RV Accident US 131 in Michigan

Ron Gratz wrote:

myredracer wrote:
The rule of thumb below to minimize sway has been around for a number of years (from David's RV Tips). I've seen it elsewhere too. Doesn't seem to come up much. If the Armada wheelbase is 123", the max. TT would be 23', well under what the TT appears to be.

The First Guideline
(This guideline was first used by the RV Consumers Group rv.org)

For the first 110" of wheelbase, this allows you 20' of trailer.

For each additional 4" of wheelbase, this gets you 1' more of trailer.

Wheelbase / Trailer length
110" = 20'
114" = 21'
118" = 22'
and so on

According to this ROT (rule of thumb), Suburbans (including 3/4 ton Suburbans) should not be used to tow trailers which are longer than 25'.

No one seems to be able to provide any information about how the numbers were derived. And, IMO, no one has presented any convincing arguments as to how increased TT length should make a TV/TT combination less stable assuming that the TT length is the only thing that changes.

IMO, we have no clear understanding as to how TT length affects TV/TT yaw stability. However, IMO, it is pretty clear that there are four primary factors which do affect stability. These are:

• Tow Vehicle Weight
• Tow VehicleWheelbase
• Hitch Overhang (distance from TV rear axle to ball coupler)
• TT Weight
• Tongue Weight Percentage

The "guideline" attributed to RV.ORG ignores four of these five factors. My guess is that the "data" which were used to formulate the "guideline" might have contained some correlation between TV weight (which might be correlated to TV wheelbase) and TT weight (which might be correlated to TT length).

One could then take an "average" wheelbase for a range of TV weights and take an "average" length for a range of TT weights and come up with a wheelbase-length relationship for "safe" and "unsafe" TV/TT combinations. However, correlations that might have been appropriate for TV/TT combinations which existed in the 1950/60s (or whenever the unknown data were collected) might not be appropriate for combinations in use today.

IMO, staying within all the TV manufacturer's weight ratings is the primary consideration. If you do that, then the TT length probably will be acceptable also.
Perhaps someday we'll have a "guideline" which properly accounts for all of the primary factors.

Ron

Very good points.

myredracer wrote:
The rule of thumb below to minimize sway has been around for a number of years (from David's RV Tips). I've seen it elsewhere too. Doesn't seem to come up much. If the Armada wheelbase is 123", the max. TT would be 23', well under what the TT appears to be.

The First Guideline
(This guideline was first used by the RV Consumers Group rv.org)

For the first 110" of wheelbase, this allows you 20' of trailer.

For each additional 4" of wheelbase, this gets you 1' more of trailer.

Wheelbase / Trailer length
110" = 20'
114" = 21'
118" = 22'
and so on

According to this ROT (rule of thumb), Suburbans (including 3/4 ton Suburbans) should not be used to tow trailers which are longer than 25'.

No one seems to be able to provide any information about how the numbers were derived. And, IMO, no one has presented any convincing arguments as to how increased TT length should make a TV/TT combination less stable assuming that the TT length is the only thing that changes.

IMO, we have no clear understanding as to how TT length affects TV/TT yaw stability. However, IMO, it is pretty clear that there are four primary factors which do affect stability. These are:

• Tow Vehicle Weight
• Tow VehicleWheelbase
• Hitch Overhang (distance from TV rear axle to ball coupler)
• TT Weight
• Tongue Weight Percentage

The "guideline" attributed to RV.ORG ignores four of these five factors. My guess is that the "data" which were used to formulate the "guideline" might have contained some correlation between TV weight (which might be correlated to TV wheelbase) and TT weight (which might be correlated to TT length).

One could then take an "average" wheelbase for a range of TV weights and take an "average" length for a range of TT weights and come up with a wheelbase-length relationship for "safe" and "unsafe" TV/TT combinations. However, correlations that might have been appropriate for TV/TT combinations which existed in the 1950/60s (or whenever the unknown data were collected) might not be appropriate for combinations in use today.

IMO, staying within all the TV manufacturer's weight ratings is the primary consideration. If you do that, then the TT length probably will be acceptable also.
Perhaps someday we'll have a "guideline" which properly accounts for all of the primary factors.

Ron

The rule of thumb below to minimize sway has been around for a number of years (from David's RV Tips). I've seen it elsewhere too. Doesn't seem to come up much. If the Armada wheelbase is 123", the max. TT would be 23', well under what the TT appears to be.

The First Guideline
(This guideline was first used by the RV Consumers Group rv.org)

For the first 110" of wheelbase, this allows you 20' of trailer.

