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  1. #1
    Senior Member AltheCyclist's Avatar
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    Seat post or frame mount trailer?

    I'm trying to find a basic trailer for road riding. Cargo will be mostly liquids (you know, beer). I need quick release from the frame as this is going to be occasionally attached.
    I was just going to buy a basic Burly cargo trailer but LBS guy said they are kinda wobbly to ride with the triangle attach. I've seem similar with quick-release that attaches to seat post that might alleviate this problem.
    Any advice either way? Or suggestions on other quick-release cargo trailers that would fit above needs?

  2. #2
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    If you are just hauling groceries or camping gear, the BOB trailer is great. Don't even notice it's there, never tips over on turns. Only holds smaller items and up to 75 lbs though.

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    Senior Member AltheCyclist's Avatar
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    Quote Originally Posted by crackerdog View Post
    If you are just hauling groceries or camping gear, the BOB trailer is great. Don't even notice it's there, never tips over on turns. Only holds smaller items and up to 75 lbs though.
    Yeah, I like the BOB style models but I really want a fast release and those take some fidgeting to get on/off.

    Anyone ever try this one? http://www.burley.com/home/bur/page_416/travoy.html

  4. #4
    Senior Member katcorot's Avatar
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    Quote Originally Posted by AltheCyclist View Post
    Yeah, I like the BOB style models but I really want a fast release and those take some fidgeting to get on/off.

    Anyone ever try this one? http://www.burley.com/home/bur/page_416/travoy.html
    I've a friend who go one of those, pulls it with his dahon folder I think. Whichever he loves the trailer and it's usefulness.
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  5. #5
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    Quote Originally Posted by AltheCyclist View Post
    Yeah, I like the BOB style models but I really want a fast release and those take some fidgeting to get on/off.

    Anyone ever try this one? http://www.burley.com/home/bur/page_416/travoy.html
    I purchased one about two months ago and cannot say enough about the Travoy. I looked a several trailer options including the BaW trailers, but the Travoy is much better suited for day-to-day uses. I use mine daily for commuting and shopping.

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    There is no perfect way to hitch a trailer to a bicycle. The perfect hitch would attach to the contact patch of the rear tire, or maybe to the ground ahead of that. Clearly impossible. With a multi-bar linkage, you could create a virtual pivot at that point, and simulate such a hitch but it would be complex, heavy, and introduce a lot of slop. Not at all practical.

    All the practical hitching methods have trade offs. Most of them can be made to work, and work well enough that the user won't notice any downsides. So I am sure to annoy someone who has a setup that works "just fine" by pointing out the downsides of that setup. Hopefully, being aware of the downsides will help trailer builders/buyers negotiate the tradeoffs and end up with something that works well for them.

    The steering pivot is the hitch, basically, but some trailers like the BOB have separate steering and pitch pivots, and two wheel trailers need a roll pivot as well, so the bike can bank and the trailer keep both wheels on the ground.

    For good directional stability, that steering pivot needs to be at or ahead of the contact patch of the rear tire, or the axle. This is the main issue I have with most of the commercial one wheeled trailers. They put that steering axis behind the rear tire. This can still work if you keep the trailer light and the speed down. Loaded heavy, though, this really wants to fishtail in any situation where the trailer is pushing on the bike..stopping or braking on a hill.



    With a two wheeled trailer, seatpost hitching can create a problem due to roll-steer interaction. As the bike leans back and forth (for example climbing off the saddle) it also steers the trailer right and left. Depending on lots of factors, this can lead to instability. In general it will be stable when the bike is pulling the trailer. The pull of the trailer will be trying to stand the bike back upright. When braking, though, the trailer will be trying to push the bike over even farther. With a light load in the trailer, the rider may accommodate this effect without even noticing it. A heavier load will require some effort, and a really heavy load may overwhelm the rider.

    When a bike leans, it pivots about the point where the tires touch the ground. The higher up you go the farther that point moves side-to-side when the bike leans.

    Hitching a two wheeled trailer to the chain stay or dropout greatly reduces this issue, because nearer the ground, leaning the bike doesn't steer the trailer nearly as much as seatpost hitching. Note that this is still not perfect, and you could still get in trouble with very heavy trailers. Also, this hitching method limits how tight you can turn, and may have heel clearance issues depending. Also, to avoid pulling the bike to one side, the trailer needs to track centered on the hitch point, not centered on the bike. Trying to fix this "problem" leads to a real problem of the trailer fighting the bike.

    With a one wheeled trailer the hight of the hitch point doesn't matter. It leans with the bike no matter how high the attachment point. Attaching to the seatpost puts the steering pivot well forward of the axle, so directional stability is excellent. The trail-a-bikes all use this, and as long as the joints and attachment are not sloppy, it works well.

    There is an issue with seatpost hitching that effects both one and two wheeled trailers: Wheelies on acceleration/hard climbing. When starting out, the mass of the trailer is pulling rearward on the seatpost, and especially on a tall, short wheelbase bike, it may be difficult to keep the front wheel on the ground. When stopping this will tend to reduce the weight on the rear wheel, making it easy to skid, which can cause loss of control. Many bicyclists do not make sufficient use of the front brake in normal circumstances, so may have difficulty stopping such a trailer if they are unwilling to learn to use the front brake.

    ALL hitching methods will be more stable if you keep the load low and forward.If the load balances behind the trailer wheels (negative tongue weight) then stability will be poor in all cases. For stability, the mass of the trailer must be centered ahead of the axle... and the heavier the tongue, the more stable, but a too heavy tongue can cause other issues, so we are back to tradeoffs. The BOB puts the axle well back and the load very low to gain some of the stability it loses to too-far-aft hitch steering.
    Last edited by kevbo; 05-23-11 at 09:45 AM.

