17-inch rim · tyre size comparison
215/40 R17 vs 215/45 R17
215/45 R17 is 21.5 mm (0.85 in) taller than 215/40 R17, a +3.56% difference in overall diameter. That is just outside the ±3% limit commonly used to screen a tire size change, so expect a noticeable speedometer error; it is a nominal calculation, not a fitment approval.
- Diameter difference
- +21.5 mm
- +0.85 in · +3.56%
- Indicated 70 mph
- 72.5 mph
- Actual speed on 215/45 R17, if the speedometer was accurate on 215/40 R17.
- Sidewall height
- +10.75 mm
- 86 mm to 96.75 mm.
Dimensions side by side
| Measurement | 215/40 R17 | 215/45 R17 | Difference |
|---|---|---|---|
| Overall diameter | 603.8 mm23.77 in | 625.3 mm24.62 in | +21.5 mm (+3.56%)+0.85 in |
| Section width | 215 mm8.46 in | 215 mm8.46 in | 0 mm0 in |
| Sidewall height | 86 mm3.39 in | 96.75 mm3.81 in | +10.75 mm+0.42 in |
| Circumference | 1,896.89 mm74.68 in | 1,964.44 mm77.34 in | +67.54 mm+2.66 in |
| Rim diameter | 431.8 mm17 in | 431.8 mm17 in | 0 mm0 in |
| Revolutions per mile | 848.41 | 819.24 | -29.17 |
| Revolutions per km | 527.18 | 509.05 | -18.13 |
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.
Speedometer with 215/45 R17
If the speedometer was accurate on 215/40 R17, fitting 215/45 R17 means the car is travelling 3.56% faster than it shows, and the odometer under-records distance by about the same amount.
| Speedometer shows | Actual on 215/45 R17 | Difference |
|---|---|---|
| 30 mph | 31.07 mph | +1.07 mph |
| 50 mph | 51.78 mph | +1.78 mph |
| 60 mph | 62.14 mph | +2.14 mph |
| 70 mph | 72.49 mph | +2.49 mph |
| 50 km/h | 51.78 km/h | +1.78 km/h |
| 100 km/h | 103.56 km/h | +3.56 km/h |
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.
What changes from 215/40 R17 to 215/45 R17
Wheels
Both fit 17-inch wheels. Our rim-width starting estimate is 6.5 to 7.5 inches for 215/40 R17 and 6.5 to 7.5 inches for 215/45 R17, so a 6.5 to 7.5-inch wheel sits in both ranges. The exact tyre's approved rim range takes priority.
Sidewall and ride comfort
215/45 R17 has 10.75 mm more sidewall (96.75 vs 86 mm). A taller sidewall usually rides a little softer and gives the rim more protection from potholes and kerbs, at the cost of some steering sharpness.
Contact width
Both are 215 mm in nominal section width, so the tread is about as wide. Contact patch area is set mostly by load and pressure, so grip differences come more from the tyre model than this size change.
Wheel well clearance
Ride height changes by about +10.8 mm, and the top of the tyre moves the same distance closer to the arch. On the same wheel, the sidewalls stay in roughly the same place side to side. Check clearance at full steering lock and full suspension compression, especially on a lowered car.
Gearing
The effective final drive changes by -3.44%: 3,000 rpm at a given road speed becomes about 2,900 rpm. Gearing gets noticeably longer, so cruising revs drop and acceleration in each gear softens.
ABS, stability control and AWD
These systems compare wheel speeds. Fit the same size on both ends of an axle; with a 3.6% diameter gap, never mix 215/40 R17 and 215/45 R17 on an AWD car, 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.
Explained in our guides
- Plus-sizing wheels: tyre diameter and speedometer changesWork through a 17 to 18 inch wheel change, compare tyre diameters and speedometer effects, and understand why a 3% rule cannot approve fitment.
- Staggered vs square wheels: tyres, rotation and AWDCompare square and staggered wheel setups, calculate front-to-rear tyre diameter, and understand rotation limits and all-wheel-drive requirements.
- How to read a tyre size, load index and sidewall markingsDecode tyre width, aspect ratio, rim diameter, load and speed markings, then calculate sidewall height and diameter using a 225/45 R17 example.
Cars in our guides using these sizes
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.
215/40 R17
- Ford Fiesta ST Mk7 (2013–2017)Popular setup
- Honda NSX NA1 (1990–1997)Popular setup
- MINI Cooper S / John Cooper Works R56 (2006–2013)Popular setup
- SEAT Ibiza 6J (2008–2017)Factory trim
- Toyota MR2 SW20 (1989–1999)Popular setup
215/45 R17
- Honda Civic Type R EP3 (2001–2005)Popular setup
- Honda S2000 AP1 / AP2 (1999–2009)Factory trim
- Lexus IS300 / IS200 XE10 (1998–2005)Factory and popular setup
- Mazda MX-5 Miata ND (2015–present)Popular setup
- MINI Cooper S / John Cooper Works F56 (2014–2024)Popular setup
- Nissan 180SX RPS13 (1989–1998)Popular setup
- Nissan Almera / Versa sedan N17 (2011–2019)Popular setup
- Nissan Silvia S15 (1999–2002)Popular setup
- Renault Clio Renaultsport 197 / 200 Mk3 (2006–2012)Factory and popular setup
- SEAT Ibiza 6F (KJ) (2017–present)Factory trim
- Subaru BRZ ZD8 (2022–present)Factory trim
- Toyota Chaser JZX100 (1996–2001)Popular setup
- Toyota GR86 ZN8 (2022–present)Factory trim
- Toyota GT86 / 86 ZN6 (2012–2021)Factory trim
- Vauxhall Corsa VXR D (2007–2014)Factory trim
- Volkswagen Polo GTI AW (2018–present)Factory trim
More comparisons
Questions
Can I use 215/45 R17 instead of 215/40 R17?
Both fit 17-inch wheels. The diameter difference is +3.56%, just outside the ±3% screening limit, so most fitters would treat it as a different size class rather than a direct replacement. That does not approve fitment: check the car maker's approved sizes, load index, speed rating, rim width and clearance first.
How much bigger is 215/45 R17 than 215/40 R17?
Overall diameter is 21.5 mm (0.85 in) larger: 625.3 vs 603.8 mm. Section width is the same, and the sidewall is 10.75 mm taller. These are nominal figures; real tyres vary by model and rim width.
Will 215/45 R17 change my speedometer reading?
Yes, by 3.56%. If the speedometer was accurate on 215/40 R17, an indicated 60 mph would be about 62.1 mph on 215/45 R17, and an indicated 100 km/h about 103.6 km/h. You would be going faster than the speedometer shows.
Which is better, 215/40 R17 or 215/45 R17?
Neither in general. 215/45 R17 has the taller sidewall, which usually rides more comfortably; 215/40 R17 usually steers more sharply. The size listed for your car's trim, on its placard or in the handbook, is the safe default.
Check the exact tyre
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.