WDH tuning questions

[homeagaincda]

Hello, and thank you in advance for your help.
We took delivery (finally!) of our mew Apex 251RBK and have had it out for the first weekend trip. On the way, I stopped at a nearby MTO scale to get weights.

The Apex has a GVWR of 7000 lbs, and my loaded weights were around 6100 lbs., so I have lots of spare capacity.

I tow with a 2022 Tahoe Duramax diesel and have a dealer installed Reese Dual Cam hitch. They set it up with 6 chain links under tension. Unloaded, my front wheel well opening was 37", fully loaded without WDH it was 38", and with 6 links under tension it was 37.5". Chevrolet recommends reducing the delta by half, which this did.

On the short drive to the weigh scale, there were gusty winds, and I found the steering of the truck very twitchy. Weigh scales showed I had 705 lb tongue weight (11.6% of trailer weight). I decided to put increased tension on the torsion bars and reduced the number of links under tension to 5 links. This returned the wheel well opening to 37" the same as the unloaded height, and added about 150 pounds to the front axle weight and 66 pounds to the trailer axle. Note Chevrolet recommends removing half of the wheel well opening rise - this reduced it fully and the front axle weight was back to exactly the truck alone weight.

The truck road much better. Much firmer steering and no porpoising that I had previously at low speeds.

However after the trip, I reviewed the weights and calculated the tongue weight. The tongue weight had changed to 639 lbs, which is 10.5%. Ideally, I'd like to be in the 12-14% range. Further, I plan to put a bike rack and two bikes on the back of the trailer (on dealer installed welded hitch) and know this will reduce the tongue weight further.

After the trip, I decided to try the setup with 5 1/2 links under tension. I achieved this by inserting a bolt into the chain on each side, effectively reducing the chain length. Back at the nearby MTO scales, I reweighted and now find a tongue weight of 728 lbs which is 11.9%, and the wheel well height is still 37.5". Drive performance on the short trip to and from the scales were much better than 6 links under tension, but not quite as good as 5 links.

I also took the opportunity to reweigh with the torsion bars disconnected. The "unassisted" tongue weight was 882 lbs which is 14.4%.

My questions are:
1) when reviewing tongue weight and tongue weight percentages, should I be looking at the "torsion bar assisted" weights of 728 lbs and 11.9% in my last example, or the "unassisted" weights of 882 lbs and 14.4%? I assume it is the "torsion bar assisted" weights that matter.

2) The 5 1/2 link setup was certainly better than the dealer setup of 6 links, but on the short trip comparison, I don't think as good as 5 links. Should I be concerned that 5 links reduced the wheel well rise by 100% not the 50% recommended by Chevrolet? I am thinking that as long as I am not adding front axle weight, I should be good.

3) The 5 link setup only had 10.5% tongue weight, and this is before I add 150 pounds of bike rack and bikes to the rear of the trailer. Although it road better, I am concerned I will get down to or below 10%. Would adding another battery to the tongue, or water to the fresh water tank at the front help offset?

4)other thoughts / advice?

I am going to the dealer for a gas line installation mid week, and would like to have him adjust the Reese cam locations - they aren't centered on the trunnion curve with the 5 or 5 1/2 link setup. Your advice will help me make this decision to have him adjust or not.

Thank you.

[Ray,IN]

During my years of RVing and reading information; this is the best and most accurate description of how to properly set up a WDH I've ever read.

[LanceKeys]

I say just set it up which ever way tows the best. You have gone much deeper into this than I ever would have. Just keep the tools to adjust while on the road, it sounds like you have it dialed in good. Go out there and enjoy your new rig.

As detailed as you are, I’d like to read a write up of your towing experience with the little diesel.

[steve52]

Tightening up the WD bars does not change the tongue weight. It changes the load on the rear axle, but the tongue weight is still there. In fact, you can calculate how much weight will be moved to the front axle and to the trailer axles without even knowing the tongue weight. It is a function of the stiffness of the WD bars. The link posted above explains all this in great detail.
Set it up so it tows most stable, and call it good.

[move on]

Originally Posted by homeagaincda

Hello, and thank you in advance for your help.
We took delivery (finally!) of our mew Apex 251RBK and have had it out for the first weekend trip. On the way, I stopped at a nearby MTO scale to get weights.

The Apex has a GVWR of 7000 lbs, and my loaded weights were around 6100 lbs., so I have lots of spare capacity.

I tow with a 2022 Tahoe Duramax diesel and have a dealer installed Reese Dual Cam hitch. They set it up with 6 chain links under tension. Unloaded, my front wheel well opening was 37", fully loaded without WDH it was 38", and with 6 links under tension it was 37.5". Chevrolet recommends reducing the delta by half, which this did.

On the short drive to the weigh scale, there were gusty winds, and I found the steering of the truck very twitchy. Weigh scales showed I had 705 lb tongue weight (11.6% of trailer weight). I decided to put increased tension on the torsion bars and reduced the number of links under tension to 5 links. This returned the wheel well opening to 37" the same as the unloaded height, and added about 150 pounds to the front axle weight and 66 pounds to the trailer axle. Note Chevrolet recommends removing half of the wheel well opening rise - this reduced it fully and the front axle weight was back to exactly the truck alone weight.

The truck road much better. Much firmer steering and no porpoising that I had previously at low speeds.

