The Dangers Of Shifting Both Derailleurs Simultaneously

The front and rear derailleurs are marvelous machines that allow cyclists to fine-tune their cadence and cover greater distances filled with more obstacles.

Hence, it is important to develop proper shifting habits. Failing to do so could result in sub-par performance, unnecessary fatigue, and technical difficulties.

One of the frequently asked questions in regards to shifting protocols is whether it’s ok to shift the front and rear derailleur at the same time.

Today, I’ll cover this topic.

Is shifting the front and rear derailleur simultaneously a bad practice?

Simultaneous shifting of the front and the rear derailleur is not a correct shifting technique and can cause unpleasant consequences. When the front and rear mech work at the same time, the chain loses too much tension, and you risk dropping it. This outcome can trigger a multitude of other problems. E.g., breaking the rear derailleur and possibly the wheel.

Simultaneous Gear Changing Disrupts the MECH Harmony

Concurrent shifting creates a bad synergy between the front and rear derailleur.

For instance, if you downshift to a lower chainring at the front, the chain tension drops during the shift. If while doing so you aggressively shift to a higher gear at the back (a smaller cog) too, the rear derailleur may fail to make up for the chain slack caused by the front shift.

As a result, the chain could drop off the front chainring and get stuck in the bottom bracket area.

Note: The terrain matters too. Simultaneous shifting while riding over a bumpy road greatly increases the possibility of dropping the chain as the bike will be vibrating.

You don’t even have to be mountain biking to experience this problem. In some cities, there are cobblestone streets that personally drive me crazy even though I ride a hardtail with fairly wide tires.

The bicycle in the image above is in 1×2 gear (the smallest chainring at the front and almost the smallest cog at the back). Note home much chain slack there is.

What Can Happen If My Chain Drops?

The aftermath that a dropped chain can cause is bigger than many people envision.

In the best scenario, you will only have to put the chain back on the chainring which can be fairly easy if the chain isn’t jammed badly.

If there’s no damage to the chain, you could proceed to recovery right away.

But if the chain gets caught between the cranks and the bottom bracket or between the chainrings, and you keep pedaling, you could destroy many of its links and render it useless.

If you are in the middle of nowhere, and you don’t have a spare chain, this outcome could greatly complicate your life.

Unfortunately, the damage could be even greater. For example, the chain may jam at the rear mech area and pull the derailleur towards the spokes of the wheel.

This development of events could destroy the chain itself, the derailleur, the derailleur hanger, the wheel, and potentially damage even the frame of the bicycle.

Thankfully, this scenario is fairly extreme, although it’s not unheard of.

If simultaneous shifting is no good, what would be the proper technique to double-shift?

If you find yourself in a situation requiring front and rear gear change, do one after the other.

For example, if you want to downshift at the front and upshift at the back, shift the front derailleur to a smaller chainring first and only then begin manipulating the rear.

This “delay method” is the safest way to “double-shift” as it avoids unnecessary stress on the chain.

With a little practice, the move will be happening in seconds and from the side it may even look like you’re shifting both derailleurs at the same time.

In what situations is double-shifting useful?

A sudden and unexpected change of the relief could necessitate a more extreme gear change. To cope with the situation as quickly as possible, the rider may find themselves double-shifting.

For example, if a sharp descent is followed by a steep ascent requiring you to be in the lowest chainring upfront, you may have to shift at the front and then upshift at the back to preserve your cadence.

The shifting at the back to a smaller cog (higher gear) is meant to preserve some of the momentum built up from the descent. After the inertia is gone, you’ll have to shift to a lower gear at the back (bigger cog) to keep climbing the hill.

If you wait and shift to the small chainring at the front when you’re already pedaling hard up the hill, you would be putting unnecessary strain on the drivetrain and increasing the chances of a derailleur malfunction due to the increased load on the system.

A downside of this method is the increased chance of cross-chaining – placing the chain on two gears strongly opposed to one another and thus creating a diagonal chain line. E.g., the smallest cog at the front and the smallest cog at the back.

The chain in the image above is cross-chained. (smallest chainring + 2nd cog)

A quality chain can sustain some cross-chaining, but there are other side effects too – you are losing pedaling efficiency while putting yourself in a situation complicating your future gear changes.

For example, if you put the chain on the smallest ring at the front and the back, and then you find yourself in need of a faster gear, you would have to upshift to the second chainring and then go all the way to the middle of the cassette to keep your cadence.

Planning Ahead is Key

Planning your gear shifts ahead of time according to the upcoming terrain as well as to your momentary physical capability is the textbook shifting method.

This technique minimizes the need for “surprise” shifts” and the possibility of mechanical problems.

Of course, planned shifting isn’t always possible. After all, cycling is a dynamic activity that puts you in unexpected situations fairly often.

Nonetheless, if you try to plan your shifts in advance, you’ll do it successfully more often than you may think.

Frequently Asked Questions

I’ve heard of people who shift the front and back gears simultaneously without problems. What’s up with that?

Simultaneous gear shifting does not guarantee problems, but it does increase the risk.

Even if nothing happens today, the habit of shifting the front and rear derailleur at the same time creates many future opportunities for a bug in the system to manifest.

All that shifting talk is confusing me. Is there a way to simplify things?

If you’re new to cycling, the material may be a little overwhelming, but inherently, the shifting etiquette is pretty simple:

  • Don’t shift gears if you are not moving (unless you have internal gears)
  • When you shift, don’t press hard on the pedals. Keep it soft.
  • Don’t put pressure on the chain until the shift is fully complete.
  • Plan your shifts before a change of the terrain rather than after.
  • Reduce cross-chaining to a minimum.
  • Don’t shift the front and rear simultaneously.

How to minimize cross-chaining?

Even though you could ride in all kinds of gear combinations, every chainring at the front of a triple system isn’t technically designed to work in conjunction with every cog at the back.

The gear combinations on a triple 3×8 set-up look a little something like this:

1 (smallest chainring) x 8 (biggest cog), 7, 6, 5

2 (middle chainring) x 6, 5, 4, 3

3 (biggest chainring) x 5, 4, 3, 2, 1 (smallest cog)

Note: Shifting to a larger or smaller chainring has a great effect on your cadence because the jump is big.

Consequently, to avoid abrupt cadence changes, you would often find yourself shifting up or down the cassette upon moving to a larger or a smaller chainring.

For example, if you are riding at 2×3, and then you face a hill and shift to the smallest chainring, you will also have to move to a bigger cog at the back.

Ultimately, with practice, shifting will become significantly easier than you think.

Nonetheless, if you’re tired of thinking about front derailleurs, you could consider looking into the 1×10,11,12 drivetrains as they eliminate front shifting.

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