Bicycle Tires 101
To most, a tire is nothing more than a simple ring/donut-shaped piece of rubber which holds air, and allows for us to ride our bikes. That is a simple thought about the tires on our bikes, but they are much more sophisticated and important once you take a closer look.
History of Bicycle Tires
The first bicycles didn't have tires. Instead, they had bare rims. Eventually, bicycle companies placed bare rubber on the rims, although over time the rubber cracked. The bare rims and flat rubber tires, however, resulted in a harsh ride. Pneumatic tires did not come into existance until 1887. A man by the name of John Dunlop developed the first pneumatic (or air-filled) tires for his son's tricycle in 1887 in Ireland. Soon after, pneumatic tires were commonplace on bicycles all across the world.
Thomas B. Jeffery was a bicycle manufacturer in Chicago, Illinois, who manufactured the Rambler bicycle. He developed the clincher rim, which is still used by most bicyclists to this day.
Tubeless tires were devloped in the later part of the 20th century, after they became commonplace on cars.
Types of Tires
To understand about bicycle tires, and the information on this page, you must understand the various types of tires. Despite bicycle tires being simple things, they are much complicated with various types of tires.
The most common type of bicycle tire is the Clincher, or Tube-type, tire. The Clincher rim was originally developed in the 1890s by Thomas B. Jeffery for use with his bicycles, and the clincher rim was used in automobiles until balloon tires took over.
Clincher tires are composed of three parts.
Clincher tires offer many advantages. The biggest advantage is being cheap. Clincher tires are easy to install, repair, and change. However, the disadvantages with clincher tires are that they consume more weight than their counterparts. Tubes can vary in quality, and tubes can catastrophically fail or leak faster when punctured, whereas a tubeless tire would controllably leak.
At low pressures (typically below 10 PSI), the inner tube and valve stem will move inside the tire as there is less pressure to hold the tube against the tire casing. This can eventually separate the valve stem from the tube, which can't be repaired.
Tubeless tires are much different from the clincher (or tube-type) tires found on most bikes. Tubeless tires are typically found on higher-end bikes, such as road bikes and mountain bikes. Tubeless tires are much more difficult to install, typically requiring chemicals, with special rims and tires.
The advantage of tubeless tires are that they weigh less, which mean they are much more favored by racist bicyclists and others who value less weight for better performance. Another advantage is that tubeless tires offer better puncture resistance,However, the disadvantage is that they are much more difficult to install, and are difficult to repair. Tubeless tires can't typically be repaired in the field, often requiring the rider to carry at least one spare tube. Tubeless tires offer less customization in the pressure you can run, as they can't safely be overinflated or underinflated.
Tubeless tires are also found on cars. The only part of a tubeless tire system is a special tubeless-ready tire, and a tubeless-ready rim. However, some people use the "Ghetto Tubeless" method to convert a clincher/tube-type rim to tubeless.
Don't let this term confuse you. Tubular tires are basically a tube-type tire in a package. A tubular tire, someitmes referred to as a sew-up tire, or a tub, is essentially an inner tube sewed inside of a tire. Most tubular tires have the Presta valve stem. Most tubular tires are found on indoor racing bikes.
The advantages of tubular tires are that they can be easily installed. They glue on to the rim, requiring minimal tools to be installed. They can typically be installed in the field. However, tubular tires have many disadvantages. They are difficult to repair, requiring to be unsewn, repaired, resewn, and reinstalled. Tubular tires also are much easier to puncture, and are much rarer.
Airless tires have no air in them, requiring no maintenance, and can't be punctured. Clincher-style tires can be retrofitted to airless by using a mousse tube. A mousse tube is essentially an inner tube made of foam. They are typically found on motorcross and dirt bikes.
Types of Valves
There are three types of valves found on bicycle tires.
The Schrader valve is found on most lower-end and older bikes. The Schrader valve is the same type of valve found on car tires. They are short and fat, with black rubber surrounding the outside of the bottom of the valve stem (although some come threaded, with a locking nut, similar to threaded presta valves). A schrader valve uses a valve core to hold the air in, which has a plunger to let air in and out.
They require no special tools or adapters to be inflated with a standard air compressor or tire pump.
Schrader valves can be deflated by using either a valve core removal tool to remove the valve core assembly, or finding an item to fit down inside the barrel of the valve stem, to push down the plunger and let the air out. I've used tweezers to remove the valve core, and I've also used my fingernails to let air out of the tire.
Keeping a dust cap on your schrader valves will keep debris and dirt out of the valve, which will maintain tire pressure. Dust caps typically come with inner tubes or schrader valves themselves, but custom dust caps can be purchased online, automotive or bicycle shops, or even WalMart. Tire pressure can be checked with either a tire pump or air compressor equipped with a tire pressure gauge, or (if the pressure is below 40 PSI) an automotive pressure gauge.
Presta valves are typically tall and skinny. They are either smooth or threaded, and the threaded variations usually include a locking nut which helps prevent the tube or stem moving around within the tire. Presta valves are typically found on higher-end bikes, such as mountain and road bikes.
Presta valves are much more difficult to inflate, often requring a special adapter or special tire pump to inflate. Tire pressure can be checked with a tire pump or air compressor equipped with a tire pressure gauge, as most tires with presta valves are inflated at higher pressures, often higher than regular automotive tire pressure gauges.
