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| [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163158] |
Fri, 16 March 2012 12:17  |
tmaki
Messages: 200
Registered: September 2005
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In the interest of sharing a little information on the topic
of pulling a trailer, I'm going to point those interested to
the MVP RV Web site. There you will find PDFs of the
Towables Owner's Guide that I wrote for them a couple of
years ago.
I've spent 32 years of my life in the RV business writing
owner's manuals, service bulletins, warranty manuals, flat
rate manuals, parts catalogs, training materials, etc. for
brand "F" (for 21 years) and several other RV manufacturers
as an independent contractor/consultant.
The chapters in the MVP Owner's Guide are the latest version
of a long evolution of information about owning and towing a
trailer. It has a lot of information that is specific to
MVP's products, but the general towing information contained
in the chapters I reference below apply to nearly all
trailer types and situations. If you're looking for a
general guide to towing, I think you'll find the information
useful. Some may disagree with some of the specifics, but
it's the general frame of mind that is important.
Go to http://www.mvprv.com
Click on the "Customer Service" tab, then on "Product Manuals".
Download chapters 5, 6, 7, 8, and 18. You can also download
any other chapter or the whole thing (whole thing is 236
pages). I would suggest chapters 3, 4 and 20 as well. There
is a lot of general RV care and maintenance information that
you can use. The specific product information won't help you
much unless you have some of the components covered
installed in your GMC (unlikely), but you'll figure out what
is useful. You can substitute "motorhome" for "trailer" in a
lot of the general information. Everything is not applicable
in all situations. Use the info you can, toss the rest.
There is no reason to run around ignorant about the topic.
I'm offering this as a source of general information. Hope
it helps.
Toby Maki
'73 Glacier 230
Riverside, CA
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163162 is a reply to message #163158] |
Fri, 16 March 2012 12:46  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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Good information for all. I do have a couple of issues as always 
The industry standard hitch ratings to date show a max tongue weight rating that is 10% of the hitch tow capacity--not 15%. We are working with the hitch industry to increase that to 15% but you need to stay within what is marked on the hitch. The hitch system rating is the lowest of the combination of the hitch, the ball mount and the ball--all three of those will be clearly marked with the max rating. Additionally, you should never exceed the gross rear axle weight rating that is marked on the door jamb of your vehicle. You should also look up what the GCWR (gross combined weight rating) of your vehicle is--that is the rating you need to stay within when towing. As you can see, the max capacity is determined by the lowest of any of the hitch system, the GCWR, and the GRAWR (rear axle weight) ratings.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163163 is a reply to message #163162] |
Fri, 16 March 2012 13:05 |
tmaki
Messages: 200
Registered: September 2005
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On 3/16/2012 10:46 AM, Bob de Kruyff wrote:
>
>
> Good information for all. I do have a couple of issues as
> always :)
>
> The industry standard hitch ratings to date show a max
> tongue weight rating that is 10% of the hitch tow
> capacity--not 15%. We are working with the hitch industry
> to increase that to 15% but you need to stay within what
> is marked on the hitch.
No problem, Bob. The industry has been duking out the
specific %-ages for all the time I've been involved. One
year it's 10-15%, the next it's 9-12%, or some variation.
Our engineers at "F" spent days, months, years on the
Belgian blocks, proving grounds, and in the engineering
shops with sensors and strain gauges attached to measure
various parts of the tow vehicle frame, trailer frame,
hitch, sway bars, 5W hitch boxes - you name it - studying
the effects of loading, speed and sway proclivities. Reese,
RBW, et al, were involved and contributed valuable
information that was included in the owner's manuals. We
respected U-Haul's position in the industry enough to
observe the labels and cautions/warnings that U-Haul uses,
and incorporate applicable ones into both the product and
manuals, most recently for the MVP chapter on cargo
trailers. I spent a full day at a U-Haul store photographing
and studying the tags to get a general idea of what should
be included for that type of trailer.
Even the definitions of GAWR, GCWR, etc. evolved and changed
over time - sometimes back to what they changed from - and
then back again.
As with most things, the truth is in the middle. It is
always, IMO, to err on the side of safety.
Toby Maki
'73 Glacier 230
Riverside, CA
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163168 is a reply to message #163163] |
Fri, 16 March 2012 13:22 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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We're certainly not totally pure on this stuff either since in our case we are in the "occasional" towing business which we feel is somewhat different than towing most of the time. Where this comes into play relates to what the manufacurers recommend. Their ratings take into account warranty and cooling issues that aren't necessarily safety related. I agree with you that good judgement is a big factor! Even though I came from GM and we did a lot of towing, being on the trailer side has been quite an education
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163178 is a reply to message #163166] |
Fri, 16 March 2012 13:49 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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| idrob wrote on Fri, 16 March 2012 12:20 |
Toby and Bob:
Have you seen this information on towing dynamics developed by an Australian. It makes a lot of sense to me, once I get the english sorted out (a tug is a tow vehicle, a van is a caravan or trailer in our usage).
