Condensed Answer: It’s fine to install a rear rack via the quick-release skewers when the following conditions are met:
- The rack isn’t overloaded (less than 17kg/37.4lbs)
- The support struts of the rack do not interfere with the disc brake caliper (if there’s one)
- The quick-release skewer is long enough, in good health, and of decent quality.
The Quick-release Skewer Is Not a Support Structure
The quick-release skewer doesn’t support the bike. It’s only a clamping mechanism with an internal or an external cam that squeezes the fork or the frame’s dropouts against the hub.
The weight of the bike is sitting on a hollow axle through which the skewer’s rod passes. The skewer’s responsibility is to pressure the dropouts against the hub’s locknuts so that the axle is securely attached to the dropouts.
The axle remains stationary while the hub is rotating around it via a bearing system that falls under the cup & cone category most of the time.
Thus, the quick-release skewer is not meant to resist vertical pressure. This is the axle’s job.
The Problems With Installing a Rear Rack Via The Quick-release
The main issues that one faces when mounting a rear rack via a QR skewer are:
- Lack of space
- Not enough strength
It’s not possible to attach the struts supporting the rear rack directly to the axle as that space is reserved for the dropouts of the frame or fork.
Therefore, the only option is for the struts to sit outside of the dropouts.
This peculiarity creates an issue because quick-release skewers are not support units, but have to be in this case.
For that reason, manufacturers lower the weight limit when a rear rack is mounted between the quick-release end caps and the frame.
That said, some people argue that quick-release skewers are still capable of supporting more weight than what commuters carry daily.
If you’re a touring cyclist, however, and plan on loading the rear wheel to the maximum, it would be wiser to go for a stronger and safer solution.
Since the purpose of the quick-release skewer is to secure the wheel to the frame or fork, every time you remove the rear wheel, it will be necessary to completely remove the quick-release skewer to get the wheel out.
If the rack is loaded, you will have to fully unload it to complete the procedure. This could be extremely annoying if the rack is carrying odd objects or tons of touring gear. Ideally, you will have a quick-release basket or panniers with a quick snap-on mounting system (the Ortlieb style).
There are two attachment methods – direct and indirect.
In the first case (direct), the struts mount directly to the quick-release skewer.
Very important: This method could work only if the attachment points on the struts are as flat as washers. If they aren’t flat, they will interfere with the original function of the quick-release and thus create a potentially dangerous situation due to insufficient clamping power.
The indirect method involves the use of flat adapters that serve as a middle-man between the skewer and the rack.
Those adapters have a strategically chosen shape that accomplishes two tasks:
- It gets the rack away from the frame (beneficial if there is a disc brake).
- It changes the direction of the stress applied to the quick-release skewer by manipulating the lever arm.
The image above shows the Tubus QR Adapter. Note the shape of the adapters. Normally, the rack and the weight on it will stress the quick-release skewer only vertically (straight down).
With those adapters, some of the vertical stress is reduced as the adapter is essentially a lever that could potentially rotate around the skewer. Thus, some of the downward tension is dissipated. Of course, the quick-release skewer is still under stress.
Some rear racks designed for quick-release skewers or to bypass the caliper of a rear disc brake will have similar ends welded to the rack. In that case, adapters are not needed as the struts’ ends already have that shape and function.
The next photos show the Tubus Disco rack. This model comes with U-shaped attachment points welded to the support struts.
Some Models Designed For Disc Brakes Cannot Be Used
A good number of rear racks out there have wide struts with threaded ends meant to bypass the disc brake caliper. Usually, the ends have an L-shape pointing towards the frame.
Those models cannot be used with a quick-release skewer unless the ends are bolted and can be replaced with the aforementioned adapter.
The Advantages of Mounting a Rear Rack To a Quick-release
Ideally, you will mount the rear rack to a set of eyelets on the frame made specifically for that purpose. This is the classic way to mount a rack. It’s clean and gives the most strength without creating the aforementioned issues.
Therefore, the only advantage of using the quick-release skewer is the ability to install a rack on frames without eyelets.
In short, this is a compromise rather than a solution that one would seek deliberately for some benefit.
Before proceeding to this solution, you should know that there are other methods to mount a rear rack to a bicycle without eyelets. I will list all that I know below:
- P-clamps/Pipe Clamps On the Seat Stays
It’s possible to use a set of clamps bolted to the seat stays as a connection point for the struts.
It’s important to note that similar racks should NOT be used on carbon frames. Carbon is a material that doesn’t hold well under clamping force and can therefore disintegrate when clamped severely.
Steel and aluminum frames, however, can handle the stress.
If you don’t have access to similar clamps, you can use P-clamps or modified pipe clamps.
So far, I’ve had no problems. I did load the rack to the maximum on a couple of occasions. My wooden front rack can carry more weight than I am comfortable transporting on a bike anyway.
- Alternative Racks
There are a few rear racks with alternative mounting solutions. In most cases, those models are designed for full-suspension MTBs and cannot match the weight capacity of touring racks. \
Nonetheless, they’re still an option, especially for people who don’t plan on carrying a ton of cargo.
Thule Tour Rack
The image above shows Thule’s Tour Rack. It has a very clever design that allows the user to mount the rack to the seat stays or to the fork’s blade (the rack can be used at the front too).
The weight limit of this rack is 10kg/22lbs for the front and 11kg/24lbs when installed at the rear.
Topeak Tetrarack M2
Topeak’s Tetrarack M2 is another rack that can be mounted to a full-suspension MTB. The weight capacity is 12kg/26lbs.
Aeroe Spider Rear Rack
This is a super light rear rack (only 641g ) and fits the criteria too. It has a unique mechanism for clamping to the seat stays. The weight capacity is decent too – 16kgs/35 lbs. You can find the official page here.
Summary: What You Need To Know
- It’s possible to install a rear rack via the quick-release skewer, but it’s not the ideal option. If the bike has dedicated eyelets, use them instead.
- Quick-release skewers are fundamentally a clamping mechanism rather than a support architecture. The weight of the bike rests on the hollow hub axle through which the rack passes rather than the skewer itself. For that reason, rear racks mounted via the QR skewer are more of a comprise and have lower weight capacity for safety reasons.
- It would be inaccurate to conclude that a QR rear rack is not safe. If the support struts have flat ends and do not interfere with the original function of the skewer, then the rack can be used as long as the weight limit is respected.
- It’s preferred to use a rear rack with curved attachment points (or adapters) as those reduce some of the vertical stress reaching the quick-release skewer.
- It’s also possible to use P-clamps (or some pipe clamps) to mount the struts directly to the seat stays. The advantage of this method is that you won’t have to remove the entire quick-release to unmount a wheel.
- If you choose to mount a rear rack via the QR skewer, you will have to unload the rack every time you remove the wheel.
- Rear racks designed for full-suspension bikes mount directly to the seat stays and thus allow you to have a rack without eyelets and without messing with the QR skewer of the bike.
- Rear racks with L-shaped ends designed to bypass the caliper of a disc brake cannot be used with a quick-release skewer.
Bonus Tip: If you don’t plan on carrying a lot of cargo, you might also consider a saddle bag (I recommend Carride SQR) or a rear rack mounted to the seat post.
(I compare frame-mounted and seat-post rear racks in great detail in this article.)