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If you’re looking for a way to transport your kids on daily bicycle errands and shopping trips, a bike trailer is the solution.
You’ll save money on fuel or public transport costs and get fit at the same time.
Bike trailers are also handy for carrying camping gear or sports gear.
Maybe you’ve thought of all this but find the idea of attaching a bike trailer daunting? This article tells you how it’s done.
How Trailers Attach To Bikes – The Different Types Of Trailer Attachments
When it comes to attaching a bike trailer to your bike, you have options.
Seat Post Attachment
A bike trailer that attaches to your seat post will have a hitch (or arm) that curves upwards towards the bike seat.
Before attaching the hitch to a seat post, you’ll need to attach a hitch receiver to the post. This may require the use of a shim or bushing to achieve a tight fit.
Although bike trailers will attach to most types of bikes, it’s inadvisable to attach a hitch to a carbon seat post. Carbon is susceptible to damage from clamping forces and a seatpost is not designed for lateral stresses.
If you’re going to attach a seat-post hitch, you’re best off using a sturdy metal seat post.
A trailer hitch or arm that reaches out at a lower angle normally attaches to the rear-wheel axle of the bike. This involves attaching a hitch receiver to the axle before you can hook the trailer up.
You can attach a bike trailer to any kind of axle, though thru-axles are sometimes more troublesome than quick-release axles.
A small minority of bike trailers attach to the chainstay on the bike frame.
The Different Bike Axle Types
If you’re going to attach a bike trailer to the rear axle of your bike, you first need to identify what type of axle you have.
Most bikes with disc brakes are going to have a thru-axle. You can identify this by its connection to the bike. Rather than slotting into a U-shaped dropout like a quick-release wheel, a thru-axle passes through a fully encircled hole.
Note that some thru-axles still have a quick-release lever for tool-free removal and fitting of the bike. Aside from the solid hole that the axle passes through, a thru-axle is also thicker in diameter than a quick-release skewer.
A quick-release axle (or skewer) is narrower than a thru-axle. It connects to the bike via a U-shaped dropout and clamps to the bike using a cam mechanism.
Quick-release axles are commonly used on bikes with rim brakes. They aren’t often used with disc brakes. Thru-axles are stiffer and keep the disc-brake rotors properly aligned.
Traditional bikes or budget bikes may have a bolt-on axle, whereby the axle is attached to the bike using old-fashioned threads and nuts. You need to use a socket wrench or adjustable wrench to loosen the nut (usually 15mm) on each side.
What Type Of Bicycles Are Suited To Bike Trailers?
You can attach a bike trailer to many bike types as described below.
Intuitively, a sporty road bike may not seem ideal for pulling a bike trailer. In fact, it’s ideal, because it’s designed from the get-go for efficiency on the road. A road bike is light, aerodynamic, good for power transfer and has multiple gears.
The qualities that make a road bike ideal for pulling a trailer are the same ones that benefit you without a trailer.
A mountain bike is strong and has a wide-gear range that makes pulling a trailer easier. Its wide tires help with stability and comfort.
The main downside of an MTB is that it’ll be slower than a road bike when ridden on smooth surfaces. You can mitigate this somewhat by installing slick tires and using a hardtail MTB rather than a full-suspension bike.
Video: Off-Roading With A Bike Trailer
Hybrid bikes bridge the gap between road bikes and mountain bikes. If you intend to go off-road with a trailer, which is doable as long as the trail isn’t too rough or hilly, a hybrid gives you that versatility.
If you only ever intend to ride on roads, a hybrid makes less sense for pulling a trailer. It’s heavier and slower than a road bike, though it will have plenty of gears as a counterpoint and be comfortable to ride.
A cruiser is fine for pulling a bike trailer provided the terrain is flat. You won’t go as fast as you will on other bikes because of the nature of cruisers. They’re heavier and slower with wide tires and few or no gears. Comfort is the main benefit.
Gravel Bikes & CX Bikes
Gravel bikes and cyclocross (CX) bikes are similar in shape to road bikes and can be used to pull a bike trailer.
