Stop Utiltiy Trailer Bounce.

So I've got the HF 4x8 folding trailer. It's been a decent little work horse behind the Volvo, we still don't have a truck.

I've used it quite a bit, moving furniture for friends, hauling scrap, runs to the hardware store for large things (lumber), parts, 4 wheeler, etc.

The biggest issue is that the little thing BOUNCES, I mean sometimes you can see daylight between the pavement & the tires. I've learned anytime that I think I'll be okay with 2 ratchet straps, I go ahead and do 2 more.

I've messed with tire pressure some, but haven't noticed any real difference. I'm typically 5 or more below speed limit with a load, and at speed limit empty. I hit a seam in an overpass at about 40 mph this evening with about 250 lbs of lumber, and the trailer took a leap.

Is this something you just learn to live with, inherent to light trailers?

The trailer uses the typical slipper spring leaves, nothing special.

I've thought about adding shocks, more specifically I've thought about adding some air adjustable shocks, one of those kits from Monroe or Gabriel, and possibly removing a leaf.

I know a lot of boat trailers have shocks, and I've seen a camper or two with shocks, but not ever on a utility trailer.

I'm not trying to build a better mouse trap, but SWMBO has gotten more and more into antique furniture over the past few years. There's been a Craig's List find or two lately that I would have perused more seriously if I wasn't so worried that the trailer ride home would destroy it. If I could tame my trailer with shocks, or some other magic I'd be all over it.

Am I smoking crack, or is there merit to my hair brained idea?

• Lee

Slipper springs won't work well with shocks, but if you converted to shackle springs you could add shocks. I've had a couple of trailers with them and not noticed a lot of improvement.

Trailer springs are remarkably stiff. I typically like to run 3500# springs with my 6000# axle trailers and take at least one spring out of the stack with a 3500# axle. For lighter trailers with <2000# axles all you really need is the big main leaf. Softer springs will let the suspension actually move.

Along the same lines, trailer tires are very stiff and swapping to car ones might take some bounce out too.

Take out the smallest leaf. Also, how much pressure are you actually running? I usually only run about 25 lbs in them max.

In reply to oldopelguy:

Rated at 1195 lbs, while I've yet to come close to that, I don't want to lose much of my payload capacity if I remove too many leafs.

In reply to mtn:

It's only got 12" wheels, narrow STIFF wall, HF Chicom specials. Book calls for 60 psi. I've taken it down to 45 psi with negligible improvement. 25 psi seems really low when 60 psi is recommended.

• Lee

If you put 1200# on that trailer I would be willing to bet the springs won't squat 2", and will have 3-4" of travel left. With just the top spring you will probably have 1-1.5" of travel left fully loaded.

But, if that really is a concern for you, you could take your spring pack apart and add a 1/4-1/2" spacer between the main leaf and the rest. That would make the pack act a bit more progressively and help out at least a bit empty and lightly loaded.

In for suggestions. I have similar issue with a different brand trailer that I use to haul karts. I also wandered into Northern Tool for the first time in years and holy crap, trailer part depot! Just don't know where to start.

In reply to oldopelguy:

Something like this?

I've got some scrap HDPE, it's not got the impact resistance of UHMW, it's only a little over 1 ft-lb/in but has similar tensile strength of UHMW. Just a spacer between the main leaf and the rest of the pack, or more spacers like pictured?

Curious why slipper springs don't work as well with shocks as a shackle spring? Insomnia Google searching last night found a few slipper spring/shock combos, but the vast majority were shackle spring/shock.

• Lee

Would increasing the wheels and tires in diameter help? Something bugs me about small trailer tires...

My 5x8 was the same way with the 13" wheels and rock hard trailer tires...it was awful. I put some 15" wheels and Bridgestone Blizzaks on it (seriously I did) and it rides like a dream. I was amazed at the difference it made! I put the blizzaks on it because they came as a spares on a 6 series BMW I bought one time.

Slipper springs are meant to only push against the bottom of the trailer frame, all the bolt or clip below the spring does is keep it from falling off. A shock, particularly an air shock, pushes the spring away from the frame and against that parts not really meant to be pushed against.

As to the spacer, poly or whatever will smooth up the spring operation but the real issue is stiffness. Adding a metal spacer would allow the bulk of the spring pack to function like overload springs. Empty or lightly loaded it would use just the main spring (which I think is all you really need) but when that spring deflects enough it will engage the rest.

In reply to bigdaddylee82:

If you have the stock HF trailer springs, I would consider upgrading to a longer and softer spring. lower pressures (not sure how low though) or upgrade tires as well.

I built a 4.5' x 6' x 2' high steel utility trailer with a tailgate, a hard lid (think toneau cover) and extendable tongue. I used a 2200 axle, I thnk 1250 lb springs that were long, and 13" wheels, and it rides nice and smooth, even empty (better loaded). My trailer is 780 pounds empty.

Here's 2 good resources for HF trailer frame mods.

http://tventuring.com/trailerforum/forum-5.html

http://www.tnttt.com/viewforum.php?f=35&sid=33d8f85bdcda3458a5bec1a40c9ff0b2

I'm watching this one intently. You saw my thread as a new trailer owner and my hard learned lesson with cheap tie-downs. But yes, I wince over every pothole and freeway expansion joint here in OH.

Maybe that's why the tire pressure was so low when I checked it after purchase? I assumed it had just sat unused for awhile. Thinking it might have been 20-25# or so, and the sidewall said 35?

