Quick Answer
- Low profile means a short sidewall, which is a low aspect ratio, the second number in the size. There is no official cutoff; tire retailers commonly call 50 or lower low profile, so a 235/45R18 (aspect ratio 45) counts.
- The sidewall is width x aspect ratio / 100: on a 235/45R18 that is 105.8 mm, or 4.16 in (calculated). USTMA says aspect ratios typically run from 30 to 80.
- USTMA says lower aspect ratio tires typically aid performance and handling but may give a less comfortable ride, may wear more quickly and be noisier, and are more susceptible to pothole and curb damage.
Sidewall Height by Aspect Ratio
A 225 mm wide tire on a 17 inch rim, changing only the aspect ratio. The 50 or lower cutoff is a retailer convention. Calculated.
| Size | Sidewall mm | Sidewall in | Overall diameter in | Low profile by 50 or lower |
|---|---|---|---|---|
| 225/80R17 | 180.0 | 7.09 | 31.17 | No |
| 225/70R17 | 157.5 | 6.20 | 29.40 | No |
| 225/65R17 | 146.3 | 5.76 | 28.52 | No |
| 225/60R17 | 135.0 | 5.31 | 27.63 | No |
| 225/55R17 | 123.8 | 4.87 | 26.74 | No |
| 225/50R17 | 112.5 | 4.43 | 25.86 | Yes |
| 225/45R17 | 101.3 | 3.99 | 24.97 | Yes |
| 225/40R17 | 90.0 | 3.54 | 24.09 | Yes |
| 225/35R17 | 78.8 | 3.10 | 23.20 | Yes |
| 225/30R17 | 67.5 | 2.66 | 22.31 | Yes |
Low Profile Tire Sizes: Examples
Sidewall height and overall diameter are calculated from the size. For any size use the sidewall height calculator.
| Size | Aspect ratio | Sidewall mm | Sidewall in | Overall diameter in | Low profile (50 or lower) |
|---|---|---|---|---|---|
| 205/55R16 | 55 | 112.8 | 4.44 | 24.88 | No |
| 215/60R16 | 60 | 129.0 | 5.08 | 26.16 | No |
| 225/65R17 | 65 | 146.3 | 5.76 | 28.52 | No |
| 225/45R17 | 45 | 101.3 | 3.99 | 24.97 | Yes |
| 235/45R18 | 45 | 105.8 | 4.16 | 26.33 | Yes |
| 245/40R18 | 40 | 98.0 | 3.86 | 25.72 | Yes |
| 255/35R19 | 35 | 89.3 | 3.51 | 26.03 | Yes |
| 245/35R20 | 35 | 85.8 | 3.38 | 26.75 | Yes |
| 285/30R21 | 30 | 85.5 | 3.37 | 27.73 | Yes |
| 305/25R22 | 25 | 76.3 | 3.00 | 28.00 | Yes |
Going Low Profile With Plus Sizing
Moving to a larger rim and a lower aspect ratio while keeping the overall diameter close to stock. Closest standard size for each step, calculated; Continental advises staying within 3% of the original rolling circumference. Check approved rim widths with the plus sizing options calculator.
| Stock size | New rim | Closest size | Diameter change | Sidewall (stock to new) |
|---|---|---|---|---|
| 205/55R16 | 17 in | 225/45R17 | +0.4% | 4.44 to 3.99 in |
| 205/55R16 | 18 in | 195/45R18 | +0.1% | 4.44 to 3.45 in |
| 225/65R17 | 18 in | 205/65R18 | -0.1% | 5.76 to 5.25 in |
| 225/65R17 | 19 in | 245/50R19 | +0.5% | 5.76 to 4.82 in |
| 235/60R18 | 19 in | 215/60R19 | +0.2% | 5.55 to 5.08 in |
| 235/60R18 | 20 in | 255/45R20 | -0.2% | 5.55 to 4.52 in |
What USTMA and Continental Say
| Source | Statement (paraphrased) |
|---|---|
| USTMA, Care and Service of Passenger and Light Truck Tires (2017) | The aspect ratio number typically ranges from 30 to 80 and is the section height as a percentage of the section width. Aspect ratios are also called series. |
| USTMA | Lower aspect ratio tires typically aid performance and handling but they 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 | When choosing a tire with a different aspect ratio, check that the overall diameter of all four tires is within the vehicle manufacturer's tolerance, that load capacity is at least the original at the placard pressure, that the speed symbol is equal or higher, and check rim width and offset recommendations. |
| Continental Tire, plus-sizing guidance | Match the original rolling circumference as closely as possible; a deviation above 3% can affect speedometer accuracy, ABS and stability control. |
Related: ride comfort guide, how to read a tire size and the tire size comparison calculator.
Frequently Asked Questions
Sources: USTMA, Care and Service of Passenger and Light Truck Tires (2017); Continental plus-sizing guidance. The 50 or lower cutoff is a common convention, not a standard. Dimensions are calculated.