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Burley uses a polymer hitch (the black plastic) which allows some degree of movement between the trailer and bike:

burley hitch

Most inexpensive trailers use a spring to provide that flexibility:

Cheap trailer

I've only used the cheap spring hitches which can easily absorb the twists involved when the bike falls over or the trailer flips (don't ask). I wonder what would have happened with a Burley. It seems the polymer would have broken. Are the Burley hitches stronger than they seem and do they have advantages over the simpler spring design?

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    For what it's worth, I had an old Burley trailer as a kid that had the spring design. So Burley must have made the decision to switch over to their current design -- but why exactly, I don't know. Maybe it's intended to better prevent the trailer from flipping? – Nick Weinberg Aug 26 '17 at 5:39
  • Notice the orange thing inside the spring in the bottom photo - That bolts to the draw-bar alongside the spring's eye, and essentially does the same job. In combination with the spring, perhaps its cheaper? Or does the Burley have a spring inside the polymer bit ? – Criggie Aug 26 '17 at 5:59
  • Burley's design would make it hard for the trailer to flip unless the polymer hitch mount can twist 90-180 degrees. But I'd worry about it tearing. The spring is definitely cheaper - the whole spring attachment + hitch mount is $20 while the Burley equivalent is $20+25 = $45 US. – RoboKaren Aug 26 '17 at 6:01
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    Separate thought - the spring provides no comfort against a rearwood "shunt" so if you ride the combination through a valley (ie a down-and-up) then the trailer will clang into the bike with a shock when the spring is fully compressed, as pictured. I don't know the phrase but that spring has no space for compression, its at-rest mode is the same as fully compressed. – Criggie Aug 26 '17 at 6:01
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    @Criggie it's just called an extension spring, as opposed to a compression spring. Obviously it's possible to make one that can extend or compress from its neutral position; they tend to be custom-made. I wonder how a trailer with an off-centre mount would handle when braking if the mount could compress. – Chris H Aug 26 '17 at 8:23
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The spring hitches seem to be a cheap/simple way to allow the flexibility needed to both bend and twist when the tow bike corners, but they have an annoying side effect. In my experience when accelerating hard on a bike with a loaded trailer connected by a spring hitch you can feel the spring stretch with each hard pedal pulse then snap back in to place with a bump.

So Burley might have this new design to eliminate this bouncing effect.

Chariot/Thule hitches don't use a spring, they use both a ball joint and a flex polymer arm which makes them feel a lot better. Their ball joint rotates easily for normal cornering and leaning, and the stiff polymer doesn't normally flex or stretch noticeably but can bend in extreme situations as a kind of 'fuse' to save the aluminium arm from breaking and/or the bike frame.

thule trailer mount

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  • Good answer - the only solution to reduce jerkiness is to pedal in smooth circles, which is not very easy while accelerating, but much easier when at speed. Welcome to the site! – Criggie Jan 15 '18 at 8:00
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    Something similar applies to speed bumps, where the spring stretches as the trailer climbs (while the bike is descending), then when the trailer comes over the top, it pushes forwards on the bike. This is related to @Criggie's comment under the question, but the spring is extended to start with in the case I describe. – Chris H Jan 15 '18 at 9:55
  • It might be new to Burley, but rigid hitches are very old. The reason many trailers use springs is, as noted, that they don't break. And they don't break your bike, either. Part of the problem with a broken hitch is that now your trailer is free to wander off and get into trouble. – Code Abominator Jan 17 '18 at 22:55
  • @CodeAbominator this is why chariot adds secondary leashes (nylon straps). If the plastic hitch arm somehow breaks the nylon strap keeps the trailer arm attached to the bike. Chariot actually uses two leashes, one at the trailer/trailer arm connection and one at the trailer arm/bicycle connection. – Rider_X Jan 17 '18 at 23:00
  • Yep, so that the trailer hitch swings into the rear wheel and you crash. It's a good way to ensure surviving riders always check hitch integrity. – Code Abominator Jan 17 '18 at 23:04

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