DIY Tutorials

Flat tires on your bicycle, while frustrating, are easily dealt with if you’re prepared. Always carry a spare tube, repair kit, tire levers and a pump and follow these simple directions to get back on the road or trail quickly.

Here are the four basic steps to fixing a flat:

1. Remove the bike wheel

It's much easier to fix a flat if you first remove the wheel from your bike. Removing the wheel is a 2-step process:

First, Release Your Brakes

Most brake assemblies sit very close to your wheel rims and use a quick-release system to disconnect and reconnect them. The exact location and design of these release systems will depend on your style of brakes.

Some have a knob at the end of the pull-cable that catches on a notch in the caliper arm. Squeeze the brake arms together to release the cable.

Others have a quick-release lever, just like on your axle, which can be opened to release the brakes.

If your bike has disc brakes—most mountain bikes have these—be careful not to touch the rotor when opening the quick-release mechanism. The rotor is located very close to the quick-release lever and can become hot enough to burn you.

Then, Release Your Wheel

Once you've disengaged the brake assembly, your wheel is still held to the frame or fork (depending on if it's the rear or front wheel) by the wheel axle. To release the axle, check to see if you have a quick-release lever—most bikes have this—or a bolt-on nut and then follow the steps below.

Quick-release Axles:

Front wheel: Open the quick-release lever and unscrew the securing nut slightly on the opposite side as needed to release the tension holding the wheel in place.

Note: Some bicycles have retention devices designed to hold a wheel in place even when its quick-release lever is open. If your wheel doesn't pop out after you open the quick-release lever, check the owner's manual for details on its particular release-and-retention system. Or consult with a bike pro at your local REI.

Rear wheel: Before removing your rear wheel, shift your chain onto the smallest rear cog. To do so, adjust the shifter up then raise your bike and crank the pedals until the gear-shift is complete. Turn the bike upside down, then turn the rear axle quick-release lever until it's fully open. You may need to unscrew the nut slightly on the opposite side. Pull back on your rear derailleur to give yourself some slack, then lift out the wheel with your other hand. The wheel should pop free without getting tangled in your chain. If your wheel stays put, it's likely there's a retention device holding it in place (see the note above).

Bolt-on Axles:

To loosen a bolt-on axle, simply grab both ends of the axle with 2 good-fitting wrenches and turn both wrenches a couple of full turns. If you only have one wrench, alternate between ends of the axle bolt, loosening each a half turn or so at a time.

If you're removing a bolted rear wheel, follow the procedure described above to avoid getting it hung up in your chain.

2. Remove the tube

To find the source of a flat tire and fix it, you need to remove the tube from the tire.

Getting Inside Your Bike Tire

First, release all of the remaining air from your flat tire by depressing the small plunger in the center of your tire valve (Presta valves must be opened first. To do so, remove the valve cap and turn the valve counterclockwise.) Next, unseat your tire bead using the following procedure:

Attempt to unseat your tire by hand by pushing one bead edge in toward the center of the rim. If this doesn't work, use tire levers to get some additional leverage.

When using tire levers, start on the section of your tire opposite the valve (to avoid damage to the valve stem). Use the longer end of one tire lever to pry the bead of the tire up and over the edge of the rim.

If you can't unseat the tire with just one lever, place a second one in a similar manner, 2 or 3 spokes to either side of the first. (Tires levers come with a handy notch that can be secured against a spoke, keeping the lever in place.)

Once a section of the tire bead is free, you should be able to unseat the rest of the bead with your fingers. Remove the inflatable tube from beneath the tire by pulling the valve stem out through the rim first. The rest of the tube should slide out easily when pulled. Be careful when pulling the valve out through the rim, as its sharp edge could damage the valve.

3. Find the cause of the flat

While removing the tube, it's important to look for the origin of your flat tire. It may be a nail that is now long gone, leaving you with a hole in your tube and tire. Or it may be a thorn or piece of glass that is still stuck in the tire and could damage your newly repaired or replaced tube.

When searching for the cause of a flat, begin on the outside and work your way in.

First, check the outer surface of the tire for any signs of damage or wear—things like foreign objects lodged in the tread, cuts or tears in the tread or tire sidewall, or worn/cracked tread patterns.

