THE WIKE BLOG
Bicycle Trailer Capacity
July 26, 2021
Have you ever wondered how much weight your bike trailer can carry? What factors determine capacity? These questions answered, and more.
Bike Trailer Capacity
Factors that affect static bicycle trailer capacity
- Quality tires play an important role if you are loading heavy objects in your trailer. Smaller diameter (16”) wheels require higher pressure than standard 20” with the same loading in the trailer. If you are carrying heavy loads you should consider high pressure tires.
- Single walled rims are used in almost all bike trailer applications. When fewer spokes are used then double walled rims can be used to compensate. A double walled rim with 36 spokes is used in extreme applications where higher weight capacity is required.
- Axles used in bicycle trailers are typically 10 or 12mm, or ½”. Use of cartridge bearings improves weight capacity and makes trailers easier to pull.
- Single perimeter frames are used in most bike trailer applications. These consist of a perimeter tube around the trailer and an axle tube to connect the two wheels.
- Double frames are also used around the wheels to support each end of the axle or around the perimeter to disperse the loading of a cantilevered axle.
- The larger the length and width of the trailer, the stronger the frame must be to support the load. It is always best to load a trailer so the weight is balanced equally front to back over the axle.
- The towbar has historically been the most limiting element of bicycle trailer capacity. It is subject to constantly oscillating forces and frequent shocks from collisions with stationary objects. Towbar structural failure could cause the trailer to disconnect from the bicycle.
- The flexible hitch that completes the connection between the end of the towbar and the bicycle must allow the bicycle to turn freely from the trailer. It also needs to allow the bicycle to lean and lay flat without upsetting the trailer. And lastly it should assist in keeping the trailer upright during sharp turns or side to side bumping such as road curbs. The flexibility of the hitch should diminish as trailer capacity increases
Factors that affect the dynamic bicycle trailer capacity
- The distribution of total weight between the bicycle and the trailer is a critical consideration when attempting to carry heavier trailer loads. The ability of the cyclist to control the dynamics of a bicycle/trailer combination decreases with increasing speed and with the relative weight of the trailer to the bicycle. With speeds under 20 kph the load in the trailer should not exceed 40% of the weight of the bicycle plus rider. This is the reason that Bicycle Trailer Standards worldwide currently advise to limit capacity to 100lbs. It is not the capacity of the trailer but the ability of the bicycle to stop the trailer that is the determining factor.
- The use of trailer brakes can ameliorate the relative weight issue but can’t resolve it completely. With the advent of electric bicycles the desire to carry greater loads will continue. These increases in loads should be shared on both the trailer and the bicycle. A heavier bicycle will help to control a heavier trailer
Height of Load
- Trailer tipping due to high loads, uneven ground, or fast turns is common. Wider wheelbase, lower center of gravity, and slow speeds increase dynamic stability