Having tires of different sizes on your vehicle can lead to a variety of problems. The most obvious issue is that it will make your vehicle uneven, which can affect handling, ride quality, and tire wear. Let’s explore this issue in more detail:
1. Why would the tires be different sizes?
There are a few reasons why one tire may end up larger than the others:
- Replacing a damaged tire with a different size – If you have a flat tire or a blowout, you may not be able to find an exact replacement, so you put on whatever is available.
- Mixing tire types – Putting different tire types on the vehicle like all-season and winter tires.
- Installation error – The wrong size tire was installed by mistake.
- Using a spare – If you are using the spare temporarily it may be a different size.
- Modification/customization – Some people intentionally use different tire sizes to change the look and handling.
So in most cases, the mismatched tires are unintentional due to damage, emergency repairs, or mistakes. Only rarely is it done purposely for appearance or performance.
2. How much size difference matters?
A small difference in tire size, say less than half an inch in diameter, will have minimal effect on the vehicle. But as the difference increases, so do the potential problems. Here are some general guidelines on size differences:
| Tire Size Difference | Potential Impact |
|---|---|
| Less than 1/2 inch diameter | Minimal effect on handling or wear |
| 1/2 to 1 inch diameter | May notice some handling changes |
| 1 to 2 inches diameter | Adverse handling, should be fixed ASAP |
| More than 2 inches diameter | Extremely dangerous, do not drive |
As a rule of thumb, once the size difference is more than an inch in diameter, you risk damage to the drivetrain and adverse vehicle handling. At more than two inches difference, the vehicle may be undrivable.
3. How does it affect handling and control?
Having tires of different sizes will make your vehicle pull to one side and handle unpredictably. This occurs because the larger tire has greater circumference, so it travels farther with each rotation. Here are some handling problems caused by mismatched tires:
- Pulling in the direction of the larger tire
- Wandering and loss of directional stability
- Decreased steering responsiveness
- Longer braking distances
- Rollover risk due to handling differences
These handling changes can be sudden and severe as you switch which tire is on the pavement. The differences in grip, traction, and circumference throw off the entire dynamic balance and feel of the vehicle.
4. Effects on drivetrain components
In addition to handling, having mismatched tire sizes can damage drivetrain components like the transmission and differential. Here are some potential issues:
- Increased driveline wear – The different speeds and forces strain components
- Gear slipping and transmission damage
- Axle seal leaks from pressure imbalance
- Differential gear damage from torque imbalance
- Four-wheel drive binding due to different speeds
These problems arise because the tires are traveling at different speeds. The differential allows wheels to spin at different rates when going around turns. But it can’t compensate for the large constant speed differential caused by different tire sizes.
5. Effects on tire wear
Mismatched tires will wear out more quickly due to the speed and force imbalance. Some particular wear issues include:
- Fast wear on the smaller tire from over-rotation
- Shoulder wear from aligning to the larger tire
- Center wear on the larger tire from load imbalance
- Vibration and impact damage from bouncing
- Irregular, unpredictable wear patterns
You’ll need to replace the tires much sooner, sometimes after only a few hundred miles. Driving any further once you notice unusual wear can risk blowouts and make new tires a necessity.
6. Is it illegal to drive with mismatched tires?
Most states and provinces do not have laws specifically prohibiting mismatched tire use. However, it may still violate general safety regulations or inspection requirements. Driving with dangerously mismatched tires can lead to citations for:
- Unsafe vehicle operations
- Failure to pass safety inspections
- Hazardous moving violations
- Non-working vehicle equipment
Law enforcement has discretion to issue these broader citations if they deem mismatched tires a hazard. Insurance may also deny accident claims if mismatch was a likely factor.
7. Temporary options for mismatched tires
While you should replace mismatched tires as soon as possible, you may need a temporary fix to safely drive for a short distance:
- Inflate all tires to match circumference
- Move smaller tire to non-drive wheel
- Limit highway speeds and avoid hard braking/turning
- Drive gently and steadily on level roads
- Transfer tires side-to-side for even wear
Use these temporary measures only until you can get correctly matched tires installed. The right size matters for performance, safety, and preventing costly damage.
Conclusion
Driving with one tire a different size than the others is extremely hazardous. Even a small difference can throw off the handling balance and accelerate tire wear. Just one very mismatched tire can make the vehicle uncontrollable. The only safe solution is to replace all tires immediately so they match in size as well as tread condition.