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Bike Prepping

How to prepare your bike for a journey across Korea.

What’s your biggest fear? Death? Taxes? Bears? What about your bike chain snapping halfway up a mountain in Korea?

Don’t fret. Korea’s dense. Bike shops and pop-up vendors cluster around popular cycling spots. However, some paths bring you to half a day’s walk from civilization.

We think limping home should be your last solution. Let’s give your bike a quick checkup to ensure its safety and reliability.

You don’t need an engineering degree to tune it up yourself. With this guide and a few tools, you can get your bike ready for a long bike trip across Korea.

The List
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Inflate the Tires

A picture of a bike pump and bike tire.
Pump up your tires to make your ride smooth, quick, and safe.
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You can spend a fortune replacing parts, buying carbon forks, and shaving extra grams off your bike. But you can increase your performance with one simple and cheap method. Put air in your tires.

Tubes and tires lose air. Older tubes and tires lose air faster. It’s natural.

So just before every ride, pinch the sides of your tires. If they feel firm, you’re good to go. If they feel mushy? Put some air in. 

But don’t over or under inflated your tires. You’ll cause a mess of problems.

Over Inflation

When you put a lot of air in a tire, the outside becomes more round. Good, right? Less rubber on the road means less friction.

Yes, and no.

Yes, in a laboratory setting with ideal, smooth surfaces, decreasing contact surface area reduces resistance. And that equals easy speed..

In the real world, however, you’ll find greater forces at play.

When you increase pressure, the tire becomes hard. This lessens your tire’s ability to absorb all those bumps, cracks, and divots in the pavement. All that shake, rattle, and roll slows your momentum.

If you lower the pressure, your tire acts as a shock absorber. It smoothes out the road rattle and lets you coast over the unevenness.

Softer tires also blunt the jolts that shoot through your bike and into your arms and backside.

Less rubber on the road also means less grip. Grip? What is it good for? Turning. Accelerating. Stopping. What you need to ride and survive.

Under Inflation

Not enough air in your tires? You’ll find a whole new set of problems.

First, less air puts more rubber on the road. This increased surface area will slow you down. The shock absorbing quality of depress tires doesn’t outweigh the friction.

Low tire pressure also increases the chances of a sidewall puncture. What’s that?

Roll over the lip of a curb with speed. Because there’s not enough air to push back, the momentum will force the tire and metal rim to sandwich together, or bottom out. This will pinch your inner tube, punching two holes on either side of the tube. It looks like a snake bite.

Worse yet, tire pressure holds the inner tube in place between the wheel and tire. If there’s no pressure, your tube will wiggle around inside.

You’ll notice this most when taking a sharp corner. Your bike will squirm. Not good at high speeds. So pump, pump, pump it up.

Finding a Balance

A close-up picture of an inflated bicycle tire.
Make sure you find the right tire pressure. Too much and too little air can slow you down.

So how much air should you put in your tires?

Look at the side of your tire. You’ll find “psi” (pounds per square inch) and “BAR” (barometric pressure), each with a number range in front. (Imperial unit countries use psi. Metric countries use BAR.)

These numbers state the minimum and maximum amount of air you should place in your tire.

(Note, the inner tube doesn’t have a psi limit because it conforms and presses out against the tire. The tire holds the pressure.)

Where should you place your tires in the range? Simple answer: in the middle.

Complicated answer: depends on three factors.

Tire Width

Narrow  road bike tires need lots of air. Wide mountain bike tires need less. Why? Volume, baby.

Narrow tires have less mass. There isn’t much cushion. Your tire will bottom out if you strike a curb without a strong phalanx of air to push back.

Wider tires have a larger volume of air. They can get away with less pressure. The extra mass of rubber and air absorb and disperse jolts of energy from roots and rocks and whatever.

Total Weight

Set your tire pressure to achieve a 15% drop in the height of a tire.

Take an average adult road bike. Pump the tires to the middle of its recommended psi range and drop a kid on the saddle. The tire won’t compress much. Maybe a sliver. 2%.

Take the kid off and drop loaded panniers and a bodybuilder on. The tire will bottom out. 97%. Just rubber sitting on metal.

The pressure in your tire pushes back against the total weight of the rider, bike, and gear attached. More weight needs more air.