Pressure valves are easy to deflate. In order to inflate or deflate a Presta valve, unscrew the valve lock nut (top locking nut, commonly covered by dust cap) and place the adapter or pump onto the valve. To deflate, press down on the plunger to let air out. In presta valves, the air will escape much faster than the schrader counterpart. Be sure to screw the valve lock back down tightly, to ensure that no air leaks once the dust cap is screwed back into place.
Be sure to lock the locking nut down tightly flush with the rim, so that the stem is held tightly into place.
Underinflation vs. Overinflation
There are three types of bicyclists - those who underinflate their tires, those who overinflate their tires, and those who inflate their tires just right. What are the risks of underinflation and overinflation, as well as the benefits between the two.
Much like underinflating the tires on your car, underinflated tires will require more effot to be exerted to gain speed. However, underinflated tires offer a smoother ride, as the tire cushions the bumps and imperfections in the road surface. Puncture resistance is also greatly increased with underinflated tires. Underinflated tires also offer greatly improved traction, as the surface area of where the tire touches the ground is increased.
However, underinflated tires can offer issues. For one, there are two types of punctures which plague underinflated tires. The first type of commonly found puncture with underinflated tires is the snakebite flat. A snakebite puncture is two parallel punctures in the inner tube, caused by the pressure of the rim poking holes in the thin tube. The other type of puncture is the pinch flat, where the tube is caught between the tire and rim, and bulges outside of the tire. This will often cause the tube to explode.
Underinflated tires can also cause the inner tube to move inside of the tire, which can result in the valve stem coming separated from the tube, which can't be repaired.
Overinflating your tires will provide a more firm ride, with little cushioning. However, overinflating your tires will require less effort to gain speed.
However, overinflated tires have many problems. Overinflating any tire is much riskier, and is like blowing up a balloon too much. If you overinflate your tire too much, or the tire was improperly installed or has weak spots, the tire can explode. This will ruin the inner tube, and can ruin the tire and even the rim. This will also ruin your fun.
Overinflated tires also offer less puncture resistance, and fail more catastrophically than underinflated or properly inflated tires.
WARNING: Tubeless tires should NEVER be overinflated. Doing so can ruin the tire, and cause disasterous consequences. Tubeless tires should never be inflated over their recommended pressure rating. Often times, tubeless tires and tubeless rims will feature a sticker or have a warning paragraph molded into the tire warning of the consequences of overinflating a tubeless tire.
Properly Inflated Tires - "Just Right"
Inflating your tires to the proper or recommended inflation pressure is always recommended, as it offers the best of both worlds in most cases.
I typically "air down" - or partially deflate - my tires when riding on gravel trails and in rough conditions. I also have to underinflate the tires on my 1981 Free Spirit Pinnacle, due to rim issues. However, I otherwise run my tires at the proper pressures.
Inflating and Maintaining Your Tires
The recommended pressure rating is stated on the sidewall of most tires. The rating is either stated in as "Recommended Inflation Pressure -- PSI - -- PSI (-- kPa - -- kPa)" or "Maximum Inflation Pressure -- PSI (-- kPa.)" Tire pressures are rated in PSI, or Pounds per Square Inch (Imperial/English units) or kPa, or kilopascals (metric unit.)
When installing my tires, I typically try to position the pressure rating on the sidewall of my tires above or near the valve stem. This allows for easy access to the recommended pressure range while inflating the tires.
It is never recommended to use an air compressor, especially an unregulated air compressor, for inflating tires. Since bicycles tire have a lower volume when compared to car tires, they will be filled faster. It is easy to extremely overinflate bicycle tires with an air compressor.
I typically try to use a tire pump to inflate my bike tires. Other methods exist, though, which include CO2 inflators, which are typically used in emergency situations, such as flats in the field far from gas stations or local bike shops (such as off-road and trails.)
It is recommended to check your tire pressure at least once a week if you are running butyl tubes, and every time before riding with latex tubes. Tubeless tires can be checked safely every two weeks. It doesn't hurt (in fact it is better) to check your tire pressure more often, and I try to check tire pressures before leaving.
When going on a long trip or riding on the trails, off-road, or on the road, bring an emergency backpack. This should have all the tools you need in case something goes wrong on your trip. This emergency backpack should feature all the tools you need to remove your wheels from the bike, a spare inner tube (for tubeless or tube-type tires), a tube patch kit, duct tape, glue, and a First Aid kit. It is a good idea to check your emergency backpack and take "inventory" each time before you leave for a long trip, as being stranded with a flat tire is no fun. If you're going to extremely remote locations (i.e. where there is no cell service, and the nearest town is twenty or thirty miles away at least) it is a good idea to carry a GPS phone. In case of an emergency, this can save your life. You should also carry a frame pump at the very least, or CO2 cartridges to limp to the nearest town. (Frame pumps often require more energy, and are tricky, to use to inflate tires. However, it can save your life. CO2 cartridges will inflate a tire much quickly, if it is the proper size and properly used. However, CO2 leaks out of tubes much quicker, especially latex tubes, and will often only be able to get you to a gas station or shop to inflate with proper air. CO2 cartridges are also much more expensive and difficult to use.)
I hope this lengthy page on tires will help someone. Bicyclists typically debate on whether tube-type (clincher) or tubeless tires are better, or whether butyl or latex tubes are better, or whether overinflating or underinflating their tires will help them. Anyone reading this should evaluate their priorities and determine what is best for them. If it doesn't work well, you can easily change it. Tire pressures can be experimented around with to your liking on tube-type tires, and can depend on the environment you'll be riding in. You can always lower (deflate) or inflate your tires to your liking, just as long as it doesn't hit the extremes.