16" LT tires now a subframe lift? UPDATE Subframe complete!

[wuhungsix]

UPDATE: pictures of subframe on page 4!

So I originally created a post on upgrading 15” ST tires to 16” LT tires (https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27525229.cfm) and finally got around to doing this on my 2014 Forrest River Palomino Puma 259RBSS fifth wheel.

I went with BFGoodrich Commercial TA LT215/85r16 on 16” steel Dextar wheels. Old tires were Akuret ST225/75r15. I have plenty of clearance between the two tires but have about 1” of clearance on the rear axle from the top of the tire to the darco materiel on the underside of the trailer. I was going to drive it around town to see if and how much it may rub but have not had the time yet.

Now my trailer has never been level with my 2012 Ram 3500 SRW. It has come up a little with the added 1” in height on these BFGs compared with the old STs. But I’m sure I’m going to need more clearance with these new tires.

SO I have two options that I can tell,
LPI Correct Track which gains 2” or a full sub-frame build. I got a local quote for the Correct Track installed ($925) and another for a full sub-frame build ($750). I’m obviously leaning to the Sub-Frame build as it’s going to be sturdier if built correctly as well as cheaper. I initially wanted to tackle the Correct Tract install myself but don’t feel comfortable supporting the trailer up.

My question is, does anyone here run with similar (1-2”) clearance between tires and underbelly without any issues? I have a short camp trip in a few weeks and may not have time to get the sub-frame build done in time. Wondering if I can make it there and back or if it’s a bad idea. It’s about 250 miles back and forth on standard CA highways.

Here are some pictures of the new tires and wheels,
New and old tires side by side




New LT on left and old ST on right


Both new LTs installed


Old OEM ST set up


Clearance between wheels,
LT


ST


And how the trailer sits mounted with truck on old ST (no current pictures with LT tires)

[greende]

Nice Job!!

[wuhungsix]

Just wanted to add this last pic I took this afternoon.

I measure it from the ground to the undercarriage at the front and back and it's off and inch sloping to the rear bumper.

[wuhungsix]

Yea I'm definitely going to need some blocks for the stabilizers. Or maybe another pack of leveling blocks.

I already bent my bumper mounted spare tire coming off a driveway on a dump. I think it should be all good now.

[noteven]

Now how are you going to drag the rear corners on gas station entrances which have The World's Steepest Approaches because hardly any vehicles use them ...:) ?

[jaycocamprs]

Looks good, and I don't think you will have any problems with it. But don't forget to take 6" of blocks for your rear stabilizers, and maybe some timber to go under the landing gear. Oh and a stool for the step!

[wuhungsix]

Me Again wrote:
With the three cross tubes forming a complete new carriage setup for the axles, how it is attached to the trailer should be just find. This carriage assembly has the required strength within it's shelf, and relives the I-Beams from a lot of the forces. Looks like they did nice work. Cost?

$750.

[wuhungsix]

bpounds wrote:
I like the way that was done. You won't have any issues in my opinion. I am surprised to not see any corroplast belly cover.

I don't have a belly cover because this is a economy (aka low end) entry level trailer. Not a whole lot of bells and whistles in my rig. Still lover her though.

[wuhungsix]

larry barnhart wrote:
It does look like a nice job and it made me think where can you jack it up for a tire change?

chevman

I would think you can just jack where you normally would. Under the axles at the spring hanger.

[larry_barnhart]

It does look like a nice job and it made me think where can you jack it up for a tire change?

chevman

[Me_Again]

Well for some that has experienced cracks in the web of their I-Beam and had it repaired, I think I have enough experience to say it looks pretty good. We did gusset the cross tube to the hangers on my repair that I pictured near the beginning of the thread. However this is a much lighter trailer and should do just fine. Chris

[tsetsaf]

Looks great to me! It is custom work so everyones opinion is just that... an opinion. You get to be the road tester! Fine craftsmanship.

[Poppy_s_5th_Whe]

Wow, obviously lot's of educated engineers on this forum. Cool

I just stayed at a Holiday Inn myself. Heck, I've heard of many instances of spring hanger failure on these rig,s without any additional stress. Personally I wouldn't risk additional stress on an oem application with something it wasn't designed for without shoring it up. I'm not referring to the new cross members as those do nothing to help the actual oem hanger connections to the frame. Maybe if the fabricator had replaced the oem hangers with the stout hangers he added to the new sub-frame that would have made me more comfortable.

Again, just my uneducated observations. YMMV

[P_Kennedy]

The original I beam frame took the stress of the original 6 points of suspension without any detrimental effects and now the same 6 points are mounted to a sub-frame. With the new sub-frame made from box tube it will be stronger and absorb all of the cross torqueing of the springs when turning and less prone to twisting. The sub-frame will also spread any torque evenly to the original mounts unlike the axles in turns.

[Dayle1]

goducks10 wrote:

wuhungsix wrote:
I may go back to him to have him relocate my spare from rear bumper to underbelly. Maybe I can have him add some gussets.

JMO but you shouldn't need gussets since he welded the cross bracing in. That keeps the tubes from rolling. Very cleaver idea. Time saver as well. Looks like he painted it with some Rhino liner type coating. Whoever did the job for you knows his stuff.

The cross bracing keeps the sub frame tubes from rolling, but with increased leverage on the I-beams, there is nothing additional to keep them from rolling.