Weight Distribution

Without panniers or bags attached to the bike, your rear wheel usually carries 55% of the total weight. Your front wheel hauls 45%.

Once you find your ideal psi, add about 5% more pressure (multiply by 1.05) to your rear wheel. Take away 5% from your front wheel (multiply by 0.95).

If you loaded your bike with panniers, handlebar packs, and a saddle bag, guesstimate. What percentage of the total do you think each wheel’s carrying? Then do the math.

Tire Pressure Chart

Check out our tire pressure chart below. Though not intended for all tires, it’ll point you in the right direction.

For further info on tire pressure, watch this video or read this guide.

Road Bike Tire Pressure Chart
Hybrid Bike Tire Pressure Chart
Mountain Bike Tire Pressure Chart

Test the Brakes

A picture of bike brakes and tire rim.
Make sure your brakes are tight and positioned on the wheel correctly.
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What’s the most important part of your bike? Derailleurs? Crankset? Chain? No. It’s the thing your spouse cuts to cash in your life insurance policy. The brakes.

Both the Gyeongbuk and Gangwon Bike Paths have steep descents. Saejae has two mountains. You don’t want your brakes to overheat or fail halfway down.

So check them before heading out.

Note, in this article, we’ll discuss rim brakes. Read this to learn more about disc brakes.

Give It a Test

To test your brakes, grab your brake levers. Push, then pull your bike. The front and rear wheels should stay locked and lift off the ground.

No? The wheels won’t lift. The bike skips forward. Well, you’ve got one or two common problems. Let’s fix them before the ink dries on your insurance policy.

Adjust Cable Tension

Problem one: your brake cables could be loose.

Your brakes rely on the correct amount of tension, or cable length, to pull the brake calipers onto the rim of the wheel. If there’s too much, your brakes will rub against the rim as you ride. If there’s not enough, the brake pads won’t produce the friction needed to slow down.

Overtime, your brake pads wear down. This increases the distance between your brake lever and the caliper. You’ll notice you need to pull the brakes more before you feel the bike slow.

How do you fix it? Adjust the tension in your cables.

Barrel Adjuster

The simplest way to increase cable tension: screw the barrel adjuster.

You’ll find the cylindrical bead somewhere along the brake cable — near the shifters or on the brake calipers. This is the barrel adjuster. Turn it counter-clockwise half a turn. It’ll tighten the cable and move the brake pads closer to the rim.

Now grab the lever of the brake you adjusted. It’ll feel tighter. It won’t pull back as far.

Try to lift the wheel off the ground by pushing your bike forward or back. It still won’t hold? Add more tension. Screw the barrel adjuster half a turn.

A picture of bicycle rim brakes with the barrel adjuster circled.
Screw the barrel adjust above your rim brake calipers to adjust the dial in the right tension in your brake cable.

Try to lift the wheel off the ground by pushing your bike forward or back. It still won’t hold? Add more tension. Screw the barrel adjuster half a turn.

Cable Reset

You’ve turned the barrel adjuster as far as it can go? It still won’t shift? Reset the cable.

First, unscrew the barrel adjuster all the way clockwise, then counter-clockwise a turn. This’ll give you room to either tighten and loosen once you reset the cable.

A picture of a bike's brake cable released from its bolt.
Reset the cable if you can't dial in the right amount of tension with the barrel adjuster.

Now, break out your hex wrench. Unscrew the bolt holding the cable to the brake calipers. The cable will detach and the calipers will spring open.

Grab either end of the calipers. Pull them together against the wheel. Now, back the pads off the rim, leaving a few millimeters between.

Re-tighten the bolt that holds the cable. Turn the barrel adjuster to dial in the correct tension.

Wheel in the air? Give it a spin. Back off the tension if the pads rub the brakes.

Brakes still catching on your wheel? You might have an alignment issue.

Caliper Alignment

Sometimes rim brakes get knocked out of place. The brake calipers spun in the frame. One brake pad sits closer to one side of the rim than the other.

You can push the calipers into position by hand. Just nudge them so there’s equal distance between both pads and the rim. 

Pull the brake lever to test. If the brakes fall back into misalignment, take out your hex wrench again.

