Is the problem with trailers, if indeed they have a problem...
 

the pivot point of the load?
I was bringing some shopping home in the kid's two wheel trailer we have, and though it wasn't that bad, going up hill, there was a lot of resistance.
After I'd unhooked the trailer at home, I wheeled it into the garage, load intact. I noticed that when I lifted the trailer by its attachment bar, as the load moved from in front of the wheel to above it, it got lighter and easier to move.
Would the same be true if it were attached to the bike like that, or rather, if a trailer were designed not with the wheel at the back, but with A Wheel more central, so the load could be placed over it, rather than in front of it?
I'm no expert, but I seem to remember the basic principle of loading a wheel barrow is put all the weight over the wheel. If that is the case, why do so many trailers have the wheel right at the bacK?

If the weight was on the wheel it would wag badly. Weight is weight when you are pulling it. With the wheel at the back and the front obviously hooked to your bike you are spreading the weight between the two wheels. The differance you were feeling was probably just tongue weight shifting as you lifted it over center.

I've only used trailers with central wheels, and loaded them in such a way to balance over that pivot point. Uphill riding was still a lot of work. The central wheel design isn't so much about making the riding easier, as it is about not overloading your rear wheel...that's the wheel that already carrying most of your own weight, and - in most configurations - the bulk (if not all) of the cargo loaded directly on the bike.

The basic problem with trailers is that you can put a lot more weight on the trailer than you ever could on a bike. Also, an extra set of wheels adds more rolling resistance. One wheeled trailers also make balance more complicated, and can introduce side to side torques on the frame that will fatigue the bike over the long haul.

Ahhh, I see. Thanks for the input, guys.

Which can be minimized by putting high pressure, high quality tires on your trailer. So many folks will spend all this time and money putting the best tires on their bike, and then tour with the cheap stock tires that came with the trailer.

Not to nit pick but high pressure has nothing to do with quality nor will they decrease rolling resistence. I would also think they would make for a really bouncy trailer.

I just recently read an article on this here somewhere in BF, using supporting data from a wheel testing lab in Norway.

One of the things the article said was (and I'm paraphrasing) that all other things being equal (AOTBE), higher tire pressure lowers rolling resistance. It also said that AOTBE, greater diameter reduces rolling resistance. The third tidbit I took away was that AOTBE, a narrower tire does not necessarily have lower rolling resistance.

All this apparently comes from the fact that rolling resistance largely depends on the energy "lost" from forward momentum and converted to energy required to deform the tire under load. AOTBE, a tire with higher pressure is more difficult to deform for a given load. That seems pretty intuitive to me.

Have you read something contrary to this explanation, and would you care to share the info? I'm not trying to challenge your comments, rather I'd just to know the truth in this matter.

I actually bought a 100psi Kenda Kwest tire for my Bob Yak years ago partly for this reason.

I googled some terms and this was the first hit (there are probably better examples, but I think this supports the other article findings).

http://www.rouesartisanales.com/article-1503651.html

Down the page is a link to test data. It clearly shows rolling resistance is lower at higher pressure, on all 12 of the 12 tested tires (actually, it shows energy required to spin wheel under test condition is lower on the higher pressure tires).

http://ddata.over-blog.com/xxxyyy/0/...lar-specs.html

After a moments thought, I realized the energy loss to rolling resistance is probably trivial compared to the weight of cargo a touring cyclist lifts over hills and mountains, and even insignificant compared to the energy required to push all that very non-aerodynamic gear through the air. The frontal area of a touring bike with panniers, powered by an upright-sitting cyclist must be twice that of the average club cyclist out on a group ride on their road bike.

trailers , particularly auto towed, there is better handling with some tongue weight
over the axle would make it teeter totter like, and less safe.

my Carry Freedom city, a folding bike trailer , has its 2 wheels toward the back, and tows OK.

I think my translation may be different then yours. The narrower the tire is the less the overall resistence. This is mostly because of wind drag. A softer tire be it compound and or air preasure will deflect less there for lowering "rolling resistence". In the aplication we are discussing, the trailer itself should already block most wind. Now, I am no scientist (ditch digger by trade) but it seems to me for a trailer I would want a nice fat tire to roll smooth and eat up the bumps. I have not pulled one yet but will be this summer and I guess I will put my theory to pavement then I will know for sure. Although i am certain that we are discussing very negligable amounts of resistence maybe its better left for lab discussions