Adding big deck/ extra axle to a 5er. Carry 4 motorcycles.

[me2]

I have a 355 Chaparral that we love. Sleeps 10. Great loft, layout, etc. I pull it about 2500 miles every summer.

The stock 355 has a ULVW was 10,200 pounds. GVWR is 14,000. I upgraded the stock axles and tires from 6,000 pounds to 8,000 pound torsion units with hydraulic disk brakes. This all works great.

I also added a 40 inch HD rack and raised bicycle rack to the back and put on a roof rack. We presently haul 3 adult kayaks on the roof as well as 3 to 5 bicycles and and 2 dirt bikes on the back racks. The trailer presently weighs 13,500 pounds loaded up. We generally travel with empty tanks.

I've used the trailer like this for 8 years with no problems.

I'd like to upgrade it further. I want to haul 2 full size road motorcycles as well as 2 dirt bikes on a large rack on the back. Total bike weight will be 1700 pounds, plus the weight of the rack.

The trailer has a 10" drop frame in the back for the back bedroom. Currently it runs under the main 12" frame beam by about 6 feet.

I'm thinking of doing the following:

- remove the current running gear
- adding 10 feet of 10" beam to each side under the existing 12" frame in front of the drop frame. This will put a double frame (10" and 12") under the entire running gear, plus a few feet forward.
- adding 2x6 x 1/4" square tubing under the entire new length of the 10" frame and back under the 10" drop frame.
- bolting 3 8,000 pound torsion axles to the 2x6 beam. This raises the trailer about 6", which would be perfect as it sits a bit low right now. The trailer will now be a triple axle, with the extra axle to the rear of the existing axles.
- running the 2x6 past the trailer by a couple feet. This will be the base for the folding rear deck. I think it will be about 10 feet long.

So the frame will be:

- stock from a couple feet in front of the running gear to the front of the trailer.
- 2x12 stacked on top of 2x10 stacked on top of 2x6 from a couple feet in front of the running gear to the drop frame for the back bedroom
- 2x10 stacked on top of 2x6 under the back bedroom back to the rack itself.

The axles will go from 2 x 8,000 pound torsion hydraulic brakes to 3 axles.

Current loaded weight is 13,500 pounds. The new loaded weight will be about 15,000 pounds. The pin box is rated for 16,000 pounds.

I've run some calculations on frame bending moments and trailer hitch balance with this setup and it seems like a reasonable thing to do.

Current hitch weight is about 2,000 pounds without the dirt bikes, about 1800 with the dirt bikes. If my calculations are correct the new hitch weight will be 2400 pounds without the 4 bikes and 1800 pounds with the 4 bikes.

Adding the extra rear axle really decreases the frame bending moments. Adding the 2x6 under the entire rear portion of the frame really strengthens up the frame back there.

Has anyone done anything like this ?

[fj12ryder]

Definitely a slick way to load the bike.

[Me_Again]

me2 wrote:
These may be of interest.

https://www.youtube.com/watch?v=cUAp3cqzH-w
https://www.youtube.com/watch?v=dO5VXJKdUYs
https://www.youtube.com/watch?v=Vt66nwvxlRw

Clickable. Chris

[me2]

These may be of interest.

https://www.youtube.com/watch?v=cUAp3cqzH-w
https://www.youtube.com/watch?v=dO5VXJKdUYs
https://www.youtube.com/watch?v=Vt66nwvxlRw

[me2]

4x4ord wrote:
Have you done a bit of figuring to find how much ground clearance you need at the back of the deck. Without thinking much about it I'll guess you'll want at least 3 feet.

At least 3 feet. Maybe more.

I struggle with that part of the design because the current 40" rack on the back of my trailer scrapes from time to time. The departure angle on the back of the trailer is very low with such a long rack, because of the distance from the back tires to the end of the rack is so long.

I'm thinking of making my rack foldable, so that the trailer isn't so long when I'm not using the rack. I'm wondering if I could make it hinge upward during use so that it has some movement if it does contact the ground. It would need to do this in a manner that didn't hurt the bikes. I could also have the rack slanted upward while in the travel position.

If my trailer had hydraulic landing gear I'd be tempted to leverage the hydraulic pump by using a hydraulic cylinder to fold and unfold the rear rack.

[4x4ord]

Have you done a bit of figuring to find how much ground clearance you need at the back of the deck. Without thinking much about it I'll guess you'll want at least 3 feet.