A picture of brake misaligned calipers on a bicycle.
If you have rim brakes, make sure the brake pads are equidistance from your wheel..

From behind, loosen the bolt that attaches the brake to the bike frame. Gripping the brake lever, re-tighten the bolt.

Let off the brake lever. Check for equidistance.

Brake Pad Alignment

Look at the shape of the brake pad on your rim brakes. You’ll see a slight curve. The arc follows the circular shape of the wheel.

A picture of a misaligned brake pad on a bicycle wheel.
Make sure your brake pads are lined up over the metal rim of your wheel.

When you pull the brake lever, the brake pad should only contact the metal rim of your wheel. If it snags the rubber of the tire, you’ll lose stopping power.

Are your pads off kilter? Pull your hex wrenches out. Loosen the bolt that attaches the brake pad foot to the brake calipers.

Lightly pull the brake lever. Maneuver the brake pad so it only touches the metal rim of your wheel. Re-tighten the bolt.

Replace Brake Pads

Like all of us, brake pads have a lifespan. They wear down from years of stress. If you hear squeals when braking, find a nice farm where they can run free and play. Replace them.

Rim brakes have pads with three vertical grooves. Change your pads when the grooves run shallow or you can’t spot them at all.

(Replace your disc brakes pads if you spot a millimeter or two of padding left.)

With cheaper rim brakes, you must replace both the foot and the brake pad. Better rim brakes allow you to unscrew a tiny bolt with a hex wrench and slip in a new brake pad.

Read more about brake pad replacement here.

A picture of a bicycle's rim brakes and brake pads.
Replace your brake pads if they're worn down. How can you tell? Do you see those grooves on the pad? No. Replace them.
M Check

An M-Check is a checklist that verifies the safety of a bike. Its name comes from the M shaped pattern you take while inspecting your bike: front to back; down, up, down, up, down.

The check will take you on a tour of your bike. It’ll help you tighten every bolt, properly seat every wheel, and spot every deformation.

Here is the checklist.

Adjust the Saddle

A picture of a bike saddle.
To save your back, legs, and rear, adjust the height, tilt, and forward positions of your saddle.
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Time and distance amplify. A small rock in your shoe becomes Hattori Hanzō steel. A weighty backpack transforms into a Sisyphean boulder. And a maladjusted saddle (seat) brews an achy breaky cocktail of pain in your arms, knees, and butt.

A lot of calculations go into finding the right saddle position. You can find exact measurements with online guides, videos, or by visiting your local bike shop. 

If you go the DIY route and ballpark your measurements, it doesn’t take many tools to dial in the right saddle position for you. Check out our guide.

Saddle Height

No matter the bike you ride (road, hybrid, mountain), you can prevent pain in your knees by adjusting the height of your saddle. 

Your knee should bend a 25% to 35% angle when you extend your leg on a downstroke.

If your seat sits low, you’ll put a lot of excess pressure on your knees. If your seat perches too high, you’ll overextend your hips by reaching on every downstroke.

A gif of a bicycle seat post and saddle going up and down.
Make sure your saddle is the correct height. Too low? you'll hurt your knees. To high? You'll wreck your hips.

You can avoid early hip and knee surgery by adjusting the seat post up or down.

Height Adjustment

Saddles attach to your bike’s seat post. The seat post drops into your frame’s seat tube.

Leisure bikes use quick-release clamps for riders to adjust their seat height on the fly.

A picture of a bicycle's seat post collar highlighted.
To shift your saddle up or down, loosen the color at the base of the seat post. Beware, you might need a set of hex keys.

Most high-end bikes fix the seat posts in place with a seat clamp, a collar that sandwiches the bike frame and seat post. A hex bolt tightens the clamp.

To find the right saddle height, climb aboard your bike. Holding a wall or post, place your feet on the pedals. Drop one foot to its lowest position..

Feel like you’re reaching? Or does your extended knee rest at ninety-degrees?

Climb off. Undo the seat clamp and slide the seat post up or down.

A centimeter adjustment has a larger effect than you’d imagine. So make incremental changes until your extended knee comes to a comfortable, thirty-something-degree angle. Then lock it down.

(If your seat tube is an actual tube shape, make sure the saddle sits straight. You don’t want to ride a couple hundred kilometers on a cock-eyed seat nose.)

