Got My New Trailer Today...SWEEET!!

[gobbler]

On the OEM hitch from GM, there have been many published cases of this hitch failing and at the very least deflecting.

Go to RV.NET and search on "GM Hitch", you'll get many hits about the quality of the hitch. I myself tow a 5th wheel, so I have no experience using the GM factory hitch on my 2500HD, but from the pictures I've seen, I'd change it out pronto.

 

[Highbeam]

Yes, I too have been on RV.net and learned a lot. Been surprised to see the GM receivers from the 99 and up bodystyle fail that way. Luckily for me and my 98, the pre-99 receivers are of the standard design and not prone to that type of failure. GM blew it on that one.

 

[KAB]

This is being directed at no one in general. From my research on towing, there are some general principles to follow. If any of my information is wrong let me know or post the corrections.

Seasalt - sorry about hijacking your Nice new trailer thread but as I stated before, if it helps a somebody not used to towing and trying to figure out what they need it is worth the effort.


Most of the info is from memory and I usually do this verbally instead of trying to keep it condensed.

Trailering 101:

Numbers to work with:
Truck:
Curb Weight (needs to include vehicle adds for real life situations)
Cross Combine Weight (GCW)
Gross Vehicle Weight
Tow Capacity
Payload Capacity

Trailer :
Trailer Curb Weight (needs to include Trailer adds for real life situations)
Gross Trailer Weight
Trailer Payload Capacity

Note:
Vehicle and trailer adds include items like running boards, tool boxes, chains, hitches, etc. (anything added after manufacturing)

Calculations:
GVW – Curb Weight = Payload Capacity
Trailer GVW – Trailer Curb Weight = Trailer Payload Capacity
GCW – Curb Weight = Tow Capacity
Payload - Tongue Weight = Available Vehicle Payload
(effective tongue weight = ((distance from rear axle to ball / vehicle wheel base) +1) * Tongue Weight - This is needed for the pivot action caused by placing weight behind the rear axle.)

For a 2004 Chevy Suburban Z71 w/3.73 axle
Estimated Numbers and published numbers used. Actual vehicle can vary.

Curb Weight 6000
GCW 13000
GVW 7200
Payload 1200
Tow Capacity 7200

Trailer in question
Curb Weight 3000
Trailer GVW 12000
Trailer Payload Capacity 9000

Now:
How much weight can I tow on the trailer?
Tow Capacity – Trailer Weight – (150# *2 (Govt std weight for driver and passengers)
7200 – 3000 – 300 = 3900#

If I am towing 7000# w/ 15% tongue weight how much payload can I add to the vehicle?
Trailer weight * .15 = tongue weight
7000# * .15 = 1050#
((Rear Overhang/ Wheel Base) + 1.0) * Tongue Weight = Effective Tongue Weight
((52.3 / 130”) + 1) * 1050 = 1470
Payload - Effective Tongue Weight = Available Payload
1200 – 1470 = -270

If we use 10% tongue weight, available payload would be approx. 220# not considering a CW of 12,730. This would mean a calculated payload of 270# is really 50# high and the driver has not got in the truck yet.

I have not found where a WD hitch changes these calculations, but common sense says that it does. So it does give another reason to use a WD hitch.

disclaimer:
The numbers that I am using can vary from vehicle to vehicle. There can be other discrepancies in the numbers since I did not manually verify all of the numbers involved. This is being shown as an example only and may not accurately reflect any vehicle in production. To get the numbers that I used (rounded to simplify the math) can be found at GMFleet info. To get more precise weight info at this site, click on “Model and Options Weight” on the left half of the page.

 

[KAB]

FYI,

2005 and newer GM HD models seam to have a different hitch. They are now rated for 7500# dead weight instead of 5000# found on 04 and earlier.

KUrt

 

[Highbeam]

"2005 and newer GM HD models"

As in vehicles other than a 1/2 ton Z71, right? The sticker on the receiver plainly states this information, no magic or mirrors.

For giggles, my 2500 lb empty trailer actually put 350 lbs of weight on the rear axle and lightened the front axle by 100 lbs without W/D. That's 250 lbs of tongue weight but it was already lifting the front end of the teeter totter.

 

[KAB]

That is correct. Only the "HD" series for 2500 and 3500.

As for </font><font color="blue" class="small">( For giggles, my 2500 lb empty trailer actually put 350 lbs of weight on the rear axle and lightened the front axle by 100 lbs without W/D. That's 250 lbs of tongue weight but it was already lifting the front end of the teeter totter. )</font> that is the basic idea. when the back of the vehicle goes down the front comes up. Most trucks are in the 15 - 35% range. A Suburban with the long rear overhange increases that percentage. A long bed 2500HD ext cab is approx 34% while a short bed is approx 32%. So it would probably be around 340 lbs. (I don't have the actual rear overhang numbers so I am using a calculation of Total Lenght - wheel base - front overhang = rear overhang)

This is something that I usually don't mention to the people that I work with because they don't tow and it's hard to get through the basics. To help them understand this I usually hop up on the tailgate and let them see how far the bed moves down, then I step up to about 4" ahead of the rear axle in the bed and see the rear of the bed come up. Has the load in the truck changed? No. All that changes is the placement of the cargo in the bed. When I move infront of the axle now the front axle is supporting part of the weight. (once again this can be calculated but as long as the cargo weight is less than payload and positioned correctly in the bed, its not an issue.)

Actually thinking about this now it helps to explain the Weight Distibuting affect of a WD hitch. We are reversing the pivoting (teetering) of tongue weight. Connection (hitch) sits higher and transfers that weight to the front tires on the tow vehicle and the rear tires on the trailer.

Also a snowplow on the front of a truck works just the opposite. Front goes down - Back comes up.

Kurt

 

[gobbler]

KAB, I think your calculations are on the mark.

Most people just don’t realize how easy it is to overload a ½ ton vehicle, especially ½ ton suv’s. There is nothing you can add to your tow vehicle that can change the GVWR, not heavier shocks, airbags, or anything else, it is what it is.

One more thing, WD doesn’t change any of your calculations unless you break down the vehicle weight into front/rear axle weights, which you’ll find on the door sticker for maximums

 

[Highbeam]

Thanks again for coming to the party folks. I learned this stuff in the RV world with travel trailers and of course in school. It applies perfectly to all aspects of bumper pull trailering. I wasn't liking being the lone ranger on this one.

 

[MikePA]

This discussion is why I like, and bought, a GN horse trailer. /forums/images/graemlins/cool.gif Put the weight directly above the rear axle plus easier to maneuver, IMO, at the expense of cargo capacity in the bed. /forums/images/graemlins/frown.gif

 

[gobbler]

What I hope people take away from this thread is that towing any type of trailer involves more than just hooking it up and stepping on the gas pedal. You owe it to yourself and the rest of the motoring public to ensure that your setup is safe.