However after the trip, I reviewed the weights and calculated the tongue weight. The tongue weight had changed to 639 lbs, which is 10.5%. Ideally, I'd like to be in the 12-14% range. Further, I plan to put a bike rack and two bikes on the back of the trailer (on dealer installed welded hitch) and know this will reduce the tongue weight further.

After the trip, I decided to try the setup with 5 1/2 links under tension. I achieved this by inserting a bolt into the chain on each side, effectively reducing the chain length. Back at the nearby MTO scales, I reweighted and now find a tongue weight of 728 lbs which is 11.9%, and the wheel well height is still 37.5". Drive performance on the short trip to and from the scales were much better than 6 links under tension, but not quite as good as 5 links.

I also took the opportunity to reweigh with the torsion bars disconnected. The "unassisted" tongue weight was 882 lbs which is 14.4%.

My questions are:
1) when reviewing tongue weight and tongue weight percentages, should I be looking at the "torsion bar assisted" weights of 728 lbs and 11.9% in my last example, or the "unassisted" weights of 882 lbs and 14.4%? I assume it is the "torsion bar assisted" weights that matter.

2) The 5 1/2 link setup was certainly better than the dealer setup of 6 links, but on the short trip comparison, I don't think as good as 5 links. Should I be concerned that 5 links reduced the wheel well rise by 100% not the 50% recommended by Chevrolet? I am thinking that as long as I am not adding front axle weight, I should be good.

3) The 5 link setup only had 10.5% tongue weight, and this is before I add 150 pounds of bike rack and bikes to the rear of the trailer. Although it road better, I am concerned I will get down to or below 10%. Would adding another battery to the tongue, or water to the fresh water tank at the front help offset?

4)other thoughts / advice?

I am going to the dealer for a gas line installation mid week, and would like to have him adjust the Reese cam locations - they aren't centered on the trunnion curve with the 5 or 5 1/2 link setup. Your advice will help me make this decision to have him adjust or not.

Thank you.

As to point no. 2, it is not recommended to exceed 50% front axle load restoration. Taking too much load off the rear wheels can destabilize your rig.

[jerome951]

Everything I've always read is to set and measure tongue weight without the WD bars connected. Then measure front fender change as you've done and adjust the WD bars accordingly.
You may have a bit too much tongue weight at 14% and could benefit from reducing closer to 12% and setting the WD bars to achieve the 1/2 front fender rise as you've done.

[Zulu Kono]

You lost me at "porpoising".

[homeagaincda]

By porpoising, I meant the hitch undulating up and down when going over small bumps - very springy. It usually means not enough tension on the weight distribution bars.

[move on]

Originally Posted by homeagaincda

By porpoising, I meant the hitch undulating up and down when going over small bumps - very springy. It usually means not enough tension on the weight distribution bars.

I find the opposite to be true. It's the existence of springs at the hitch point that causes the bouncing. If you take the WD hitch away it will bounce less. You still have the springs on the tow vehicle rear axle but the rear axle has shock absorbers to lessen the bounce. Also, excessive tongue weight will make the bouncing worse.

[homeagaincda]

Re cause / solution to porpoising, I think we may be saying the same thing but seeing it from different angles.
E-trailer says "Most of the time when a tow setup is porpoising with a weight distribution system all you have to do is add[U] a bit more spring bar tension to minimize the porpoising.". This is what I found as well in my situation.
Your comment that it is heavy tongue weight is also true, but it may be that it is really tongue weight that is not appropriately distributed to truck and trailer by correctly set spring bar tension.

[move on]

Originally Posted by homeagaincda

Re cause / solution to porpoising, I think we may be saying the same thing but seeing it from different angles.
E-trailer says "Most of the time when a tow setup is porpoising with a weight distribution system all you have to do is add[U] a bit more spring bar tension to minimize the porpoising.". This is what I found as well in my situation.
Your comment that it is heavy tongue weight is also true, but it may be that it is really tongue weight that is not appropriately distributed to truck and trailer by correctly set spring bar tension.

I'm coming from the point of view that it's the WD hitch that causes the porpoising because you are adding a spring system at the hitch point. Depending on the waviness of the road surface and the speed you are going the harmonics could change with either increasing or decreasing the spring tension, so yes, I agree.

[LanceKeys]

Find a section of road that gives you trouble. Drive over it, stop, make an adjustment and try again. Adjust it up see what it does, adjust it down see what it does. I’m going to guess that it is just a matter of getting used to it. I also had luck with lowering the front tire pressure just a little bit below max sidewall (rear at max sidewall).

If all else fails go buy an F-350 dually.

[move on]

Originally Posted by LanceKeys

I also had luck with lowering the front tire pressure just a little bit below max sidewall (rear at max sidewall).

This is a good point. When towing a trailer you should increase the truck's rear tire pressure to the maximum allowed as stamped on the sidewall. The front tire pressure should be lower than the rear as this will help prevent oversteer.

[CamperLifer]

Originally Posted by move on

This is a good point. When towing a trailer you should increase the truck's rear tire pressure to the maximum allowed as stamped on the sidewall. The front tire pressure should be lower than the rear as this will help prevent oversteer.

A weight distribution hitch adds weight to the front of the TV so you need increased tire pressure and/or heavier rated tires there also. I run LT E rated tires all around my truck that are 80 psi max. I run 60 psi in all 4.