295/40 R22 vs 305/35 R23

Calculated from the nominal size codes, without load or tread wear. Real tyres vary by model, rim width and pressure, so the exact tyre's published dimensions take priority.

If the speedometer was accurate on 295/40 R22, fitting 305/35 R23 means the car is travelling 0.36% faster than it shows, and the odometer under-records distance by about the same amount.

UN ECE Regulation 39, used in the UK and EU, does not allow a speedometer to show less than the true speed, so many read slightly high from the factory. A taller tyre uses up some of that margin. Calibration varies by car; these figures are the tyre-size effect only.

• Wheels

  These sizes need different wheels: 22-inch for 295/40 R22 and 23-inch for 305/35 R23. The larger wheel usually weighs a little more; the smaller one must still clear the brake calipers. Check rim width, offset and load rating for whichever wheel you fit.

• Sidewall and ride comfort

  305/35 R23 has 11.25 mm less sidewall (106.75 vs 118 mm). A shorter sidewall usually sharpens steering response, but rides a little firmer and leaves the rim more exposed to potholes and kerbs.

• Contact width

  305/35 R23 is 10 mm wider in nominal section width (3.4%). A wider tyre usually puts a wider, shorter contact patch on the road, which can help dry grip, but it may follow ruts more, clear standing water less readily and add some rolling resistance.

• Wheel well clearance

  Ride height changes by about +1.4 mm, and the top of the tyre moves the same distance closer to the arch. On the same wheel width and offset, each sidewall moves about 5 mm further out towards the arch lip and further in towards the suspension. Check clearance at full steering lock and full suspension compression, especially on a lowered car.

• Gearing

  Effective gearing changes by -0.36%, too little to notice from the driver's seat.

• ABS, stability control and AWD

  These systems compare wheel speeds. Fit the same size on both ends of an axle, and follow the car maker's rolling-circumference limits, which can be much tighter than 3%.

General tendencies from the nominal numbers, not a test of any tyre. Load index, speed rating, tyre construction and the car's approved sizes matter more than these rules of thumb.

Factory trims and popular community setups from our fitment guides. A popular setup is not a factory approval; each guide explains its trims, axles and clearance limits.

Size codes give nominal dimensions. Before buying, confirm the size is approved for your car and check the exact tyre's load and speed ratings and published dimensions.