bike tires - I Love Bicycling

It can be tough to find that perfect tire pressure for both mountain biking and road biking, because there is no easy answer. The perfect tire pressure can vary from day to day depending on the conditions, the type of trail, or the weight of the rider.

If you’re used to riding on smooth, paved roads, it can be difficult to switch your thinking around. The goal of tire pressure for road biking is to minimize the surface area of the part of the tire that makes contact with the road. With mountain biking, however, in many cases you actually want to increase the surface area to create better grip on the terrain.

What is PSI?

Psi stands for ‘pounds per square inch’ and is measured by a gauge that is included with most bike pumps. Check out “How to use a bike pump” for a step by step guide.

What is the right tire pressure?

As mentioned above, there really is no “right” pressure, just the right pressure for you. However, the best starting point is around 25 Psi for tubeless tires and 28 for tubed tires. Invest in a quality tire pressure gauge and use it consistently, as readings can vary depending on the gauge.

Your tires will most likely have manufacturer’s minimum and maximum pressure printed on the side. The max pressure will not be an issue for most mountain bikers (you will run below this number), but take note of the minimum pressure. If you go below this number, you are more likely to risk sidewall damage or pinch flats. Likely your perfect Psi will be somewhere between these two numbers.

Generally speaking lower psi will allow for a smoother ride, as your tires will absorb more of the trail, roll faster, and increase traction (surface area) on the trail. If your Psi is too high, you will find your tire bounces off every little rock or root, making for an uncomfortable ride.

Things to consider:

The Rider

Weight – The heavier you are, the higher your tire pressure will need to be to counteract the pressure you are putting down on the tires. 30 Psi may feel too hard for a 130lbs rider, but will be too soft for a 250lbs rider.
Style – Do you huck yourself off drops and ride down rocky hillsides with aggressive abandon? If so, then you will need to run a slightly higher tire pressure. Contrarily, if you are a bit more reserved, always light on your bike and finding the smoothest lines, then you can run a lower pressure without risking a pinch flat.

The Tire

Volume – Gone are the days of the uniform 26in tires, with plus size 27.5 and 29ers becoming increasingly popular. When switching up to a larger size, you are also increasing volume, which means you will need to find a new magic number that works for you.
Rim width – The rim width determines just how low you can go without compromising performance. The wider rim, the lower pressure you can run, as it will support the tire better than a narrow rim.
Construction – The outer casing of your tire and the TPI (threads per inch) will determine how the tire feels with more or less pressure.

The Environment

Conditions – If it has been raining for weeks on end and you’re heading out onto to slick, muddy trails, lower tire pressure will give you more grip and stability.
Terrain – Perhaps one of the more important elements to think about before heading out, your tire pressure can vary from trail to trail. Fast and flowy trails can handle a lower tire pressure to absorb those small bumps and have you feel like you’re flying. However, if the terrain is full of jagged rocks and drops, the same tire pressure will have you on the side of the trail with a flat in no time, so you’d want to bump that tire pressure up before heading out.

Finding the Magic Number

Finding your magic Psi is more of a trial by error than a science. A great place to start would be to choose a short section of trail (the type of trail you usually ride) and start at 27 Psi. Ride the section, taking note of whether the tire is compressing to the rim often or is glancing off small obstacles. Increase or decrease the pressure little by little, riding the same section and noticing the difference in grip and speed.

You will be able to run a lower pressure with tubeless or tubeless-ready tires than with a tube-and-tire setup.

The Number 1 Mistake Beginner Mountain Bikers Make

Everyone believes that more pressure = faster, but in mountain biking that is rarely the case. High tire pressure reduces traction and slows forward momentum when hitting a bump.

Professional cross country mountain bikers will run as low as 18 psi in a tubeless tire. Although you may not be a professional, your goal may still be the same, to have the smoothest and fastest ride possible. So change your thinking, less is more.

Tires are one of the biggest contributors to bike handling performance. They could be considered the most critical component on your bike. They are also the most consumable item on your bike, but what makes tires wear out? When should you replace bike tires? In some cases it’s obvious — missing or smooth tread for example. In other instances, it might be that your bike handles or rides poorly.

The major cause of premature tire wear is prolonged use of the tire with low pressure — it’s just that simple. It’s because sidewalls of tires usually fail before the tread is worn out. Low pressure causes the sidewall to bend and flex over and over again much more so than it would if it were properly aired.

Signs You Need To Replace Bike Tires

Cracks

Cracks along the sidewall of road tires or mountain bike tires is a dead give-away you have sidewall damage and your tire needs replaced. Another indicator is uneven tread wear such as a smooth or bald band on the right and left side of the tire, with good tread in the middle. Checking and adjusting the inflation pressure before each ride with a pressure gauge is the most important thing you can do to prolong the life of your tires.