For each additional 4" of wheelbase, this gets you 1' more of trailer.

Wheelbase / Trailer length
110" = 20'
114" = 21'
118" = 22'
and so on

Who's this Y'all? I was raised on a ranch in NM, lived in OK on one and work in the cattle industry in TX. Never met anyone from CA called people Y'all. He looked overloaded to me.

The time my in-laws ended up looking a bit like this, it started when a vehicle next to them blew a tire and clipped the back of their TT. In their case the TV also ended up on it's side sliding down the freeway.

Not likely any normal rig configuration could have overcome the inertia caused by the other vehicle hitting their TT that hard.

Oh I certainly wasn't blaming or judging. I was just very recently choosing between a half ton or a large SUV and looked at Armadas. One of the reasons I chose the truck over the Armada (and a couple other large SUVs) is because there wasn't a tongue weight limit of 900 pounds and because I could get more payload by either going with a model with less frills, or adding on a maximum towing package to a model with all the frills. My comment was really just saying that I understood how easy it would be to be at/over the limits with a larger trailer. I have no idea if this particular accident was over any limits or if it was, if that contributed to the accident at all. Again, I just hope everyone was okay.

The stats posted above on the Armada are pretty much the same as my truck or any other 1/2 ton pick up on the road. The difference a truck has versus the SUV is a longer wheelbase which helps with stability and control.

Just so everyone understands, an overloaded tongue weight, trailer carrying capacity or over loaded payload doesn't magically make a truck and trailer flip over on the highway. It takes an event for this to happen; wet or slippery roads, high winds, reaction to being cut off or something on the road, etc. This really comes down to driver reaction and a toss of the dice. If you are within your weights and your tow vehicles capacity, it certainly helps you regain control, but not necessarily. If you are over your weights, it is likely harder to regain control.

There seems to be way too much blame happening on weights, size of truck and length of the trailer, when it really just comes down to how the driver reacted to a situation on the road that we don't know. Everyone's reaction is different, I don't think we can say 100% that everyone who sees their trailer go sideways in the mirrors will remember to hit the trailer brakes first, not the vehicles brakes....

While the Armada has a decent tow capacity, it doesn't have a huge payload. The one I just looked at could tow 9000# and had a 1300# payload. Max tongue load can be 900# so with a trailer that big a 900# tongue is likely right? So it's possible that a 900# tongue was too light depending on trailer weight, or overloaded beyond the 900# to get it a better ratio for the trailer weight, or vehicle could have been over payload with a couple passengers and cargo and a 900# tongue.

Or the trailer, tongue and payload was just fine and it was some other random set of circumstances that caused this. ;) I just hope everyone was okay.

thomasmnile wrote:

dspencer wrote:
I have to go now and buy a Freightliner to pull my 26ft Bunkhouse. :R

Are you sure that will be enough truck...........;)

Well if I pack very light I think I can get by. No firewood, lawn chairs etc. :B

Ron Gratz wrote:

E&J push'n wind wrote:

opnspaces wrote:

hddecker wrote:
I let up on the throttle a bit next thing I see in the mirror, backend of the trailer about three feet to the left of center.

Trucks going straight, a little tap to the brake controller switch and the trailer gets back where it belongs.

Sure was happy I had the Hensley Hitch that day.

Did anybody catch this post by hddecker? Not picking on you at all hd, just caught the part that your Hensley let the trailer get out of shape. I thought that supposedly wasn't possible?

I tow with a Hensley too, yeah.., I did catch that but let it go. No, it is not possible unless something is bending or the shear bolts have let go in which case you'll have a mess on your hands. I'd like to hear how that is possible.

I think we should not imply that "hddecker" was seeing things.
It's entirely possible -- especially in a low traction condition as might have happened if you're driving in Canada at Christmas time.

It the trailer tires lose their ability to generate lateral force, there is nothing to prevent the trailer from swinging to the side -- makes no difference whether towing with a HA/PP hitch or a conventional hitch.

When "hddecker" let up on the throttle, the 4-bar linkage might have produced a "bump" event which resulted in the trailer swinging to the side.
Even with no "bump", the trailer still can swing if the tire/pavement friction cannot generate sufficient lateral force.

Ron

Hi, Ron

Nope, no bump. Just an absolute skating rink that day. It that you could have played hockey on that piece of highway that day.

I think it was you that explained why I have never had a Hensley bump occurrence. I keep the strut bars adjusted and my brake controller set to being the TT as soon as I hit the brake pedal.