Is 40 PSI too much for tires?

The recommended tire pressure for most passenger vehicles is between 30-35 PSI. Tire pressure that is too high or too low can negatively impact handling, ride quality, tire wear and fuel economy. So is 40 PSI too much for tires? Let’s take a closer look.

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What is the ideal tire pressure?

The ideal tire pressure is the pressure specified by the vehicle manufacturer, which is typically found on a placard in the driver’s side door jamb or in the owner’s manual. This is called the “recommended cold inflation pressure”. It provides the best combination of ride comfort, handling, tire wear and fuel economy when the tires are cold (meaning they haven’t been driven on yet that day).

The recommended pressure accounts for the vehicle’s weight, suspension design, tire size, and other factors. It is the minimum required pressure to support the weight of the vehicle and optimize performance. While underinflation causes excessive wear and poor fuel economy, overinflation reduces traction, braking performance and ride comfort.

Why is the recommended pressure usually between 30-35 PSI?

Here are some of the reasons why most passenger vehicle tires call for inflation pressures in the 30-35 PSI range:

Improves ride comfort – Higher pressures transmit more road shock into the vehicle and decrease the tire’s ability to absorb bumps.
Optimizes handling – Too much pressure can make the tires feel stiff, reducing grip when cornering.

Minimizes uneven tire wear – Overinflated tires wear more in the center of the tread.
Prevents tire failures – Very high pressures increase the risk of impacts or potholes causing tire damage or blowouts.
Boosts fuel economy – Rolling resistance increases at higher pressures, reducing MPG.

For most drivers doing typical commuting and errand running, 30-35 PSI offers a good balance of comfort, performance, safety and economy. High performance tires and heavy duty truck tires may call for higher pressures.

Is 40 PSI too much?

For most passenger vehicles, 40 PSI is considered excessive and could lead to problems or reduced performance in a few key areas:

Ride Comfort – At 40 PSI, expect a firmer, harsher ride over bumps and rough pavement. The tires have less give and flexibility to absorb shocks.

Handling – Overly stiff sidewalls from too much pressure can reduce cornering grip and make the tires more prone to sliding in wet conditions or sudden maneuvers.
Tire Wear – When inflated above the recommended pressure, tires wear excessively in the center of the tread. This causes uneven wear and reduces the life of the tires.
Fuel Economy – Rolling resistance increases as inflation pressure goes up. This makes the engine work harder to turn the tires, decreasing MPG.

Blowouts – Overinflated tires are more likely to be damaged by potholes or debris in the road. The lack of shock absorption raises the risk of punctures, bubbles or blowouts.

Additionally, tires that are overinflated beyond the vehicle manufacturer’s recommended pressure are legally considered “overloaded”. This can result in dangerous handling characteristics or tire failure that leads to liability issues in the event of an accident.

What are the benefits of 40 PSI?

While 40 PSI is not optimal for most vehicles, here are some potential benefits of inflating to higher pressures:

Minimizes risk of underinflation – Tires inflated to 40 PSI are less likely to leak down below the recommended pressure over time.
Extends tire treadwear – Overinflated tires tend to wear in the center rather than the edges, spreading out wear.
Improves fuel mileage – Up to a point, higher pressures reduce rolling resistance and improve MPG marginally.

Carries heavier loads – For vehicles frequently hauling or towing near max capacity, slightly higher pressures help support the load.

When is 40 PSI tire pressure appropriate?

Here are some situations where inflating passenger vehicle tires up to 40 PSI could be appropriate:

Heavy duty pickups or commercial vans – Heavier vehicles often max out pressures around 50 PSI for rear tires.

Vehicles with stiff suspensions – Sports cars or performance sedans can benefit from more inflation to prevent bottoming out.
Severe underinflation – Increasing pressure up to 40 PSI temporarily to seat beads before adjusting to recommended pressure.
High speed driving – Slightly higher pressures marginally improve handling at high speeds.

Carrying heavy loads – When a vehicle is near its max load capacity, extra pressure helps support the load.
Off-roading – Low tire pressures are used for traction in sand or mud. Higher pressures on highways prevent overheating tires.

In most cases, the vehicle manufacturer’s recommended pressure is ideal. But temporarily inflating to 40 PSI is unlikely to cause immediate problems, as long as the pressure is reduced to the proper level shortly after.

