Bike Heavy-Duty Derailleur (Beginners Guide)

Bike Heavy-duty Derailleur

The bike derailleur looks like a small tool, but its function cannot be overemphasized. The derailleur is one of the crucial parts of your bike since it helps you move your gear easily.

It also helps you tackle any slope you come across while cycling. You may read more about whether Cycling Count As Steps On Garmin?

But choosing the right derailleur can be very challenging, especially for a heavy-duty bike. This article will let you know everything about choosing a heavy-duty bike derailleur.

A bike heavy-duty derailleur is responsible for shifting your bike silently and rapidly. A bike derailleur is a bike gearing ratio system equipped with a chain, numerous sprockets with varying lengths, and a tool to move the sprockets. 

Uses of Bike Heavy Derailleur

Bike Heavy-duty Derailleur

The mountain bike derailleur is for changing the gears’ positions through the sprockets’ chain movement.

They also allow you to climb bigger hills and mountains and ride your bike for a long time. There are two types of derailleur; rear bike derailleur and front bike derailleur.

#1. Bike Rear Derailleur:

The bike’s rear derailleur functions in two ways:

  • It keeps the chain tense
  • It switches the mountain bike gear

Regardless of the gear you switch to, the bike’s rear derailleur will regulate its position to maintain the chain tension.

Placing your chain on the front and back biggest chain will allow it to be wrapped around the sprocket, leaving the derailleur with limited slacks to handle.

But placing the chain on both the front and back at least sprockets will give it more slacks to handle. 

The bicycle’s rear derailleur switches the gear by thrusting the chain end sideways. As a result, the tension is placed on the chain roof when you step on your bicycle’s pedal.

The reason is that the leg force you applied while pedaling the bike pulls the chain roof tight.

The bike chain roof is accountable for transmitting tension on the front sprockets.

The rear bike derailleur reduces the load on the bottom of the chain by ensuring that the chain undergoes light friction.

As a result of this reduction, your rear bike derailleur will allow the chain to move about when you put more force on your bike.

#2. Front Derailleur

The front derailleur is responsible for shifting the chain within the three sprockets in the front. This device’s major role is to move the chain roof under tension while you are pedaling.

So you have to lessen the pedal load to switch sprockets in front.

Will Any Derailleur Fit My Bike?

Not just any derailleur can fit your bike. Choosing the wrong derailleur can lead to ineffective shifting and a poor ride. When choosing a derailleur, you need to consider the cage length.

This device comes with numerous cage lengths, and not just anyone fits your bike.

A cage length is a space between the upward and the downward pulley. The cage length helps the derailleur haul the chain stretch, which results from moving the gears.

How Do I Know What Derailleur I Need?

The cage length is not the only factor to be considered when choosing the derailleur you need.

There are other aspects to consider when choosing compatible mountain bike derailleurs. They are;

#1. Check the Smallest and Largest Cog.  

Using an 11 to 23 and above cassette requires a long cage derailleur. The reason is that when you shift from the smallest to the largest gear, your chain ring will experience a slack.

A short cage can not handle this slack.

#2. Examine the Size of Your Chain Ring 

The length of your derailleur cage can also be deduced by the various sizes of the chain ring. When your bike comes with an 11-20 gear ratio cassette, it will use a derailleur with a short cage.

However, almost all mountain bikes have bigger cassettes and larger gear ratios. So the mountain bike derailleurs must come in long cages.

Road bikes utilize a short cage. However, road bikes equipped with triple chainsets are more compatible with derailleurs with long cages.

When you don’t know your bike cage length, always go for a derailleur with a medium length. The medium-length can work on almost any bike.

If you are still uncertain whether the derailleur is compatible with your bike, ask your mechanic for guidance.

What Do the L and H Mean on a Derailleur?

A derailleur owns two types of limit screws: the high (H) and low (L) limit screw.

