I am looking into mounting a toolbox to put batteries in on by back bumper. The bumper itself looks to be pretty solid and the weight will be distributed over 4' of the bumper. Anyone have anything heavy hanging off their bumper? I figure I will be putting about 300 lbs on the bumper.

Loading the rear bumper is the worst possible place to add weight, especially 300#. You will need to increase your tongue weight by at least that much and you will still be inducing sway. Most trailer bumpers won't take the weight of a bike rack and a couple of bikes without being susceptible to failure much less 300#. If you go ahead with this project check with a welding shop about beefing up your bumper substantially. Good luck. :C

I would not recommend !!! My Son had two bikes mounted on his TT bumper and the bumper broke and bikes scraped on the Freeway. Luckily they never broke looseand caused an accident. One of the bikes were brand new, $300.00 birthday present. I don't even carry my TT spare tire on the back bumper. I put it under the bed in the front of TT. Less room for the DW to fill up. LOL

The whole goal of the project is to remove tongue weight. Right now my 7k trailer has about 1100 lbs of tongue weight. If I can remove 300 lbs of weight and get closer to 12% tongue weight I would be much happier and so would my TV. My calculations are this:Currently on Tongue2 GC2 Batteries - 130lbs (62 each)1 Group 24 Deep Cycle - 50 lbsTotal Weight - 180 LbsPlanned on Bumper4 GC2 Batteries - 250 LbsBattery Box (with cables, disconnect, etc) - 40 lbsTotal weight: 290 lbsIt is roughly 2.5 times as far from the hitch to the tires as it is from the bumper to the tires so if you cut that number in half you get about 115 lbs of tongue weight removed plus the 180 lbs of batteries you get 300 lbs off the tongue.

I wouldn't move batteries to the back, especially not on the bumper. Tongue weight is the best anti-sway possible. Good luck.

Why are you trying to drop weight in the fornt?

How much weight can my bumper support? | Good Sam Community

S_more_campers
Explorer
Feb 26, 2014
samsontdog wrote:
... I don't even carry my TT spare tire on the back bumper. I put it under the bed in the front of TT. Less room for the DW to fill up. LOL
Desert_Captain
Explorer III
Feb 26, 2014
S'more campers wrote:
samsontdog wrote:
... I don't even carry my TT spare tire on the back bumper. I put it under the bed in the front of TT. Less room for the DW to fill up. LOL

LMAO! Best giggle I've had on this Forum in a long time. Thank You!

:B
GordonThree
Explorer
Feb 26, 2014
westend wrote:
If you install batteries just behind the axles, you'll decrease tongue weight. If it's necessary to mount them inside the cabin of the trailer to accomplish this, you'll need a battery box that is vented to the exterior. I have two 6V's in a vented battery box inside my rig. I did it to better balance side-to-side weight and keep some weight off the tongue. It is a fair bit of work to make it happen.

I second this approach. If you buy your GC2's from Sams Club, you can get Duracell (East Penn DEKA) AGM golf-car batteries, which do not off-gas nearly as much as flooded batteries... they are rated for indoor use.

I put several AGM in a storage cubby that's part of my dinette. They are rear of the axle maybe 12 inches and did not affect the tongue weight of the trailer in appreciable amount.

When you add new batteries to the rear, any chance you can remove those batteries from the tongue, this will help with your weight? Unless you're spending a lot of money on HEAVY cabling, the two banks will not be working in parallel to drive large loads.
69_Avion
Explorer
Feb 27, 2014
Without knowing the quality of the frame, I wouldn't recommend putting that kind of weight back there. To be honest, if the TV will handle what you have with a good WDH, I would stick with what you have and just move as much inside heavy storage toward the back.
usmc616
Explorer
Feb 27, 2014
On my previous TT I mounted a bike rack on the rear bumper. Sometimes we carried all 3 bikes on it. When we sold that TT 2 years later I noticed the rear bumper was bent slightly downward. My guess is it was only a matter of time before the welds on the rear bumper broke.
GrandpaKip
Explorer II
Feb 27, 2014
tkoden wrote:
I am looking into mounting a toolbox to put batteries in on by back bumper. The bumper itself looks to be pretty solid and the weight will be distributed over 4' of the bumper. Anyone have anything heavy hanging off their bumper? I figure I will be putting about 300 lbs on the bumper.

