wreckerboy wrote:
Keith wrote:
On my Miata, I tie the car down with the control arms. Not that there's much bounce in it anyhow, but it does prevent the shock loads on the straps. I also cross the straps (RR goes to LR, LF goes to RF, etc) - any words for or against that? Hasn't been a problem in the last 10,000 miles of towing or so, and I know it makes a big difference on a roller dyno with a FWD car if you do cross them.
No, no, no. Use the factory tie down points or the tow hook points most sanctioning bodies now require. The last thing you want is the car, tied down by the control arms, free to bounce along and oscillate to it's heart content, independent of whatever rate the trailer is bouncing at. You can end up with what could be considered a variation of a motorcycle head shake that may well be uncontrolable. Snug the car down so that it doesn't move, but not so far down that the shocks are bottomed out.
Crossing the straps is a nice idea, but not really necessary. Apparently the crossing comes from the drag race world where the soft sidewalls of the slicks allowed the cars to walk back and forth on the trailer. I used to cross my straps front and rear until I discovered that in my application the M-speed tow hook was not really designed for side loading like that in the back. I still cross the fronts and use a sleeve between them to control/limit abrasion. I've been towing for four years on that set up (probably in excess of 10K miles) with no load shifting problems.
I agree,
after 40 some years of car haulin'
I would NEVER use an A arm
And NEVER block a suspension solid.
That is just begging for damage.
The car needs to move.. some.
and cinching the suspension down some keeps the straps or chains tight.
The only time I've had a car come loose?
When AAA flatbeded my Sonett home from an OVR autocross ( after blasting a throwout bearing...)
he hooked the rear tie down to the original factory tie down hole in the sheet metal tub.
He had to E stop and the thrity year old sheet metal hold down gave way to rust. And crushed the nose of the car into the front of the flatbed!
IMHO, I double the load rating for straps.
Cross strap for any trip longer than a block or two.
The only time I used a chain and solid cinch was on my gas dragster with no rear suspension, except the slicks
I also learned how to rig loads as external cargo (ie: lifting by crane but mainly under the helicopter) 
