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Old 03-14-2010, 04:46 PM   #21
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Originally Posted by mtnguy View Post
After messing with a ruler suspended over an ink pen, I am now confused. Maybe my other reply is not exactly correct. Picturing a see-saw, 150 lbs. on 1 end should take off 150 lbs. from the other.....but what about the weight on the fulcrum (axles) ???

Maybe the weight taken off from the tongue would only equal 1/2 of the 150 lbs., with the other 75 lbs. going to the axles ???? That would be if the axles were exactly in the middle, and more on the axles and less taken off of the tongue because most trailers have the axles toward the rear ??? my brain hurts.

I need for someone else to chime in here.....any geometry majors on board ???
I was going to try to explain my Idea with the flucrum theory in my first reply but couldn't get my thoughts together that's why I gave the distances between the tires from front to back and this is how I envision the bike rack on the back, and by the way the 150 lbs weight limit on the bumper is not to exceed 6" out away from the bumper, just thought I would pass that on.

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Old 03-14-2010, 05:33 PM   #22
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Originally Posted by flyrotor View Post
I did a lot of research about carrying bikes on the rear bumper when I first bought my pop-up trailer, and every post I could find using google all recommended against it. Rationale was that putting the extra weight sticking out beyond the bumper caused excess sway.

If you think about it, when you put weight in the back of your trailer, you can change your tongue weight, but when you extend it beyond the back of the trailer, you can actually change the weight of your tongue by MORE than the actual weight of the bikes, this is the same effect of using a cheeter bar when loosening a stuck nut, the leverage is much greater.

However, with all this stated. My research conclusion was the problem was worse with pop-up's more because they are usually shorter in length, and most are a single axle trailers.

My pop-up was one of the largest and longest available with single axle, I chose not to put the bikes on the rear, rather I put some Thule rails on the roof, and used a roof top bike carrier and accessories to hold the bikes.

I strongly believe that when you exceed 20 feet in your trailer length, two axles and a dry weight of 4600 lbs, 600+ tongue weight (dry) that adding 150-200 pounds on a receiver hitch will have no ill effect on sway. I think that loading camp equipment, water, etc will offset your tongue weight and you will be ok. You MUST also be sure that you do not exceed any of your weight limits, including your axle weight limits when loading any of your equipment. (including bikes)

Again, I think the biggest problem comes from single axle configurations, two axle configurations will absorb much more of the weight balances.
flyrotor, thanks for your input and I see your point as well, I was thinking a little different because my camper is approx 33' long and my over all length hooked up to my tow vehicle is 53' long and with the hitch system that I have I did not think that 150lbs would make a differences and the reason is the 10' over hang in the rear and 18' to the front of the axles.

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Old 03-15-2010, 10:52 AM   #23
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Originally Posted by rockwood06 View Post
I thought that the extra weight on the back would be absorbed by the suspenion of the camper due to the fact that the distances between the coupler and the face of the front tire was 18'. Thanks for the over view, it is a great reply.....
as to suspension, remember most trailers only have springs with no shock absorbers. that's why bumper-mounted rear bike racks end up bouncing so much and breaking the bumper welds. same thing goes for animals in carriers, you don't want to put them in the trailer while traveling. it not a fun ride!
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Old 03-15-2010, 11:32 AM   #24
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You know I realize something else, I have found that if I put the bike rack in a class 3 receiver there is more play in it then there is in a class 4 receiver and reason I say this is because when I install the bike rack in the receiver on the camper just like you say there is room for bounce and it is a class 3, but when I put the bike rack in the receiver to what I use to have, 3/4 ton Suburban that came standard with a class 4 receiver it fit tight, I know it sounds strange. The hitch that I use to tow my camper fits sloppy in my new truck and it is a heavy duty 1/2 ton with a class 3 receiver, now this is the same hitch I used on the 3/4 ton Suburban and the hitch fit tighter. Have I gone off the deep end or has anyone else noticed this? So I am thinking if what I have said is true then maybe I should change the receiver out on the back of the camper to a class 4 so that the bike load will bounce with the camper instead of it doing it's own thing. I have not had any problems with sway, but I like to be safe and protect those that are behined me while traveling.
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Old 03-15-2010, 11:39 AM   #25
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First one a class III on the new truck, second one is a class IV on the Suburban.
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Old 03-15-2010, 01:18 PM   #26
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Looks like this probably has nothing to do with class III or class IV, rather different manufacturing specs.

Thule bike racks are mounted with a 9/16" (3/4" head) bolt that has a nut welded to the inside of the receiver stem, when tightened it eliminates any play, locking it tight in place. When I first got the bike rack, I drilled an extra hole in the Thule stem with intent to use a standard receiver pin, but quickly discounted this idea when I noticed how loose it was. I am glad I didn't drill through the nut at the time, thus I preserved the original mount.
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Old 04-05-2010, 11:28 AM   #27
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I thought I would reopen this thread because of my post #16 which is incorrect. Even after all of these years, I still engage my mouth (or fingers in this case) before I put the brain in gear.

Wade got me thinking in his comment on that post, and I now realize that I was way off base.

So, my new understanding of adding weight to the bumper:

Since the axles are a fulcrum, they take some of the weight added to the rear bumper, in proportion to where they are located on the trailer. If the axles are exactly at the midway point between the tongue and bumper, then 1/2 of the added bumper weight would go to the tongue, and 1/2 would be absorbed by the axles. In the case of my trailer, the wheels are approximately 2/3 of the way back from the tongue to the bumper. So, adding 150 lbs. to the read bumper should add 50 lbs. to the tongue, and 100 lbs. to the axles.

I did some experimenting last week trying to tweak my tongue weight. Rounding off to the nearest 5 lbs. since I was using the bathroom scale method, for every 40 lbs. that added to the bumper, I took off 15 lbs. on the tongue....the other 25 lbs. was going on the axles (or somewhere).

Moving to the back end of the camper, but about 2 feet further foward than the bumper, I added 50 lbs. to the hot water heater and only got a 10 lb. reduction on the tongue.

Now mind y'all, these figures are rough, since I had to read the scale and multiply everything out, but I think it gives me enough knowledge to be, I mean informed.

Sorry for the previous misleading post.


Chap , DW Joy, and Fur Baby Sango
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