How to choose correct Leaf spring rating?

I'll probably put shocks on them later. It had shocks oem but all of them were bad. Yes bearings are china and unwrapped :(

May as well add shocks while you're at it, unless your rig already has them.

Shouldn't those bearings be wrapped? I hope they're not coming out of the box like that these days.

Given the general concensus that the major frame builders build to minimum spec I upgraded my spring pack from a 6 to a 7 leaf. Don't know what the ride diference is for the trailer since I don't ride back there but I do tow with much more confidence that I am not going to have catastrophic spring failure due to being borderline undersprung.

Almost all of my major upgrades have been related to what is unseen under the trailer.

If 2400 covers the GVWR you are fine. I replaced my sagging 1750 springs with 2250 and it has never ridden better. GVWR is 7880.

http://www.stengelbros.com/UtilitySprings.htm

My swap shown click here

The previous owner had multiple bearing failures on the 3500 axles and ruined the spindles so I needed 2. The trailer store said to go 5200 for bigger bearings and brakes. Price was negligible something like less than $40 per axle over the 4400 which is essensially a 3500 with only a slightly bigger outter bearing and a 3" tube instead of a 2-3/8". The 5200 bearings are HUGE in comparison!! (Old one right, new one left). IMO you can't have too big of a bearing and the 12" brakes over the 10" ought to be a worthy improvement too.





Anyway I'm going to tell the guy I want the 2400lb springs then

Springs are normally rated in lbs/inch. That is, how many pounds of force does it take to deflect the spring 1 inch. If you know the design spring travel, then you can size the spring accordingly.

For instance, if the designed suspension travel is 5 inches and you want the spring to support a 2500 lb load with the spring in the middle of its travel (2.5 inches deflection), then you would want a (2500 lbs/2.5 inches =) 1000 lb/in spring. If you wanted the spring to deflect only 2 inches under a 2500 lb load, then you would want a stiffer (2500 lbs/2 inches =) 1250 lb/in spring. The remaining unused travel gives room for jounce (compression) when the wheel hits a bump.

The calculation method above assumes a linear spring rate. The calculations for a progressive spring rate are a bit more complex - a progressive spring gets stiffer as it compresses.

Unfortunately, the method they use to sell these RV leaf springs (it's a 2500 lb spring - period) doesn't really tell you everything you need to know to understand the deflection and ride characteristics you're going to experience with each particular spring. You need to know the allowable spring travel and the spring rate.

Rusty

I am no suspension expert, but I would not want to over spring an RV, that could cause extreme rough ride, or bounce. I don't know your situation, but don't understand the big bump in axle size? It seems to me an upgrade from 3500# to 4400# would have been enough.

My 5200# axles and springs give my FW a GVWR of 12,110.

I think you are right to go with the 2400 lb spring set, rather than the heavier 2900. Maybe someone with more knowledge of RV suspension can better advise, but I would not go with springs that are way over kill.

Many light FWs come with 4400# axles, and have a GVWR of near 10,000.

Jerry