Technical Question on trailering

Opinion please. When I trailer a car, the one thing I hate to see is watching my car bouncing up and down after hitting a dip or bump in the road. So, along with the normal tie down methods, I like to use motorcycle type tie down straps, two on the front bumper and two on the back just to provide tension on the suspension. This is not for added security but just to reduce the bounce. I have been told this is the wrong thing to do that I need to let the suspension "work". Am I wrong?

 

I let my suspension work If i have a vehicle on a trailer

 

Ditto

 

The car will get a softer ride if you let the suspension work. Trailer suspension is pretty rough.

 

When you see them on a transport truck they are tied down by the frame, and the suspension is loaded to prevent bouncing. A lot of vehicles even have tie-down loops attached to the frame by the factory, so there must be a reason for it. I sold and shipped a couple of 72 Chevy pickups this past spring, and the transporter tied them down by the frame, and cranked quire a bit of load into the suspension with the tie-downs.

 

I let the suspension work on the car. Right or wrong, never had any problems. If you tie the frame down just make sure to strap it down enough so the car has nearly no downward travel possible. If it can still go down this means your straps are loose every time it goes down and there's a chance they could come loose. On a lot transporters they are usually stacked and you definitely don't want them bouncing up.

 

Let the suspension work. The car does not know if it is on a trailer or the road.

 

They are secure on multi-car transporters so they don't hit the car above. I think there can be a case made for each way otherwise. As some have said if you pull it down it has to be all the way down. If the trailer is spring too heavy it will pull those chains right out of the frame it happens on new cars quite often.

 

strapping just the suspension and letting the weight of the car bounce puts more stress on the straps, think slide hammer. you really want to secure the load/weight to the trailer. holding just a few hundred pounds of axles and letting the weight move is not the best way. yes it is done, and yes you can get away with it, when i was a teenager i towed a car on a trailer and all we did was put it in park. wrong? it worked.

 

And if ya really hit a big bump or pot hole you'll tweak your bumpers, I'd never do it

 

The suspension is doing the job it's suppose to do.

I would worry about tweaking the bumper the way you have suggested. HRP

 

Tie the load to the trailer, & Let the trailers suspension do the work. Especially for a long trip. A few miles trailering across town is one thing and it's usually enough to see why it's way different.

With the car bouncing on its suspension it's constantly changing the load on the trailer and on the tow vehicle. Also the load is moving, shifting weight around on the trailer. The cars suspension shifts it's weight on the road, it's going to do it on the trailer too.

As far as multi haulers go, can you imagine what 8 cars bouncing any way they want to on a trailer would do to it as far as handling characteristics?

Using the bumpers is probably not a good to do it either.

 

I have trailered a LOT of cars over the past couple of decades......four for 500 to 900 miles each in just the past few weeks. My fewest and shortest tows are a couple of miles, my longest was about 2200 miles. The distances probably average about 200 miles. I usually tie down by the front 'A' arms, or front axle if so equipped, and rear axle, and let the chassis ride on the springs..

My concern is less about up/down movement of the chassis than fore/aft. I want it to stay on the trailer. The vehicles DO NOT move fore and aft when the axles ('A' arms) are adequately secured. Strapping the chassis down puts much greater strain on the tie down straps, chains, fittings, etc. as you are imposing loads much greater than just the vehicle's weight.

Think about it. Say the vehicle weighs 4000 lbs. If you secure the vehicle by axles or equivalent, you are only securing that much weight as a 'rolling load'...[plus the increased inertia from acceleration/deceleration when starting and stopping or serious dips in the roadway. I use 10,000 lb straps on all four corners.

However, if I compress the springs fully to eliminate body/chassis verticle movement, the continuous load on the straps is going to far exceed the static weight of the vehicle, otherwise the springs wouldn't be compressed. And, when I hit that big dip in the road the verticle inertia is going to be greater still.

I have, on occasion, strapped the chassis at the front end, where the original tie down brackets were in place (my '38 and '40 Buicks had them, for example) and tied down the axle at the rear. That has worked well enough but is not my standard practice.

Ray

 

The car should be loaded from the chassis. I know I'll get shit for this statement but all the shock and suspension manufacturers recommend this also. The shock heat up while they are providing your riderless car with a smooth ride, also with the trailer bouncing around and your car bouncing around it's a hell of a task towing the combination.

Pat

 

I totally disagree with your conclusions. A trailer in good condition and adequate for the load being carried rides just as well as your average car or pickup. It absorbs most of the road irregularities and some residual bump load may be passed on to the vehicle being trailered. Unless you are on an exceeding rough road, that is minimal.

As for "shock heat up", they are doing what they are designed to do.........

Ray

 

One other factor not mentioned so far is...the towing vehicle. It is a major factor in stable towing over all manner of road surfaces. A softly sprung pickup or SUV or station wagon, especially in combination with marginal capacity and/or under inflated tires, does not provide a sufficient platform for safe and comfortable towing of a standard sized/weight vehicle even with a suitable trailer.

