Bicycle Repair - Tire changing lesson

Blowouts and air leaks are one of the most common faults when riding outside. A tyre burst when you are out riding, and when you are in a wilderness without a spare tire or maintenance tools, it will not only affect the original itinerary plan, but also destroy the joy of going out for riding. For bikers who intend to continue cycling, go out of the urban area, and expand new paths, "replacement of inner tubes" is a must-learn skill. Today, let BoneTalk demonstrate how to replace bicycle inner tubes.

Bicycle Repair|Tire changing lesson


1. One inner tube with the correct specifications

2. One set of tire levers

3. One upright/portable pump

4. A French to American nozzle conversion head

Equipment list. If you need to carry them on your bike, installing a saddle bag for your tools is recommended.

How to choose a "correct size" inner tube? You have to start with the outer tire. Just like when choosing clothes and shoes, the size of the tube must match the tire to ensure that it fits properly and comfortably after replacement. The design of the wheel frame determines the type of tube and the specifications of the outer tire can be found on the side of the tire.

Close up view of the rear tire gauge. This tire is 700x23C.

The first number, 700, refers to the approximate "diameter" of the outside of the tire, which is about 700mm, and is sometimes indicated as a new 622 (inner diameter of the tread lip), while the second number, 23, refers to the "width" of the tire, which is 23mm.

The above image with 700 X 23C and 25C are the most popular specifications for road bikes in the current market, while the wider 28C and 32C have recently become popular for disc brake models and crossover bikes. To be safe, it is still best to squat down and check the wording on the outer tire.

48mm length valve in high frame
The width of the wheel is correct...but the valve doesn’t seem to be long enough?

In addition to the diameter and width, you should also pay attention to the "frame height". The height of the wheel frame is different for flat track and lightweight climbing wheels, and will need to allow enough length on the valve for it to be inflated, so it needs to be at least one centimetre higher than the frame. The inner tube valve lengths with 48m, 60mm, and 80mm are currently available on the market, so you can choose according to the height of your wheel frame.

If an American style valve is placed on a French style frame, you won’t be able to get it into the hole!

Bicycle inner tube valves are also divided into "American", "French", "Japanese" and "British" styles. American style valves are also used on normal motorcycles. French-style valves are widely used on bicycles and are thinner than American-style valves, and the valve needs to be twisted open when pumping. Due to the size of the frame hole being different, the two types of American and French valves are not interchangeable.

American valve and French valve side by side
French style valve needs to be turned on

If you know the diameter and width of the tire, plus the valve length and valve type, you can go to the nearest bike store to choose an inner tube. If you can't confirm or have other bicycle-related problems, it's better to take your bike directly to a shop technician for evaluation.

Complete inner tube package
Inner tube white label

The inner tube has a permissible width range. The 18/25 on the package above means that it can be used on outer tires with a width between 18mm and 25mm. 23 is within this range, so it is suitable.

Now you have the inner tube and tools, next, you can start to change the tire!.

The first step is to switch the gear to "small on small", that is, use the smallest gear for the big disc and the smallest gear for the rear flywheel, this gearing allows the chain tension to be minimal, which makes it easier to disassemble the rear wheel. If your flat tire is on the front wheel, you can omit this step.

Switch the front disc and the rear flywheel to the smallest gears

Then release the rear C-clamp brake quick release button. Because the tire will be inflated after the completion of the tire change, this can reduce the hassle when you want to install the tire and will not affect the brake settings and cause jamming.

Clamp quick release button is tight
Clamp quick release button is loose

After removing the water bottle, Bone Bike Tie,stopwatch, wallet and other accessories and personal belongings, you can gently turn the bike upside down. Be careful not to get your clothes dirty from the chain and the gear plate.

Close up of the Bike Cell Phone Tie
Turn the bike upside down

Release the quick release lever, if it is too tight or rusty and stuck, you can use a hard object such as a key to pry it open. After loosening it, hold the wheel with one hand, and gently pull the gearbox with the other hand to simply remove the rear wheel.

Release the front quick release lever
Loosen the rear quick release lever
Pull the gearbox
Remove the rear wheel from the hook and chain

Remove the air nozzle dust cap, remove the retaining ring, and release the remaining air inside the inner tube. "Massage" the outer tire all the way round, allowing the lip to sink into the frame to create a better clearance for inserting the lever. Generally speaking, the opposite side of the valve is the best place to use the lever.

Use the hooked end to hook the outer tire on one side, do not hook the inner tube, pull the lever down and slide it along the frame edge to get the outer tire out of the frame. If you find it hard to move the tire by pulling it down and sliding it, you can try another position or use two tire levers at the same time.

Before pulling down
Sliding after pulling down

After one side of the outer tire comes off, the other side is much easier, as long as the tire is pressed out from the same position opposite to the nozzle, you can remove the outer tire, along with the inner tube, and finally pull out the inner tube nozzle. Then the whole tire can be removed from the body of the wheel frame. At this point, do not separate the inner tube and outer tire and do not change the relative positions of them.

Press the other side of the tire
Place it flat to separate

There must be a reason for the tire to have deflated, it could be a nail, an old cracked outer tire, insufficient tire pressure during the ride causing the frame to squeeze and press through the inner tube, or the inner liner did not protect the tube...... If you just replace the inner tube with a new one, it will probably only end up leaking again. However, there are thousands of reasons it could have happened, and the tire size is not small, so how do we find out the main reason?

