Rear end bouncing/Equal-i-zer 4-point 10K hitch

So, we finally got our first travel trailer - a Grand Design Imagine 2800BH. Just picked it up last weekend and took it right out for a shake down run. So far, pretty much everything ok. Biggest issue we are having is that it doesn't pull smoothly on the highway. Get a lot of oscillation type bouncing from the rear end.

Now, the roads are not great around where we have towed so far, but I don't think it should be pulling like this. Gets this small oscillation like bouncing from the back end. Doesn't really seem to affect the front end. Front end steering and feel is pretty much same as unloaded, but this back end gets going (not huge up down bouncing, but just constant oscillation).

Just trying to figure out what to try next to get rid of that. Here are numbers:

Tow Vehicle:

- 2016 Chevy Silverado 1500 4x4, crew cab, short box
- Truck weight with full tank of gas, my daughter and me in it: 5960 lbs
- Front tire pressure towing: 40 psi
- Rear tire pressure towing: 41-42 psi

Travel Trailer:

- 2017 Grand Design Imagine 2800BH

Measurements:

- Front: ground to fender lip, unloaded: 36.25"
- Front: ground to fender lip, loaded with WD bars on: 36.5"
- Front: ground to fender lip, loaded, no WD bars: don't have this measurement yet

Hitch setup: Equal-i-zer 4-point 10K

- Hitch head: has 4 washers in it
- L-brackets: mounted with 1 hole left at bottom
- WD bars install with slight up angle towards back - bars not completely level with a-frame

Weights:

- Just truck: 5960

Loaded (CAT scale numbers):

- Front Axle weight: 3320 lbs
- Drive Axle Weight: 3260 lbs
- Trailer weight (loaded for camping): 6080 lbs
- Combined Weight: 12,660

From that, tongue weight is right around 620 lbs. So just over 10% on tongue weight.

So, I have read and gotten opinions, but trying to figure out what to try or look at to get rid of the back end bounce. I have had some say need to increase tongue weight to around 12-14% (730 - 850 lbs). My question is, how do I increase that properly. We only have front pass through storage outside which is where most things are kept. Inside is just mostly items in kitchen area we loaded which is middle area of TT and little to nothing off back end. So not sure how else to re-load trailer for more tongue weight.

And what about adjustments to the hitch setup? Will adjusting the L-brackets for the bars help at all? Maybe drop brackets one hole to take a bit of load off the bars? We are getting zero sway and the other numbers look like we are setup good, so not sure if moving L-brackets will help or hurt. Input appreciated.

And what about tires. I know the stock "P" tires are not ideal for towing, but want to look at upgrading to LT tires as last resort given expenses and only 4600 miles on stock tires. Goodyear says max psi for these tires is 51 psi (Goodyear Wrangler SR-A ****). Would going to 44-45 psi, at least on the rears when towing, help at all?

And if there are good instructions or something out there to help understand the Equal-i-zer hitch setup and affects of changes, please point me towards it. The hitch owner manual doesn't help a whole lot. Would seem to be that if I drop the brackets one hole it will take a bit of WD out which means a little weight off the front and back to the rear axle. But none of that affects tongue weight still, correct? Just which axle it is distributing that weight to?

Any assistance or input appreciated.

Thanks,

Highway_4x4
Explorer
Jul 25, 2016
On a washboard freeway it feels like my truck is being shook apart by the TT. When not towing the same freeway is not as bad. I would take the tire PSI up to the max cold and see if it makes a difference just to start. Is that 620 tongue weight a measured or on from the factory info. If you really need to add weight you might be able to fill a holding tank in front just to see if that helps. Then if it does add the weight.
mkirsch
Nomad II
Jul 25, 2016
When you adjusted the bars, did you work your way back down to unloaded ride height in the front, or did you hit it "spot on" on the first try?

If you got it "right" on the first try, I submit to you that you probably have too much tension on the bars. The reason being, there are "jounce bumpers" that the IFS 4x4 Chevys ride on at unloaded ride height. It is impossible to push the front end below unloaded ride height. So you may think you're right on, but you're really way over.
Eric91Z
Explorer
Jul 25, 2016
Thanks for both of those items.

1. I will try air pressure. That is one thing has is on my too do list for sure next time I take it out.

2. As for front ride height with bars, it was actually set by the dealer we bought from, on the day we got it. And basically took it home, loaded up, stopped and weighed, and headed out. Had the bouncing both unloaded and loaded. So, you are right, it could be too much if that is case with bump stops. Although, it looks like they originally had the L brackets up one set of holes further and raised one for how we left with it. So might need to drop brackets back down and re-measure. As well as getting front height with trailer hooked up, but WD bars not on.

3. Tongue weight is based on loaded truck weight (from scale) minus unloaded truck weight (from scale). So it was difference of the two weighed weights from scale weighing.

4. One other thing we weren't aware of, is that there was a fair amount of water in the fresh water tank. Not sure when that was there. We only were hooked up to City Water connection and shouldn't have been filling the holding tank, but did make sure it was empty before leaving the site and it drained quite a bit out.
BarneyS
Explorer III
Jul 25, 2016
mkirsch wrote:
Snip...

If you got it "right" on the first try, I submit to you that you probably have too much tension on the bars. The reason being, there are "jounce bumpers" that the IFS 4x4 Chevys ride on at unloaded ride height. It is impossible to push the front end below unloaded ride height. So you may think you're right on, but you're really way over.

According to his numbers, he is not trying to push the front axle below the stock unloaded ride height. He is .25in above the stock height when the WD bars are tensioned.

