How tall sub frame do I need?

rhagfo wrote:

Dayle1 wrote:
I agree with putting the trailer up on 2x8 blocks till it is level, that should give you the most accurate number since weight will be better balanced between the two axles. Also, you should load the trailer as you would for camping, since a lot of weight in the storage compartment, full propane tanks and cargo in the bedroom may bring the truck rear down some. But based on the numbers you provided and assuming the front 29" number was taken at the landing gear and not at the pin, you might be looking at more than just 8" (29" minus 21").

More bad math.

Front is at 29" (at the LG), between the axles is 24", to bring the axles level with the front would be 5", then maybe another inch for the rise to the pin for a total of 6".

You are right, using 24" is correct, not 21". But, in reality, the king pin is about 8 feet in front of the landing gear and based on the numbers it is likely another 2-1/2 inches higher. A 6" lift will be much better, but the fiver will still be slightly nose high.

Lift blocks on a trailer isn't a wise idea for several reasons. Your area big rig trailer repair shop can feed you info on that idea.
Both big rig shops in my area refused to add suspension blocks. One flatly refused and the other said if I sign a liability waver they would but wouldn't go over 1" in height. Both recommended the sub frame method as the safest for long term use.
Their 2nd recommendation was 3/8" side plates added to each side of the main frame rails as spring hangers with adjustable holes as some RV trailers come OEM with.
Depending on type of main frame rails fish plating or boxing may have to be added.

Would it be possible to use lift kit blocks with longer u bolts ?
I'm thinking 5" should level it up.

Dayle1 wrote:
I agree with putting the trailer up on 2x8 blocks till it is level, that should give you the most accurate number since weight will be better balanced between the two axles. Also, you should load the trailer as you would for camping, since a lot of weight in the storage compartment, full propane tanks and cargo in the bedroom may bring the truck rear down some. But based on the numbers you provided and assuming the front 29" number was taken at the landing gear and not at the pin, you might be looking at more than just 8" (29" minus 21").

More bad math.

Front is at 29" (at the LG), between the axles is 24", to bring the axles level with the front would be 5", then maybe another inch for the rise to the pin for a total of 6".

I agree with putting the trailer up on 2x8 blocks till it is level, that should give you the most accurate number since weight will be better balanced between the two axles. Also, you should load the trailer as you would for camping, since a lot of weight in the storage compartment, full propane tanks and cargo in the bedroom may bring the truck rear down some. But based on the numbers you provided and assuming the front 29" number was taken at the landing gear and not at the pin, you might be looking at more than just 8" (29" minus 21").

if you can get around 3" of lift at the wheels you should be pretty much level.

I had to adjust my suspension 1" on the hangars and I'm getting the other inch from taller LT tires on 16" wheels. You may have some adjustment on the hangers as well and depending on your wheels spacing and room in the wheel well you may be able to stuff either 215/85R16's (30.3" tall vs 28.3" for your stock setup) or 235/85R16's (31.7" tall).

take some photo's of the suspension and wheel spacing and such, more details we can suggest better options for you.

One more suggestion. Just make sure you do not exceed a total height of 13' 6" at the tallest part of your RV when done.

garyp4951 wrote:
Yes the springs are on top of the axle, and thanks for the measuring idea. I've also looked at the correct track, and 3" blocks under the leafs, for 5" total. It's not going to be cheap any way I go.

While I did the Correct Track, I would never put more than a 1" block under the springs, for an additional 3" I would have a sub frame built.

Yes the springs are on top of the axle, and thanks for the measuring idea. I've also looked at the correct track, and 3" blocks under the leafs, for 5" total. It's not going to be cheap any way I go.

rjxj wrote:
Are the axles flipped? Pull the rig onto some 2x8 and see how much it takes to get it level. The flip can be calculated by adding the radius of the axle + the perch + the spring pack. I installed new sprigs and noticed that they didn't arch as much as some trailers I've owned. Correct track can also provide about 2 inches of lift I believe.

Correct on the Correct Track, it does provide 2" of leveling.

Flipping the axle will provide the diameter of the axle + the spring pack + 2* the perch thickness.

Rjxj, you just forgot adding it back under the spring pack.

It does look like the axles are already on the bottom of the springs.