Potential risks of prolonged 40 PSI inflation

While an occasional need to inflate tires to 40 PSI won’t likely cause issues, here are some potential risks if 40 PSI is maintained long-term on a vehicle intended for lower pressures:

Premature tire replacement – Excessive center treadwear shortens overall tire life.
Poor wet weather handling – Harder rubber compounds have less grip when overinflated.

Wheel & suspension damage – Lack of cushioning transfers more shocks into other components.
Ride discomfort – Passengers feel more bounce, vibration and road imperfections.
Reduced braking traction – Firm treads have less grip, increasing stopping distances.

Decreased stability – Tires may skid more easily in turns or during sudden maneuvers.

To maximize safety, performance and economy, confirm the recommended pressures in your owner’s manual and use a quality gauge to maintain them accurately. Consider 40 PSI an absolute maximum, not a target pressure.

Signs your tires are overinflated

Watch for these signs that your tires may be inflated well beyond the recommended PSI:

Harsh ride – Suspension and tires transmit more vibration into vehicle.
Reduced grip – Tires may slip or skid more frequently on acceleration or turns.
Center treadwear – Tires show excessive wear down the middle of tread.

Decreased fuel economy – Engine has to work harder to turn overinflated tires.
Bumpy/noisy ride – Loss of shock absorption makes tires louder over bumps.
Wandering steering – Vehicle may pull or drift due to uneven contact patches.

If you notice any of these indicators, use a quality pressure gauge to check inflation. Deflate down to manufacturer’s specifications if above 40 PSI.

Is 40 PSI dangerous for tires?

While not inherently dangerous in the short-term, running 40 PSI in tires intended for lower pressures does present some safety concerns:

Increased blowout risk – Overinflated tires are more prone to impacts or punctures causing bubbles/blowouts.

Reduced wet traction – Tires have less grip to channel water, increasing hydroplaning risk.
Degraded handling – Stiff sidewalls reduce cornering grip and stability in evasive maneuvers.
Decreased braking – Tires have less contact area and slip more easily, lengthening stopping distance.

Wheel & suspension damage – Lack of cushioning transfers more shocks into components, increasing failures.

To maximize safety, follow the vehicle manufacturer’s inflation recommendations. Only use 40 PSI temporarily as an absolute max when needed, and reduce to proper pressures as soon as possible.

Tips for maintaining proper tire pressure

Here are some tips for keeping your tires inflated to the vehicle manufacturer’s recommended PSI:

Use a quality pressure gauge – Don’t rely on gas station gauges. Invest in your own quality air pressure gauge.
Check pressures cold – Inflation should be measured when tires haven’t been driven on yet, as driving heats up tires and pressures.
Check at least monthly – Tires naturally lose about 1 PSI per month through porous rubber.

Inspect when handling seems off – If you notice vibrations or changes in ride, braking or handling, check pressure.
Purchase nitrogen – Nitrogen leaks out about 25% slower than compressed air if you need to maintain pressure.
Check spare tire too – An inflated spare won’t help if it’s also underinflated when you need it.

Look for uneven wear – If inner treads are wearing faster, chronic overinflation may be occurring.
Load properly – Adjust to recommended pressures, not maximum pressures, when carrying heavier loads.

Maintaining proper tire pressures is essential for safety, performance, economy and extending the life of your tires.

Conclusion

For most passenger vehicles, the recommended tire pressure is typically between 30-35 PSI. This inflation range optimizes ride comfort, handling, safety, tire wear and fuel efficiency.

While 40 PSI is higher than what most vehicle manufacturers specify, it is not immediately dangerous if maintained temporarily. However, prolonged use of 40 PSI may lead to uneven treadwear, poor wet weather traction, wheel and suspension damage, decreased stability and shorter tire life.

Check your owner’s manual or door jamb sticker for the automaker’s recommended cold inflation pressure. Use a quality gauge and maintain this pressure consistently. Consider 40 PSI an temporary maximum pressure to avoid, not a target pressure to maintain at all times.

With proper inflation, checking pressures monthly and making inflation adjustments when carrying heavier loads or towing, you can maximize the safety, performance and longevity of your tires.