Reply
 
Thread Tools Search this Thread Display Modes
 
Old 01-25-2011, 08:19 AM   #1
2 Rivet Member
 
Section8's Avatar
 
Vintage Kin Owner
Wellford , South Carolina
Join Date: Jan 2011
Posts: 28
Images: 7
Axle weights limits vs. combined weight - What am I missing?

I towed my newly-purchased Avion 34V 200 miles from VA to my SC home this weekend. It towed like a dream, with the only noticeable difference being the truck's ride was a lot smoother and I had to push on the gas a little harder on the hills, but just a little. The truck never seemed to be under a strain at any time, engine temp ran about a "needle width" higher on some of the hills (and there were some fairly steep hills on the way home, but none that I would call a long grade).

Anyway, when I scaled the TV and trailer at the first oppotunity (an hour into the trip), I saw that my gross weight of 14,700 lbs was 1200 lbs over my TV's Gross COMBINED Weight Rating of 13,500.

Axle weights, however, were all below their limits by a good margin, and like I said above, the Amtrak car/Avion towed like a dream. What am I missing here?

Here are the weights from the CAT scale ticket:

AXLE WEIGHTS (vehicle ratings in parenthesis):
Front: 3,680 (TV rated at 4100 max. 3037 curb wt)
Drive: 4,280 (TV rated at 6084 max. 2452 curb wt)
Barge: 6,740 (Avion rated at 9500 max. Stated Dry weight 6940 lbs)

Gross: 14,700 (TV rated 13,500 max combined, 9000 max by itself)

For the record, I used a Husky WD hitch (rated 1000 TW/10,000 GW) and set it up as explained in many places on this site, and as described by the manufacturer. The bars were 800lb rated, and had a slight bend, just as I expected from all the instructions. The train car/Avion was perfectly level, and the TV's front and rear seemed to be loaded equally since their "loaded" heights were within 1/2" or less of their original "unloaded" heights (relative to each other).

Also, I shortened the chain on the bars by one more link, which took some effort (6th link from the bar), and reweighed:

Reweights:
Front: 3,800 (120 lbs more)
Drive: 4,100 (180 lbs less)
Barge: 6,780 (40 lbs more)

Gross: 14, 680 (20 lbs vanished somewhere - we did take a pee-break in between)

I suspect I was good/better-distributed before the adjustment.

Anyway, using all three of my brain cells, I can see that I am under the rated limits on all axles, under the gross (not combined gross) capacity of the TV (9,000 GWR), under the gross weight of the trailer and it's axles (3), yet i am over the TV's gross COMBINED weight. What am I missing? Better yet, what am I hurting?

(The TV is a '98 Chevy 3500 crew cab longbed, single rear wheels, 350 vortec engine, automatic w/overdrive, Draw-Tite receiver rated 1000/10,000 using a WD hitch.)
__________________

__________________
***
"Quit assin' around and get in here, boy!" -- My Dad, to me as a child

"Assin' around is man's purpose in life. Everything else is just a means to that end." -- Me, as an adult
***
Section8 is offline   Reply With Quote
Old 01-25-2011, 08:57 AM   #2
4 Rivet Member
 
1973 31' Excella 500
Spring Green , Wisconsin
Join Date: Aug 2010
Posts: 265
Section8, well presented data and question.
It would seem to me that your basic TV is surely enough truck to pull your trailer so I'm going to take a WAG (mostly because I want to be subscribed to this thread) and say the Max rating of 13,500# has more to do with the capacity of the power train and or braking system than anything else.
Hopefully you'll get some definitive responses to your question as it is a very interesting one.
__________________

__________________
Lew TAC #WI-6
Nobody can help everybody, but everybody can help somebody.
driftless is offline   Reply With Quote
Old 01-25-2011, 10:48 AM   #3
Rivet Master
 
87MH's Avatar
 
1978 31' Sovereign
Texas Airstream Harbor , Zavalla, in the Deep East Texas Piney Woods on Lake Sam Rayburn
Join Date: Jan 2003
Posts: 2,435
Images: 292
Quote:
Originally Posted by Section8 View Post
I towed my newly-purchased Avion 34V 200 miles from VA to my SC home this weekend. It towed like a dream...
Anyway, using all three of my brain cells, I can see that I am under the rated limits on all axles, under the gross (not combined gross) capacity of the TV (9,000 GWR), under the gross weight of the trailer and it's axles (3), yet i am over the TV's gross COMBINED weight. What am I missing? Better yet, what am I hurting?

(The TV is a '98 Chevy 3500 crew cab longbed, single rear wheels, 350 vortec engine, automatic w/overdrive, Draw-Tite receiver rated 1000/10,000 using a WD hitch.)

