Spread Axle trailer tongue %

[pomocamper]

We just bought a Coachmen Freedom Express 29bhds. It has the spread axle design. With no load distributing hitch to tongue weight comes out to 750lbs, 10.4% of the 7200lbs loaded trailer weight. But with the weight distributing, not only are we pushing load to the front TV axle, we shed between 50 and 100lbs (depending on the number of chain links) to the trailer axles. This puts our tongue in more the 9% range. This seems low. I am wondering, however, if the 9-15% does not hold for spread axle trailers which are naturally more stable. I can't find a recommended range. We wouldn't worry, but our F150 is porpoising on bumps, which of course affects handling. We added it up, and with passengers, bikes, tongue, we are pretty much at the 7700lbs GVWR of our 2010 F150 with max tow/max payload.

[VanDiemen23]

Well being at max ought to tell you something. Towing at Max is what you do once or twice when necessary, not what you plan to do as usual. A single percentage point in tongue weight is not likely to be the issue, the magnitude of the weight being controlled is more likely the issue.

I towed a similarly sized trailer with a 89 Chevy 2500 and killed the transmission in about six months of towing once a month. The technology has come a long way, but it appears you need a bigger truck.

Are the rear shocks OK? If you bottom the shock hard enough it will kill the valve at the bottom, and it will be OK on rebound, but have very little bump damping left. loading the rear at max will make it easy to bottom the shock. If you remove the top bolt and the piston rod just falls into the shock it's done.

[Cumminsfan]

Been there done that. 2010 F150 maxtow 7650 GVW, with 4000lbs on the RAWR of 4050lbs. We have a NorthTrail 26LRSS which also has the spread axle. Brochure weights have the tongue weight near 10% or less. I have ignored the spread axle theory and load the front to 900lbs, which is near 12%. I had put SuperSprings on the F150 to help with the load and for the most part it was just okay. IMO too much TT for a max loaded truck. We moved up to a 12 Ram CC LB 4x4 6.7 diesel and now the truck pulls the TT instead of the TT pushing around the truck. Not a big fan of the spread axle design myself. If it was that great all trailers would use it. Funny how TT's of the same layout from different companies use different axle spreads.

[pomocamper]

Yes, we are feeling like we need a bigger truck, but it strikes us that pretty much everyone using an F150 towing with a family must have overloaded their TV, or be pretty close to the wire. We have the max payload which seems to be a rather rare option as it took us a lot of looking to find one with it, and even with that we are at the line with two small kids. Folks even pulling a TT with a lower tongue saving a couple hundred pounds, but without the max payload are right back to being at max. Have a couple teenagers instead of little kids and they are over. We figure most look at tow limits, and some look at GCVWR, but very few look at their GVWR and actually add passengers, fido, the bikes and firewood in the back.

Yes, we do think we need to look at our shocks, and that will help, but doesn't solve the issue of being near our max GVW much of the time, it will just help with the symptoms. What specifically is the limiting factor for GVWR? Component wear, or handling? Shouldn't be breaking.

[tuffr2]

I towed a 5,500lb trailer with a 2011 F-150 5.0 litre. Tow limit was 8,500 lbs. The truck towed the trailer ok but not great. I knew the trailer was back there. I could tell the weight distribution hitch was working. I did not have too much bouncing. Bouncing usually means bad shocks.

How well does the spread axle rig track? I think that was the design benefit sales pitch.

[VanDiemen23]

The other thing you have to remember is that the load bar mechanisms on weight distributing hitches are undamped springs. They get some damping from the shocks on the tow vehicle, but the tow vehicle shocks are matched to the spring rates they are attached to, so adding several hundred more lbs/in may make them somewhat ineffective. Also, they are probably undersized anyway - rear springs on tucks are somewhat progressive and then you add in the overload leaf - if the shocks were sized for the loaded spring rate you'd complain loudly about the resultant ride.

You might make this problem less noticeable by adding shocks to the trailer, that end of the system has no damping whatsoever so it will wag the dog.

[SmokeyWren]

Originally Posted by pomocamper

But with the weight distributing, not only are we pushing load to the front TV axle, we shed between 50 and 100lbs (depending on the number of chain links) to the trailer axles. This puts our tongue in more the 9% range. This seems low.

No, you misunderstood something. You want at least 10 percent, and preferably 12 percent, of gross trailer weight on the ball of the hitch before you hook up the spring bars of the W/D hitch. You need to use a tongue weight scale to check the hitch weight before you tie onto the tow vehicle. If you know the trailer grosses about 7,200 and your hitch weight is about 750 pounds, that's 10.4%. Pretty close to the right weight distribution, but it wouldn't hurt to move something heavy from behind the trailer axles to in front of the trailer axles to increase hitch weight a bit.

A properly adjusted WD hitch will transfer about 20% to 25% of that hitch weight to the front axle of the tow vehicle and another 20% to 25% to the trailer axles, leaving about 50% to 60% on the rear axle of the tow vehicle. So the result will be about 375 to 450 pounds of the total 750 pounds of hitch weight remaining on the rear axle of the truck with a properly-adjusted WD hitch. 375 is 5.2% of gross trailer weight of 7200, and that's just fine and dandy. But double-check your weights with a CAT scale to be sure you have at least 5% of gross trailer weight on the rear axle of the TV after the WD hitch is tightened up.

I prefer to have two different CAT scale tickets for my wet and loaded rig, one with the spring bars cinched up and one without the spring bars. Plus I use a tongue weight scale to know exactly how much wet and loaded tongue weight I have before I hook up the trailer to the TV. Then you can tell exactly how much weight your WD hitch setup is moving from the rear axle of the TV to the front axle and the trailer axles. If your WD setup is moving less than 100 pounds of the 750 pounds total hitch weight to the trailer axles, you need to tweak the adjustment of the WD hitch by changing the angle of the ball in the ball mount. The install instructions probably specified 15° angle, but your setup may require more or less angle to get the weight properly distributed.

Also how much you tighten the chains on the WD hitch will affect how much weight is transferred off the ball. If your spring bars are the proper weight capacity for your tongue weight, that's easy. Be sure the trailer and TV are level front to rear, then cinch up the spring bars so they require some effort, but not a lot. One chain length can make a big difference. If a healthy adult female cannot lift the handle to tighten the chain without struggling and groaning, then you probably need to add another chain length to the setup.

But if you have 1,200 pound spring bars for your less-than-800-pounds tongue weight, then it's very easy to get the chains too tight, which will transfer too much weight off the ball. Your hitch should have 800-pound spring bars for your 750 pounds hitch weight. If they are heavier than that, then consider replacing your spring bars with the ones rated for 800 pounds hitch weight. (That assumes your tongue weight scale says you never exceed 800 pounds hitch weight).

Yeah, I know. Replacement spring bars cost almost as much as the entire WD hitch. But that's part of the cost of having a safe RV setup.

Here's my tongue weight scale:
Sherline Trailer Tongue Weight Scale - 2,000-lb Capacity Sherline Tools 5780

If you happen to need a Replacement Round Spring Bar for Reese Weight Distribution System - 800 lbs TW, here's the replacement bar:

Replacement Round Spring Bar for Reese Weight Distribution System - 800 lbs TW Reese Accessories and Parts RP58114

Note that price is for one. Over $150 for the pair.