At this point, it is time for us to check the old inner tube. By inflating the old inner tube, you can find out the location of the hole and whether it is located on the inside or the outside. Before separating the inner tube from the outer tube, mark the position of the inner tube valve on the outer tube.

Mark the position of the valve with a tire cutter

Remove the inner tube and connect it to the pump; if the inner tube deflates instantly, you will definitely find a big hole that is visible to the naked eye. If it is a small hole, you need to continue to inflate the inner tube to expand it. After that, stop pumping, calm down and use your cheeks and ears to feel and listen for the air escaping out from the inner tube.

Inner tube against the cheek
Close up of the hole
French to American valve adapter

Once you find the hole in the inner tube, you can deduce the point of the blowout based on the location of the valve on the outer tube and the valve hole on the frame, as just indicated. It should be noted that there is no front or back on the inner tube and during the inflation process you may forget which was the front or back, so the symmetrical position also needs to be checked.

Generally speaking, if the hole is located on the inside (the inside is the side with the nozzle), it will be a lining problem, which can be solved by replacing the 700C road lining; if it is on the outside, it is mostly caused by a foreign object in the outer tire, which needs to be checked and removed.

Check if the inner lining is ruptured and old, or if the position has shifted

If you can't find out the cause after careful inspection, there is a small chance that the foreign object has already escaped from the outer tire, so all you can do is to check thoroughly and pray the new tube installs properly..

When putting the new inner tube into the outer tire, there are several tips:

1. Pre-inject a little air into the inner tube to avoid tire rotation and pinching from carelessness.

2. Align the inner tube nozzle with the mark on the outer tire, which will not only look good but also saves the marking action of changing the tire later.

Inner tube is pinched in the outer tube
Align the valve with the mark on the outside tire

The rear wheel frame and the outer tire have to be fitted in the correct direction. The cog wheel of the frame must be on the same side as the chain on the body, and the arrow of the tread pattern must face forward when the road tire is moving (if there is a special mark on the tire, the outside tire shall prevail), but as we are changing the tire upside down, the arrow of the tread pattern needs to face backward instead.

The gears and the chain are on the same side, and there is also a positive and negative direction when the tire is mounted on the frame.

After confirming the positive and negative sides of the frame and tire, you can start installing the tire. Insert the valve into the wheel frame first, and then put in one side of the tire. The other side also starts from the nozzle, and the tire is inserted into the frame evenly from left to right. The last step of tire fitting, which also requires the most strength and ingenuity, is to insert the last bit of the exposed and taut tire into the wheel frame, which will release the little air that has just been injected and make the final part of tire fitting smoother. The degree of difficulty in putting on the tire is very much related to the material of the tire, so pay attention! Even if it is difficult, it is not recommended to use a tire lever to avoid inadvertently damaging the inner tube.

The last step of fitting the outer tire is the most laborious

Don't be in a hurry to pump the air! Check that the outer tire is completely wrapped around the inner tube and that the inner tube has not been pinched between the outer tire and the rim. If this happens, push the outer tire back and forth until the inner tube is completely covered.

Trapped tire indication
With the correct indication, you should be able to see the color of the lining directly

If you can see through the gap that the inner tube is pinched, do not directly inflate, the correct way is as shown on the right, where you can directly see the color of the wheel lining.

Inject a little bit of air, check the tire once again, and make sure there is no pinching, then you can pump the inner tube to the "rated tire pressure". The rated tire pressure of each outer tire is different, MIN is the lowest required tire pressure, MAX is the highest bearable tire pressure. Taking into account the hot climate in Taiwan, tire aging and other factors, usually take the highest tire pressure minus 10 to 20 psi.

When the inflation is completed, screw on the valve retaining ring (if not omitted), valve and dust cap, then you can put the whole rear wheel back on the bike. When putting the rear wheel back on, pay attention to the position of the chain. The top and bottom should not be crossed and reversed, and the rear derailleur can be toggled to let the rear wheel slide in smoothly and avoid collision with the brake clamps, which could change the brake setting. Check whether the axle on both sides has been completely placed in the groove.

Axle not fully inserted
Axle is fully embedded

The installation method of quick release is "tightening" instead of "locking". Rotate the quick release plate until you feel the resistance at about 90 degrees (in a straight line) and continue to press it to the end to secure it. When the bike is upright, the direction of the rear wheel quick release plate should be upwards to avoid the danger of it hooking objects while riding. Thus, as the bike is still inverted, the direction of the quick release plate should be facing downward.

Rear wheel quick release plate facing down
Quick release handle should be facing up when riding

Turn the bike back upright, adjust and tighten the quick release button of the brake clamps, lift the bike slightly so that the rear wheel is off the ground, turn the pedals to let the chain return to the correct gear, and finally check whether the brake clamps are positioned in the center and evenly clamped on the rear wheel frame. Then put back the water bottle, bike phone tie and other personal accessories, and the whole tire change operation is complete. Don't forget to check if there are any items that have been missed on the floor and again make sure everything is tightly locked, then you can continue your journey!

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