Good for you for weighing and posting your results - the limits, well, they are what they are as posted by the manufacturer. Just a guess, I would suspect your TV lacks a tow package or has a low ratio axle (3.42?).

One word of caution - don't pull with the OD engaged - I burnt my '95 Dodge 3/4 ton tranny (at 80,000 miles) while towing in OD - after a rebuild (and adding a tranny cooler) I have put 50,000 more miles on it (partial towing only) with no problems.

On the front axle - my opinion is that the "Best" WD setting is to restore the front axle weight to ALMOST the weight that was on it prior to dropping the tongue on the rear end.

Luck - if you want the PDF of the '99 tow ratings drop me a PM.

Welcome to the Forum!!! - I shall strive to NOT refer to your Avy as a "Stepchild" - they are great units, unfortunately, they do not have the widespread mystique that Airstreams enjoy. Bet you got a great deal on it.

One other thing - check the age of the tires - many active member of the Forum here swear on replacing the tires after 5 years. I had a three year old tire blow out last year - a thrown casing can cause an incredible amount a damage to aluminum skin.
__________________
Dennis

"Suck it up, spend the bucks, do it right the first time."

WBCCI # 1113
AirForums #1737

Trailer '78 31' Sovereign

Living Large at an Airstream Park on the Largest Lake Totally Contained in Texas
Texas Airstream Harbor, Inc.
87MH is offline   Reply With Quote
Old 01-25-2011, 11:30 AM   #4
2 Rivet Member
 
Section8's Avatar
 
Vintage Kin Owner
Wellford , South Carolina
Join Date: Jan 2011
Posts: 28
Images: 7
Quote:
Originally Posted by 87MH View Post
Good for you for weighing and posting your results - the limits, well, they are what they are as posted by the manufacturer. Just a guess, I would suspect your TV lacks a tow package or has a low ratio axle (3.42?).

One word of caution - don't pull with the OD engaged - I burnt my '95 Dodge 3/4 ton tranny (at 80,000 miles) while towing in OD - after a rebuild (and adding a tranny cooler) I have put 50,000 more miles on it (partial towing only) with no problems.

On the front axle - my opinion is that the "Best" WD setting is to restore the front axle weight to ALMOST the weight that was on it prior to dropping the tongue on the rear end.

Luck - if you want the PDF of the '99 tow ratings drop me a PM.

Welcome to the Forum!!! - I shall strive to NOT refer to your Avy as a "Stepchild" - they are great units, unfortunately, they do not have the widespread mystique that Airstreams enjoy. Bet you got a great deal on it.

One other thing - check the age of the tires - many active member of the Forum here swear on replacing the tires after 5 years. I had a three year old tire blow out last year - a thrown casing can cause an incredible amount a damage to aluminum skin.
I don't know if it came with a tow package, either. But it does have 2 electrical tow hookups in the factory harness, a 4.10 rear with full floating axles, the hitch receiver was on it but I don't know if it's factory or not, and the tires are the "E" rated ones.

Most of the weight info I got on the truck was from a search of the vin# online. The Avion's info is from the original manual that came with it.

I did use overdrive whenever I was at speeds above the point where the tranny would shift back and forth, which it did not do most of the time.

The tires are now 200 miles/3 days old.

I don't mind being called a "stepchild" here with the Avy and all, I have felt very welcome here so far, and I know what you mean about the value thing; I was previously an Airstream owner.
__________________
***
"Quit assin' around and get in here, boy!" -- My Dad, to me as a child

"Assin' around is man's purpose in life. Everything else is just a means to that end." -- Me, as an adult
***
Section8 is offline   Reply With Quote
Old 01-25-2011, 01:11 PM   #5
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
re: "Axle weights, however, were all below their limits by a good margin, and like I said above, the Amtrak car/Avion towed like a dream. What am I missing here?"

The combined rating (GCWR) is a wild guess based on assumptions about frontal area and other things. This is why the SAE is adopting a set of tests to help create better and more meaningful information about towing capabilities.

The issue of weight ratings creates a lot of heat as some think safety is directly involved, that being an ounce over a rating is a severe legal liability problem, that RV's get pulled over and ticketed routinely for being over ratings, that brakes will not be able to stop the vehicle and on and on. The FUD is ferocious.

The facts are a bit different. Each rating has its own importance (tire and wheel ratings needing most attention, for instance). Drivers can (and usually do) compensate for rig weight as needed. Your taking note of how your vehicle responds is what is needed for safe driving. Follow up with adjustments (including considering the OD precaution noted above), upping maintenance attention and inspection care, and so forth should take care of things.