Next, get inside the tire (see below) and check both the inner tube and the inside surface of the tire for similar damage.

Tube damage can be difficult to spot. If you don't see any obvious punctures or blowouts, try inflating the tube so you can check for escaping air. To find very small leaks, pass the tube close to your eye to feel for air or submerge it in water and look for bubbles.

Tip: Leave the tire in its same location on the wheel so you can check for tire damage once the tube leak is discovered.

If you can't find any tube damage, check the valve. If the valve stem or base is cut, cracked or severely worn, it may be leaking. If so, the entire tube will need to be replaced.

If the valve is in good condition, check the thin strip along the inside of your rim. Look for protruding spoke ends or areas where the strip may have come free and pinched the tube against spoke-hole opening.

Once the tube damage has been found, check your tire for damage as well. Use the valve stem to align the tube so you can find the same location on the tire. Look for any embedded objects in the outside tread. Then carefully feel and look inside the tire, making your way slowly around the tire. If you have taken the tire completely off the rim, turn the tire inside out and do a full visual inspection. If you find any cuts, squeeze the ends of the length of the cut to push apart the rubber and look for anything embedded in the tire. Remove any foreign debris.

4. Repair or replace the tube

If your tire has sustained little or no permanent damage (as is often the case), your decision will be whether to repair your tube or replace it.

Repair: Most commercial patching kits contain everything you need to create an effective patch in the field, including step-by-step instructions. However, patching a tube should be considered an emergency repair. For maximum reliability and safety, replace a patched tube as soon as possible.

Typical patching steps:

1. Find the damaged area.
2. Clean and dry the damaged area.
3. Rough up the surface of the damaged area with sandpaper (to help the glue adhere).
4. Spread the glue (vulcanizing fluid) and allow it to set until tacky.
5. Apply the tube patch and hold it in place with pressure.

Replacement: You must replace your tube any time the damage is too extensive or severe to patch, when a patch job fails to hold or when the tube’s valve is damaged.

Replacing a tube is simply a matter of using the right size. Size information is sometimes available on the tube itself, on the sidewall of your tire or in your bike owner's manual.

Note: Replacing tubes is more expensive than patching them. However, the resulting tire/tube combination is generally stronger and longer lasting than a patch job.

Steps for putting your tube and tire back on

1. Make sure the rim strip is seated properly.
2. Partially inflate your new or repaired tube to give it shape and ensure it holds air.
3. Starting with the valve stem, lower the tube onto the wheel, inserting the valve into the rim valve hole. Check that the valve stem is straight and not at an angle.
4. Then place the rest of the tube inside the tire.
5. If you completely removed your tire from the rim while fixing your flat, push one edge (or “bead”) of the tire inside the rim.
6. Beginning at a point opposite the valve, push the other tire bead inside the rim.
7. Proceed around the wheel (in both directions at the same time), working more of the tire bead inside the rim. This will get harder as you go. Pinch both sides of the tire in towards the center of the rim to make things easier, or carefully use a tire lever to complete the job. Use caution when using a tire lever to avoid pinching the tube.
8. Once the tire and valve are in place, check along its edges to make sure that the tube is not caught between the rim and the tire bead. This could cause another flat.

Now inflate your tire slowly, checking both sides of the rim to make sure that the tire bead stays firmly seated. Double-check the valve as you go to ensure it remains straight. To make sure your tube doesn't get caught between your tire and the rim, go around the whole tire once and pinch both sides of the tire inward.

Inflate the tire to its recommended pressure (printed on the tire itself or in your owner's manual). If you don't have a gauge, use your thumb as a guide. If your thumb presses in easily, keep pumping.

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Bicycle brakes become less effective over time. Cables stretch and pads slowly wear away. If you can squeeze the lever fully on without the brake engaging, urgent action is required.

Test your brakes

Stand next to your bike. Squeeze the front brake lever and try to push the bike forward. The rear wheel should lift and the lever shouldn't touch the handlebar. Now repeat this test with the rear brake. The rear wheel should lock and skid as you push the bike forward. If either brake isn't working properly, it's likely to be a result of slack in the cable – unless your bike has hydraulic brakes, in which case they probably need 'bleeding' to remove air bubbles. (That's a job for the bike shop or a confident home mechanic.)