You've got a new camper. Why not contact your dealer, and Keystone, and ask them?
tkoden
Explorer
Feb 27, 2014
When you add new batteries to the rear, any chance you can remove those batteries from the tongue, this will help with your weight? Unless you're spending a lot of money on HEAVY cabling, the two banks will not be working in parallel to drive large loads.

Yes, the plan is to remove the batteries from the tongue. The net would be 300 lbs roughly 150 off the tongue and 150 added weight on the rear.
westend
Explorer
Feb 27, 2014
tkoden wrote:
When you add new batteries to the rear, any chance you can remove those batteries from the tongue, this will help with your weight? Unless you're spending a lot of money on HEAVY cabling, the two banks will not be working in parallel to drive large loads.

Yes, the plan is to remove the batteries from the tongue. The net would be 300 lbs roughly 150 off the tongue and 150 added weight on the rear.
So what you're contemplating is moving all of your batteries to the rear? I wouldn't do it because of the inertial moment mentioned previously and the cost. Having nearly all of the accessory weight of batteries, box, and carrier outboard of the frame might lead to severe sway events. Also, you'll need some big wiring to pull this off, probably 4/0, to keep voltage drop down and the effectiveness of a big bank. I don't know the specifics of the layout of your trailer, but I would look for a different mounting location.
Huntindog
Explorer
Feb 27, 2014
tkoden wrote:
The whole goal of the project is to remove tongue weight. Right now my 7k trailer has about 1100 lbs of tongue weight. If I can remove 300 lbs of weight and get closer to 12% tongue weight I would be much happier and so would my TV. My calculations are this:

Currently on Tongue

2 GC2 Batteries - 130lbs (62 each)
1 Group 24 Deep Cycle - 50 lbs
Total Weight - 180 Lbs

Planned on Bumper

4 GC2 Batteries - 250 Lbs
Battery Box (with cables, disconnect, etc) - 40 lbs
Total weight: 290 lbs

It is roughly 2.5 times as far from the hitch to the tires as it is from the bumper to the tires so if you cut that number in half you get about 115 lbs of tongue weight removed plus the 180 lbs of batteries you get 300 lbs off the tongue.
I have done what you are proposing. I had 1160# TW, and the TT hitch socket was rated for a max of 1200#. Too close for my comfort zone.
So I cut off my rear bumper and welded 1' frame extensions on, then rewelded the bumper to them.
I used some angle iron and expanded metal to make mounts for my two 6 volt batteries, and a large basket (for outside storage items like carpet, leveling blocks etc.) between the new extended frame rails. I had a 8" tall I beam frame, and got exact matching pieces at a metal supply yard for the extensions.
There are some considerations for this project.
First I wouldn't be too concerned about a high TW in itself. Only if it can become a problem. Such as being too high for any of the rated components.
TV, receiver hitch, or TT hitch socket.
Next, just how stout is the TT frame? There are some pretty lightweight ones out there, and I would make sure that it is strong enough for this modification.
Keep in mind that the loaded TW is not a static number. It will change in the course of a trip. As items are consumed/used and redistributed in different locations in the TT. Freshwater gets used and ends up in the black and grey tanks. Food/beverage from the fridge and cabinents gets consumed and ends up in the black tank(s), propane gets consumed and it's weight removed from the TT, and some other items may get used and then loaded in different locations for the trip home.
This can have the effect of increasing OR decreasing the TW. There are a LOT of variables in this calculation. Everyones TT is laid out differently, and everyones usage is different as well.
So after considering all of this, and you still want to do it.. Don't use the bumper to support any weight. It is made of really thin metal and will fatigue easily and tear like tissue paper.
About the only safe thing to store in it is a sewer hose. Other than that, it is for decoration only.
merlin8735
Explorer
Mar 05, 2014
GrandpaKip wrote:
tkoden wrote:
I am looking into mounting a toolbox to put batteries in on by back bumper. The bumper itself looks to be pretty solid and the weight will be distributed over 4' of the bumper. Anyone have anything heavy hanging off their bumper? I figure I will be putting about 300 lbs on the bumper.

You've got a new camper. Why not contact your dealer, and Keystone, and ask them?

Contacting Keystone will get you the standard "Any modification to the frame or suspension will void any warranty and may render the coach unsafe". Unless you call them very early in the morning before anyone in the front office gets to work. You can, under certain circumstances, get to talk to one of the workers in the plant who will be candid. Otherwise, you just get a scripted response.