I would enjoy your take on what he says.
http://www.caravanandmotorhomebooks.com/articles/caravan_dynamics_cw.pdf
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Yes-that article gets the root of sway stability. There are some scary equations we use to determine critical speed and damping ratios that will scare the entire crowd away. Then of course we confirm the designs with physical testing. Our issue is that we never quite know what people put in the trailers and how well they load them, so we have to add a lot od safety factor. If you ever go on line at Uhaul.com you can enter your vehicle and what kind of trailer/hauler you want to use and it will do the math for you. What really gets tricky is the car hauler since a pick up vs a pick up with life long belongings in the back can really change the inertia properties. One thing to remember is that when you hook a trailer to your car(truck,GMC) it is no longer the car that you knew and were familiar with.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163187 is a reply to message #163166] |
Fri, 16 March 2012 14:10 |
tmaki
Messages: 200
Registered: September 2005
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On 3/16/2012 11:20 AM, Rob Allen wrote:
>
>
> Have you seen this information on towing dynamics
> developed by an Australian.
>
> I would enjoy your take on what he says.
>
> http://www.caravanandmotorhomebooks.com/articles/caravan_dynamics_cw.pdf
After just a cursory reading, I think he makes some good
points. He takes 10 pages to get to three basic points:
1. Use the right equipment (that goes for choosing the right
tow vehicle for the trailer you intend to tow, or
conversely, choosing your trailer for the tow vehicle you
intend to use). Also includes the hitch system and ancillary
components.
2. Load correctly. Both the tow vehicle and trailer. The
manuals that I have been involved with spend a lot of ink on
correct loading.
3. Slow down. Or at least drive at a speed that does not
induce or amplify the factors that contribute to trailer/tow
vehicle instability. If you do get into an unstable
condition, know what to do to correct it quickly and safely,
even if that means pulling over and stopping so you can
change your underwear.
Also, consider that no specific set of "rules" will work for
all towing situations. There are an infinite set of
variables. The author of the article alludes to that. You
have to use your best judgment, use the best information you
can get from the equipment and vehicle manufacturers, and -
if nothing else - leave the "buckaroo" attitude in your home
driveway (not that you have that...). No one will be amused
reading an epitaph that reads "His b***s were bigger than
his brains."
Happy towing!
Toby Maki
'73 Glacier 230
Riverside, CA
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163191 is a reply to message #163158] |
Fri, 16 March 2012 14:41 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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Bob, Toby: thanks for your feedback on the Australian article on tow stability. I was especially interested in the information about the weight (mass) distribution in the trailer front and back vs. center (with bias to the front) and the double pendulum "chaos" ideas.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163252 is a reply to message #163158] |
Sat, 17 March 2012 08:26 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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Yes, I am replying without a quote because this is referencing the entire thread.
Rob, Thanks for the link, I'm going to store that one to be passed along the next time I am asked.
As my late father often said, " The problem is the nut behind the wheel."
At a trailer tow symposium presented by my then employer, I was asked how much can the tow rating be exceeded by safely? The situation precluded my first choice response. If I had not been in the front of the room wearing a jacket and tie and name tag, I would have found a heavy wall to ram my head against for a few minutes. (How did he sit there and miss everything???)
A great number of problems can be avoided by thinking about the situation in advance. That includes, being aware of the manufacture's ratings, the weather conditions and the balance of the assembled rig. Unfortunately, I can prove that much of the general population is not capable of this (those are the people Bob has to ready for).
As I have been telling clients (and friends) for years, "Thinking is the most cost effective thing to do."
Thanks for a great thread guys.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner, GMC or 2CV [message #163433 is a reply to message #163252] |
Sun, 18 March 2012 19:57 |
Greg and April
Messages: 263
Registered: December 2011
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Some people just do not deal well with abstracts and need set data points to
understand things.
.
Greg H.
I don't just march to the beat of my own drum - I have an entire brass band
to keep me company.
.
----- Original Message -----
From: "Matt Colie" <matt7323tze@gmail.com>
To: <gmclist@temp.gmcnet.org>
Sent: Saturday, March 17, 2012 7:26
Subject: Re: [GMCnet] Pulling A Trailer - Whether with a Freightliner,GMC or
2CV
At a trailer tow symposium presented by my then employer, I was asked how
much can the tow rating be exceeded by safely? The situation precluded my
first choice response. If I had not been in the front of the room wearing a
jacket and tie and name tag, I would have found a heavy wall to ram my head
against for a few minutes. (How did he sit there and miss everything???)
A great number of problems can be avoided by thinking about the situation in
advance. That includes, being aware of the manufacture's ratings, the
weather conditions and the balance of the assembled rig. Unfortunately, I
can prove that much of the general population is not capable of this (those
are the people Bob has to ready for).
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