Visual checks

Is the brake properly set up? V-brakes have a quick release so that the wheel can be removed and refitted easily. The 'noodle', which is a J-shaped metal guide tube, can be disengaged from its cradle. In this state, the brake will not work. Sidepull brakes often have a small quick release lever on the caliper, enabling it to open wider (as shown). Ensure this lever is closed, otherwise the brake pads will be too far from the rim.

Examine the brake pads. There should be a good thickness of braking surface remaining. (If your brakes make grinding noises in use, there's no pad material left: you're applying metal to metal!) Time for new pads? Head to the bike shop.

Adjust cable tension

All cable-operated brakes should have a barrel adjuster – a hollow knurled bolt where the cable exits the lever or enters the caliper. Some bikes use 'inline' adjusters part way along the cable outer instead.

To increase cable tension, turn the barrel adjuster anti-clockwise. Try one full turn initially, then half turns, repeating the brake test periodically. If the barrel adjuster has a threaded lockring or locknut, unscrew this to enable the barrel to turn, then screw it flush to the lever or caliper to keep the barrel firmly in its new position.

Re-clamp cable

If a few turns of the barrel adjuster don't solve the cable tension problem, try re-clamping the cable. First wind the barrel adjuster back in. Then undo the bolt that anchors the cable to the brake.

Use one hand to squeeze the brake mechanism together. This is easy with sidepull brakes and V-brakes: simply hold the brake blocks against the rim. With a cable disc brake, push the caliper's brake arm up to engage the brake. The brake doesn't need to be jammed on; just touching the rim or rotor is okay. Don't let go of the brake until you've re-clamped the cable.

Then with your other hand, pull more cable through the cable clamp, until the cable is just taut. Let go of the cable now and tighten the clamp bolt.

Finally, let go of the brake mechanism.

Since you weren't pulling on the cable when you re-clamped it, there should be enough slack that the brake pads don't rub the rim or rotor. If there's too much slack, use the barrel adjuster. If the cable is too tight and the brake rubs constantly, repeat the above process but don't squeeze the brake mechanism fully against the rim or rotor – just hold it tight enough that you can pull the cable through further than its previous clamping point.

Centring the brake

Sometimes just one of the brake pads will rub. In this situation, you need to centre the brake.

Sidepull brakes often have a small adjuster screw on top of the caliper, at one side. Screw this in or out – slowly, so you can watch the brake arms move.

If your bike's sidepull brakes lack this feature, slacken the fixing bolt that holds the brake to the frame or fork, move the brake, then retighten the fixing bolt.

V-brakes have a small screw at the bottom of each brake arm. These adjust the spring tension. To move the brake pad away from the rim, increase the spring tension by screwing inwards. To move it towards the rim, decrease the spring tension by unscrewing. As the brake pads' positions are determined by the spring tension on both sides, you'll often tighten one side and unscrew the other to get it right. Work in small increments – e.g. a half turn at a time.

Disc brakes, whether cable or hydraulic, are held to the frame or fork by two large (5mm) Allen bolts. Undo these two bolts enough that you can move the disc caliper side to side by hand. Then squeeze the brake lever so the brake is fully on. Without letting go of the brake lever, use the 5mm Allen key in your other hand to tighten the caliper's frame/fork bolts.

If the pistons on both sides of the caliper move – all hydraulics and some cable discs – the caliper should now be centred. If, as with most cable discs, only one piston moves you may need to adjust the position of the fixed one (see below).

Pad adjustment

The pads of sidepull brakes and V-brakes need to be in line with the braking surface on the rim. Pads set too high will touch the tyre and rub a hole in it; pads set too low will develop a lip that can hold the brake pad against the rim. To adjust pad position, undo the bolt on the pad, then carefully tighten as you hold the brake manually against the rim.

With cable disc brakes, the piston (and pad) nearest the wheel is usually fixed; it doesn't move when you squeeze the brake lever. But you can move it in or out to get it the right distance from the rotor. Reach through the spokes with the relevant Allen or Torx key, turning anticlockwise to move the pad away form the rotor and clockwise to move it towards the rotor.

The position of the moving piston/pad is usually determined only by cable tension, but on some brakes (e.g. Avid BB7) it can be moved in or out independently with a ratchet dial.