Increase the downforce. Put a Turbowing on springs that increase the angle with wind/trailer speed. You could be "World of Outlaw" antiquer. HTH

Jerry wrote: I'm watching this one intently. You saw my thread as a new trailer owner and my hard learned lesson with cheap tie-downs. But yes, I wince over every pothole and freeway expansion joint here in OH. Maybe that's why the tire pressure was so low when I checked it after purchase? I assumed it had just sat unused for awhile. Thinking it might have been 20-25# or so, and the sidewall said 35?

pretty much any tiedown will stretch and/or the load shifts which causes them to get loose. You really need to check them often....especially a few miles after leaving because generally the load will settle. I have cheap tie downs and real expensive ones and they all need to be adjusted occasionally.

those HF trailer tires are not radials, so they need to be run at a pressure where they don't bulge out, or you'll overheat and blow em up.

think about what you've got, a super cheap trailer built with the cheapest materials to get the lowest production cost. yes, if the leaves were longer, the ride would be smoother while still giving the same load rating, but they'd cost more.

you don't need shocks on the slipper springs because the friction between the leaves and against the frame provide the damping. bouncing is just something that you'll deal with on small, lightweight trailers, especially when unloaded. we used to have an all-steel 8' utility trailer that would hop all over when unloaded, and that thing weighed like 400lbs empty. if you're going to be hauling mostly loads like your 250lb lumber run, then what is the worry of reducing the spring capacity by removing a leaf? even if you loaded it completely down, the carrying capacity is in the axle, not the springs.

you should tie your load down so that it doesn't move, and check it often to make sure the tiedowns aren't coming loose. as long as the trailer and load remain as one, it can bounce all it wants, its not going to hurt it. if you get it loaded closer to capacity, i'm sure the bouncing will be reduced. i have a double jet ski trailer on 14x5.30 tires that will still bounce with 1100lbs of skis plus tools on it.

Well, I've got a homemade smoker trailer that needs new tires, I think it has the same bolt pattern wheels as my HF trailer. It would kind of make sense to put the HF wheels/tires on it, and buy some larger wheels & passenger car tires for the HF trailer.

Amazon has 13" wheels for $20 each, and Chinese 175/70R13 tires are around $30 a piece. So I could have new better tires for $100 before shipping. There aren't just a whole lot of options for 12" passenger car tires.

I can do the spring spacer trick with scrap I've got laying around.

I think I'll approach those options before shocks.

Here's an interesting way to do high clearance shocks with slipper springs. I'd think the frame mounted end needs to be turned 90° to not bind during axle articulation though. Maybe the rubber eye busing has enough flex?

• Lee

What diameter tires?

I know some of the HF trailers come with TINY tires. Increasing the diameter makes a huge impact on ride.

In reply to ProDarwin:

Came with 4.80-12

• Lee

What about adding mountain bike shocks to one? I've got one of the tiny 4x4 trailers for my son's kart and that sucker bounces like a beach ball.

Was thinking about something like these or these, but removing the spring part and just use the shock part.

Just weld up a stronger cross brace above the axle and then weld tabs to the axle and frame.

Thoughts?

-Rob

I have the 12" tires on my 40"x48" HF trailer and yes, it bounces like a basketball.

I cut the pressure down on light loads. It rides great with a yard of mulch.

To add terror to some, I used to run my old motorcycle cargo trailer at 6psi max when fully loaded. Zero to 2 psi when empty.

Seriously, that little trailer weight and a tiny load, you're effectively running iron wheels. Drop that pressure.

To feel vaguely safer experimenting with this, tow it empty with 10 psi and toodle around. Get out and check the tires as much as you wish. Cut it to 5 even. You'll find much less bounce and no overheating. Obviously more pressure when loaded. But learn to proportion the pressure for the load.

foxtrapper wrote: To add terror to some, I used to run my old motorcycle cargo trailer at 6psi max when fully loaded. Zero to 2 psi when empty. Seriously, that little trailer weight and a tiny load, you're effectively running iron wheels. Drop that pressure. To feel vaguely safer experimenting with this, tow it empty with 10 psi and toodle around. Get out and check the tires as much as you wish. Cut it to 5 even. You'll find much less bounce and no overheating. Obviously more pressure when loaded. But learn to proportion the pressure for the load.

This. I run my HF trailer fully loaded at about 25psi max.

bigdaddylee82 wrote: Well, I've got a homemade smoker trailer that needs new tires, I think it has the same bolt pattern wheels as my HF trailer. It would kind of make sense to put the HF wheels/tires on it, and buy some larger wheels & passenger car tires for the HF trailer. Amazon has 13" wheels for $20 each, and Chinese 175/70R13 tires are around $30 a piece. So I could have new better tires for $100 before shipping. There aren't just a whole lot of options for 12" passenger car tires. I can do the spring spacer trick with scrap I've got laying around. I think I'll approach those options before shocks. Here's an interesting way to do high clearance shocks with slipper springs. I'd think the frame mounted end needs to be turned 90° to not bind during axle articulation though. Maybe the rubber eye busing has enough flex? - Lee

I like this idea, IIRC, the shortest shocks you can get cheap/easy are the fronts for a Chrysler Cordoba.

Of course that shock only does something if the spring deflects, which it won't because it is too stiff.

In reply to oldopelguy:

Thats why you remove a leaf or two, the idea being that the shock now prevents it from easily bottoming out on bumps, rather than a ridiculously stiff spring pack.