Integrating a 3x FD In a 2x Drivetrain (High IQ Tactics)

from Rookie’s Keyboard

Hello, friends

I’ve been on fire lately. Despite pulling pretty long hours at the courier warehouse where I’ve worked for a while, I have a lot of energy. But honestly, sometimes, we have pretty “low traffic” hours there.

Today, I will tell you a little technical secret that the bicycle world doesn’t want you to know (semi-serious here). 

Wait for it….

You can effectively integrate a 3x front derailleur in a 2x drivetrain. You don’t have to buy a separate unit. 


The key to performing this mod is setting the limit screws of the derailleur to the correct position.

Technically, this is a 2x FD, but its architecture makes it very easy to understand the operation of the limit screws.

Derailleurs don’t have clicks (unlike shifters). They have an amplitude (swing). If you grab a front derailleur, you can move its cage over that amplitude pretty easily. And you will see that it’s not segregated into steps. It’s a smooth motion.

The limit screws limit (as expected) that movement.

The goal of the limits screws is to stop the derailleur from dropping the chain into the frame or beyond the largest chainring.

The limit screws have an “L” and “H” label – short for low and high.

The “L” screw limits the inward movement towards the frame. The “H” screw limits the outward motion away from the frame.

Tightening the screws reduces the movement of the cage in the respective direction; untightening increases it.

Option 1: 

If you have a set of 3x cranks (three chainrings) and want to transition to a 2x setup, one of the options is to just drop the large chainring and replace the other two with bigger ones. This method will give you a fairly balanced gear range. 

And if you choose that route, the L screw shouldn’t require re-adjustment as the position of the smallest chainring is the same. The H screw, however, will have to be tightened so that the derailleur doesn’t overshift in an attempt to cover a large chainring that no longer exists. 

Option 2: 

The other alternative would be to replace the cranks and chainrings with a dedicated 2x combo. In that case, you will still have to adjust the H screw as the position of the new large chainring won’t match that of the old, and an overshift can occur. 

You will also have to play a bit with the L screw to acquire a perfect shift from the small to the large chainring.

This method is somewhat cleaner and more aesthetically pleasing. But the downside is that you have to buy new cranks and rings. 

On 3x shifters… (this is very important information – don’t skip it)

I’ve already presented the main idea. But there are very important details about 3x shifters that you have to be aware of.

Using a 3x Shifter With 2x Cranks

Chances are that many of you would want to use the original 3x shifter which offers two shifts (one from the smallest ring to the middle; and one from the middle to the largest chainring) to save money and make the procedure faster and simpler. 

This can be done, but you have to be aware of a few specifics. 

The two shifts on a 3x drivetrain are of different lengths due to the distance between the chainrings.

The distance between the smallest chainring and the middle chainring is longer than the distance between the mid chainring and the largest chainring.

Consequently, the first shift pulls 11mm of cable whereas the second 7mm. 

Meanwhile, the distance between the small and large chainring on a 2x drivetrain is equal to that between the mid and large chainring on a 3x setup. 

What does all of this info tell us, rookies?

Well, if you are going to combine a 3x front shifter with a 2x crankset, you have to use the second shift of the shifter as your main one. Otherwise, the shifter will overshift.

How do you do that?

Simple. Make the first shift (from smallest to mid) and then adjust the L screw to the point where the first shift causes virtually no movement of the derailleur. That way even if you accidentally use the first shift, the chain won’t go into the bottom bracket.

You can also use a 3x shifter to trim the derailleur. Trimming of the derailleur refers to controlled and deliberate small movement of the cage made to eliminate rubbing against the chain and increase the number of viable gear combinations. 

A combo consisting of a 3x shifter + 2x cranks allows you to make your own “ghetto version” of a trim function. 

Here’s how – Once you adjust the L screw and the H screw as explained above, loosen the L screw a bit so that the chain moves slightly with the first shift that is originally designed to switch between the smallest and the mid-chainring of a 3x setup.

The chain should remain on the chainring. The movement is minimal.

In other words, the shift should not trigger a shift AT ALL – just a small movement of the derailleur cage.

When using the shift downwards, it will move the derailleur’s cage ever so slightly closer to the frame and increase the space between the inner wall of the cage and the small chainring. 

This additional space will allow you to combine the small ring with the larger sprockets without chain rubbing.

When shifting up, the derailleur’s cage will move slightly away from the bike and create extra space between the outer wall of the cage and the small chainring. This will make it possible to shift to the smallest cog at the back without experiencing chain rubbing. 

You can also do something similar when using a 3x shifter and a 3x crankset “hacked” into a 2x setup. 

The difference is that you will have to play with the second shift (the one that originally moves the chain from the mid to the largest chainring) and the H screw.

Also, you will be able to trim the derailleur only when it’s on the new larger or the previous mid-ring.

Is it worth it? 

Personally, if I already have a working 3x setup in good condition, I wouldn’t disrupt it and switch to a 2x mod. 

But if the chainrings are already near their end, I don’t see the issue. You will save some weight (if that matters to you) and acquire a bike with a cleaner silhouette. 

Other notable advantages would be:

  • Saving some money

Let’s be honest, fellas. The main reason to hack a 3x derailleur into a 2x system is to save money.

  • Bash guard

In the past, MTB riders running 3x cranks hacked into 2x would remove the largest chainring and replace it with a bash guard which protects the chainrings and the frame from obstacles on the trail.

  • Going back is easy

If you preserve your 3x setup, you can switch to a 3x crankset whenever you feel like it.

And don’t forget that a 3x derailleur can be used on a 2x setup, but the opposite (2x FD on a 3x system) is not possible because 2x front derailleurs have a shorter cage making the shift from the small to mid cog prone to failure.

Ok, friends. 

It’s time for me to return to the warehouse.

Until next time,

– Rookie






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