Towing DISASTER!!! - PeachParts Mercedes-Benz Forum

progun · #1 06-16-2008, 09:15 AM

Yesterday, we were going to tow the Benz to Maringouin to work on the transmission. We have done this many times before. This time to make it easier we backed the car onto the dolly. NEVER do this! We know now. The weight distribution was totally wrong and caused an out of control condition. The Equinox rolled once and the Benz was broken loose when the hitch broke loose. No one was hurt seriously. Here is what it looked like at the scene. Paul

winmutt · #2 06-16-2008, 09:25 AM

Just goes to show how safe mercedes are

. LOL Glad to hear no one was hurt.

kerry · #3 06-16-2008, 09:26 AM

Jeeezuz man, I'm glad no one was hurt seriously. There have been a number of discussions on here about not putting the rear wheels on dollies. I guess this confirms the wisdom of that idea.
What exactly happened?

vwbuge · #4 06-16-2008, 09:28 AM

Glad to see nobody was hurt.

The only way to tow a MB safely (for the car and yourself) is to put it on a flatbed.

babymog · #5 06-16-2008, 09:29 AM

How does backing on the dolly change weight distribution and cause an out of control condition? Sounds more like the steering wasn't properly secured, the dolly doesn't care which end you're rolling.

Glad you're okay.

lutzTD · #6 06-16-2008, 09:37 AM

Quote:

Originally Posted by babymog

How does backing on the dolly change weight distribution and cause an out of control condition? Sounds more like the steering wasn't properly secured, the dolly doesn't care which end you're rolling.

Glad you're okay.

the heavy side needs to be on the dolly, otherwise it wants to strear the tow vehicle instead of the other way around and this makes it unstable at speed. it will sway side to side until it finds a harmonic then it will throw you off the road. same issue with improper loading of a car trailer, the engine should always be in the front, too light tongue weight will do the same thing.

to the OP, wow, glad you are OK....

rg_stephens · #7 06-16-2008, 02:38 PM

Bingo. A few weeks ago this almost happened to me trying to pull a Dodge Durango backwards with a 1-ton Ford church van. Even with the steering wheel was locked very tight, it was VERY unstable above 60MPG.

Think about the distance between the center of the vehicles' masses and the pivot point (the hitch). If this this distance is large enough, it may hit a resonant mode at highway speeds and will rotate (yaw) around the pivot. Tires (single, normal aspect ratio) have poor resistance to this yawing/rolling motion, which also lowers the frequency.

Robert
engineering student

Quote:

Originally Posted by lutzTD

the heavy side needs to be on the dolly, otherwise it wants to strear the tow vehicle instead of the other way around and this makes it unstable at speed. it will sway side to side until it finds a harmonic then it will throw you off the road. same issue with improper loading of a car trailer, the engine should always be in the front, too light tongue weight will do the same thing.

blackestate · #8 06-16-2008, 09:45 AM

Glad that you are ok....

Fix or total the van???

babymog · #9 06-16-2008, 09:48 AM

The heavy end has to be in the front on a trailer to maintain proper tongue weight, on a dolly there is no significant overhang behind the wheels, completely different scenario.

We've got people towing all kinds of cars backwards on tow dollys all across the country behind motorhomes in our group, I'd better tell them that it can't be done LOL.

Works fine for me. You just need to secure it properly to the dolly, and make sure that the steering is secure.

Brian Carlton · #10 06-16-2008, 10:30 AM

Quote:

Originally Posted by babymog

The heavy end has to be in the front on a trailer to maintain proper tongue weight, on a dolly there is no significant overhang behind the wheels, completely different scenario.

We've got people towing all kinds of cars backwards on tow dollys all across the country behind motorhomes in our group, I'd better tell them that it can't be done LOL.

Works fine for me. You just need to secure it properly to the dolly, and make sure that the steering is secure.

By guess........without any data..........is that the problem is a combination of two issues.

The heavy end of the MB was at the back of the rig. This is less desirable for controlling sway and would limit the speed of the rig.

The towing vehicle was probably of similar weight as the combined weight of the dolly and the M/B.

When the heavier tail end of the Benz started to sway at high speed, the relatively light towing vehicle was subject to increasing oscillations until it was uncontrollable.

Either a heavier tow vehicle or a reduced towing speed would have prevented this accident. My guess is that it occurred at above 45 mph.

vstech · #11 06-16-2008, 10:49 AM

Quote:

Originally Posted by Brian Carlton

When the heavier tail end of the Benz started to sway at high speed, the relatively light towing vehicle was subject to increasing oscillations until it was uncontrollable.

Either a heavier tow vehicle or a reduced towing speed would have prevented this accident. My guess is that it occurred at above 45 mph.

this is my guess as well...

hcainesjr · #12 03-19-2015, 12:18 AM

I've towed a 300D with the rear wheels on a dolly 600 miles with no issue. the steering wheel has to be locked or strapped down. even then, if the tie rods or idler arm bushings are worn out you may have too much play causing it to sway.

I once towed an old car that had a non locking steering wheel but I was able to screw the adjustment bolt in all the way on the steering box unit.

vwbuge · #13 06-16-2008, 10:50 AM

I used a tow dolly once when I towed my Dune Buggy to the beach. I pulled the front wheels on the dolly. The Buggy has a very short wheelbase but most of the weight was in the rear, off the dolly. I towed it with my '91 Subaru Legacy Wagon. I reached speeds up to 70mph while towing and had no sway whatsoever.

I inquired about towing home a 300SD a few years ago. I didn't want to tow it with a dolly because if I had the rears on the ground I would have burned the trans. I was informed not to put the rears on the dolly as it would cause weight dist. problems. (see picture above)
The only choice was a trailer with the brakes. I towed it home with the wife's Ford Expy and had no problems whatsoever.

The right tools for the job.

rcounts · #14 06-16-2008, 06:56 PM

Quote:

Originally Posted by Brian Carlton

By guess........without any data..........is that the problem is a combination of two issues.

The heavy end of the MB was at the back of the rig. This is less desirable for controlling sway and would limit the speed of the rig.

The towing vehicle was probably of similar weight as the combined weight of the dolly and the M/B.

When the heavier tail end of the Benz started to sway at high speed, the relatively light towing vehicle was subject to increasing oscillations until it was uncontrollable.

Either a heavier tow vehicle or a reduced towing speed would have prevented this accident. My guess is that it occurred at above 45 mph.

Ditto. 3 essentials

1) Towing with something heavier than the load
2) Locking the steering down
3) Keeping it under 45

Thankfully everyone came out of it OK. Any word from the insurance company yet?

vstech · #15 06-16-2008, 09:53 AM

I GOTTA know what you did wrong.
I have never seen any description of problems with weight distribution on a tow dolly before.
steering must have not been locked, or there must have been a problem with the dolly itself.
I am Very glad nobody got hurt!
post some more pics!