Transporting a large load on vehicle roof bars

Question

What is the best way to attach a bed (160cm-by-200cm = 64"-by-80") to the roof bars? The car is Citroën C4 Picasso, with the bars as shown in the image below. I need to transport it only for a couple of miles, but without damage (it will be new and might have to be returned to the store.) I think about tying it with cords, so the question is mostly about how to tie in the most secure way. However, I am open to other suggestions/ideas.

(image source)

Additional info:
Bed is just rectangular (no headboard) - perhaps 20-30 cm thick (8"-12"), packaged in plastic or cardboard. Bars are about 120cm long (48") and spaced at about 80cm (32").

Answer 1

Beds and cars are off topic here, but I'm writing an answer because I've brought substantial amounts of lumber and sheet goods home on my wife's Audi A3 using this technique^*.

• Secure a few 8' 2x4s or 2x6s to the rack using suitable rope technique or something like ratchet straps and head to the store. Four is better since you can avoid the arch in the middle of the bars to some extent; two solid ones would probably be adequate. If using rope, see YouTube for lessons. Trucker's hitches are great, but maybe not for this first step. You need a lashing knot or bend.

• Position the bed on the wooden rails in a suitable manner. Be sure to distribute the load fairly evenly. Pay attention to the lifting notes on the carton or package. For longer loads than a mattress, bias to the rear to reduce the chance for wind lift.

• Secure the bed to the lumber rails and the car bars using more rope or straps. By wrapping around the load and through the bars, locking against the bar supports, the possibility of lateral movement is eliminated. This is one nice benefit of a wide load. Snug the lashings up enough that neither the load nor the rails can shift in a sudden stop. If appropriate, run around the load front-to-back, looping over the bar a couple times to lock position.

• Don't exceed about 50 mph, corner gently, and keep a close eye on the front for uplift. Things get destroyed in high wind, maybe on or in the traffic behind. Stop and adjust, if needed. Watch carefully for potholes or dips--bounce can dramatically increase the dynamic weight of the load on the roof.

If using rope, good technique is critical. Inexperienced people tend to leave room for shifting loads, which instantly loosen the tie. You must eliminate or accommodate that possibility.

Also note the possibility that interior boards or load items can be loose by virtue of the shape of the load. If they are, secure them further or move them outward.

Of course, heed the total load rating for your vehicle (to a degree--the rating assumes central loading and you're mostly loading the ends, ideally). You don't want the bars or the roof coming off at an inopportune time with a pile of roofing shingles splattering out behind.

And protect your car's roof. Hand buckles to a helper so they don't bounce. Secure rope and strap ends so they aren't whipping. Use caution when lifting the load over.

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_{* I want a bumper sticker for my ol' BMW 330i reading, "This little car has probably hauled more lumber than your giant pickup".}

Answer 2

Seriously, rent an truck or pay someone to haul it for you.

1. I think that the bed frame, due its dimensions, cannot rest directly on the rails. That means the flimsy packaging needs to be strong enough that the roof rails won't punch through the packaging. I suppose here that the bed is either empty in the middle, or does have some flexible mattress inserts. I don't think that this will work, as proper ratchet straps need tension to keep the load from falling down.

2. The package hangs over the roof, as your roof is supposedly narrower than the 1.6m. That could mean legal troubles.