Let’s make assumptions. First, we’ll say that your trailer has adequate capacity to safely haul your autocross car, the axles are of sufficient capacity, the bearings are maintained, the tongue weight is correct, yada yada yada. We’ll also figure that you’re using proper tie-down equipment, and well-engineered tie-down points on the trailer. But as with so much in life, it’s not the equipment that lets you down, it’s the way you use it. To that end, let’s look at how to strap your car to a trailer.
Let’s consider over-the-tire straps. This method allows the car’s suspension to move while towing down the road, and it will undoubtedly help damp the trailer’s movements, but it seems that this will result in a certain amount of wear to the car’s shocks from the constant movement. On the other hand, locking the car down will allow repeated movement through a smaller range. Maybe it’s a wash.
With tying to the chassis, there’s plenty to consider. Tying a car down going front-to-back is fine, but this doesn’t eliminate side-to-side motion. Over a thousand-mile trip, that car may migrate. Crossed straps solve this, as triangles are magical things. The concern with crossed straps, however, is if a ratchet comes loose, the car could shift sideways, loosening up other straps in the process. This is never good.
Tying to the chassis is also complicated by the arrangement of tie-down points on the car. Tie-down slots in the front of the rear tires or behind the front tires pretty much dictate crossing the rear straps. To that end, sometimes a hybrid solution is the only one available, with straight straps on one end and crossed on the other.
If you are dealing with factory tie-down points, you have to find the tie-down points. Sometimes they are obvious, accessible, and usable, while other times they’re covered by plastic plugs, placed somewhere you can’t get to with the car on the trailer, or are in otherwise unfortunate locations. For a dedicated track-only car, you can largely do whatever you want as far as tie-down points. Rings, hooks, slots, whatever – just put them somewhere you can get to.
In the 35 years I’ve been running National Solo events, I’ve towed at least 13 different vehicles. Let’s go through some highlights.
Conquests had loops on the front, but nothing at the back. I looped a strap over the rear cross-member but found that the cross-member would saw through the webbing in a few miles. A visit to the shoe repair shop to get a leather pad sown over a new strap, and we had a long-term solution.
The Neon was a bit of an adventure. It had T-hook slots on the subframe in the front, right under the front seats. It had slots in the rear subframe just inside the bumper. A bit of pondering resulted in loading the car on the trailer backwards.
Second-generation MR2s are pretty easy, as they have T-hook slots up front and wire loops below the rear bumper. I used a chain with J-hooks at the back of the car, and ratchet straps on the front. The benefit of this was that the chain was a fixed length, and the car always ended up in the same location, so the trailer balance never changed.
And, finally, J-hooks seem to fit in Porsche jack points, and the BMW M2 hides its T-hook slots in the plastic jack adaptors.
But no matter how you tie down your car, just make sure it’s still on the trailer when you get to the autocross event.