ElpiAuto235/85R16 vs 305/70R16
305/70R16 is 1.08″ (27 mm) taller than 235/85R16, a 3.4% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
The section widths are very different — these are not a like-for-like swap. Confirm wheel width and arch clearance separately.
| Measurement | 235/85R16 | 305/70R16 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.73″ | 32.81″ | +1.08″ | +3.4% |
| Section width | 9.25″ | 12.01″ | +2.76″ | +29.8% |
| Sidewall height | 7.86″ | 8.41″ | +0.54″ | +6.9% |
| Circumference | 99.68″ | 103.08″ | +3.40″ | +3.4% |
| Revs per mile | 635.6 | 614.7 | −21.0 | −3.3% |
| Revs per km | 395.0 | 381.9 | −13.0 | −3.3% |
Speedometer: with 235/85R16 as the original, 305/70R16 makes an indicated 60 mph really about 62.0 mph, and the axle sits ~0.54″ higher.
Reading this comparison
The overall diameter is what matters here: 305/70R16 is the taller tire. It sets ride height, gearing and how far the tire travels per revolution — which is what the speedometer and odometer count. Width and sidewall change fit and feel (a wider tire needs a wider wheel and more clearance; a shorter sidewall sharpens steering) but not the gearing.
Figures are geometric estimates from the size codes; real moulded tires vary by brand by 1–3%. Confirm load rating, wheel width and physical clearance on your vehicle before fitting. To compare any other two sizes, use the tire size comparison tool; to decode one size and see what else fits its wheel, the tire size calculator.