[me2]

harley hitchiker wrote:
the biggest problem I see in doing this is no matter how many axles you add the legal GVW is printed on the side of the trailer

I don't give a darn what the "legal" GVW on the side of my trailer says.

The trailer was hardly safe with the stock 6,000 pound axles, Chinabomb tires and electric brakes. It is much, much safer as it sits now with 7,000 pound axles, 265 LT tires and hydraulic disk brakes. It will be even safer as a triple axle trailer with a heavier frame.

Adding the 3rd axle and beefing up the frame more than makes up for any risk that adding the rear rack adds.

[harley_hitchike]

the biggest problem I see in doing this is no matter how many axles you add the legal GVW is printed on the side of the trailer and raising it is very difficult in my state ,I don't know about where you are. The addition of axles and tubing and bikes will likely put you over the original GVW. Chances of being caught are slim but you could be stopped and not allowed to continue without correcting the overload situation . This would be one of my concerns.Good luck

[me2]

I ran a pin weight calculation for loaded and unloaded and it stays within reasonable limits. The 3rd axle transfers a lot of weight to the pin. In fact, the pin might be on the heavy side without the bikes.

I'm going to add a 2nd fresh water tank to the trailer if I do this. I'll use it as ballast if the pin is too light with the bikes on.

The real solution to all this would be to have sliding axles like on some commercial trailers.

I got my axles from Southwest Wheel.

[mapguy]

What you propose is doable - my only real concern is Pin weight. Currently you are running about 15% of loaded weight without dirt bikes. For me 15% of loaded weight would be the minimum target Pin weight. Pin weights less than 15% of load tend to have ride and control issues in my experience.

What brand of torsion axle did you use?

[me2]

Each to their own. I don't want a toyhauler.

[fj12ryder]

Most of your issues with toyhaulers can be addressed, except for the paid for aspect.

1. They are not necessarily more expensive than a comparable equipped 5th wheeler. Just depends.

2. They are not necessarily heavier than a 5th wheel of comparable length, unless you have the toys onboard. And with what you're considering, you're really worried about weight? 🙂

3. Yes, sleeping and living space can compromised when the toys are loaded depending on the number of people sleeping in the trailer, but most of your time will be with the toys unloaded, so it's arguable that it's not as important as it would seem.

4. The garage will only smell of fuel and oil if you're sloppy and slosh the stuff around. Our toyhauler never smells of fuel or oil.

5. Our garage is very nicely fitted for when the toys are out: , granted we can only haul two bikes.

6. Can't argue that the toyhaulers can be longer, but you're talking substantial length on yours if you don't pull the bikes out, plus while a toyhauler may be longer, it's much more convenient.

7. I suppose it's possible for the rear door/ramp to be an issue, that's not a really common problem on most toyhaulers.

[me2]

laknox wrote:
Jeez, get a toyhauler, already.

I gave this a lot of thought. Here are the reasons I don't want a toy hauler.

1) They are generally a lot more expensive, especially for a higher interior trim level.

2) They are generally a lot heavier than they need to be to carry the toys I want to carry.

3) Sleeping and living space is compromised when the toys are loaded in the trailer. Sleeping while travelling is problematic without unloading the toys.

4) The garage often smells of fuel and oil after the toys are removed.

5) The garage isn't outfitted very nicely for living once the toys are removed. Toy hauler layouts are centred around the garage aspect.

6) A toyhauler is generally longer than desired. I plan to make my rack fold up, so the trailer goes back to near normal length once the toys are removed or if they aren't along for the trip. I'm finding it harder and harder to get campsites that are big enough to accommodate long trailers.

7) The folding rear doors frequently give trouble.

😎 I have all the bugs out of my current trailer and it is paid for. I don't want to buy a new one.

[laknox]

Jeez, get a toyhauler, already. :B

Lyle

[4x4ord]

me2 wrote:


That is a friggin beefy frame rail. Most trailers have a ~12" C channel with no 2x2. I'd venture to say that you don't need to beef that up at all. I'd have to run numbers to make that decision though.

Do you have any pictures of your trailer and the rack on the back ?

When are you going to do yours ?

Yes i plan on keeping the first two axle in the factory position and adding a third axle behind with the same spacing as the tandems.

My rack is quite a bit different than what your planning.

Click For Full-Size Image.