If you think of a bike trailer you probably envisage what's basically a lightweight, small platform or box with two wheels and a towbar hitch attached to the end of the bike axle. The Carla Cargo trailer completely reimagines what a bike trailer can be.
This is a three-wheeled trailer especially suited to powerful electric bikes. It weighs nearly 45kg and has a payload rating of 200kg. Features include twin hydraulic overrun braking to automatically spread braking to each of the rear wheels. The clever towbar system also acts as handle with which you can manoeuvre the trailer when unhitched. It will also stand on its end to lean against a wall for easier storage (though at 2.3 l x 0.94 w x 0.79 h metres it's certainly one of the biggest trailers out there).
It is distributed in the UK by Manchester Bikes and we tested it with one of the most capable electric load haulers out there, the Tern GSD, fitted with a bespoke 'towball' attachment. The Carla is conventionally fitted directly to a seatpost but the elongated rear of the Tern means the towbar on the Carla would not reach it.
It's worth noting that Manchester Bikes also supply the E-Carla which has its own electric motor on the front wheel of the trailer, for use with non-electric bikes. This is not legal to use with an e-bike (as you would have a vehicle setup with two motors). You can also get a bike carrying attachment (for loading one or more bikes onto the trailer easily) and a large metal carrying box that fits the flatbed area exactly.
Who are Carla?
This specialist trailer manufacturer are based in Germany's Baden-Württemberg state, well-known in Germany (at least) as a powerhouse of engineering and manufacturing. The main parts for the trailer are made there and those that are not are made nearby, so Carla boasts of short lead times and strong availability.
The trailer we tested is the 2021 version and includes the following updates:
- Claimed 'world first' hydraulic cargo overrun brakes using Big Magura Twin units that also claim to be self adjusting. Magura say the 'Big Magura Twin hydraulic disc brakes system is one the most effective twin systems for lightweight vehicles such as pedicabs or rickshaws or cargo tricycles.'
- New CNC towbar machined from a single piece of aluminium alloy
- SON hub dynamo to power dual rear lighting LEDs
- Tough metal Curana mudguards
- CNC cut plywood base
With a £4,000 price tag you would expect the Carla Cargo to be hugely capable and the 200kg load rating puts it way beyond any other trailer out there, into the class of both heavy duty home and commercial use.
The Tern GSD we have rated as one of the best and most capable bikes we've ever tried. With the addition of the Carla Cargo you have a setup that, on paper at least, looks just as capable for load hauling as a small car. Let's see how if our testing proved that to be the case.
I started off cautiously, transporting a couple of e-bikes with a combined weight of around 50kg before moving up to 100kg of timber and then 150kg of materials for a building project I was helping out with locally.
Riding was a total revelation. No doubt it helped to be using one of the most capable load pullers out there with it's Bosch Cargo Line mid-drive offering up to 400% pedal assist.
Pulling a heavy load on a two wheeled trailer without overrun brakes means you can certainly feel the trailer affecting the bike's handling, as the load pushes or tugs back on the bike. Using a bakfiets style box bike the effect of a heavy load is different but just as pronounced, as care is needed to balance the bike, especially when stopped or at low speeds.
There was much, much less effect on handling with the Carla Cargo, even with the max loading we tried of 150kg. On the flat and on moderate gradients, once you are underway, it's often hard to know it is there.
The overrun brakes appear to do a very good job of stopping the trailer pushing the bike forward and destabilising handling. As they work automatically on downhills - the weight of the trailer compressing a piston inside a box that the towing arm feeds into - it's difficult to know exactly when they are actually doing their job (in a good way). Only on steeper downhills and when I put the brakes on a little more quickly than usual was the effect obvious - you just hear the wheels lock up up a little. But again the actual effect on bike handling wasn't too great - the Big Magura Twin hydraulics coming into action pretty gradually but powerfully to slow or stop the trailer without you having to worry about it.
Why so much more stable? The presence of three wheels is the obvious factor. On a two wheeled trailer, even if the load is nicely over the axles, there's always doing to be some weight on the towbar itself (or some lifting force on a very poorly loaded trailer). The three wheel design pretty much eliminates this potential difficulty. We've already commented on the overrun brakes which also help to give a stable tow.
Whilst it's not generally advisable to mount a trailer high up on a bike the Carla/Tern system works very well. It takes the form of a miniature towball attachment. This is normally attached to a seatpost but as the Tern is a longtail the towbar is too short, so Manchester Bikes supply a bespoke GSD mount that bolts onto the top of the rear rack. (Note the downside of this is that you cannot use the top of the rack whilst towing). As the 'towball' design allows the bike to lean and tilt as normal, with minimal forces from the bike, it promotes stable, predictable and reassuringly bike-like riding.
The inbuilt, dynamo-powered lighting is also a nice touch and worked very effectively.
Of course, usual bicycle towing techniques are strongly advised. The heavier the load the more you should moderate your speed. Excessive speed is not advised with heavy loads (especially downhill) and acceleration and movement should all be as gentle as possible.
The load should be secured properly. We found these Halfords retractable ratchet straps ideal for quick and easy loading by one person as they easily hook onto the trailer's upper rail.
One area that can be tricky with conventional two wheel trailers is loading heavy cargo. This would normally be done with the trailer attached to the bike and the load can wobble and even topple the attached bike whilst you are loading it onto the trailer.
It's a doddle with the Carla. The parking brake can be activated with a brake lever at the end of the towbar ensuring a hugely stable load base (the front V brake is also activated in this case so all three wheels are locked in place).
The towbar also acts as a handle with which to pull the trailer when it's off the bike. It's more manoeuvrable when not attached to the bike and has a much tighter turning circle. We used it to load materials at the back of a house then pull it round to the road through a narrow passage and round a tight turn.
The only obvious improvement we would put on the wishlist is some kind of suspension - especially if your roads are littered with big potholes and aggressively ramped speedbumps as some of ours are. You do find these give the load a bit of a noisy jolt and on small steep ramps you can feel the trailer pulling back on the bike as the load's momentum is suddenly slowed.
Manchester Bike Hire stock a number of container type solutions that will neatly fit onto the trailer, though we found it extremely useful just as a flatbed making maximum use of the 1650 x 650 mm loadbed area.
All in all the Carla Cargo is a delight to use and a very practical tool. Can you justify £4,000 for a bike trailer? Clearly most regular e-bikers won't need such mammoth carrying capacity on a regular basis.
Where it really does appear to have come into its own is in a commercial setting and there are numerous examples of the Tern GSD plus Carla Cargo in operation. (It doesn't have to be a Tern than pulls the Carla, but it often is.) There are delivery companies (like New York's Dutch X), bike share schemes (like Ireland's Bleeper) and all manner of individual businesses that have found the combination suitable for their business needs.
If you are interested but not ready to commit to buying, it's notable that 'bike library' style hire and loans are becoming increasingly common. Manchester Bikes' work with various organisations in Manchester to make the bikes available to a wider audience as just one example.
Ebiketips have covered plenty of e-cargo bike options from the relatively affordable Mycle Cargo to the more school run orientated Raleigh Stride 2 (and of course the Tern GSD itself will carry an awful lot on its own). However, for stable and safe towing of truly heavy and sizeable loads there is nothing available in the UK that can claim to match the Carla Cargo.