235/45 R18 vs 245/45 R18

What changes when you change tire size?

245/45 R18 stays within the configured tolerance for 235/45 R18: +1.3% diameter and +1.3% speedometer effect.

Geometric comparison

Geometric comparison
Metric This size: 235/45 R18 Alternative: 245/45 R18 Difference Verdict
Overall diameter 26.33 in 26.68 in +1.3% Within tolerance
Section width 9.25 in 9.65 in +0.39 in Computed difference
Sidewall height 4.16 in 4.34 in +0.18 in Computed difference
Circumference 82.71 in 83.82 in +1.3% Within tolerance
Speedo 0.0% +1.3% +1.3% Within tolerance

Compare sizes

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Units
Editorial preset

These are TireFitLab editorial diameter-screening presets. Regional names choose a preset, not a national legal limit, ETRTO rule or vehicle approval. The AWD preset does not establish an allowable drivetrain mismatch. Use the exact vehicle and tyre manufacturer instructions; nominal geometry alone cannot approve fitment.

Minor variationWithin tolerance · Diameter +1.3% (+0.35 in) · US preset (±3%)
  • Minor variation · This rating covers tire geometry only, not vehicle compatibility.
  • Diameter +1.3% · Ride-height change +0.18 in.
  • Speedometer reads low · 60 mph → 60.8 mph.
  • Sidewall +0.18 in · Width +0.39 in.
Diameter+1.3%+0.35 in
Speedo @ 60+1.3%60 mph → 60.8 mph
Sidewall+0.18 inWidth +0.39 in
Ride-height change+0.18 inDiameter ÷ 2
How this result is calculated

Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check vehicle placard approval, load/speed rating, rim-width range, wheel-arch, suspension or brake clearance.

Methodology

Before fitting

  • Check the vehicle placard and owner’s manual first.
  • Match or exceed the required load index and speed rating.
  • Confirm rim-width range, bolt pattern, hub bore, offset and fasteners.
  • Inspect wheel-arch, suspension and brake clearance under real vehicle load.
  • Check TPMS, cold pressure and local roadworthiness rules.
Diameter
26.33 in 26.68 in+0.35 in
Sidewall
4.16 in 4.34 in+0.18 in
Width
9.25 in 9.65 in+0.39 in
Circumference
82.71 in 83.82 in+1.3%
Revs / mile
766 756
Speedo @ 60
60 mph 60.8 mph+1.3%
Ride-height change
0.00 in +0.18 in
True distance per 100 indicated
100 mi 101.3 mi+1.3%
Δ⌀ +0.35 inΔ↔ +0.39 in
  • Current — 235/45 R18
  • New — 245/45 R18
  • Grounded to the road: the axle rises +0.18 in.

Tires and wheels in one comparison

Result report

235/45 R18 245/45 R18 · Minor variation · Within tolerance

Plan budget for this size: 245/45 R18

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Plan budget for this size
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Estimated budgetBudget$100–$140Per tireMid-range$130–$185Per tirePremium$185–$260Per tire

Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.

In-tolerance alternative sizes

In-tolerance alternative sizes
SizeDiameterSpeedo @ 100Use this
−1″ 235/50R17-0.3%-0.3%
OE 235/45R18+0.0%+0.0%
+1″ 235/40R19+0.3%+0.3%
+2″ 235/35R20+0.6%+0.6%

235/45 R18 · 245/45 R18 · Methodology