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Tire sizes

325/60R20 — the widest metric casing in this catalogue

The one place metric notation outreaches the flotation sizes it is usually accused of undercutting.

Metric notation · Light truck (LT-metric)

Overall diameter
35.35 in
898 mm
Section width
12.80 in
325 mm
Sidewall height
7.68 in
195 mm
Aspect ratio
60%
sidewall as a share of width
Wheel diameter
20 in
the hole in the middle
Circumference
111.1 in
2821 mm
Revolutions per mile
570.5
geometric, not measured
Revolutions per km
354.5
geometric, not measured
Typical load index
108–129
2205–4079 lb per tire

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.

The load-index range shown is the band this CLASS of size is typically produced in — not a list of what is in stock for this exact size today. Load index and speed symbol are printed on the sidewall of the specific tire you are holding, and the required minimum is on the placard of the specific vehicle you are fitting. Read both.

Nearest real sizes in imperial notation, same wheel

  • 35x12.50R2035.00 in tall-0.35 in
  • 37x12.50R2037.00 in tall+1.65 in
  • 33x12.50R2033.00 in tall-2.35 in

Compare any two sizes, including ones this site has no page for, in the comparison tool.

Nothing in the vehicle records here ships 325/60R20 or lists it as an upgrade. It is a wide-fitment replacement size, and it is the only 325 mm code in the catalogue.

Wider than the flotation tires it sits beside

The standing complaint about metric truck sizes is that they match a flotation tire's height and concede an inch or more of width. This size does the opposite:

Size Diameter Section width
33x12.50R20 33.00 in 12.50 in
35x12.50R20 35.00 in 12.50 in
325/60R20 35.35 in 12.80 in
37x12.50R20 37.00 in 12.50 in
38x13.50R20 38.00 in 13.50 in

It is 0.30 in wider than every 12.50 flotation size on the wheel and 0.35 in taller than the 35. The only imperial code here that beats it on width is 38x13.50R20, which is also 2.65 in taller — so within the 35-inch band, this is the widest tire available in either notation.

What 60 aspect points do at 325 mm

7.68 in of sidewall comes out of a middle number that reads as fairly low. That is the recurring consequence of applying a percentage to a large section width: 60% of 325 mm produces more casing than 65% of 285 mm, which yields 7.29 in.

Set against the flotation 35 on the same wheel, this size carries 7.68 in against 7.50 in — the wider tire is also the deeper one, by a small margin, despite the aspect ratio reading like a low-profile figure. The aspect ratio reference works through why the number cannot be compared between widths.

Its closest neighbours

295/65R20 is 0.26 in shorter and 1.18 in narrower. 35x12.50R20 is 0.35 in shorter and 0.30 in narrower. Both are within one per cent in height, so a truck moving between the three sees an indicated 70 mph land between 69.3 and 70.0 mph.

Below that cluster the wheel drops away quickly: 285/65R20 is 2.17% down, 33x12.50R20 is 6.66% down. The 35-inch band on a 20-inch wheel is crowded, and everything else is some distance from it.

Related

Class: Light truck (LT-metric). Every figure above is computed from the size code, not stored — see how these numbers are calculated.