Frequent Flats

Frequent flatting is a red flag. Several flats in a week or multiple flats on longer rides likely means that your tire needs replaced. This is a no-brainer really. It happens because the tread is so thin it can no longer protect the tube from sharp objects. It happens to road tires and mountain bike tires alike.

Tread Wear

Worn out tires are obvious to a professional, but if your tires wear out gradually you might not notice it. The solution is simple — when your tires are new, make a mental note of how thick the rubber is on the contact point of the tire to the pavement, or how much tread they have, and visually monitor it over the miles. Keep checking it and you’ll see it disappear. When it does, consider replacing the tire.

Squaring Off

Even if the tread on your road bike tire seems fine, another indicator, squaring off, could also mean that your tire is history. Mountain bike tires often get a smooth center while the knobs on either side look fine. Squaring off happens mostly to rear tires because of the extra weight. Squared off tires handle poorly and aren’t as fast. It’s a sure sign that you need to replace the squared off tire as soon as you can.

Exposed Casing

Exposed casing is also very obvious if you look for it. This occurs on front and rear tires if you ride them long enough. If you keep riding on the tire, you’re asking for trouble because the only thing keeping the tube inside is a thin section of casing, which was not designed to contact the road and will wear much faster than the rubber tread. Exposed casing looks like a series of diagonal threads, typically on the side of the tire, but can occur almost anywhere on the tire.

Bulges and Bubbles

This one happens all the time. You’re riding along, and feel a regular bump. Or you might just notice a bulge in your tire before you get on your bike particularly on the sidewall of the tire. This is dangerous because the tire can burst at any time causing you to crash. If you have a bulge or bubble in your tire, fix it immediately with a tire boot if it’s small, or replace the tire altogether.

By Mileage

If you’re still not sure if your tires are worn out, there are a few guidelines applicable per mileage for road bike tires. Most road bike rear tires require replacement in the range of 1,500 to 3,000 miles. Front tires usually run upwards of 2,000 to 4,000 miles. Back tires wear more quickly than the front because about 60 percent or more of your weight is on that tire. Mileage data is not applicable for mountain bike tires because riding style (abuse) is too much of a factor. Another part of the equation for both mountain and road tires; the lighter you are, the longer your tires will wear. The more you weigh, the faster they wear out.

Attrition by Age

Tires wear out even if you don’t ride the bike. If you store a bike for more than a few months be sure to check the tires. Wear is not always obvious because you haven’t been riding the bike. But rubber hardens over time and cracks. Even more serious is that the casing — sometimes referred to as the sidewall — can rot, crack, and separate. Also known as dry rot, if you see frayed threads or cracks, or rotting of any type, don’t ride. The tire may appear to hold air just fine, but it won’t for long when you hit the road. Blowouts are common on aged tires. Blowouts scare the hell out of you and cyclists riding close to you — and can lead to a crash.

Ride Quality

It might be that your tires pass the test for wear but you still hate them because your bike is slow, feels heavy, or cornering is twitchy or unstable. Poor handling is common on puncture-resistant, heavy tires made for flat protection, or even some of the all-weather tires. But they have their advantages. If you live in an area of inclement weather, bad roads or puncture weeds, they are worth their weight in gold. The choice is yours. Lighter tires handle and accelerate better but you’ll be fixing more flats and replacing them more often because they wear out faster.

Experiment With Tire Pressure

It’s been previously stated that proper pressure is important to your tire, but what good are rules unless you can break them. In the last decade it has become trendy to pump up tires as high as they will go. Or that the more pressure, the faster the bike will ride. At least one brand of tire actually requires 140 psi. That much pressure can make a bike ride harsh. Super high pressure can make the bike bounce depending on how heavy you are. It transmits road shock, fatigues the rider, causes the premature failure of bike frames and wheels and makes tires more prone to flats.

Stay at the lower end of the pressure zone for comfort and rough roads. Running lower pressure can yield a bike that corners better and gives a far nicer ride. Properly inflated tires roll over bumpy roads smoother and faster and get you home without shaking your teeth loose. On ultra-smooth roads however, when rolling resistance is crucial, such as in a time-trial or triathlon, go as high as 140 psi if your tires are rated to take it. The suggested inflation range is a good starting point but don’t be afraid to experiment with it. The point is, when should you replace your bike tires? Keep an eye on them and they will take care of you.

What tire pressure should I run on my mountain bike?

What is PSI?

What is the right tire pressure?