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    Kevbo, good explanation. Works for me.

    My "tradeoff" point is being able to turn my bike in either direction in close quarters. The side mount hitch point just doesn't allow that for me, so I built this:



    Seems to do OK, until I put >100lb in the trailer. Even then, the problem appears to be more the trailer than the hitch. With 75 lb and less, I hardly notice the trailer, except for the additional effort to climb hills. Seems to be stable while braking, no fishtailing etc., just additional stopping length.
    Last edited by Charlie_R; 06-08-11 at 04:58 PM.

  8. #8
    Gammal cyklist Reynolds's Avatar
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    Thanks kevbo, good explanation. I'm considering using a seatpost hitch, but my concern is if that could stress the seatpost/frame more than a dropout/chainstay/seatstay hitch would.

  9. #9
    coprolite fietsbob's Avatar
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    Left side mounting, axle end or dropout fittings generally
    tow with that being the center.
    so the trailer is a bit further left.

    seatpost mount puts the tow in the center, ..

  10. #10
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    I've hauled all kinds of heavy cargo ( well, up to about 80 or 90 pounds ) with my Burley Nomad using both the plastic triangle style hitch they use and also the metal hitch that bolts to your rear axle. Never once an issue either way. I prefer the hitches that mount low like this to the kind that mount to the seatpost. My feeling is that I'd rather have whatever weight I'm hauling influence me at the lowest point possible on the bike. A certain amount of weight impacting the bike down low would seem to me to have less detrimental impact that up high on the seatpost. I'm no physics expert, just my gut feeling. Especially with the metal axle-mounted hitch, taking the trailer on and off is a snap...a few seconds. Plastic style, maybe 10-15 sec. The Burley trailer arm is set up (angled) such that it compensates for the hitch being to the left of center. I love the Nomad. You'd have a hard time selling me anything else. Now, if you hauled larger cargo a lot, it wouldn't work. You'd need something homemade or like the Burley flatbed. Either way, the Burley style of hitch has worked well for me as long as your rear axle is 10mm or less.

  11. #11
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    I'm almost finished building my first trailer and was wondering if their would be an issue with mounting the trailer arm to the side of the trailer vs center. The trailer is all box tubing, two wheels, square shaped, and super heavy as is. I used an air hose attachment as a quick release that doubles as the pivot that allows the bike to lean into corners. The hitch is mounted low and on the left via the chain stay and seat stay.
    Thanks for any input!

  12. #12
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    An update on what I've been doing with mine:

    http://www.bikeforums.net/showthread...hitch-and-rack

  13. #13
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    Wow, that hitch is...well...something! No kill like overkill I guess!

  14. #14
    Senior Member AltheCyclist's Avatar
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    I ended up getting the frame-mount style (similar to Burley Nomad). Seems to work well, it did come loose when I was hauling full grill tank of propane the other day but it didn't go into the spokes so no harm done.

  15. #15
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    Quote Originally Posted by kevbo View Post
    Wow, that hitch is...well...something! No kill like overkill I guess!
    I tried a minimalist approach with my first prototype. lasted about a year before it came apart. Rough roads, and hopping curbs etc. with it. Did a bit more engineering on this one, should last a bit longer.

  16. #16
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    Quote Originally Posted by syncro87 View Post
    I've hauled all kinds of heavy cargo ( well, up to about 80 or 90 pounds ) with my Burley Nomad using both the plastic triangle style hitch they use and also the metal hitch that bolts to your rear axle. Never once an issue either way...
    I second this. I've used a Burley metal hitch with a child trailer and hauled around 250 pounds in it. Yes, it was slow going, and no, I don't recommend doing it often as I'm sure it exceeds the designed capacity, but it handled it fine. The Burley hitches are so well designed that Black Oak Fabrications, a custom bicycle trailer company out of Portland, OR uses them.
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    Exclamation

    *DANGER* - A seat post mount will transfer the weight of the trailer to the seat post when the brakes are applied. During a turn, that weight transfer will have a tendency to topple the bike since the attachment point is high up and the load is being applied sideways. Trailers mounted at the rear axel or chain stays do not have that problem to the same degree, since the weight transfer is much lower down on the bike. A lower mount limits the amount of leverage given to the sideways pushing force.

  18. #18
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    Quote Originally Posted by BigBri View Post
    *DANGER* - A seat post mount will transfer the weight of the trailer to the seat post when the brakes are applied. During a turn, that weight transfer will have a tendency to topple the bike since the attachment point is high up and the load is being applied sideways. Trailers mounted at the rear axel or chain stays do not have that problem to the same degree, since the weight transfer is much lower down on the bike. A lower mount limits the amount of leverage given to the sideways pushing force.
    This is right. When I was a teenager I got one of these seat post mounted heavy duty steel trailer. I got it for free from the trash and rebuilt it with a wooden box. Similar to that:
    Swedish Military Bicycle Trailer - $149.95 :: Colemans Military Surplus LLC - Your one-stop US and European Army/Navy surplus store with products for hunting, camping, emergency preparedness, and survival gear
    My parents had a leased a small property outside our town where they grew stuff and which was used for partying. To mow the grass I hauled the lawnmower on this trailer. The trailer itself was way above 50lbs. I guess 60+. With the extra weight of a gasoline lawnmower, gas can and some tools this trailer was pushing really bad. Not just in corners but also on the straight. Plus my bike back then was only a 3 speed with weak brakes. Fortunately there were no hills.

    But nowadays I would still be interested in getting a seat post mount trailer for grocery shopping. Something like that:
    http://www.amazon.de/Fahrradanh%C3%A...SZ6RVZJWSPRH1W
    The reason I like these: You can take them into the grocery store and use them as shopping cart. But I have not seen these type of trailers here in the US. And not for a cheap price.

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