Saddle Tilt

No matter the bike you ride (road, hybrid, mountain), you can prevent pain in your knees by adjusting the height of your saddle. 

Your knee should bend a 25% to 35% angle when you extend your leg on a downstroke.

If your seat sits low, you’ll put a lot of excess pressure on your knees. If your seat perches too high, you’ll overextend your hips by reaching on every downstroke.

A GIF of a bicycle saddle tilting up and down..
Place a bubble level on your saddle. It should sit flat. If it doesn't, you'll fear your rear after a long ride.

Is your backside sore after a long ride? Check the angle of your saddle.

If your saddle tilts forward, your body weight will shift forward. This puts extra strain on your hands and shoulders as they grab the handlebars.

A backward angled saddle alters your hip position. This affects your pedaling motion and leads to a sore waist after long rides.

What’s that golden angle? Saddle makers design their product to support the average rider when the saddle sits flat, parallel to the ground.

Riders come in different shapes and sizes, though. So bike fitters adjust the saddle angle so your sit bones carry 90% of the weight. Aided by machines, they’ll make half a degree change.

We recommend that you adjust your saddle to a flat position. Make fractional adjustments to improve your comfort.

Tilt Adjustment

To adjust your saddle angle, first make sure your bike rests on level ground. Drop a bubble level on your saddle, nose to tail. (You can download a bubble level app for your smartphone.)

If your saddle has a curved design, place a board on the seat to create a flat surface.

Does the bubble float in the middle? Yes. You’re golden. No? Let’s make some adjustments.

There are a variety of systems to mount saddles to seat posts. Some use a clamp with one bolt. Others use a two bolt clamp. They all have one thing in common: they required a hex wrench.

Loosen the saddle and maneuver it so the bubble floats in the middle. Re-tighten the bolt and hop aboard.

Go for a ride and bring your hex wrenches. Hop off if something feels amiss. Make small, one-degree adjustments. Repeat until it feels right.

Note that saddles aren’t La-Z-Boys. You’ll never eliminate all pain. So don’t waste time fussing with the exact angle of your saddle.

Saddle Position

A GIF of a bicycle saddle sliding forward and backward..
Make sure the forward and backward position of your saddle is set correctly. This will reduce strain on your shoulders and hands.

No matter the bike you ride (road, hybrid, mountain), you can prevent pain in your knees by adjusting the height of your saddle. 

Your knee should bend a 25% to 35% angle when you extend your leg on a downstroke.

If your seat sits low, you’ll put a lot of excess pressure on your knees. If your seat perches too high, you’ll overextend your hips by reaching on every downstroke.

While you’re changing the tilt, we’ve got one more saddle adjustment: fore-and-aft saddle position.

The forwards and backwards position of your saddle affects the angle in which your hands grab the handlebars.

Saddle too forward? It’ll shift your body weight onto your hands and arms, causing aches in your palms and stress in your wrists.

Saddle too far back? You must reach farther for your handlebars. This strains your shoulders.

Fore-and-Aft Adjustment

You’ll need to do a bit of measuring before you adjust the fore-and-aft position of your saddle.

Sit on your bike. Hold the wall or get a friend to stabilize you. Rest both feet on your pedals (or clip in). Position your crankset’s crank arms so they are parallel to the ground.

Now take a plumb line (a string with a weight at the end) and hold it to your knee. The line should descend by (through) the ball of your foot.

If the plumb line falls behind the ball of your foot, slide the saddle forward. If the line drops in front of your foot, slide the saddle backward.

Most saddles have two mounting rails. Loosen the seat post clamp and slide the saddle forward or back. Re-clamp and measure again.

Watch this video and check out this guide for more detail on getting the perfect saddle position.

Lube the Chain

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“A wet chain is a healthy chain.” What does that mean?

A picture of bike chain lube.
A bottle of lube will keep your chain and gears spinning.

Every machine with moving metal parts needs lubricant. Just ask the Tin Man. Oil reduces friction between parts and ensures smooth operation.

Bike chain lubricant serves two purposes. First, the lube keeps the metal chain links from grinding against each. Second, it keeps water out.

Because oil and water don’t mix, bike lube stops water from sneaking between the links. If rain gets in, rust will follow. That extra grit and grinding will seize the linkages and damage other bike components. 

