<div dir="ltr">I had the exact same experience years ago, the first time I hit highway speed with the new sub on a new trailer. In seconds the trailer was 90 degrees sideways. It blew out both tires on that side, and was the closest call I've ever had. I did two things in response, and its been on rails ever since:<div><br></div><div>1) Moved the sub a couple of inches forward to increase tongue weight.</div><div>2) Installed one of these things. Its the best small investment ever. </div><div><br></div><div><a href="https://www.etrailer.com/Accessories-and-Parts/CURT/17200.html?feed=npn&gad_source=1&gad_campaignid=1672411894&gbraid=0AAAAAD_vMtmZbb1-gLY0fxVHu9dx9gqzA&gclid=Cj0KCQjw6bfHBhDNARIsAIGsqLhJ1AWcofS_689Y-tXWO3OPvo-coVHMfWktkrxVQb69uMwZghVDgYYaAsgDEALw_wcB">https://www.etrailer.com/Accessories-and-Parts/CURT/17200.html?feed=npn&gad_source=1&gad_campaignid=1672411894&gbraid=0AAAAAD_vMtmZbb1-gLY0fxVHu9dx9gqzA&gclid=Cj0KCQjw6bfHBhDNARIsAIGsqLhJ1AWcofS_689Y-tXWO3OPvo-coVHMfWktkrxVQb69uMwZghVDgYYaAsgDEALw_wcB</a></div><div><br></div><div>Having said all that, Jon's issue is vertical bouncing and that I've never had. But I've always used torsion axles, so maybe that has something to do with it. </div><div><br></div><div>Best,</div><div>Alec</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Oct 14, 2025 at 7:22 PM via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"><span style="color:rgb(0,0,0);font-style:normal;font-weight:normal"><span style="font-size:12pt">Jon,</span><br></span></div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"> </div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"><span style="color:rgb(0,0,0);font-style:normal;font-weight:normal"><span style="font-size:12pt">A huge concern could be what might happen if you had to brake hard to avoid another vehicle and the trailer decided to jackknife either to the left or right. If you were on even a slight curve it would be even more critical. Now add dust on the road or a light sprinkle. I can think of a couple more possible compounding factors.</span></span></div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"> </div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"><span style="color:rgb(0,0,0);font-style:normal;font-weight:normal"><span style="font-size:12pt">I rented a trailer once to haul tear-off roof shingles. I loaded everything as far forward as possible. The single axle should have been farther back. On the highway the #@%& thing started oscillating left and right at full 90 degrees before I could safely get to the shoulder of the road. Fortunately no one was in the adjacent lane, and the only damage was the bent rims on the trailer.</span></span></div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"> </div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"><span style="color:rgb(0,0,0);font-style:normal;font-weight:normal"><span style="font-size:12pt">Another time I saw a trailer with a boat on it exit a road and come right across a parking lot. Didn't even see an associated vehicle, however at the moment that wasn't my biggest concern.</span></span></div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"> </div>
<div style="font-family:arial,helvetica,sans-serif;font-size:10pt;color:rgb(0,0,0)"><span style="color:rgb(0,0,0);font-style:normal;font-weight:normal"><span style="font-size:12pt">Jim T.</span></span></div>
<br>In a message dated 10/14/2025 2:25:29 PM Central Daylight Time, <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a> writes:
<div> </div>
<div>
<blockquote style="padding-left:5px;margin-left:5px;border-left:2px solid blue">
<div dir="ltr">Speed...highway speeds, 65-70mph, 104-112kph.<br clear="none"><br clear="none">Tongue weight...that's a long story. It's a dual axle (tandom) and was originally 10% with the submarine loaded slightly forward of the front axle. But this resulted in the equalizer (between spring sets) being offset toward the front axle, not "equal". The result was about 6mm of clearance at the front side of the equalizer and 3-4 inches of clearance at the back side of the equalizer, causing the trailer frame to bang hard against the equalizer when going over the slightest bump. On a long trip it wouldn't last long. To combat this, I slid the submarine rearward until the equalizer was equally spaced from the frame on both sides which results in the submarine being positioned directly over both axles. This solved the frame banging on the equalizer since there was now enough distance (about 2-3 inches) between both ends of the equalizer and the frame. However, in this configuration because the submarine is directly over both axles the tongue weight is near zero (maybe 25 pounds at most). I can literally pick up the tongue and rock the trailer up and down. I took it this way to Michigan and the trailer still tracked very well with zero sway, but it resulted in a bumpy ride at the hitch which made for a rough ride inside the truck. Since that trip and prior to heading south this week, I added about 250 pounds in front of the submarine but behind the hitch. I did not measure but I'm guessing my tongue weight is now somewhere around 3-4%, still low, I know, but it was enough to result in a much smoother ride and I did not notice any lifting or bumping at the hitch. The remaining issue is that when traveling at highway speeds and traversing a large enough pothole, or transition from road to bridge where in many cases there is a mismatch in road level (think speed bump) the energy will cause significant bouncing up and down of the trailer at the wheels. Sometimes looks like a pogo stick in the rear view mirror.<br clear="none"><br clear="none">I can't change the position of the submarine or else the equalizer between springs won't be equal and I'll risk severe banging of the equalizer parts against the frame of the trailer. I know that will cause failure of bolts and other parts eventually. I could add more weight at the front to get more tongue weight, but even with my original configuration that gave me 10% tongue weight (I measured it) the bouncing of the trailer was still significant over a large bump. There's just a LOT of weight (4500) lbs concentrated in a relatively small area over the axles.
<div id="m_4789610659480347067yqtfd33244"><br clear="none"><br clear="none">Jon<br clear="none"><br clear="none"><br clear="none"><br clear="none"><br clear="none">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a href="mailto:Personal_Submersibles@psubs.org" shape="rect" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="noopener" shape="rect" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a></div>
</div>
</blockquote>
</div>
</div>_______________________________________________<br>
Personal_Submersibles mailing list<br>
<a href="mailto:Personal_Submersibles@psubs.org" target="_blank">Personal_Submersibles@psubs.org</a><br>
<a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="noreferrer" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br>
</blockquote></div>