Unstable trailer - what changed?

[MMeier]

I say not enough tongue weight. Going rounds now with a guy that bought a new trailer from me recently, trying to blame the trailer for whipping all over the road AND GET THIS, taking out his driveshaft also, What an idiot!! He tows with a 73 Blazer thats been lifted then has his show truck,a 68 or so GMC truck loaded right at the back edge of the trailer. No W/D or anti sway control either!! THEN, where he has this thing tied down waaaayyy under ,damn near in the middle of the truck for christs sake from both ends!! I offered to go down to the local Highway patrol and see if they would tell him whats what, but he won't so basically I told him to go get some opinions from people and see what they think. If he calls again, i might take a picture and post here and let you guys tell him whats wrong with his set up.

 

[The Warden]

Russ and MMeier, that makes sense...except, again, I've pulled this trailer with this truck before, and have not had a problem. Nothing on the trailer has changed since the last time I moved it (last May, actually), and while I made some major changes to the engine on my truck, the only other change was the tires. The suspension and chassis are unchanged.

Having some extra weight in the bed makes sense, but I didn't do that in the past. Why didn't I have a problem then?

Not saying you guys are wrong, but it still seems to me like the tires were the only major thing that changed, and therefore that's the most likely problem...

 

[rthomas]

tim, not to say it cant be the tires but over the years ive had 3 different tire/ wheel combo's and the gripe that i had with the bigger tires was hydroplaning and fuel economy but they were fine towing even with the heavier loads ive pulled.
if you grab your bedrail and shake the truck side to side how much does it move at the tires? can you compare to someone elses truck?
was there any wind the day you towed it?
how are the trailer tires?
can you tow something else and see how that feels?
in your pic it looks like you have some tongue weight but a trailer that size with a single axle would surprise me if it towed well even under the best conditions. id be hesatant if someone asked me to tow that thing on the freeway.

 

[The Warden]

Russ, I just went out and shook my truck...and there was, in my opinion, quite a bit of visible sidewall flex. Wasn't able to compare it to anyone elses' truck, but I wasn't shaking the truck that much, and I saw flexing at the front wheel as well. I'm starting to think that this may also at least be playing a role in the steering system issues I've been having...

There was wind the day I towed the trailer. However, I've pulled the trailer over the San Mateo Bridge in the past (going over the San Francisco Bay, and it's usually very windy at the summit of the bridge) without it reacting like this.

Trailer tires are relatively new; I think they're 3 years old now, and the trailer doesn't get moved very much.

Unfortunately, at the moment, I don't really have access to anything else that I can hitch to the back of my truck to see how it does.

I'm thinking at this point on the lines of finding a set of used-but-in-decent-shape stock-size tires and going from there...that way, if nothing else, I can absolutely determine whether it's the tires or not, without spending a bloody fortune.

Thanks again!!

 

[The Warden]

For any of you who were following this soap opera, I got the trailer back up to Napa yesterday.

Prior to this, one of my front tires actually went flat due to a nail popping the tire and coming back out. I went to Big-O to get it repaired under their warranty, and they deemed the tire irreparable and replaced it. I had them replace the tire with a 235/85 E-rated tire, and bought a second 235/85...so I now have two new E-rated Big-O A/T tires on the front rims. I went to a used tire shop and got two used Toyo 235/85 E-rated tires with a good amount of tread left on them for $120, for the rears...hopefully, I'll get 3 years or so out of them while saving up to put a new set on the rears.

Hooked the trailer up and went back...and still had issues. She wasn't swaying anywhere near as bad as she was before, so it appears to me that the tires were definitely a big part of the issue. However, my steering gearbox is loose enough (and the adjustment's maxed out ) that I could hold the truck/trailer steady without any outside influences...but, if for whatever reason I had to correct the steering, it would take 15 to 30 seconds to get the truck stabilized and the trailer would have started swaying by this time.

So, I did the trip back at 35 to 40mph (instead of 25 to 30 mph, so there was at least some improvement), and I'm going to have the steering gearbox changed out on the 17th (same day my "new" tranny goes in; I already have a rebuilt gearbox sitting here, and I would do it myself except I don't have the equipment to pull the Pitman arm). So, until next year...

Thank you all again!

 

[82fordtruck]

Oh, man. I'm sorry to hear all that. Posts like this one sure make me glad I've got a dually.

 

[bikepilot]

How does the trailer sit when hooked up to the truck? Is it a little nose high? If so, try a drop hitch so that the trailer is slightly nose-low. This will give you a little more toung weight and should improve stability,

good luck

 

[holtzer1]

i have found in my trailer towing ventures...new tires are more suseptible to sway, due to the deep tread blocks. sounds crazy, but i had 35" tires on my CTD and only ran into trouble when the tires were brand new....after about 15k all the sway went away.

 

[Full Monte]

Warden,

It has to be a combination of more than one problem, near as I can tell.

1, truck tire sidewalls too flexible.
2. trailer tire sidewalls too flexible.
3. too much weight behind the trailer axle.
4. trailer outweighs the truck by too much.
5. less than 10% of trailer weight on the tongue
6. some wierd oscillation caused by the ratio of truck wheelbase length vs. trailer tongue-to-axle distance
7. need for rear stabilizer on the truck
8. need for air bags on the truck
9. loose steering like you said
10. wrong towing height...too low or too high relative to trailer.

 

[The Warden]

Monte, in retrospect, I think the old rear tires were a commercial-grade or something on those lines...maybe with stiffer sidewalls than most 235/85 tires (something like what towcat mentioned earlier in this thread). They weren't all-terrains, and that was the only thing that changed between one year and the next. Those tires are long-gone, so this is just speculation...

But, not my problem anymore After what happened last year, they found someone else (with a dualie) to move the monster...and the trailer wound up not being available this year in any event...

 

[gonecamping]

Trailer Sway

Just a thought or two. Trailer tires must be designed different than
our truck tires. My 5ver has "D" load range tires, However it also says on the
tires for trailers only. Also how are your springs, shackles, and wheel bearings.
Single axles do have a tendency to sway more than tandems. How about
a anti-sway brake or the tire pressure on the truck tires.

Sorry for the late response.
Darrell

PS Use to be a Prune Picker
Born/raised Stockton,Ca.

 

[Full Monte]

Warden,

I was wondering...are the trailer tires radials? I recall a tire man telling me that radials are a no-no on trailers. Every trailer I've ever towed had really stiff sidewall tires on it...like 6 ply. Even my boat trailers are not radials. And these trailers aren't as big as the one you talk about.