This doesn't mean to ignore weight ratings but just to keep in mind they are ratings and not limits. There is no need to be obsessive about such numbers. Instead be reasonable and learn what they mean and what they do.
__________________
bryanl is offline   Reply With Quote
Old 01-25-2011, 03:50 PM   #6
Rivet Master
 
Mikethefixit's Avatar
 
1977 27' Overlander
Trotwood , Ohio
Join Date: Jul 2007
Posts: 2,153
Send a message via Yahoo to Mikethefixit
Section 8
Remember what chain link you used,I think you said 6 links and thats exactly what I use with my Reese DUAL CAM .The second weights look really great exactly proportioned as they should be. I bet it rode great ,it should have according to the weights,which look very similar to the weights I got when I scaled out Overlander Out.
You did good.
ROGER
__________________
Roger & MaryLou
___________________
F350 CREWCAB SW LONG BED
7.3 liter Power Stroke Diesel
1977 27ft OVERLANDER
KA8LMQ
AIR # 22336 TAC- OH-7
May your roads be straight and smooth and may you always have a tailwind!
Mikethefixit is offline   Reply With Quote
Old 01-25-2011, 04:21 PM   #7
Wise Elder
 
Jammer's Avatar
 
2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,119
bryanl speaks my mind.

The "meaning" of the gcwr comes up in most RV forums from time to time. Some people believe it is a hard and fast limit.

I believe that there is a good deal of marketing involved. Tow ratings are one way the automakers encourage people to buy expensive power train upgrades.

Running heavier will reduce the useful life of the power train. Trucks with a higher gcwr are in theory built to withstand these stresses to a greater degree. We all make our tradeoffs.

Finally, Airstreams do tow better and safer than SOBs because of the rounded corners and the lower overall height. So if you're "safe enough" with an SOB right at gcwr then perhaps you're just as safe with an Airstream that is somewhat over gcwr.
__________________
Jammer is offline   Reply With Quote
Old 01-25-2011, 07:53 PM   #8
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,585
Images: 1
What an individual decides to do and what the rest of us should advise him to do on questions of hitch rigging & towing are two different things. It's just as reasonable to say to respect the manufacturer limits on GCWR (or other) as it is to advise respect on tire limits and the rest.

I've yet to see anyone tell me to exceed the tire ratings, but I can find a whole slew of them to tell me to tow heavy. None will explain the difference in principle, much less fact.

The J2807 "standard" has holes big enough to drive through. Being voluntary makes it even more meaningless. It won't be any help.

It doesn't sound to me like your all that far off. I'd not worry over it for awhile. Better to go through the TT brakes & tow-related wiring (make better than new); same for safety chains & breakaway plus some LED signal and brake lamps. Tires, shocks, suspension bushings, wheel alignment & balance plus welds would concern me more than slightly overweight on the list of things that might go wrong.

Given that the truck is old I'd go there next, with a plan of how long I'd keep it and attention to systems not just components. Wholly new systems trump piece-by-piece parts replacement any day. New parts, not rebuilts (unless selling). How's the timing chain?

You've done a very nice job in the opening post, and, as I was just PM'ng another Avion owner with a request for scale weights a few minutes ago and the rest: Thanks! as it may be my next trailer as well. The more comparisons I have, the better.

Show us some pics once it's cleaned up. Or not. But show us some pics and tell us about it.
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 01-26-2011, 09:08 AM   #9
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
Let's not toss out the baby with the bath water ...

re: "It's just as reasonable to say to respect the manufacturer limits on GCWR (or other) as it is to advise respect on tire limits and the rest." -- blindly following anyone's recommendation or rating is foolish, IMHO. There is a very significant difference between how tire and wheel ratings are derived and how GCWR is derived and that difference, if you understand its origins, should guide you - not some blind adherence to some sticker.

re: "The J2807 "standard" has holes big enough to drive through. Being voluntary makes it even more meaningless. It won't be any help." -- if that's the number for the new SAE standard, I'd suggest that having specific criteria is much better than having none at all. Any standard has holes, which gets back to why you can't just take the numbers on placards and stickers as some sort of holy gospel.
__________________
bryanl is offline   Reply With Quote
Old 01-26-2011, 10:31 AM   #10
Wise Elder
 
Jammer's Avatar
 
2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,119
The essence of the difference between GCWR and, say, tire ratings, is that manufacturers frequently choose a lower GCWR for reasons of: product line differentiation (in other words giving people a reason to buy the big engine or the diesel), product marketing (don't want the vehicle to be perceived by the market as a utility vehicle. The Dodge Charger is a good example of this), controlling warranty expenses, or to control testing expenses.

None of this goes on with tire ratings. The tire carries what it says it can carry; exceed those ratings at your peril.

