14-inch vs 15-inch rims · tyre size comparison
165/55 R14 vs 165/50 R15
165/50 R15 is 8.9 mm (0.35 in) taller than 165/55 R14, a +1.66% difference in overall diameter. That is inside the ±3% limit commonly used to screen a tire size change; it is a nominal calculation, not a fitment approval.
- Diameter difference
- +8.9 mm
- +0.35 in · +1.66%
- Indicated 70 mph
- 71.2 mph
- Actual speed on 165/50 R15, if the speedometer was accurate on 165/55 R14.
- Sidewall height
- -8.25 mm
- 90.75 mm to 82.5 mm.
Dimensions side by side
| Measurement | 165/55 R14 | 165/50 R15 | Difference |
|---|---|---|---|
| Overall diameter | 537.1 mm21.15 in | 546 mm21.5 in | +8.9 mm (+1.66%)+0.35 in |
| Section width | 165 mm6.5 in | 165 mm6.5 in | 0 mm0 in |
| Sidewall height | 90.75 mm3.57 in | 82.5 mm3.25 in | -8.25 mm-0.32 in |
| Circumference | 1,687.35 mm66.43 in | 1,715.31 mm67.53 in | +27.96 mm+1.1 in |
| Rim diameter | 355.6 mm14 in | 381 mm15 in | +25.4 mm+1 in |
| Revolutions per mile | 953.77 | 938.22 | -15.55 |
| Revolutions per km | 592.65 | 582.99 | -9.66 |
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 165/50 R15
If the speedometer was accurate on 165/55 R14, fitting 165/50 R15 means the car is travelling 1.66% faster than it shows, and the odometer under-records distance by about the same amount.
| Speedometer shows | Actual on 165/50 R15 | Difference |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 mph |
| 50 mph | 50.83 mph | +0.83 mph |
| 60 mph | 60.99 mph | +0.99 mph |
| 70 mph | 71.16 mph | +1.16 mph |
| 50 km/h | 50.83 km/h | +0.83 km/h |
| 100 km/h | 101.66 km/h | +1.66 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 165/55 R14 to 165/50 R15
Wheels
These sizes need different wheels: 14-inch for 165/55 R14 and 15-inch for 165/50 R15. 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
165/50 R15 has 8.25 mm less sidewall (82.5 vs 90.75 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
Both are 165 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 +4.5 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 -1.63%: 3,000 rpm at a given road speed becomes about 2,950 rpm. Gearing gets slightly 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 1.7% diameter gap, never mix 165/55 R14 and 165/50 R15 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.
165/55 R14
- Suzuki Swift / Cultus sedan 2nd gen (SF) (1989–2003)Popular setup
165/50 R15
- Skoda Felicia 6U (Typ 791) (1994–2001)Popular setup
More comparisons
165/55 R14 compared
Questions
Can I use 165/50 R15 instead of 165/55 R14?
Only on 15-inch wheels, not the 14-inch wheels that take 165/55 R14. The diameter difference is +1.66%, inside the ±3% screening limit. 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 165/50 R15 than 165/55 R14?
Overall diameter is 8.9 mm (0.35 in) larger: 546 vs 537.1 mm. Section width is the same, and the sidewall is 8.25 mm shorter. These are nominal figures; real tyres vary by model and rim width.
Will 165/50 R15 change my speedometer reading?
Yes, by 1.66%. If the speedometer was accurate on 165/55 R14, an indicated 60 mph would be about 61 mph on 165/50 R15, and an indicated 100 km/h about 101.7 km/h. You would be going faster than the speedometer shows.
Which is better, 165/55 R14 or 165/50 R15?
Neither in general. 165/55 R14 has the taller sidewall, which usually rides more comfortably; 165/50 R15 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.