There is a common misconception that overinflating tires is not a big problem and overinflated tires actually increase fuel efficiency. So does it make sense to inflate your tires above tire pressure recommended by your vehicle's manufacturer?
When you overinflate a tire, your reduce its adhesion patch - the surface area of tire in contact with the road. Overinflated tire becomes "skinny" rather than "wide". Increased tire pressure "lifts" the front and rear of tire's adhesion patch, making it shorter.
Shorter tire tread patch does offer less rolling resistance, which is the main reasoning for those claiming it helps improve fuel efficiency. But as some studies and tests have shown, improvements in fuel efficiency due to higher tire pressure are minimal and insignificant long term.
Some drivers also experience better forward traction and stopping power on snow and ice when driving on overinflated tires. That may be true, but it only works on snow and ice roads. On regular roads, 10 percent increase above recommended tire pressure results in a 20 percent decrease in forward traction and a 20 percent increase in stopping distance.
Overinflating a tire alters its sidewall flex characteristics, as well as its operating performance. Overinflated tires can become unstable in curves, and hard to handle on high speed roads. Overinflated tires are especially vulnerable to hydroplaning as overinflated tire has less time to squeeze water into the tread grooves, and instead water becomes layered between the tread patch and the road. Overinflated tires become stiffer and less flexible, making for more uncomfortable and harder ride.
Riding on overinflated tires will also contribute to irregular tire tread wear. You can tell your tire is overinflated by an excessively worn center portion of the tread.
Few drivers would say it is better to overinflate tires than run a risk of tire underinflation. That sounds like a really bad excuse. Check your tire pressure regularly to maintain tires properly inflated for optimal driving performance and safety.