The wet from wet chain doesn’t refer to water. It means keep your chain lubed.

The Two Lubes

When shopping for chain lube, you’ll find two types: wet and dry lube.

Dry Lube

Dry lubricant is for dry conditions. Think clear or cloudy days. No rain or snow.

The consistency of water, dry lube treats your chain the best. It doesn’t trap dirt and reduces friction more than wet lube.

However, because of dry lube’s low viscosity, rain or normal riding will clear it away.

Dry lube requires fresh application every 80 to 150 kilometers (50 to 100 miles).

Wet Lube

Manufacturers design wet lubricant for wet conditions. Its consistency is thicker than the dry lube. So it sticks around longer. Use it for rainy rides or when you can’t predict the conditions. 

Wet lube’s high viscosity picks up grit and keeps it around. Overtime, the dirt and flotsam will wear down your parts.

Apply a fresh coat of dry lube after 160 km to 200 km (100 to 125 miles)

Lube Application

A picture of a bike chain being lubricated.
After you lube your chain, let it sit for ten minutes. The lube will sink into the links. then wipe the excess off the outside of the chain.

If you don’t have the time or ability to clean your chain, wipe your chain off with a dry rag and apply a fresh coat of lube.

For better performance and a longer life, however, the best way to lubricate your chain is after a good cleaning.

Clean the Chain

If you can’t remove your chain using a quick link, a chain cleaner tool will get your chain sparkling clean while still attached to your bike.

Put some degreaser or isopropyl alcohol on a disposable rag or in the chain cleaner tool. Suspend your bike or turn it on its handlebars.

Pedal backwards with the rag lightly held around the chain or chain cleaner attached.

Once everything is shiny, rinse the chain with warm water and soap. This removes extra degreaser or alcohol. If it remains, it’ll stop your new lube from sticking to your chain.

Next, dry your chain with a rag.

Apply Chain Lube

Shake your bottle of bike lube, then press the nozzle against your bike chain. Pedal backwards and gently squeeze the bottle so lube drips drop by drop.

Run the chain around once or twice. Make sure you get a drop of lube on each chain link. (Some people painstakingly apply one drop to each chain link.)

Let your clean, lubed chain sit. Grab a cup of coffee as the oil seeps down into the linkages.

After fifteen minutes, return with a fresh rag and wipe the outside of your chain. This removes excess oil that will pick up dirt and stain your leg black.

Check out this tutorial or watch this video for more instruction.

Check the Shifting

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If you ride a fixie (fixed gear bike), keep sipping your craft beer. You can skip this part. For the rest of us, gears help climb hills and maintain speed on flats.

Read on and learn how to inspect and tune up our gears.

Front Derailleur

A picture of a bike's front derailleur.
Your front derailleur shifts the chain up and down your crankset's chain rings.

Your front derailleur is the spring-loaded metal cage thingy that sits above your crankset. It’s responsible for pushing your chain up and down the chainrings (geared rings).

Say your cable snaps and your front derailleur springs back to the lowest gear. You can still climb hills. But you’ll tread water on flat ground. Watch out for slow moving tractors!

Check It Out

Before a bike journey, inspect your front derailleur. First, hang or prop your bike so your rear wheel hovers an inch above the ground.

(You can flip your bike over and stand it on its handlebars. But this reverses everything and makes it difficult to get to the limit screws.)

Now pedal by hand. Set the rear derailleur to a middle gear with the right-hand shifter.

A picture of hex keys and a flat head screwdriver.
To adjust your front and rear derailleur , all you'll need are a set of hex keys and flat head screwdriver.

Shift your front derailleur up and down. Your front derailleur should push the chain to each chainring without catching or falling off.

Limit Screws

The chain doesn’t hop smoothly between rings? First check the limit screws. These two small screws sit on the top of your front derailleur.

A picture of a front derailleur and its limit screws.
The front derailleur's limit screws set limits for where the derailleur's cage rests and how far the cable can pull the cage and chain.

The L-screw (low limit screw) limits how far the front derailleur sits over the smallest chainring. If the screw lets the derailleur cage fall too far back, it will push the chain right off the crankset, onto your bottom bracket.

