The derailleur on a geared bicycle is a sensitive piece of equipment. It has to be in perfect alignment to shift smoothly and quickly. If it’s bent even slightly, the chain could start slipping, and the rider may fail to reach some gears.
How much force does it take to bend a rear derailleur? Not much. Damage can easily occur when transporting a bicycle or if it falls on one side.
Due to the relatively high risk, a derailleur guard seems like a reasonable solution because it’s fairly light and acts as a “bullbar” for the rear mech.
And despite the obvious benefit only low-end bicycles come equipped with a derailleur guard and/or eyelets for its installation.
The question is why? Isn’t a derailleur guard needed?
Derailleur guards are somewhat helpful when installed on kids, beginner, and public bikes, but the benefits diminish substantially for experienced riders who take greater care of their bicycles.
The negatives that come with a derailleur guard act as further encouragement to declare the accessory obsolete if you’re an intermediate or advanced cyclist.
Why High-end Bikes Don’t Come With a Derailleur Guard
Bicycles in the mid-range and above don’t come with a derailleur guard for the following reasons:
1. Modern Bicycles Use Derailleur Hangers
The rear derailleurs on most modern bicycles connect to the frame via a derailleur hanger made of soft aluminum. The selected material isn’t an attempt to cut costs. It’s deliberately chosen to turn the derailleur hanger into a strategic point of failure.
Since the derailleur hanger is softer than the frame and the body of the derailleur, in case of an accident, it bends before the chainstay and the derailleur and thus prevents damage to the more expensive parts.
Quick Tip: If you’re going on a long trip, take a spare derailleur hanger with you. It doesn’t take a lot of space and will be very helpful if the current one on the bike gets damaged.
Don’t throw the old one, though. Once you get home, you can straighten it with a derailleur hanger alignment gauge.
You could also consider carrying a universal derailleur hanger which can be used if a fellow rider needs one.
2. Top Derailleurs Have Low Profiles
The derailleurs found on high-end bikes have a low profile. The extra “tucked-in” position puts the rear mech in a more protected line and reduces the chances of hitting or catching an external object (e.g., a branch) with the rear derailleur.
Shimano’s line of Zee derailleurs designed for “heavy-duty” mountain biking serves as a good example of low profile derailleurs. The Zee products tuck away nicely and operate efficiently even on rough terrain.
3. Derailleur Guards Catch External Objects
Derailleur guards stick out and increase the chances of catching an external object with the rear-end of the bicycle – a strong reason for mountain bikers to avoid this piece of equipment.
If a branch slides through the derailleur guard, the drive train may pull the stick closer to the rear wheel and eventually into the spokes. This is a situation that can result in an accident and mechanical damage to the bicycle.
4. Derailleur Guards Add Weight and Drag
A derailleur guard can easily add 50-150 grams to a bicycle. Doesn’t sound like much but in the world of high-level cycling, grams are of great importance.
People obsessed with making their machine as light as possible will not even consider adding a derailleur guard.
Another downside of derailleur guards which triggers the group of cyclists concerned with building the most efficient bike is the extra rear wheel drag that a guard creates.
Of course, the effect is very small. Even a pro cyclist is highly unlikely to notice the added resistance.
5. Derailleur Guards Aren’t Part of the Fashion Etiquette
Derailleur guards are not on the list with cool bike accessories. They’re considered weird, non-professional, and unnecessary. An advanced rider who uses one has a great chance of facing ridicule from his fellow cyclists.
If you want to receive bonus points for the looks of your bicycle, avoiding derailleur guards makes a lot of sense, at least in the foreseeable future.
6. A Derailleur Guard Doesn’t Offer Universal Protection
A derailleur guard protects the mech primarily from lateral falls and side hits to the body from objects with a great surface area. A branch or a rock of the right shape could still hit the low pulley and the cage of the derailleur from below.
Furthermore, derailleur guards offer protection only from low impact hits. During a serious collision, the guard is very likely to bend and hit or compress the derailleur.
Consequently, derailleur hangers are needed even when the bike has a derailleur guard because they further minimize the negative consequences of a crash.
7. Derailleur Guards Could Stress and Damage The Frame
If a derailleur guard is attached directly to the frame it could harm the rear triangle by applying twisting force to the right chainstay.