These bikes have wider tires than road bikes. This means they’re likely to have disc brakes, which can complicate trailer installation.
Most bikes can theoretically pull a trailer. Unicycles, tricycles and recumbent bikes present practical difficulties. E-bikes with small 250W hub-based motors will struggle to pull a trailer up hills because they do not utilize gears.
How To Attach Axle-Mounted Bike Trailers To A Bike
Many bike trailers attach to the axle on the rear wheel of your bike. This is not always a straightforward process, especially with disc-brake bikes. We’ll go over the steps below.
1. Remove The Axle & Install Coupler (Hitch)
Whatever type of axle you have on your bike, you’ll need to remove it so you can install a coupler or hitch receiver to your bike.
With a quick-release axle (or skewer), you take out the skewer and then place the provided plate and coupler into position before threading the skewer back in as normal. Clamp the skewer shut with the spring outside of the coupler.
The thru-axles commonly found on disc-brake bikes are more complicated. Not all manufacturers’ couplers are compatible with the width of the axle.
You may need to buy a separate thru-axle adapter for some Burley and Thule bike trailers. Schwinn or Instep couplers should be compatible out of the box with 12mm diameter thru-axles.
Thru-axle adapters increase the cost of fitting a bike trailer considerably, so this is an aspect you might want to factor into your buying decision.
It’s a good idea to buy the thru-axle adapter after buying your bike trailer in case you don’t need it after all (more likely with Burley than Thule). Before buying an adapter, you need to know the diameter, length and thread pitch of your current thru-axle.
With bolt-on axles, you might need a longer axle before a coupler will install. This is something a bike shop should be able to help you with.
2. Extend The Tow Arm
You must now extend the tow arm of the trailer so it’s ready to connect to the bike. This will probably involve unfolding the arm from its stowed position.
3. Attach The Tow Arm
With the coupler in place, you must now attach the tow arm or hitch arm to the coupler. Before doing this, it may be necessary to fine-tune the angle of the coupler.
The tow arm is usually secured in place using a hitch retaining pin with clasp and maybe a strap that secures to your bike frame.
How To Attach Seatpost-Mounted Trailers To A Bike
Attaching a bike trailer to a seatpost is straightforward.
1. Install The Hitch Receiver
You’ll first need to install the hitch receiver onto the seatpost, which should ideally be a metal seatpost (carbon is inadvisable).
This involves detaching the saddle and post from the bike as one unit. You then slide the receiver onto the post along with any shim or bushing that goes inside it. Reinstall the saddle and post once the receiver is securely fitted.
Video: Installing A Hitch Receiver On A Seatpost
2. Extend The Tow Arm
Unfold the tow arm and extend it to join with the recently installed hitch receiver. The receiver can stay on your seat post at all times, ready for trailer attachment.
3. Attach The Tow Arm
Align any holes at the end of the tow arm with those in the hitch receiver and install the retaining pin or quick-release lever and bolt for attachment. You’re done!
Bicycle Trailer FAQs
Below are some commonly asked questions about attaching bike trailers.
Can Bike Trailers Attach To Any Bike?
Bike trailers can attach to almost any bicycle one way or another. The connection between some trailers and thru-axles on disc-brake bikes can be problematic.
How Old Should A Child Be To Ride In A Bike Trailer?
Children should ideally be at least 12 months old to ride in a bike trailer. This is the age when they can support their heads unaided. Younger children may ride in a trailer with a baby seat.
How To Attach A Bike Trailer To A Trike?
Trikes pose a problem because you need the tow arm to attach to a central portion at the rear where an axle would end on a regular bicycle. A custom adapter is probably your best bet.
Is Towing A Trailer Illegal?
Bike trailers are legal in most countries, though not all. They are illegal in Spain, for instance. We have an article on bike tow devices that goes into this further,
Are Bike Trailers Safe To Use?
Bike trailers are considered safe to use and offer a degree of security with the inclusion of seat belts and a protective cage.