The H-screw (high limit screw) stops the shifting cable from pulling the derailleur too far out. If the H screw doesn’t limit the derailleur cage, it’ll push the chain off the other side of the crankset, onto your crank arms.

Some bike component manufacturers place the “L” limit screw closer to the bike frame. Others don’t. So test which screw does which before making major adjustments.

Low Limit Screw

To adjust the limit screws, you’ll need a smaller screwdriver, #2 Phillips or #2 slotted. Multi-tools have one that’ll get the job done.

While pedaling, shift both the front and rear derailleurs to their lowest gears. The chain should sit on the smallest chainring in the front and the cassette’s largest cog in the back.

Give the cable attached to the derailleur a little pluck. It should vibrate like a deep bass guitar string. Little to no tension.

If it smacks the bike frame or sings falsetto, turn the barrel adjuster on the down tube. Twist it counter-clockwise to tighten the cable. Clockwise to loosen it.

Doesn’t work? Too much slack or tension? Take out your hex keys and unscrew the bolt holding the cable. Pull it tight by hand and re-tighten the bolt.

A picture of a bicycle's front derailleur's barrel adjuster.
Your front derailleurs barrel adjuster adds or reduces tension on the cable. It usually sits on the bottom of your bike's downtube.

Now stand above the front derailleur. Look straight down. You should see a millimeter or two gap between the metal cage and the chain.

Too much of a gap? Turn the L-screw clockwise until the cage hovers next to the chain. No gap? Loosen the L-screw. The cage will back off the chain.

Now pedal. Listen for the sound of the chain rubbing against the cage. Turn the L-screw clockwise until the sound dissipates.

High Limit Screw

While pedaling, shift into the highest gear on your front and rear derailleurs. Your chain will sit on the largest chainring in the front and cassette’s smallest cog on your rear wheel.

Won’t shift? You could have one or two problems.

A picture of someone adjusting the limit screws on a bicycle's front derailleur.
Adjust the low and high limit screws on your front derailleur so your chain doesn't fall off the chain rings.

First, take your screwdriver and turn the H-screw counter-clockwise until the cage stops moving.

Pedal again. Chain still won’t jump into the largest chainring? Add tension to the front derailleur cable with the barrel adjuster. (It’s easier to add tension when in the lowest gear.)

Once the chain jumps up to the big chainring, stand over your front derailleur and look down. The outer cage should hover a millimeter or two off the chain.

Large gap? Turn the H-screw clockwise until the cage sits next to the chain. They’re touching? Turn the H-screw counter-clockwise until the cage gives your chain breathing room.

Pedal. Listen for sounds of the chain rubbing the cage.

Check out this video and read this guide for further instruction.

Rear Derailleur

Your rear derailleur guides your chain up and down your rear cassette.

Indexing

A picture of a rear derailleur on a bicycle.
Your rear derailler shifts your bike chain up and down the cassette gears on the rear wheel of your bike.

Every time you shift down, the shifters on your handlebars gobble up a set amount of cable. This nudges the derailleur to the right and guides your chain to a larger cog (lower gear).

When you shift up, the reverse happens. The shifter releases a bit of cable and the spring in your derailleur pushes your chain to a smaller cog (higher gear).

When the cable tension is off, the shifter will pull your chain halfway between the cogs. Or they’ll guide your chain off your cassette.

Indexing is when you dial in the right amount of cable tension. We already indexed your front derailleur. Now let’s do the rear.

Check It Out

Prop your bike so the rear wheel hangs an inch off the ground. Now run through the gears on your rear shifter. They should smoothly jump up and down your cassette.

They don’t? Your chain gets stuck on the second largest cog? We can fix that.

First shift the front and rear derailleurs to their highest gears. The largest cog in the front. The smallest cog in the back.

Pluck the cable holding your rear derailleur with your fingers. Like your front derailleur, it should feel like a loose E string on a bass. Not tight. Not droopy.

Cable feels taut? Dial back the tension. Turn the barrel adjuster, located where the cable first enters the rear derailleur, clockwise.

Is the cable too slack? Reset the cable.

Take out your hex wrenches and unscrew the cable bolt. Pull the cable tight by hand and re-screw the bolt.

