Porpoising and slight low speed brake judder with new TT

Hey all,

I just picked up a new GD Imagine XLS 23LDE and, while the Tundra pulled it just fine, we experienced a couple of issues.

First, there was a good amount of porpoising on the drive home. Now, this trailer is a rear kitchen model and it was bone dry/empty with the exception of two full 20lb propane tanks and two batteries on the a-frame. However, I would’ve thought that’d have been enough tongue weight to balance it out well.

I haven’t measured the actual tongue weight but do know that the specs on this trailer from the factory are 524lbs TW and 5,598 dry weight which is a bit of an imbalance. But, again, figured the propane tanks and batteries would’ve gotten me to about a 10% TW ratio.

This being said, question for the more experienced towers out there: Is there something else that could be causing this porpoising, or is it most likely lack of TW?

Second, right at the end of our trip, when coming to a stop at a light, I noticed a bit of low speed brake judder. Wasn’t there when we first hooked it up and made a few stops heading to the freeway.

Is this possibly due to the trailer brake controller not being set to the proper gain? I had it at 7.5 which, from previous research, I thought would be good. Did totally fine on the freeway when braking at speed. Problem only reared its face when coming to a stop.

Appreciate any insights/advice on these matters!

 

Well, to be fair, I’m not a newb - I had a travel trailer previously and towed it with two different rigs without issue. Just didn’t have the opportunity to really hone anything in when picking this new one up as it was getting late and we were trying to get on the road home. Now I’m playing keyboard research jockey seeking insights before I go start messing around with things. Tons of experienced minds are better than one semi experienced mind!

I’m going to go load it up as if we’re taking it camping, or close to it, and try readjusting the WDH to see if that helps at all. I wouldn’t think I’d need any suspension enhancements with a trailer of this size. Particularly when I compare it to what some other are pulling with these things!

Also, just so I’m being clear - The porpoising only happened on rough road, not the entire time we were driving. It was quite smooth for the most part.

 

Don't assume the published tongue weight is without propane and battery. My Gulfstream includes two filled tanks and battery in their published tongue weight.

 

Ah, good to know… I WAS assuming it was without those items. My R-pod didn’t include battery or full tanks. I’ll look into that - Thanks!

 

Alright… I ran by a CAT scale today and did a quick weigh with the WDH engaged and one with the trailer disconnected.

First of all, I decided to try dropping one link lower on the WDH chains to put a little more weight on the tongue and the truck drove way better… No porpoising really. So that’s great!

As for the weights, the difference between the first measurement and second showed about 840lbs on the truck. Noting that my wife was sitting in the truck for the first measurement but not the second and she weighs about 120lbs soaking wet so we’ll call it 720lbs. Then take another 80ish lbs off for the WDH and my TW is probably just about 640lbs with my WDH set where it is.

Again, truck drove great so I may just leave it where it is.

Also ran through that Lippert burnishing process and the shudder was pretty much gone - Good day!

Thanks all for all the help!

 

Did you get the weights with the WDH up at your original setting? While the rear may have been happier with more weight/less distribution, 120lbs lighter on the nose is absolutely noticeable on my 2.5 gen.

 

No this was with the current setting. Also wonder if it’s truly 120lbs. Again, my wife was sitting in the passenger front seat for the initial weigh in with the trailer attached but not for the reweigh with no trailer or WDH on the truck.

 

Thanks. I realized I skipped a step after we left. But happy I at least got an idea of what my weights are. I'll reweigh everything the proper way when we get out on a camping trip which, sadly, won't be until March-ish... Can't wait.

 

For the porpoising, is the combo just undulating on the road transitions with the weight of the trailer? I would think that the TW could stand to be higher and that is easy to achieve even if you were to carry some fresh water (assuming tank is forward of the axles). Are you getting any sway at 65+ mph? Do you have air in the rear suspension? Perhaps increasing the pressure or adding a Timbren would stiffen up the truck to counter the transitions in the road?

 

I think the TW was too light. If you refer to my earlier post (#7) I mentioned that I dropped a link on the WDH and it drove way better. No porpoising really and I even went over 70 on accident - Was just keeping with traffic and didn’t notice as it was pulling pretty smoothly.

 

Sounds like that part of your issues is under control. Did you figure out the other part, your judder? I am running my controller gain at 6 and it seems very positive. At 7 or so, I am sure you are getting a good amount of braking.

If the trailer is new to you, have you checked the wheels/tires for roundness and if they are running on the trailer hubs perfectly true? Maybe a tire balance? I did the balance on my new tires, original ones weren't balanced but since I went to a bigger heavier LT tire, I figured I should do that. The trailer travelled so much smoother than before with the Goodyears.

 

Yeah, in that same post I mentioned that I ran thru the Lippert burnishing process and it seemed to help immensely. By the time we got back to the storage facility, I didn’t notice it at all.

Thanks for the advice!

 

I used a Sherline LM 1000 tongue weight scale (got it from Amazon) on my trailer. Worked well to get the tongue weight easily. I took it with camping to make sure I had appropriate weight on the tongue when I loaded the trailer. Well worth the $140.