dual axles, worth the money?

[Scott]

Windage is not as big an issue as some may think.

The engineers can chime in on this as I'm only a truck driver and me not too smart.

Windage from the side doesn't dramatically affect towing unless the wind is high enough to lay over what you are towing.

The difference in pressure as you pass something can induce sway. High pressure while passing,sudden relief from pressure as th pass is completed.

Consistant wind will not cause sway as your forward movement of 70 mph will shift the "Apparent towing wind" (Nautical towing jargon) nearly completely forward.

You can and will feel a Pull in steering due to wind but not necessarily an increase in sway unless you have some pretty strong and inconsistent gusts. say 0 to 40

[Catigale]

If your towing the boat with a significant bow up attitude, it wouldnt be hard to imagine 50 pounds of lift unweighting the hitch.

thats about 15% of the desired tongue weight, which will change handling.

I was thinking the OP might have seen this effect.

THis is pure speculation on my part - your lift may vary.

[Brian26x]

My tow rig is a 95 astro van, with 4.3L V6. Trailer sway is an issue, and so is the capacity of the tires. From what I have read on this site 4,000lbs seems to be the ball park GVW of the boat, trailer, and all the stuff in the boat plus 50hp Merc. That means I'm over already. I have the rig set up so the trailer is slightly nose down when towing. I do put some stuff in the v berth as well. I have never checked the tongue wt. I'll have to do that when I load it on the trailer for winter storage in a few more weeks. As for the 15" tires and a new 5,000lbs cap. Is a new 5,000lbs axle required? Will the 15" rims fit the standard axle? I guess the fenders will need to be modified if they do? Anyone know what the standard axle wt. rating is? Is it 3,500lbs? Thanks for all the input.

[bscott]

John at Super Sport Marine sez 15-16" from the ground to the top of the hitch platform without the ball. I highly recommend air bags for coil springed tow vehicles---you can lift the rear as much as 4" from 0#s to 15#s of inflation.

[Frank C]

If your rig does weigh 4,000#, and you have 380 on the tongue, then your net axle wt is 3,620 and your tire capacity is "just adequate." That's not to suggest leaving it there, rather making all factors clear. ("14-D" tires @ 1,870 each, capacity 3,740#). I found my bias-ply Titan tires were always very hot after a half-hour on the freeway. Yes, the axle is an industry-std 3,500 rating.

I wouldn't recommend staying with the factory brakes, but assuming you're not planning to upgrade the brakes ....

You'll need 2 new wheels and 2 new tires. Most here have gone with Goodyear radials. That's about $80 each for tires, maybe $45 each for the wheels, $250. I chose the 15-inch, "C-range" tires, rated at 2,150 each, or 4300 for the net axle wt.

You can special-order alloy wheels instead, and eliminate the rusty-wheel look. The MFG is Greenball Corp, price is about $75 each at America Discount Tires. (You need 5-lug wheels, usually designated as "545") Please don't resort to 15" wheels from a Jeep or such. Trailer wheels are designed to carry higher air pressures (65# for the D-range tires, or 50# for the 15C-range). Search on alloy wheels, "all terms" to find several other threads on your same topic. Recommended reading.

Yes, you'll need a welder to adjust the fender height a bit, or else you'd need to lengthen the rear spring shackles by about 2 inches. I already had the local muffler shop doing some cutting & welding on my front coupler, so he just fixed the fenders too. Fact is, they "just fit" over the new 15-inch tires at factory height, w/no changes, but I wanted some added clearance.

Regarding upgrading your single axle to disc brakes ... search on Kodiak. That will give you a nice list of threads that debated Champion/Tiedown brakes, versus the Kodiak's that I prefer.

Just from your two posts on this topic, I'd guess the Astrovan's rear suspension needs work more critically than your trailer. If you have a good friend with full-sized pickup, and a receiver at proper height (factory says 17"), you could prove this to yourself during a short test-tow. Good luck!

OnEdit: good advise just above ... AirBags for your Astrovan's axle.

