Double Stack Miata on the trailer???

In reply to accordionfolder :

There is an issue in your first post. You said the trailer is rated for 7000 lbs, and that it has twin 7000 lb axles.  That would be a 14000 lb trailer.

If I'm not POSITIVE my tongue weight is 10% or more of the trailer loaded total weight, I always check it out at the truck scales. (Has gotten so expensive, I need to invest in som corner scales!)

also, the tongue weight applied to that much overhang is a lot to consider. So definitely weigh the RV front / rear bias, before and after. Less tongue weight IS NOT the answer here! Get the trailer weights right, and if it effects the distribution on RV too much, use a W. D. hitch.

The tandems on trailer can be considered one axle, within reason. Then tongue, the rear / front of RV, loaded, but without trailer. Then rear / front of RV with trailer. 
A lot to go through, but I KNOW doing all that has saved my life before - and that's no exaggeration. 
TL, DR: turn front car around. Maybe W D hitch. 
Post the 4 data points above, if unsure how to "read" what ya need. 

In reply to lotusseven7 (Forum Supporter) :

The title put that picture in my head!

In reply to gsettle :

In reply to SV reX :

Yeah - It has 6k axles, I just checked - but I think they still under-rate the trailer. It says to only load 7100 and I know the trailer only weighs 2600.

I put 10ply tires on it, so a bit more capacity than what was on it when I got it.

In reply to accordionfolder :

The trailer is rated based on its weakest link.  Might be the tires, might be the brakes, the frame, wheels, bearings, etc, etc.  
 

If you have an overbuilt trailer with lower capacity axles, the rating is the axles not the rest of the trailer.

10k GVWR seems to be a number they don't typically go over for CDL licensing reasons or something.

GVWR 9900 minus the trailer weight of 2600 is pretty close to the payload weight of 7100.

In reply to SV reX :

Makes sense - I'm still well under the stated capacity w/ what I've got on it, I'm a touch under 7 w/ it all on there - 9900k stated on the tag. 

I was assuming it was something to do with the legal side of things.

I came here thinking stacked Miatas and thought of this trailer.  I wonder how top heavy this would be, how safe on corners etc.  I couldn't find a link for a gif or video on it working, it's a cool idea.  Using this idea, can one be cut down to be just a bit taller than a Miata roof line?

In reply to rb92673 :

Yeah, it's what I would suspect given I've dug in and around a handful of trailers and this thing is built like a tank compared to what I've seen - axles/tires/tongue are all rated way higher then the GVWR

In reply to 914Driver :

https://stacklitetrailers.com/

I want one of these!

In reply to accordionfolder :

Sounds like you're fine. You've just got to sort out the balance and tongue weight. 

SV reX said:

In reply to accordionfolder :

Sounds like you're fine. You've just got to sort out the balance and tongue weight. 

I **think** I can make the trailer handle it, the RV has an explicit "No Weight Distributing Hitch" so that might be out and I don't think it'll be happy with that much tongue weight so this might only work w/ the truck 

In reply to accordionfolder :

That stacklite trailer is a great design!

There is only one correct answer here: Take it down to the nearest CAT scales and weigh it. It's only like $13.5 for a weight and $4 for a reweigh... So for a mere $21.50 (No trailer, Miata forward, Miata backward) you can make an informed decision. They even have an app to make it easier.

In reply to Driven5 :

Copy that!

I have scales and will get the tongue weight - I know the weight of all the parts of it separately exactly. I obviously can't weigh it all together with my car scales (limit 5k) but I can throw it together and get the tongue weight with them in the various configurations.

You can get a Sherline tongue weight scale for ~ $150.  It's a pretty useful tool if you tow regularly, especially if your loads vary.

What is the motorhome hitch rated for?  A lot of those class Cs are only 3-5k.  The restriction on WD hitches would make me nervous.... seems like they don't have a lot of confidence in the strength of the frame behind the axle.

A Trailer Toad would solve that particular problem, but they're not cheap, and add about 3' of length.

With respect to vertically stacked trailers, they are a very different ballgame from a normal trailer.  The extra weight up high makes a big difference.   I will tow our stacker empty or with one car with my dually, but I wouldn't do two cars unless it was just for a short distance.  Behind our motorhome it's fine, but it's 38k loaded.

The math is really important.

I've also found that different vehicles behave differently when towing, and you won't know for sure until you put it behind that RV and head down the road. 
 

(I've got about 750,000 miles of towing under my belt)

Do the math, check the scales, then strap 'em down and try it (before spending too much $)

Rodan said:

A Trailer Toad would solve that particular problem, but they're not cheap, and add about 3' of length.

Yes the RV overhang and the extension off the back of the frame makes me a lot nervous - I was under it and it's NOT built like a tank. The Trailer Toad looks like what's needed - there's not much to it, I wonder about building my own.

The water tank is directly over the rear hitch at the very very back of the RV - so running w/ it and all the other tanks empty makes me much less nervous - as 50+ gallons of water not being there probably frees up a bunch of headroom. 

In reply to accordionfolder :

The max stress point will be where the rear suspension attaches to the frame of the motorhome behind the axle.   From that point to the hitch is a huge lever arm, and all of the tongue weight, and any weight in the motorhome will be acting on that one point.  Remember it's not just the static tongue weight, but the bouncing up/down as it goes down the highway.  That's where the Trailer Toad is really effective... it takes all of those forces off the tow vehicle.  I was really surprised the first time we towed with ours.  Our stacker is ~12k lbs, and except for acceleration and braking, I couldn't tell it was back there.

If the manufacturer of the chassis doesn't want you putting the leveling force of a WD hitch into the rear frame, I would be VERY careful...

If the RV has a legit Class III hitch, the total trailer weight is 8K lbs or less, and you can get the tongue weight where it belongs you should be fine.  That's a lot of ifs though.

accordionfolder said:

In reply to SV reX :

 more tongue is (usually) more better - I'm just not sure how much tongue that'll end up being. 

There is a ton of good info and conversation here, but I can't believe everyone let that slide. 

I'm not condoning anything and I'd do my best to keep everything within ratings...but all of this stuff has some pretty significant safety factor built into it. Our class A rv had a hitch rated for 8k but only 500lb tongue weight. We put probably 10k miles on it towing a ~7k trailer with 7-800lbs tongue weight with zero issues. We tried to keep the tongue as light as possible but it drove noticeably better at 800 and change than 700. Similarly the f150 before that saw three years and probably 20-30k miles with 11-1300lbs of tongue weight on a hitch rated for 1000 (1/2 ton trucks REALLY like tongue weight for stability). I didn't read enough to see if this is a one time thing or something you want to do regularly. If a one time thing I'd get the tongue weight as light as you can manage (but still around 10% total) and if it's within 30-50% of the hitch rating give it a shot. If it's something you want to do long term I'd be looking for a better plan. That also depends on what else is going on under back of the RV... those frame extensions can be wildly underbuilt and sketchy. And yeah you're going to have to pay very close attention to your turning radius.

In reply to bbbbRASS :

lol, I chuckled when I typed it.