The automakers are not the almighty and the rating sticker is not the gospel.
__________________
Jammer is offline   Reply With Quote
Old 01-27-2011, 09:59 AM   #11
Vintage Kin
 
slowmover's Avatar
 
Fort Worth , Texas
Join Date: Nov 2006
Posts: 7,585
Images: 1
The automakers are not the almighty and the rating sticker is not the gospel.

At present you've no other guideline. If so, offer it up.

None of this goes on with tire ratings. The tire carries what it says it can carry; exceed those ratings at your peril.


How so? Tire ratings are often exceeded, see it constantly while at the landfill with other vehicles lined up not to mention on the highways.


blindly following anyone's recommendation or rating is foolish, IMHO. There is a very significant difference between how tire and wheel ratings are derived and how GCWR is derived and that difference, if you understand its origins, should guide you - not some blind adherence to some sticker.


Show us the published data from other sources (axle manufacturers) so that I may also exceed GAWR/GCWR as set by the vehicle manufacturer.

Any standard has holes, which gets back to why you can't just take the numbers on placards and stickers as some sort of holy gospel.

Control the questions and the answers are pre-determined. "Voluntary" means just that, ergo, meaningless. Published guidelines are all we have. A new set of badly done "standards" doesn't clarify our situation.

Same problem as above: what other source can you cite, authoritatively, that isn't simply your own, unverified opinion.

And both of you entirely missed the point being made: What you do, and what you advise others to do is an ethical question. Or do these not matter?

Defending your own decisions is your own business, it has nothing to do with how others should set up their hitch rigging or how they should be advised to do so.

If you want to be helpful, show us the scale receipts, manufacturer data, and the number of miles you've accumulated while overweight on the road. Then make your recommendations of how far over GAWR/GCWR based on that another person should set his.

I don't disagree that the "ratings" need work. I believe they are relative solely to the liability of the vehicle and RV manufacturers without proper, independent testing of what is reasonable, what is possible. Doesn't change that we are on our own once we decide to step beyond them. We any of us may need to defend the decision to exceed ratings, and you or I cannot defend anothers actions . . can we?

.
__________________
1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 9-cpm solo, 15-cpm towing
Sold: Silver Streak Model 3411
slowmover is offline   Reply With Quote
Old 01-27-2011, 12:54 PM   #12
Rivet Master
 
Currently Looking...
Nowhere , Somewhere
Join Date: Jul 2005
Posts: 6,421
Blog Entries: 2
20 pounds of fuel? zz
__________________
avionstream is offline   Reply With Quote
Old 01-27-2011, 05:07 PM   #13
Rivet Master
 
1976 25' Caravanner
Vintage Kin Owner
Campton , New Hampshire
Join Date: Feb 2006
Posts: 1,113
Quote:
Originally Posted by Section8 View Post
I don't know if it came with a tow package, either. But it does have 2 electrical tow hookups in the factory harness, a 4.10 rear with full floating axles, the hitch receiver was on it but I don't know if it's factory or not, and the tires are the "E" rated ones.

Most of the weight info I got on the truck was from a search of the vin# online. The Avion's info is from the original manual that came with it.

I did use overdrive whenever I was at speeds above the point where the tranny would shift back and forth, which it did not do most of the time.

The tires are now 200 miles/3 days old.

I don't mind being called a "stepchild" here with the Avy and all, I have felt very welcome here so far, and I know what you mean about the value thing; I was previously an Airstream owner.
Check your glove box for the vehicle options , any GM dealer can decode them for you . Z82 is the trailer towing package . According to the trailering guide for '98 the 3500CC 2wd with the 350 and 4:10 the max trailer wt is 7000# , the 4wd is 6500# . With 4:56 gears it is 8500# and #8000 respectively . Interestingly it does not list a GCWR . The RAWR of the axle manufacturers are usually much higher than the RAWR of the truck manufacturer . Interestingly the truck manufacturer rating almost always match the tire rating of the OE tires .As has been stated earlier There is much more behind the manufacturers ratings than engineering facts .
__________________
ticki2 is offline   Reply With Quote
Old 01-27-2011, 05:16 PM   #14
New Member
 
Lake Ariel , Pennsylvania
Join Date: Jan 2011
Posts: 3
If you look at the manufacturers' specs you will find that the GVWR, GCWR and tow ratings don't make sense. Generally, the GCWR is less that the combination of the tow rating & the GVWR. But I don't think they intend these rating to be taken literally but to be used as guidelines in lieu of any other specs.
__________________

__________________
Farmer Tom is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Newbie with Axle Question Camp Axles 10 01-25-2011 04:04 PM
What weight antifreeze? sharptalk Classic Motorhomes 9 01-08-2011 01:02 PM
Axle, where to buy submariner Axles 26 01-01-2011 03:12 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 05:04 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.