The H- screw regulates the exterior part of the derailleur, while the L- screw governs the inner part, and their region varies with the manufacturer. 

When your limit screws are too tight, it lessens the speed at which you travel, but if the screws are loose, it enhances the travel speed.

Some adjustments can be made when your limit screws are too tight.

#1. How to Adjust H- screw

  • Change the direction of the chain to the exterior chainring and rear sprocket.
  • Examine the friction on the rear interior wire. If the friction is on the wire, it will affect the H- screw setting. To remove the tension on the wire, you need to turn the adjusting- barrel clockwise.
  • Whirl your pedal at a quick meter manually. It should be turned at about 60 rpm and above.
  •  Just pull the inside wire when you want to adjust one sprocket inwards. Regulate the tug on the interior wire until your chain cycles silently on the second sprocket. Then release the interior wire to move back to the exterior sprocket. Make sure you take note of the shift.

There are two important conditions to take note of while adjusting the H- screw;

  1. The external change from the second sprocket to the outermost sprocket.
  2. The way the chain rides on the outermost sprocket.
  • If the outer shift is satisfactory, tighten the H-screw by turning it ¼ clockwise and continue checking the shift until it is slow. Also, when the chain on the least cog continues making a noise from the second sprocket inside, it indicates a too-tight H-screw.
  • When an H-screw is overly tight, adjust the screw ¼ turn, then check the shift. Then, continue correcting the shift by ¼ turn. When there is no sign that your screw is too tight, it shows that the H-screw is in its tightest setting. 

#2. Adjusting the L-screw 

  • Change your bike to the middle chainring and the second inner rear sprocket.
  • Ride the bike at 60 rpm and above at a quick pace.
  • Hand pulls the wire to adjust the derailleur sprocket inside.

Always take note of the following two conditions when adjusting your L-screw;

  1. The interior changes from the second inner sprocket to the innermost sprocket.
  2. The way the chain rides on the innermost sprocket.
  • When the transition is done well, tighten the screw by ¼ turn and repeat the shift. Then proceed with the tightening until there are signs of a too-tight screw. The chain will not finish its shift despite the coercion on the inner wire. Instead, the chain shifts sluggishly or makes a loud noise when riding on the innermost sprocket. These signs indicate that the L-screw is too tight.
  • Loosen the screw by ¼ turn when there is a sign of a too-tight screw, then recheck the shift. Continue freeing the screw until the signs disappear. After the disappearance of the signs, the limit screw setting is finished.

How Long Does a Rear Derailleur Last?

The bicycle rear derailleur lasts for a long time even if you ride your bike often. The jockey wheels are always the first to wear out after some 10,000km compared to the other parts of the system.

The system’s longevity depends on the model, the manufacturer, the distance covered by year, and the weather conditions you ride.

What Is the Difference Between a Long and Short Cage Derailleur

Long cage derailleur Short Cage Derailleur 
They are mostly used for bikes with a 27 to 30 gear ratioIt cannot be used for bikes with gear ratios between 11 to 20
Sometimes the chain can slack and kick the frameBetter chain tension that prevents the chain from hitting the frame
As a result of the cage’s unwanted movement, there might be a decrease in the shift performance on irregular topographyThere is an accurate shift despite any irregular topography.

Which Is the Best Rear Derailleur?

There are different brands of mountain bike derailleurs. But the best mountain bike derailleur brands are:

  • Shimano zee freeride
  • Microsoft XCD
  • Shimano Deore XT long cage 
  • Sunrace MZ900
  • Sram GX eagle
  • Sram XX1 eagle AXS
  • TRP TR12

To know the price and more details about each derailleur View Amazon.


Bike derailleurs are very important in your bike and should be well maintained. Make sure you replace them when damaged.

And get the ones that are compatible with your bike for accurate shifts.

Then, after going through the various factors highlighted in this article and knowing about mountain bike derailleurs, you can select one for your bike.

Josh Matthews

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