In addition, perhaps even more important, is the weight distribution of the load on the trailer. Standard practice is around 10% of the trailer weight on the tongue. A rear weight bias, or even a light tongue load will lead to a case of the "tail wagging the dog".

Ray

 

When towing a heavy car like dad's station wagon, we would cross tie the rear frame to keep it from swaying. Normal cars I let bounce, the wagon needed extra since it was so long. If it got to swaying on the trailer, then the whole trailer and truck would start.

My vote is let it bounce. It's not moving nearly as much as you think it is!
Joe

 

Never let the truth get in the way of a good story.

So you are saying a car towed the same distance on the same road will go through more suspension oscillations than if it was driven by itself !
On a trailer a percentage of bump loads are absorbed by the trailer suspension, and the remainder is absorbed by the car / payload.

I just love how people load their cars down on the chassis with ratchet tie-down. The whole car is like a "Jack-in-the-box" waiting to go off when a strap breaks.

Some people even load their cars down onto blocks, which is about as stupid as jacking a car up by the sills. [or whacking the underside with a hammer]
The chassis is designed to absorb bump loads through the suspension.

Any shock and suspension manufacturers that recommend the car should be loaded from the chassis are just trying to "kick the can down the road" with any liability issues to their products

 

In addition, perhaps even more important, is the weight distribution of the load on the trailer. Standard practice is around 10% of the trailer weight on the tongue. A rear weight bias, or even a light tongue load will lead to a case of the "tail wagging the dog".

100% truth there^^^

Now lets talk about a spring loaded weight bouncing around on the trailer.
Does it not change the weight distribution ?

 

I did preface my statement. Here is a statement from QA1;
How should I tow my racecar without causing premature shock wear?
While towing your racecar, the suspension is continuously working during the entire trip to the track and back home. All the bumps, pot holes or uneven pavement your towing vehicle feels, your racecar feels even on the trailer. Especially when towing long distance, this causes more stress and wear on the shocks and can lead to the shocks wearing out faster. Check your shocks after a tow and you may be surprised how warm they are! To help eliminate premature shock and suspension wear, always tie your vehicle down in a manner that minimizes vehicle bouncing. Most of us generally wrap our tie down straps around the axle housing and front suspension, but this isn’t strapping the suspension down. One way to help prevent the shocks from doing any unnecessary work is to always strap the body or chassis directly to the trailer. This causes the body to move with the trailer, rather than independently and will help lessen the stress that falls to your racecar’s suspension.

Everybody is free to do as they wish, I for one will tie the chassis down.

Pat

 

Really appreciate all the information. I have actually only used this bumper tie down method once and I've towed cars from Oregon to Oklahoma many times the conventional way without bumper straps. Just thought I would try something different during an in-town tow. I only use the best straps and chains, a excellent tandem trailer and 3/4 ton duramax to do the towing.
Three comments stand out. 1. Bumper tweekin 2. Slide hammer and 3. Jack-in-the-box. Thanks!

 

Hnstray nailed it.

 

Interesting topic. My brother in law travels A LOT with his car in an enclosed trailer behind his Big Motor Home. Either a 32 Ford Cabro or nicely finished 47 Merc Convert. Like most of us, he ties onto the front and rear axles (or a-arms) and well angled side to side to limit side sway. Recently on a 1500 mile trip he took the 32 out of the trailer and quickly found the upper rear coil over shock shaft broken off. Not the cross bolt mounr but the actual shaft coming out of the coilover shock. Nothing unusual about the the shock set up, proper angles, etc. It appears that the car had UP bounced enough in the trip to snap off the shaft. Every one seems to agree thats what happened, its a 4 year old name brand trailer and as far as I know, proper air pressure in the trailer tires. I suppose that if you got into a stretch of rapid fire bumps the 32 could really jump. Hard enough to snap acoilover shock shaft? Apparently so. Either way, he now uses an additionl floor to frame strap, font and rear. BILL RINALDI

 

I do not think the weight distribution changes appreciably as the loaded trailer jostles over bumps.
I do think the load forces increase and decrease (+G / -G) momentarily as that up and down motion occurs. That is, after all, what compresses and rebounds the springs on suspended vehicles. But since the vehicle on the trailer is stationary fore and aft, and the trailer axles are nearer to the center of the loaded trailer, it is not apparent to me how weight distribution would be altered significantly in the process.

Ray

 

Sorry your BiL had such a problem. Glad there wasn't serious damage as a result. It occurs to me that a possible factor in his case could be related to the sprung/unsprung weight ratio of his '32.

With a light(er) weight body chassis, compared to the relatively heavy axles, brakes, wheels, tires, etc.,
the body/chassis is pitched upward harder passing over bumps than a heavier body/chassis given the same unsprung components.