[tlperrine]

I used to have a single axle when I bought my boat. I had a wheel come off on I-70 at speed. It was not fun! So I now have a dual axle. I had them move the axles back a bit which also helped with sway. For me it was more a matter of peace of mind, even though more expensive. I work in the aerospace industry and don't like single point failures, so redundancy is desirable. Just my two cents....
Terry

[Frank C]

Sorry ... it's important to avoid the fallacy, "Post hoc, ergo propter hoc."

Did the swaying problem diminish because of the second axle? ...
or rather, because a second axle inevitably loads more weight onto the hitch?

Tongue-weight is the answer to 90% of trailer tail-wagging!

[JonBill]

I'm a firm believer that the standard stock Mac trailer is substandard in every respect. And that the permanent, long term and safe solution is to cut it up for scrap and to go to your best local boat trailer mnfgr and have them design and build you an all aluminum trailer with dual axels, torsion bars and real saltwater brakes; keeping in mind the needs of a trailersailer. It solved all my collective trailer problems all at once.

I'm a salt-water sailor and my trailer was only 3.5 years old and a complete rust bucket by the time I just gave up on it and got a new one. I suppose I could have postponed the inevitable for a couple of years by placing anodes all over the stock trailer and was remiss in not doing that, but short of that it was doomed from the start to a short existence. Mild steel and salt water don't mix for long.

I also understand that most Mac owners tend to be on limited recreation budgets and have to find a cost effective solution to their problems. But when you can, if you do what I did, and just bite the bullet and get a first class trailer built you won't be disappointed.

Perhaps this is an issue that Frank and I disagree on but there's a first time for everything.

Kind Regards,
JonBill

[Don T]

My tow rig is a 95 astro van, with 4.3L V6. Trailer sway is an issue, and so is the capacity of the tires.

I used to tow with a 96 Safari (GM version of Astro) and never could get the thing to tow well. The rear springs are mounted in rubber sockets that are too soft. The thrust angle was way off and shifted when braking. I fixed the thrust angle but unless your rig has the early style standard steel multi leaf springs, I seriously doubt you will ever be comfortable towing with it. I went back to my old 84 GMC "G" series full size van. But not until trying greatly to solve the problem. Couldn't increase the tongue weight without lifting too much weight off the front wheels. I installed my "no sway mod" which helped but I never felt safe. Hitting the brakes with anything but a straight ahead wheel meant the boat would push and steer the van causing a lot of sway that only accellerating would halt. Just going down hill, backing off of the power, was enough to shift the thrust angle and cause severe sway. Going downhill gives no opportunity to add power. Tapping the brakes only makes it worse. Too white knuckle scary for me.

Good luck.

[Frank C]

Perhaps this is an issue that Frank and I disagree on but there's a first time for everything.

Maybe the only issue.
My trailer has had saltwater dunks, almost exclusively, since August '99. The brakes failed due to lack of maintenance, upgraded as elsewhere described. I de-rusted and re-bunked myself, about 40 bucks. The entire tires & brakes upgrade, done by the muffler shop was about 1,200 ... versus 4,400 for a new trailer?

I'd much rather use the 3,200 difference in funding a full enclosure.
Or, new sails. Or, any number of other goodies. Very few of Roger's trailers have failed, and I now monitor mine a bit better. It's the last place I'd want to spend any boatbucks ...
but different dinks, diff-oars, diff-strokes, right?

[tlperrine]

Frank,
I am sure most of the gain was from moving more weight up front. I imagine the dual axle helps. The biggest sway problems seem to be from semi's passing, but quite manageable. When I had the single axle driving faster than 60 become a white knuckle ride...
Terry

[Boblee]

Over the past year our trailer has travelled close to 10,000 klms and although I think it is way too light for the job it tows beautifully, it will be getting some work shortly but mainly strengthening and galvanising and maybe the berths will be modified with a roller at the bow. Have to agree that for security a tandem would appear safer and give peace of mind though.