This is probably just about right but I would try to get the bars parallel with the A frame so that they ride flat on the L brackets. I think I would lower them one hole and tilt the hitch head back by adding at least one more washer. For the standard sized A frame, Equal-i-zer recommends starting out with 5 washers in the hitch head and he only has 4. When he lowers the L brackets to make the bars level then he needs to tilt the head back some more to keep the same tension on the bars.

What he describes sounds like he could use a bit more tension on the WD bars so I would add two washers and try it out. Can always take one out if it puts too much tension on the bars. The porpoising he describes is a typical result of not enough bar tension.
Barney
Eric91Z
Explorer
Jul 25, 2016
BarneyS wrote:

According to his numbers, he is not trying to push the front axle below the stock unloaded ride height. He is .25in above the stock height when the WD bars are tensioned.

This is probably just about right but I would try to get the bars parallel with the A frame so that they ride flat on the L brackets. I think I would lower them one hole and tilt the hitch head back by adding at least one more washer. For the standard sized A frame, Equal-i-zer recommends starting out with 5 washers in the hitch head and he only has 4. When he lowers the L brackets to make the bars level then he needs to tilt the head back some more to keep the same tension on the bars.

What he describes sounds like he could use a bit more tension on the WD bars so I would add two washers and try it out. Can always take one out if it puts too much tension on the bars. The porpoising he describes is a typical result of not enough bar tension.
Barney

So I have heard two possible causes: 1. Not enough bar tension and 2. not enough tongue weight...

So first step, drop L Brackets one spot for bars to be parallel with a-frame and one or two washers to head to tilt that a bit and try that?
wgriswold
Explorer
Jul 25, 2016
I think it is likely that your settings are too tight. Four washers is about the recommended starting point but one hole at the bottom is not the recommended starting point for the L-brackets. My instruction manual for installation recommends to start at the 5th hole from the top and that leaves four or five at the bottom. Leaving one hole is about the equivalent of adding four more washers.

I don't think you can measure tongue weight the way you did. I think you need to use the bathroom scale and lever method or place the tongue directly on the commercial scale. Perhaps someone with a better grasp statics will correct me.

You can download the Equalizer installation manual that will lead you through the process.
TurnThePage
Explorer
Jul 25, 2016
Eric91Z wrote:
BarneyS wrote:

According to his numbers, he is not trying to push the front axle below the stock unloaded ride height. He is .25in above the stock height when the WD bars are tensioned.

This is probably just about right but I would try to get the bars parallel with the A frame so that they ride flat on the L brackets. I think I would lower them one hole and tilt the hitch head back by adding at least one more washer. For the standard sized A frame, Equal-i-zer recommends starting out with 5 washers in the hitch head and he only has 4. When he lowers the L brackets to make the bars level then he needs to tilt the head back some more to keep the same tension on the bars.

What he describes sounds like he could use a bit more tension on the WD bars so I would add two washers and try it out. Can always take one out if it puts too much tension on the bars. The porpoising he describes is a typical result of not enough bar tension.
Barney

So I have heard two possible causes: 1. Not enough bar tension and 2. not enough tongue weight...

So first step, drop L Brackets one spot for bars to be parallel with a-frame and one or two washers to head to tilt that a bit and try that?
I agree with Barney, about adding 2 washers. I would also increase tire pressure to max on both vehicles. On top of that, there's a good chance that filling your fresh water tank full might help too. Last but not least, maybe drop your hitch ball height by one notch, which will force the Equal-i-zer to transfer more weight off the rear wheels. Those steps have worked well for me on a couple different tow vehicles utilizing the same hitch you have. You might consider adding a second battery to increase tongue weight, along with the other benefits it provides. JMHO
keymastr
Explorer
Jul 25, 2016
Read the sticky at the top of this section on getting cat scale weight. You must make 3 passes to get all the info you need:
Pass 1, just the truck with the gear and people you normally tow with.
Pass 2, truck and trailer without WD bars attached but with trailer loaded as you will tow.
Pass 3, truck and trailer with WD bars hooked up. Only then will you know what your weights are and how much you are distributing to the front of the truck and back to the trailer.

The trailer also should be level front to back when hooked up on flat ground. Slightly nose down is ok but only slightly. Nose up is not recommended.
3oaks
Explorer
Jul 26, 2016
BarneyS wrote:
......................According to his numbers, he is not trying to push the front axle below the stock unloaded ride height. He is .25in above the stock height when the WD bars are tensioned.

This is probably just about right but I would try to get the bars parallel with the A frame so that they ride flat on the L brackets. I think I would lower them one hole and tilt the hitch head back by adding at least one more washer. For the standard sized A frame, Equal-i-zer recommends starting out with 5 washers in the hitch head and he only has 4. When he lowers the L brackets to make the bars level then he needs to tilt the head back some more to keep the same tension on the bars.

What he describes sounds like he could use a bit more tension on the WD bars so I would add two washers and try it out. Can always take one out if it puts too much tension on the bars. The porpoising he describes is a typical result of not enough bar tension.
Barney
Having quite a bit of experience with the Equal-I-zer 4 point hitch, I believe Barney has given you some very good advice and logically so.
mkirsch
Nomad II
Jul 26, 2016
Ok, I must have misread the ride heights originally. I could swear they both said 36.25"...

Sooooo, ignore my advice from earlier. It's not too much bar tension. Most likely it is not enough.

One universal truth of RVing is, the dealer never sets the WD bars correctly. The reality is, they can't. They don't know what you're going to be putting in the trailer. You need to go through the adjustment process yourself to get it fine tuned to your needs.