In my post immediately above, I mention the location of the trailer axles. Your BiL's situation may illustrate the greater upward pitch force of the cargo because of the trailer axle location compared to a greater space between the axles as found on conventional vehicles. Put another way, a conventional vehicle, not a trailer, usually traverses a bump one axle at a time and the upward displacement is absorbed first by the front end and then by the back end. My reasoning suggests the upward forces are somewhat divided in that scenario and consequently 'softer' than when more concentrated by the closeness of the axles on a trailer.

To some extent, even an average 2wd standard cab pickup will illustrate the difference in sprung/unsprung weight when absorbing a bump. The lighter front suspension, heavier cab, engine and occupant(s) provide a more favorable sprung/unsprung weight ratio than does the rear of the (unloaded) pickup with the heavier axle, springs, etc. versus the relatively light weight of the rear frame rails and pickup box. As the pickup passes over the bump, the front end "rides better" (springs absorb more of the upward movement) than the back end, which pitches upward more violently.

Ray

 

The OP was referring to "Towing a car"
You somehow can only see "Towing a racecar" and quote a disclaimer from a racing shock manufacturer that sells a product with a limited life expectancy

 

Unlike on the highway where suspensions need to deal with forces not only moving the suspension up and down, they also need to resist the forces toward the rear of the car imposed by the car's forward motion over a bum or into a pot hole. I would think that most of the type of force is absorbed by the trailer tires and suspension, leaving the car to deal with basically the trailer moving up and down vertically. Seems this would take much of the load of the trailered vehicles suspension. I tow a light car on an unsuspended trailer. I use straps with D rings and ratchet straps to secure the lower A frames up front and chains and binders to secure the axle at the rear, pulling down and back against the front rigging. the trailer weighs about 400 lbs and the car about 1300. The car's suspension then absorbs and dampens bumps encountered by the trailer. It has worked without problems for 30+ years. I have also used the same tie down procedure with heavier cars on suspended trailers with no problems. Granted I do not go far perhaps 150 miles, and I do stop and check things after the first 10 to 20 miles and then a couple more time during a trip.

 

Unless your going to use winches like the big boys and 3" straps to tie the car down by the frame, you'd be wasting your time, regular ratshit straps are not enough to tie the car down much less keep it from bouncing. As far as the broken shock the motor home has a lot to do with how a car rides, watch one next time and see how much up and down movement you get at the hitch, the tail of the coach allows much more movement on the trailer.

 

I haul cars a lot heavier than this group does, quite often actually. I use good straps (just bought 4 new ones this month), wheel stops on the deck, set the brake, tie down by the axles and let em eat. Something else I don't do, criss-cross the back straps. Suppose one does fail in the rear, what happens? If the one pulling left breaks won't it eventually dance over to the right? Earlier this year I had the panic stop of all panic stops in KY. Some little twit decides to stop her happy ass in the left lane with no warning! I had 4 car lengths and was travelling about 60-65, the trailer was carrying a 53 Skylark (there's a "little" car, right?). I got lucky and had a nearly 3 lane "get out" spot on the left shoulder, all paved. I think my brake pedal still says Wolverine to this day! Imagine 5k lbs worth of car, almost 5k lbs of trailer (maybe more) and 8300 lbs of D'max dually stopping in under 5-6 car lengths. My 1st order of biz after a check of my shorts was to get off and check the load. I can't begin to imagine the kinetic forces on the car and straps but I'd say it was substantial, yes? Didn't move a fraction of an inch. Nothing. Strapped down by the front and rear suspension, no frame hooks, no travel limiters. I've done exactly this for decades from MI to CA, KS, FL, and countless points in between. Maybe my trailers just ride good? It's a Featherlite 5th wheel (yes, 5th, not a goose neck). It does ride nice and the load is enough to get the truck near level. Old open trailers, hell even some new ones, ride like farm implements by comparison. I'd want my car to assist in the removing the harshness. I think it's easy on both the car and trailer.

As far as drag cars in trailers with only the suspension tied down, the real concern builders there came from the emergence of bracket racing dragsters. Those long chassis over great distances were indeed showing fatigue where they flex from the constant bounce. The solution was an inflatable "bag" get up that took up the flex. If my door car suspension wasn't up to a tow I sure as hell wouldn't count on it to CONTROL my car at trap speeds. Just sayin, carry on...

 

Welp, I learned NOT to just tie down to the trailered car's frame/chassis when I brought my 35 IHC pickup home. I used chains and binders at all 4 corners, pulling the frame down tight...or so I thought.
Just cresting a hill something caught my eye in my interior mirror,,,it was the IHC coasting back on the trailer!!!!
I feathered the brake pedal and got the truck to come back forward on the trailer....now, going down hill, I stopped to see WTF!
The little pickup had bounced violently enough to pop the binder hooks out of the slots in the front frame rails.
Only the rear chains were still atteched and they wouldnt' have kept the IHC on the trailer.
I got lucky and now I only chain/strap to the car's axles or A frames...