handfulz28

A 30 Concept should be fine on a tandem. CC or closed deck? At most you can do a tandem with 5k lb axles. If you need to go with the bigger axles, you won't save much money up front, but maintenance over the life will be less with the tandem. With the money you save, buy a spare wheel-tire, hub and spindle. And don't forget the tools you need to change those.

Sydwayz

Remember, when you ascend or decent a ramp, ALL of the weight of the entire trailer is briefly on the front axle as you crest the top of the ramp.

For this reason, DON'T skimp on the axles. Just this short time with all that weight is enough to ruin the suspension of the front axle, as its done over and over again.

handfulz28

Hey Brian, good meeting you at the Miami Show; don't think I've chimed in on the AT forum since.

It's a valid point of consideration, trailer cresting the ramp. But consder the range of loads an axle sees throughout its use. An axle is offered with a particular rating. But at that rating it's also expected to provide a range of motion beyond that experienced just from unloaded to fully loaded. I'm no engineer, and I don't know what additonal range is supposed to be acceptable, but I know it's there. And if we consider that "spring rates" in a trailer suspension are linear, then the additional range of motion in the suspension serves as excess capacity when needed.

To take the hijack to a whole 'nuther level, hypothetically:
Put a 7k lb load on a tandem with 3500lb axles and a 10.5k lb load on a triple with the same axles. Assume the axles have a range of motion capacity of twice the rating. That means that it would take 7k lbs on each axle to fully compress or twist to its design limits.
So when the trailer crests the ramp and all the weight is carried by that front axle what do we have? On the tandem we have a 7k lb load on one axle pushing it to its limit. On the triple, we have 10.5k lbs on that front axle pushing it beyond its design limits. Which one is getting worn out quicker?

Another tidbit relating to tires. Just because you have say 3500lb axles on the trailer, which typically comes with tires rated for 1780lbs each, doesn't mean you can't use tires with a higher rating. Yet another margin of safety to consider.

Sydwayz

Holy crap Micheal; get all fricking 'CigDaze' on us!!!

I definitely agree with you.

My old setup was a 26' Sonic that weighed in at 7280 lbs. It was on POS (!!) Rocket Trailer with a pair of 3500 lb. axles. Both axles had bent spindles, (one on each side) when I took ownership. I had to replace both axles, and the only parts available without re-engineering everything were 3500 lb. axles. I replaced them with entire new axles, and was much more careful about how I towed, what I drove over (we've all had to hop a curb with the trailer before), and specifically how I crested ramps; at an angle when possible.

The trailer lasted for a LONG time just fine after that, and is still in use today several years later as I rebuilt it.

I should have been more specific above, that it was not necessarily the suspension that has issues but it would be other the other axle components, i.e. spindles, lugs, and bearings.

handfulz28

I know, I was going to say Nick would be much better at sharing the theory...with drawings and finite analysis to go with.

But it's actually something I've been wondering about for a while...the total capacity/range of motion for a torsion axle. I'm sure we can all agree that a tandem dually might be a little too much overkill for a boat listed at around 5k rigged.

f311fr1

If you get a replacable spindle spare make sure that the axels have replaceable spindles.