High Limit Screw
A picture of a bicycle's rear derailleur with its limit screws highlighted.
Turn the limit screws on your rear derailleur to line up the jockey wheels under the lowest and highest cassette cogs.

Every time you shift down, the shifters on your handlebars gobble up a set amount of cable. This nudges the derailleur to the right and guides your chain to a larger cog (lower gear).

When you shift up, the reverse happens. The shifter releases a bit of cable and the spring in your derailleur pushes your chain to a smaller cog (higher gear).

When the cable tension is off, the shifter will pull your chain halfway between the cogs. Or they’ll guide your chain off your cassette.

Like the front derailleur, you’ll find a pair of limit screws on the topside of your rear derailleur.

The H-screw (high limit) stops the chain from falling off the right side of the cassette. The L-screw (low limit) prevents the derailleur from spitting the chain into the spokes of your wheel.

Some derailleurs put their H-screws on the right. Others switch it up. Give each screw a test turn. In your current gearing, the screw that makes the rear derailleur shift first is your H-screw.

Line your eye parallel to the cassette cogs. Turn the H-Limit screw so that the jockey wheels on your rear derailleur line up directly under the smallest cog.

Now pedal and shift down one click. Your chain won’t shift to the next cog on your cassette yet.

Turn your barrel adjuster counter-clockwise in ¼ turn increments. Watch the chain. Stop when it hops one cog to the left.

No luck? Try another quarter turn. Repeat until the chain jumps into the second cog.

Now shift down one more click. If the chain doesn’t hop into the third cog, give the barrel adjuster another ¼ counter-clockwise turn.

A picture of a hand turning the rear derailleur's barrel adjuster on a bicycle.
Your rear derailleur has two barrel adjusters. One perches on the frame's downtube. The other sits where the cable enter the rear derailleur.

Once you dial in the correct tension, run through your gears. Make sure the chain hits all the cogs, turning the barrel adjuster when needed.

Low Limit Screw
A picture of a screwdriver turning the limit screws on a bicycle's rear derailleur.
Use a flat head screwdriver to turn your rear derauiller limit screws. If the screws aren't set correctly, your chain will fall off your cassette.

Every time you shift down, the shifters on your handlebars gobble up a set amount of cable. This nudges the derailleur to the right and guides your chain to a larger cog (lower gear).

When you shift up, the reverse happens. The shifter releases a bit of cable and the spring in your derailleur pushes your chain to a smaller cog (higher gear).

When the cable tension is off, the shifter will pull your chain halfway between the cogs. Or they’ll guide your chain off your cassette.

Now let’s tackle the L-screw. Shift to the lowest gear (highest cog). Won’t go?

If you can’t shift to the highest cog, your L-screw (low limit) might not be giving your cable enough rope to shift over the last cog.

Does your chain jump off of your cassette and into your wheel? Well, your L-screw’s might be a little too permissive. It’s not stopping your shifter from yanking the derailleur too far.

Pedal and shift to the lowest gears on the front and rear derailleurs: the smallest chainring on the crankset. The largest cog on the cassette.

Stand behind the cassette and line your eye parallel with the cogs. Check to see that the rear derailleur’s jockey wheels line up over the largest cog on the cassette.

They don’t? Whip out your #2 Phillips or #2 slotted screwdriver.

Turn the L-screw clockwise to push the derailleur towards the cassette. Twist the L-screw counter-clockwise to release the derailleur, moving it towards the wheel.

Once you line everything up, shift through your gears once more. Listen for excessive noise.

For further info, check out this helpful guide or watch this instructional video.

What’s That Noise?

Everything’s indexed perfectly and I hear grinding. What’s that noise?

Shift to the highest (largest) chainring on your crankset, then to lowest (largest) cog on your cassette. Glance down at your chain. Look funny?

Pedaling on the two largest gears puts a lot of stress on the chain. Running it at such a severe angle also causes the chain to rub against the inner cage of your front derailleur.

The reverse is true. Shift to your lowest (smallest) chainring in the front and highest (smallest) cog in the back. The angle of your chain will scrape your front derailleur cage.

That’s your problem! What’s the solution? Don’t do that.

When on the largest chainring, stay off the largest two cogs. On the smallest chainring, keep away from the two smallest cogs.