Second axle theory?

[Hardcrab]

I'm kicking around changing to the new Mac aluminum trailer one day.
I spent some time looking at a boatless one in the MDR parking lot a few weeks ago, and saw the torsion axle just bolted to the frame rails.
That makes it easy to drill some new holes to mount a second torsion axle.

Now comes the theory questions.

Should the final result of adding a second axle require the existing "axle to hitch" distance be the center of the two axles?
Or to put it differently, move the single axle back from it's location, and place the new axle the same distance forward so the gap between the tires is the same single axle to hitch distance as stock?

That makes somewhat sense to keep tongue weights about the same to my primitive way of thinking.

Is there any real science behind two axle positioning that needs to be looked at?

Next comes the torsion (spring rate) setting.
Should the torsion be set softer (+/- half as much) so not to ride to hard?
(Also makes primitive sense to me)

What do the leaf spring dual axle guys do about this?
Use softer springs?

[raycarlson]

I used a second UFP torsion axle w/o brake(310.00 shipped to tucson).I marked original axle location as a center, then installed one axle 15" forward and one 15" aft of that center mark. this gave me 300# tongue weight which I can increase with how i load up the boat.tows very stable no sway, have had it at 80mph breifly when passing smooth as silk.axle torsion tension is not adjustable, you can adjust ride height by relocating the swing arm 2-3 splines to get more or less fender clearance but actual axle load bearing capacity is goverend by the durometer(hardness) of the rubber slugs that ufp loads in the ends of your axle.both my axles are 4200#s so all i do is decrease tire pressure from the reccomended 65# down to 45-50 psi range,this seems to soften the ride somewhat.

[Hardcrab]

Thanks for the info.
I read that the axles were adjustable, but incorrectly thought the spring rate was tied to that adjustment.
I understand now.
Duh.

A few more questions if you don't mind me picking your brain.
Were did you source the second axle?
Did did you use the 15" fore/aft to keep the tire to tire gap at minimum?
About how much is the gap between your tires?
Lastly, were you able to cut/mod/splice the stock fiberglas fenders to make them larger, or go a different route?

Thanks again for your help.

[Man~ana]

Good information,thanks for your efforts, any chance for some photos? More is better.

[seahouse]

Hi Ray --

Your dual axle setup - a great way to upgrade the safety and security of your trailer.

decrease tire pressure from the reccomended 65# down to 45-50 psi range,this seems to soften the ride somewhat.

You might want to check the load rating on your tires, a number which only applies when the tires are at the maximum pressure written on the sidewalls. The tire's load rating is decreased when you decrease tire pressure, so you don't want to fall below your trailer weight - and how would you know? (Maybe the tire manufacturer has an inflation pressure-load rating chart?) Your tire life, and fuel mileage (rolling resistance) will decrease as well.

It is more important to stick to the maximum inflation pressure in hot climates, and at higher (highway) speeds because of heat build-up. The harshness/ softness of the ride is already designed into the tire by the stiffness of the sidewall, and lower pressures will also mean less lateral stability, something that might not become apparent until an evasive maneuver becomes necessary.

Just a "heads up", I like the mod.

- Brian.

[raycarlson]

unique functional products is the supplier of axles for macgregor,u can google them for a phone number.they have two plants one in tenn one in calif.i called the one in calf, they are happy to sell u an axle with or w/o brakes,tell the salesman its for a macgregor trailer i beleive their PN# was MAC3-003 and they want the serial numberoff your cuurent axle its on a tag welded to your axle tube the 15 inch spacing on the axle placement gave me almost 2inches between tires and yes i took the factory fiberglass fenders and just cut them in half,clamped them to a jig i made from 1 X 8 and added 30 inches of glass between the two halfs over the tire tread onl y not all the way down to the trailer frame,the added section is about 8 inches wide with 1 inch lip outboard and a 4 inch lip inboard.the goodyear marathons i have are 225-75-15 D rated for 2580lbs with four i"m good for 10,000lbs so running my ties as low as 35psi still leaves them with more than enough pressure for the 4000lbs they're supporting. of

[MadMacX]

Were did you source the second axle?

I think most people get their second axle from;
http://www.championtrailers.com/
They are located in Texas, but you may be able to find someone in the SoCal area that does the same thing. I seem to remember seeing a company out there that sold trailer parts, in Ontario or Pomona.

Pat

[mikelinmon]

Guess work positioning of second set of wheels! The aluminum trailer has a small amount of space left to mount second set of wheels. Trailer frame curves about 8" fwd of the stock position. Mounting second set as far fwd as possible seems to be it for me! Any ideas on this out there. Note; we have not tested this yet! If you do it be sure to get good advise about brakes and some sort of modulation between front and rear wheels. Brakes on the fwd set only will reduce your stopping power. Many questions. Trailer expert is needed for this IMHO.
Mike Inmon

[waternwaves]

Mike,

any of the small import car adustable master cylinders will take care of that front rear imbalance. hard braking does load the rear wheels more than the front., however if the circuits are matched to sides instead of diagonal wheels, I would expect it would not be a problem. I did this technique with my last horse trailer with hydraulic breaks, and stopping was very uniform.

all wheels skidded at the same time, non locked up early.