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I recently was involved in a wreck, because I was unable to slow my trailer. I am thinking about building a refit kit to install breaks on a trailer, but I don't want to reinvent the wheel.

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What type of brakes are currently installed on the bike? My thought is this may be your best and simplest upgrade. –  mikes Nov 16 '13 at 3:06
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The bike has great hydrolic disk brakes. When the trailer is going faster than the bike you crash. You want to slow the trailer and the bike. This is why trailer brakes are required on semis and other heavy trailers. –  hildred Nov 16 '13 at 3:31
    
I did see a bike trailer once that had brakes (of the type that were activated by force on the tongue). IIRC it was a heavily-built utility trailer, and may have been homemade. I would guess that there are utility-type trailers with brakes sold in Europe, but they approach cycling differently there vs the US. –  Daniel R Hicks Nov 16 '13 at 12:59
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I don't see how the trailer can be going faster than the bike since every bike hitch I've seen is rigid, so when the bike slows, the trailer either has to slow, or pitch around and "jackknife". That said, CycleTote does sell an (expensive) automatic braking system for their trailers. Since it's an add-on accessory, perhaps you can adapt it for your bike and trailer. –  Johnny Nov 19 '13 at 18:07
    
@Johnny Fishtailing is where when because the trailer wants to go faster than the pulling vehicle it moves from side to side. as you slow the pulling vehicle, it becomes more severe. the three ways to stop fishtailing are accelerate, brake the trailer, or crash. I crashed. –  hildred Nov 19 '13 at 19:35

2 Answers 2

up vote 5 down vote accepted

http://viadukt.eu/produkt/PT6_Bike_Trailer-2-65-111.htm is the only commercial example I can find.

DIY:

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Its disappointing that with all the vendors selling bike trailers that there is only one selling one with brakes, and nobody selling conversion kits. –  hildred Nov 19 '13 at 16:25
    
@hildred - One tricky part is the way the tongue is generally arranged. It's usually on one side, so it can attach near the rear wheel axle, and this makes it difficult to design a telescoping tongue (for inertia braking) that won't twist sideways when it telescopes. –  Daniel R Hicks Nov 19 '13 at 16:44
    
@DanielRHicks my trailer has a fork hitch, which attaches to both sides. I had looked at trailers that attached to one side, but they all made me nervous. I once helped a neighbor install a trailer that hitched to the bike with a spring! can you say oscillate? but these problems can be overcome, if any one would try. –  hildred Nov 19 '13 at 16:58
    
@hildred: I have made and used a lot of spring hitches. They oscillate a bit, sure, but they're also very robust. That matters when a rigid hitch is $100+ and breaks the first time the bike falls over. moz.geek.nz/mozbike/build/masstrailer/index.html for example. –  Mσᶎ Nov 19 '13 at 21:23
    
Also, congrats on finding someone who sells one! –  Mσᶎ Nov 19 '13 at 21:27

I'm not aware of a commerically made one, I suspect the barrier is liability issues (and possible legal issues in some places). FWIW, the limits in Australia and New Zealand are the same as for any other vehicle, so the main restriction is that the trailer can't weigh more than the towing vehicle (note below). Other jurisdictions may have different rules.

Similar questions have been asked here before: Hitch for a cart for braking How to make a cargo trailer?

There are two basic ways to do this. Either have brakes on the trailer activated by a lever on the bike, or make some kind of inertia brake. Having a direct lever is very simple and intuitive for the rider, but you may find yourself limited by the length of brake cables you can buy (it's possible to buy the wire on a roll and fix the endcap yourself, but annoying).

An inertia brake is somewhat harder to build, but very effective. You need the towing arm to telescope somehow, so as the trailer pushes forward on the towing vehicle you have a small movement that you can use to apply brakes. I built a four wheel trailer that worked like this, and just used cheap V brakes on the trailer. That was sufficiently effective that I didn't bother with anything more complex. The drawbar was square tubing, with a bracket at the overlap holding one end of the brake cables.

The major caveat is that neither of those solves the real problem. Once you're sliding along the ground in front of the moving trailer, neither of those will help slow it down. In theory you could grab the brake lever and use that, but in practice you're likely to focus more on getting out from under the trailer.

My preferred solution is to use a bike with two rear wheels, either a four wheel bike or a delta trike. That way you're less likely to fall off it and you can have the trailer apply downforce between the rear wheels to help with traction.

(edit: note that the default limit is actually the unloaded mass of the towing vehicle that the total trailer mass has to be under, so most bike trailers fall well outside that limit. Here's a PDF. What saves the situation is that if the manufacturer specifies a limit that applies instead).

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I saw the discussion you mentioned for building the hitch, but I was really looking for what is being sold. Also could you clarify your point about weights, is that for trailers without brakes? I drove commercial here in the us and most of the semis pulled trailers which out massed them. –  hildred Nov 17 '13 at 18:43
    
@hildred: Like I said, I've never seen a commercial setup with a brake that could be used while riding. The only trailer brakes I've seen are on the prams that convert to kddie trailers, with brakes that can be operated from the pram end. Articulated vehicles are a special case, but I have not looked into getting a bicycle compliant with those. I have driven heavy vehicles too, but the legal issues are well outside the scope of bicycles.SE. –  Mσᶎ Nov 17 '13 at 20:38
    
Cutting a brake hose to length and fitting end caps is a 5 minute job, with a pair of wire cutters. –  Vorac Nov 18 '13 at 9:02
    
Hose, yes, but getting the hose in long lengths can be tricky (you have to select your hydraulic disk setup based on who sells hose off the roll). I'd use a knife rather than wire cutters, but cutters would probably work. For a cable setup you fixing the stop on the end is more tricky, but it can be done. –  Mσᶎ Nov 18 '13 at 21:02
    
The tricky bit with a brake hose is going to be that you want to be able to split it, so you can take the trailer off. –  armb Nov 19 '13 at 11:06

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