RE: [SilverStreak] Picking up Grandma's 78' 28ft SS in a month... ?'s

["Ken Wilson" <ke5dfr@xxxxxxxxxxxxx>]

Tow ratings as presented by the manufacturers is a lot of smoke and mirrors
but is not all that hard to understand.  There are several good sites and
one is at:
http://www.klenger.net/arctic-fox/weight/tow-calc-demonstrator.htm

Another good RV site is www.irv2.com, where I am a moderator.  We have a
vintage RV section that is getting off the ground nicely.

The tow ratings which are published by the truck manufacturers are a MAXIMUM
and they are based on a base model truck, no accessories, no cargo, no hitch
and only a 150# driver.  For every pound you add over the base model, you
reduce the towing capacity by a pound.  For a quick estimate on what you can
realistically tow, take 80% of the manufacturers rating.  So if a 1/2 ton
truck is rated to tow 8000#, you need to be looking a trailer that has a
loaded weigh of less then 6400# (loaded weight, not dry weight).

To know for sure what your truck is rated to tow, you need to find the GVWR
(gross vehicle weight rating, on the sticker on the B pillar) and the GCWR
(gross combined weight rating).

GVWR is the most or total weight you can carry on the 2 axles.  Also part of
the loading here is the rear axle GAWR (gross axle weight rating).
GCWR is the total combined weight of the loaded truck and trailer.

A properly loaded and balanced trailer will have a hitch weight of about 12%
(10% to 15%) of the loaded trailer weight. So if your loaded trailer is
6400#, your hitch weight should be about 768#, but could run anywhere from
640# to 960#.

A 1/2 ton truck is limited on the payload capacity or GVWR.

To determine the actual tow capacity, you need t weigh the truck as loaded
for travel and full fuel.  This can be called you Laden Vehicle Weight (LVW)

GCWR - LVW = max loaded trailer rate you are rated to tow.
GVWR - LVW = Max loaded trailer hitch weight you are rated to tow.

In the '60's and '70's people pulled the trailers with full sized sedans and
station wagons.  Back then, the cars had full frames and big block engines.
The newer cars and trucks now have smaller engines and you do have to be
more concerned with the frame and weight of the towing vehicle.  The truck
designers and with the internet, RVers have gotten smarter.

My truck is a lot of over kill for our 28.5' SS, but it is what we have and
it is paid for.  It is a F350 crew cab diesel dually.  It has a GVWR of
11,500# and a GCWR of 20,000#.  The newer trucks are rated higher.  The
truck weighs right at 8000# with the hitch, me and the copilot, tool box and
38 gallons of fuel.  So this leaves me with a hitch weight that I can carry
of 3500# and a loaded trailer of 12,000#.  We were pulling a 36.5' 5th wheel
and I was about 1500# over on GCW when we were loaded for extended travel.

When we first got the SS, we tried towing it with my F-i-L's 2500, 3/4 ton
Burb with a 5.7L V-8 and a 4.10 axle.  The loaded trailer was a bit under
the tow ratings.  The fuel economy at 60 MPG in central Texas (rolling
hills) was 7.4 MPG, we had to run in 3rd gear and lost speed on the hills.
With the diesel and 5er, we could run 65 to 70 MPH in OD (4th) and get about
11 MPG.  This rig weighed about 8000# more than the Burb and SS.  The Burb
would tow it, but it was work, more work than the much larger trailer.  So
we kept the diesel and sold the Burb.

I have heard from a lot of folks that complained about not enough truck, but
I have yet to hear of any complaints about too much truck.

Sorry to get on the soap box, but I am a mechanical engineer and I live by
numbers and ratings.  The ratings are there for a reason.  To protect the
people and provide a longer life on the vehicle.

Ken