x12.50R16 is the tallest size catalogued on a 16-inch wheel, and no vehicle record here lists it in any capacity. The trucks that would have wanted it were delivered on 17s and 18s instead.
- 32x11.50R1732x11.50R17 — the flotation size in a metric crowdBetween the flotation 31s and the flotation 33s, this catalogue holds two codes. 32x11.50R17 is the 17-inch one, and it lands in the busiest metric truck band on the site.
- 33x10.50R1733x10.50R17 — the 33 that five mid-size trucks listTwo flotation codes on a 17-inch wheel measure 33.00 in. Five mid-size pickups and SUVs name this narrow one among their upgrades, and only one names the wide one.
- 33x12.50R1733x12.50R17 — one number you can measure and one you cannotThe 33 in this code is an outside diameter and a tape will confirm it. The 12.50 is a section width defined at a specified measuring rim, and it is not the width of the tread that touches the road.
- 34x10.50R1734x10.50R17 — an inch from four sizes at once34x10.50R17 is the only 34-inch code in this catalogue. It sits exactly 1.00 in above both 33s on its wheel and exactly 1.00 in below both 35s, and it is narrower than all four.
- 35x11.50R1735x11.50R17 — matching a metric width but not its height35x11.50R17 is 11.50 in wide. 295/70R17 is 11.61 in wide. The two are a tenth of an inch apart across the tread and 1.74 in apart in how tall they stand.
- 35x12.50R1735x12.50R17 — the size that moves the axle-ratio arithmeticGoing from a Wrangler JL's 255/75R17 to 35x12.50R17 is a 9.17% change in diameter. The ratio that would restore the original engine speed at a given road speed is 4.07:1 from a 3.73 axle — and 4.10 is on the same truck's option list.
- 37x12.50R1737x12.50R17 — 116.2 inches per revolutionA 37 on a 17-inch wheel travels 116.2 in per turn and 545.1 turns per mile. Against a Wrangler JL's factory 255/75R17 that is 84 fewer revolutions in every mile, and an odometer that under-counts by more than fifteen per cent.
- 37x13.50R1737x13.50R17 — same casing depth, lower aspect ratio37x13.50R17 and 37x12.50R17 both carry 10.00 in of sidewall. Their derived aspect ratios are 74 and 80, and the only thing that differs is the inch of tread between them.
- 40x13.50R1740x13.50R17 — the largest size in this catalogue40x13.50R17 stands 40.00 in on 11.50 in of sidewall and turns 504.2 times in a mile. Its derived aspect ratio works out at 85, higher than any number printed on a metric code here.
- 33x12.50R1833x12.50R18 — a 33 with the casing depth of a 3533x12.50R18 carries 7.50 in of sidewall, exactly the same as 35x12.50R20. Two premium off-road platforms list it, and it is the entry point of a three-rung imperial ladder on an 18-inch wheel.
- 35x12.50R1835x12.50R18 — the middle rung of the tidiest imperial ladderThe 18-inch wheel carries exactly three flotation codes, all 12.50 in wide, two inches apart. 35x12.50R18 is the middle one, and a metric size sits 0.17 in below it.
- 37x12.50R1837x12.50R18 — a 37 on nobody's option listFour 37-inch codes are catalogued here and three of them appear on a vehicle's list. 37x12.50R18 does not. It stands 37.00 in on 9.50 in of sidewall, and the 18-inch wheel is where the market thins out.
- 33x12.50R2033x12.50R20 — the same 33 with the least air in itFive wheel diameters carry a 33x12.50, and all five compute to 33.00 in and 611.2 revolutions per mile. The 20-inch version does it on 6.50 in of sidewall, against 9.00 in for the 15-inch one.
- 35x12.50R2035x12.50R20 — one upgrade, five different speedometer errorsNine platforms list 35x12.50R20, and they leave the factory on five different 20-inch tires. The resulting diameter change ranges from 2.72% to 9.69% depending entirely on which truck asked.
- 37x12.50R2037x12.50R20 — the heavy-duty 37Three three-quarter-ton pickups list 37x12.50R20 among their upgrades, and none of the other 37-inch codes here reaches that market. It stands 37.00 in on 8.50 in of sidewall.
- 38x13.50R2038x13.50R20 — the smallest step on the flotation ladderFlotation sizes climb in two-inch increments almost everywhere. 38x13.50R20 sits one inch above 37x12.50R20, which makes it the finest rung in the imperial range and the widest tire on a 20-inch wheel.