Utility Cycling - Question about stated carrying capacities/maximum loads

Hi. I am wondering about the reason for a trailer's load limit - what part of the trailer is the weak link? There are trailers available like this, which says 40kg:

http://cgi.ebay.co.uk/Bicycle-Trailer-Cargo-Bike-Trailer-Transporter-NEW-F42_W0QQitemZ330337184495QQcmdZViewItemQQptZUK_SportGoods_CyclAcces_RL?hash=item4ce9a16aef&_trksid=p3286.c0.m14&_trkparms=65%3A1%7C66%3A2%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

And then others like this, which claim a 100kg capacity:
http://cgi.ebay.co.uk/Bicycle-Trailer-Cargo-Weather-Resistant-up-to-220-lbs_W0QQitemZ220385330592QQcmdZViewItemQQptZUK_SportGoods_CyclAcces_RL?hash=item334ffd45a0&_trksid=p3286.c0.m14&_trkparms=65%3A1|66%3A2|39%3A1|240%3A1318|301%3A0|293%3A2|294%3A50

Now, I wonder what the real difference is. The first trailer has no solid bed to it, so perhaps that's why? It's referring to the strength of the material, perhaps?
I mean, even the Carry Freedom reckons it can handle 90kg, and there's not a lot to it. I can't help thinking that any welded metal trailer will be able to take 90-100kg or more.

Basically, is it worth shelling out more for a trailer that's supposedly stronger, or could the addition of a wooden base, say, make any trailer as strong as another?

While I'm here, does anyone know anything about that last link? They're quite cheap but there's no picture of the hitch!!! Argh!

I might risk it anyway. The trouble is, they're pretty heavy, these stronger trailers. The carry freedom manages to only weigh 7kg, but some others I've seen weigh a lot more than twice that!

Thanks for any info/help

The weak points are the hitch, and on some designs of two wheel trailers, including both those you linked to, the axles. Other than that there shouldn't be anything specific, but little things like a higher spoke count, stiffer materials, and better welding make a difference. Also worth remembering is that 100kg is a lot - me and my bike together only weigh 90kg. Adding that much weight again behind would make the handling... interesting.

The beds of many trailers are fabric too, which may be their weakest point.

When I hauled the hammer-mill to donate to the little league,I used my Burley flatbed trailer. I put a couple of 1/4 plywood down over the fabric to help strengthen it. Seems to have worked.

Many things are built to a price point, I don't know how much engineering actually goes into the weight limits. In many cases I honestly believe it is put in place by the legal department.

If you want maxiumum load capacity get a Bikes At Work trailer (http://www.bikesatwork.com/index.html). If you overload a lesser trailer you do so at your own risk.;)

Aaron:)

On a slightly different note?

Just thought I'd mention this as Rock_ten put a link to one of there trailers.

I bought one of these trailers from Product Online...

http://www.woger.nl/ebaysite/fietskar/handkar/3.jpg

See example...

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=370178784903

On there page it CLEARLY states SHIPMENT COSTS £9.95.
Well i'd no sooner bought and paid for mine via paypal when I got an email from them asking for another £30?
Seems they dont class Scotland as UK mainland?

So it only costs £9.95 to post any item of theres from the Netherlands to the UK but it costs £30 to post onto Scotland.
After many emails to and from them, I told them to cancle my order. About 10mis after I cancled it I got an email saying - "Iv'e had a word with my manager and he has agreed to waver the £30".

They have since updated there ebay pages to include that added postage to Scotland.

WARNING
If anyone intends on buying one of these trailers please note that the hitch is NOT the best. All built up and hitch securly fastened on you can still pull the trailer towarm off no problem? The Cup on the towing arm isn't fully rounded and doesn't enclose onto the towball.
I only had it about an hour when it was off round to my mates to get him to weld 1/4in of tubing on the underside of the cup. - Hit a bump and trailer still pops off?

As I dont like towarms to the side or under the seatpost (When did you ever see a car towing a caravan or trailer with a pole attached to the back wheel or a pole through the back window attached to the seat?) I intend to use my new Ball Joint Hitch to attach bike to trailer -
http://uk.geocities.com/topcattc@btinternet.com/ballhitch.jpg

TC

Thanks for the replies, everyone. BossCat - yea I've noticed on other trailer listings that postage to Scotland is often more - bad luck! But it's good that you got it at the same price this time.

The terrain you traverse will directly affect the life and durability of your trailer. A simple cloth-bed trailer rated at 100# capacity will probably be able to haul 200# over several thousand miles of smooth asphalt...but try the same loads over real streets and the life of the cloth bed (tires, axles, chassis) will be reduced conversely. Sometimes you just have to size up the situation and haul stuff until the limitations of the trailer are exposed. Then, modify or create something which will meet your needs.