If you are unfamiliar with different tire and rim sizes, it can be difficult to understand why a 17-inch tire can fit on a 17-inch rim, while another 17-inch tire cannot. What’s more, it is essential to keep the tire diameter as close as possible to the diameter of the tires originally installed on the vehicle.
In fact, changing tires with a diameter only to 2% to 3% larger or smaller could damage not only the body of the car, but also the brakes and the transmission. It is also important to make sure that the tire is not wider than the rim on which it will be installed.
What else can happen if the tire is the wrong size?
Tires and rims that don’t fit your vehicle could cause the odometer and speedometer to indicate incorrect values; if it indicates a higher speed, it’s not so bad, but if your speedometer reads 50 km/h when you’re driving at 60 km/h, there’s a big problem!
What are the rules for changing tires?
If you still want to change the tires on your vehicle, here are a few rules to follow; and these are not just optional tips: they are necessary to comply with the laws in effect in Quebec.
- Choose tires with the same or slightly smaller outside diameter. For example, it is not uncommon to see vehicles equipped with winter tires that are smaller than their summer tires (17 inches vs. 16 inches for example).
- Make sure that the speedometer does not display a speed lower than your actual speed. In fact, when you drive between 40 and 120 km/h, your speedometer may display a speed up to 10% higher, but not the other way around.
- Choose tires with the same or higher speed symbols as your original tires; winter tires are not subject to this rule.
- Your new tires must have a load rating equal to or higher than that of the original tires
- Make sure that the rim size – its width and diameter – is appropriate for the tires you want to install on it.
- Make sure that the new tire and rim combination is suitable for your vehicle and that it will not exceed the wheel-arch size or create other mechanical problems.
- Seek professional advice to ensure that the tire and rim combination on your vehicle is suitable for use on the road.
The table below gives you an example of tire sizes that are suitable for a given rim size. The minimum, recommended and maximum sizes are also shown. This will give you a better idea of the tire size you should choose, but be careful to make sure that the other tire measurements also match. This includes the ratio of tire height to tire width and the inside diameter of the rim.
If you’re not sure which tire sizes are right for your vehicle – and which are approved for use on the road in Quebec – ask the specialists at blackcircles Canada for help!
| Rim | Tire Size | ||
|---|---|---|---|
| Size | Minimum | Recommended | Maximum |
| 5.0 Inches | 155 mm | 165 or 175 mm | 185 mm |
| 5.5 Inches | 165 mm | 175 or 185 mm | 195 mm |
| 6.0 Inches | 175 mm | 185 or 195 mm | 205 mm |
| 6.5 Inches | 185 mm | 195 or 205 mm | 215 mm |
| 7.0 Inches | 195 mm | 205 or 215 mm | 225 mm |
| 7.5 Inches | 205 mm | 215 or 225 mm | 235 mm |
| 8.0 Inches | 215 mm | 225 or 235 mm | 245 mm |
| 8.5 Inches | 225 mm | 235 or 245 mm | 255 mm |
| 9.0 Inches | 235 mm | 245 or 255 mm | 265 mm |
| 9.5 Inches | 245 mm | 255 or 265 mm | 275 mm |
| 10.0 Inches | 255 mm | 265 or 275 mm | 285 mm |
| 10.5 Inches | 265 mm | 275 or 285 mm | 295 mm |
| 11.0 Inches | 275 mm | 285 or 295 mm | 305 mm |
| 11.5 Inches | 285 mm | 295 or 305 mm | 315 mm |
| 12.0 Inches | 295 mm | 305 or 315 mm | 325 mm |
| 12.5 Inches | 305 mm | 315 or 325 mm | 335 mm |
