Quote:
Originally Posted by Jim-Bev-2363
While waiting to start on the actual hitch setup I have a question about somthing I read. It is said that the TT is to be in a level or front down position. I was wondering why the front down? Double axle trailers in a nose down position will shorten the wheelbase by placing the weight more on the front axle, mostly. Wouldn't a longer wheelbase handle better?
Another thought is about frame flex. How much is "normal", if any?
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Hi Jim
Sorry for so long getting to your questions, work, life and a little camping (YEH!!) has conflicted with my SOC habit....
Henry has given you a good explanation as always. I'll add some more.
There are 2 main purposes to a WD hitch and each use different parts of the hitch to adjust for their specific purpose.
First the WD part. The WD spring bars, the chains (in your case) and the head tilt feature of the WD hitch are intended to be adjusted to get the proper optimized WD on the truck. That is there purpose and only there purpose which is Weight Distribution.
Once you load up your camper and the truck as you go camping and drop the TT coupler on the tow ball, that creates a loaded tongue weight, a new rear axle weight and a new front axle weight. The WD hitch is used to create proper balance once again on the truck. Balance meaning restoring the lost weight on the front axle, moving some weight off the rear axle back to the front axle and by the laws of physics it puts some of that rear axle weight gain onto the TT axles.
By using the right combination of chain links under tension and hitch head tilt your objective is to return the front end of the truck to unhitched weight or just above unhitched. New studies by SAE now are stating they do not want extra weight on the front end from unhitched as that extra loading can aggravate an oversteer condition when towing as the truck front end can bite in so to speak in a hard turn and push the rig into jack knife. This was realized long ago just never preached much. Now this year some of the auto makers are stating this in their manuals and Progress Manufacturing the makers of the Equal-I-zer hitch.
Edit: 5-5-11 fixed my mess up of under/over steer. Sorry
Once the front of the truck is at that unhitched or slight above condition that is the optimized settings of the WD part of the hitch. The rear axle of the truck then is left taking the weight that is there. And odds are good that it will squat some, 1" to 1 1/2" is common. If it is squatting a lot, like 2 to 3" that points generally to a over twisting receiver in some cases. The rear should never be back at the same height or weight as unhitched as that is too much weight removed and now in wet conditions the TT can push and break traction on the back of the truck.
So now the WD part of the hitch is set. Now granted I did not go into the purpose of how many links under tension and how much head tilt as there are mechanical relationships for each brand and style of hitch you have that must exist when done. The point is once the WD is set, that is it, no more adjusting is needed. And also notice I never talked about the truck being level either. While being level if it happens is a nice thing, it is not the measure of proper WD adjustment.
Now the 2nd part of the WD hitch, it is to level out the TT where the new position of the tow ball is after setting the WD. Here you pull the bolts out of the hitch head and slide the hitch head up and down the shank, some times having to flip the shank up or down to get the TT to be level.
Level is best. It creates the best shot at having more equal axle loads on tandem trailers. However you are at the mercy of the centers of the bolt holes in the hitch shank on how level you can make the TT. You can only be as acurate as one bolt hole. So some times you have to choose as level is not obtainable. So do you choose nose up or nose down? Here is a guide. Many shanks are drilled on 15/16" to 1 1/8" etc centers. some maybe even more different. The goal is to be closest to level but when you have to choose on a greater distance, choose nose down. Let's say you are on 1" bolt centers on the shank for talking purposes. You can choose 1/4" high or 3/4" low to level out the camper. Well in this case I would choose 1/4" high as that is better then 3/4" low. That ~ 1/4" is about my threshold as if it is was 3/8" high and 5/8" low, I would pick 5/8" low.
Also to note when you change the hitch head height it does interact with the WD on the truck and you may have to tweak the WD a little to get back that optimized front end weight again. But do "not" be adjusting the WD part of the hitch attempting to level out the TT. If it happens by fortune that the TT is level when WD is optimum then great. It does happen some times. But do not adjust WD attempting to tweak the TT level. That messes up the optimized WD on the front end of the truck.
Yes axle loads "might" be shifted some. Notice I said might. Not all camper floor plans change tongue weight by nose height. But some do and some gain weight for nose high and some loose weight for nose high and the same for nose low. It all depends on where the center of gravity is in your TT floor plan and where your gear is. I know on mine with a 1,400# tongue weight I can go up 3" and down 3" and only change less then 50# in tongue weight. However some campers actually gain 100# 1" low.
The other part of nose high by a good amount is the way the wind can affect the top of the camper. On a level or nose low camper the wind hits the front differently then nose high. On nose high, first off it's up higher catching more wind and more wind creates more drag and can create unsettling air patterns on some camper/truck combinations and aggravate towing instability you fell in the truck. So the rule has been level is best, next is nose down but again there is some tolerance in there for nose up. AND... you do not want to be on pupurse and entire extra bolt hole too low.
You mentioned that nose low on tandem axles creates a shorter wheelbase. Well if we are talking 1" low you are going to have to go out 3 to 4 decimal places to find the shorter wheelbase from front axle to tow ball unless I missed understood what you meant by wheelbase from TT axles to tow ball center. How much the TT axles shift weight by the hitch height changes by camper floor plan and loading and how much you changed the ball height. It may only be 20 to 50# axle change in some cases for 3/4" difference in ball height.
You asked wouldn't a longer wheel base handle better? Need more info to what you are referring to. The truck or the trailer? As a general rule, longer is generally better on both for towing stability.
You asked about frame flex, are you talking the truck or the camper? If you are talking the camper, well what is normal comes back to the specific TT. 4", 5", 6" 10" etc wide frames all have different flex levels. For instance, my 10" frame on my 32 foot camper will flex more then say a 10" frame on a T264SR. The 264 is a lighter and shorter camper on a heavier weight frame.
What is your camper frame made out of (channel iron, rectangular tubing etc) and what width is it? I can take an estimate on what you might see. Trust me, they all flex and wiggle down the sides of the camper too.
Hope this helps
John
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