Finally

When you've adjusted your brakes, squeeze them on hard a handful of times, then repeat the brake test. If you're still not happy, come in to our bike shop.

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The chain and drivetrain are typically the dirtiest parts of your bike, and this dirt is bad news for bike longevity and performance. Specifically:

1. Increased rate of chain wear .
2. Reduced flexibility of chain links.
3. Added wear on derailleur assemblies and drivetrain cogs.
4. Impaired shifting performance.

This article and the above video will help you keep a clean-running machine.

When to Clean and Lube

Regular, On-Bike Cleanings

On a regular basis, look at the entire chain by standing to the side of your bike and lifting the rear wheel off the ground. Use your free hand to slowly rotate the closest pedal, inspecting individual chain links for dirt buildup, rust and/or tight links (links that do not bend easily as they pass through the rear derailleur). Check for adequate lubrication by listening for squeaks while riding. If you find either condition, your chain needs at least a spot-cleaning.

To spot-clean the chain while it's still on your bike:

• Brush out the links with a firm brush (an old toothbrush also works).
• Relubricate the links from time to time with a chain lubricant.
• Wipe off excess lubricant with a clean, dry rag. Over-lubricating can actually attract new dirt.

For a more thorough cleaning, use a chain-cleaning tool. Attach it to your chain for a quick, deep cleaning.

Occasional Off-Bike Cleanings

Every few months or so (more often for mountain bikes), completely remove your chain using a chain-removal tool. Brush it well and completely immerse it in a chain solvent to get rid of built-up grime that brushing can't remove. Let the chain soak until most of the dirt has been freed from the links and bushings. Dry the entire chain using a clean rag. Make sure that the solvent has completely evaporated, then relubricate the chain and re-install.

A Word on Lubricants

There are 2 key properties to any chain lubricant. They must:

1. Minimize the accumulation of dirt, because dirt accelerates wear.
2. Be durable, because lack of lubricant also increases chain wear.

Durability is the lesser issue as you can and should lube your chain often. Oils that are specifically marketed as bicycle-chain lubricants are superior to non-bicycle-specific products. They generally contain Teflon® and are designed to repel dirt and water.

Note: Always use a cleaner and lubricant designed for bike drivetrains. REI does not recommend using WD-40 on your bike (it is a cleaner but not a lubricant.

Problems to Watch for When Cleaning

Tight Links

These are links that no longer bend smoothly. To spot them, pedal your chain slowly backwards and watch as each link passes through the tight turns of your rear derailleur.

Most are caused by dirt or corrosion between link plates; these can be fixed by cleaning, lubricating and a little flexing back and forth. Others are the result of improper pin installation (the pin that holds the chain links together is not fully inserted through the links and rollers) or serious chain damage. Poorly installed link pins can sometimes be worked back into position by shifting them back and forth inside their chain plates by using either a chain tool or your hands. Damaged chains should be completely replaced.

Chain Stretch

As chains wear, they become longer. This is called stretch, which is a misnomer because nothing actually stretches. Chains lengthen as wear occurs between the rollers and the link pins. This creates slop or free play that leads to gear "skipping" in some cases. It also causes extra wear and tear on your chain rings and rear cog teeth.

It's much cheaper to replace a chain than it is a cog set. To check for chain wear, use a wear-indicator tool such as the one shown at right. When the prong fits into the chain gap, the chain should be replaced.

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Be prepared for flat tires or other maintenance issues on your next bike ride. Printer-friendly version (PDF)

Essential Bike Repair Kit Tools

Carry these on every ride in a small saddle pack:

• Spare tube or tubes (and/or patch kit)
• Tire levers
• Bike pump
• Bike multi-tool (with Allen wrenches)

Bike Tools for Longer Rides

Carry these in a larger pack for multiday rides or rides on dirt trails for optimal preparedness. Only bring what you know how to use.

• 6" adjustable wrench
• Patch kit
• Spare tire (sometimes foldable)
• CO2 tire inflator (with cartridges)
• Bike tire gauge
• Brake and derailleur cables
• Spare nuts and bolts
• Replacement chain links
• Chain tool
• Spare spokes (minimum of 6)
• Spoke wrench
• Lubricant
• Spare components
• Spare cleats
• Repair/duct tape
• Clean rag(s)

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