Aluminum and carbon frames are the most likely to get damaged from the impact because they are less elastic than steel and cannot be rebent into proper shape.
Having said that, the chances of this event are not as high as some may claim because high-quality frames are strong.
Moreover, the axle of the rear wheel stabilizes the chainstays.
If you apply side pressure to a chainstay, it could easily bend if there’s no axle in the dropouts to stop it from moving to the opposite side, but when there’s a wheel, the chainstay has a harder time caving in.
In What Situations Are Derailleur Guards Useful?
There are four main occasions when derailleur guards become helpful.
1. On a kids’ bike
Derailleur guards could be useful when installed on a kids’ bike because children tend to throw their bicycles around without paying attention to the rear derailleur.
And since kids are unlikely to care about the low social status of the derailleur guard, installing one on a kids’ bicycle is reasonable.
2. On a rented bike
Public bicycles shared by multiple people could benefit greatly from another layer of defense because the users often treat them as disposable machines and exploit them disrespectfully.
In consequence, a little extra protection to an already fragile area could be beneficial.
3. On a touring bike
Touring bikes are also potential candidates for a derailleur protector due to the high-level of abuse that they face during trips.
A side fall of a loaded bike could easily harm the derailleur and kill the pedaling efficiency of the machine.
And since derailleur guards are supposed to help precisely with side falls, some bike packers found the dreaded accessory helpful.
Another situation when a guard could help a touring bike is during transportation. If you’re traveling with your touring bicycle on a train, for example, the derailleur could get hit accidentally by another passenger or their luggage. A derailleur guard minimizes the risk.
Note: The terrain matters too. Installing a derailleur guard on an offroad touring bike increases the chances of catching external objects.
That said, a pair of loaded panniers stick out a lot more than a derailleur guard and negatively impact the bike’s clearance too.
4. When Transporting a Bicycle on a Plane
Experienced travelers recommend adding a derailleur protector to the bike when transporting it via plane. The extra protection reduces the risk of derailleur damage if the baggage handlers aren’t very careful.
Even though some of the more expensive bike bags include a protector, many cyclists are buying an aftermarket one because the stock ones don’t always cut it.
The Bopworx detachable guard is one of the popular products used for this purpose.
Some High-End Bikes Have a Derailleur Guard
Some luxurious bikes have an option for installing a derailleur guard.
One example would be Lapierre Zesty XM 527 – a high-end full suspension mountain bike with a carbon frame and top-end components.
This model has two eyelets designed for the attachment of a carbon derailleur guard.
Rear Derailleur Hanger Reinforcers
Another series of products built to strengthen the rear mech attachments are the so-called derailleur hanger reinforcers.
They attach to the rear derailleur and the quick-release axle to reinforce the area. The best feature of those models is that they are very discrete.
Nonetheless, they have the following shortcomings:
- The models that I could find aren’t compatible with Shimano’s Shadow rear derailleurs.
- The body of the derailleur is naked.
- They could place stress on the frame and rear dropout.
Frequently Asked Questions
Are derailleur protectors that replace the quick release nut good?
Some derailleur protectors work by replacing the quick release nut of the rear wheel.
Those models are pretty efficient and exercise a triple function – quick release nut+derailleur guard+optional light mount.
Nonetheless, they come with the following negative sides:
1. They can be easily damaged if someone steps on them.
Similar derailleur guards often have a warning label saying “Do Not Step!” It’s there for a reason. If someone places a little load on that thing, it could bend or break and subsequently destroy the quick release axle.
An adult would probably not make this mistake, but a kid might. And since children bikes are one of the primary candidates for a derailleur guard, this model doesn’t cut it because a child could easily step on it while playing.
2. They could make your axle unusable after a fall.
A fall or a frontal hit can damage the protruding protector and the axle. If you don’t have another axle, you will remain stuck where you are.
3. They don’t protect the body of the derailleur.
Those type of derailleur guards are designed with one main function in mind – to protect the derailleur if your bikes fall over somewhat gently.
Unlike the “bullbar” design, they don’t do much to defend the body of the derailleur.
My bicycle does not have eyelets for the installation of a derailleur guard. How can I install one?
You can circumvent this problem by purchasing a derailleur guard that attaches directly to the axle. Those models have a big hole at the top.
The downside of this approach is that you will have re-install the derailleur guard every time you remove the rear wheel.