Quick Answer
- Sidewall height is the main tire size variable for ride. USTMA says lower aspect ratio (shorter sidewall) tires typically aid performance and handling but may provide a less comfortable ride, may wear more quickly, may be noisier, and are more susceptible to pothole and curb damage.
- Sidewall height = width x aspect ratio / 100. A 225/55R17 has a 124 mm sidewall; a 225/45R18 at the same diameter has 101 mm (calculated).
- Set pressure from your vehicle placard, not the sidewall maximum. We have no manufacturer ranking of tire types by comfort, so this guide does not give one.
Sidewall Height by Aspect Ratio
A 225 mm wide tire on a 17 inch rim, changing only the aspect ratio. Calculated: sidewall = width x aspect ratio / 100. Check any size with the sidewall height calculator.
| Size | Sidewall mm | Sidewall in | Overall diameter in |
|---|---|---|---|
| 225/75R17 | 168.8 | 6.64 | 30.29 |
| 225/65R17 | 146.3 | 5.76 | 28.52 |
| 225/60R17 | 135.0 | 5.31 | 27.63 |
| 225/55R17 | 123.8 | 4.87 | 26.74 |
| 225/50R17 | 112.5 | 4.43 | 25.86 |
| 225/45R17 | 101.3 | 3.99 | 24.97 |
| 225/40R17 | 90.0 | 3.54 | 24.09 |
| 225/35R17 | 78.8 | 3.10 | 23.20 |
| 225/30R17 | 67.5 | 2.66 | 22.31 |
Bigger Wheels at the Same Diameter: How Much Sidewall You Lose
Closest-diameter size pairs, calculated. Per USTMA a shorter sidewall may give a less comfortable ride; no official source gives the size of that effect.
| From | To | Sidewall in | Sidewall change | Diameter change |
|---|---|---|---|---|
| 235/60R18 | 255/50R20 | 5.55 to 5.02 | -10% | +3.2% |
| 225/55R17 | 225/45R18 | 4.87 to 3.99 | -18% | -2.9% |
| 215/65R16 | 225/55R17 | 5.50 to 4.87 | -11% | -1.0% |
| 235/55R19 | 255/45R20 | 5.09 to 4.52 | -11% | -0.5% |
For sizes that keep your diameter see the plus sizing options calculator and the low profile tire guide. Noise is in the tire noise ratings guide.
What USTMA Says About Ride, Pressure and Vibration
| Source | Statement (paraphrased) |
|---|---|
| USTMA, Care and Service of Passenger and Light Truck Tires (2017) | Lower aspect ratio tires typically aid performance and handling but may provide a less comfortable ride. High performance, low aspect ratio tires may also wear more quickly and produce more noise. Low aspect ratio tires and their rim and wheel assembly are more susceptible to damage from road hazards and pothole or curb impact. |
| USTMA | The pressure on the tire sidewall is the maximum allowed in the tire, irrespective of the vehicle or load. It is not to be used exclusively for setting pressure for a specific vehicle. Follow the inflation pressure on the vehicle tire placard, certification label or in the owner's manual. |
| USTMA | Match-mounting balancing machines with ride optimization features may be used to prevent or resolve many ride and vibration complaints, and can help diagnose tire and wheel related vibration. |
| USTMA | If a vehicle has a sudden vibration or ride disturbance, gradually reduce speed, do not brake or turn abruptly, stop and inspect the tire. |
Convert pressure units with the PSI to kPa converter; check a size change against your speedometer with the speedometer error calculator.