Axle and Spring Upgrades

[Scott and Bonny]

Hello everyone,

We took delivery of our 2024 Bigfoot 25 rear twin in January 2024. We upgraded from a Casita for a larger living space, four season capability and bunch of other reasons. We loved our Casita but were ready for a larger travel trailer. We have had great experience so far but I would like to upgrade the axles and springs for some added reserve.

Looking at the posts I see that some owners have upgraded to 5200lb or 6000lb axles, 6 lug hubs, and the bigger brakes and bearings that come with this. I need to be aware that too heavy of a spring will be overkill and introduce a lot of unnecessary vibration.

My intention is not to load up the trailer so it weighs 9000 lbs but have additional reserve capacity. As everyone is aware, the stock suspension components the are fitted have limited capacity.

What I am looking to find out is what specific leaf springs from Dexter did
some of the members use when they upgraded their Bigfoot 25 trailers with the 5200lb, 6000lb axles with the 6 lug wheels, stronger bearings? Can you share specific part numbers?

I have learned that the springs are a custom length for Bigfoot based on the axle spacing on these trailers.

[CharlesinGA]

I think you may have mis-understood what axles are generally installed as replacements.

The stock axles until about 2021 or so, were a Dexter (or Standens) 3500 lb axle with a #84 spindle. That axle has a 2-3/8 outside diameter tube. For whatever reason, a good number of people with 25 and 21 ft Bigfoot trailers have bent the axle between the spring and the brake. Some severely.

What BF did in production and what is encouraged for replacements is a 3500 lb axle built with a 3 inch outside diameter tube and still with a #84 spindle. It uses the same 10 inch brakes and hubs and bearings as any other 3500 lb axle and as the previous ones had.

A FEW, and I mean very few, people had their trailers equipped with 4400 or 6000 lb axles which give you the 12 inch brakes and heavier bearings. These people were operating over gross weight, on unimproved roads. This is overkill for a trailer operated normally.

In my case, I still have the small tube axles, but was replacing my alloy wheels because 1) ugly, and 2) clear coat was becoming milky. I was able to get new wheels of the design I wanted, but in 6 lug, for about the same price as refinishing the original wheels. Yes, I had to buy new hub/drum units and install new Timken races and bearings, but what I ended up with are 3500 lb axles (1750 lb per spindle) and wheels rated at 3200 lbs EACH at 95 psi max (exact same wheel with five lug is rated at 2150 lb at 80 psi max). My tires are rated at 2830 lbs at 80 psi max. (I run them at 50 psi cold).



Should I ever damage an axle, I will upgrade to a 3500 lb axle with a 3 inch tube. My 21 ft trailer has the same 7500 lb GVWR as the 25 ft models, so it has the same axles and springs as a 25 ft of the same year would.

Two 3500 lb axles (7000 lb total) on a 7500 lb GVWR is rather normal, as the axles will never carry the total weight of the trailer. I am currently running a tongue weight of about 850 lbs, and a gross weight of about 6500 lbs. Its been a long time since I was on the scales, next trip loaded, I may weigh it again.

One of the best things you can do to a trailer, if not already equipped, is install wet bolts and the 1/2 inch wide shackles. These are much stronger and impart much stability, eliminating the side to side wobble of the thin shackles.



Charles

[CharlesinGA]

"As everyone is aware, the stock suspension components the are fitted have limited capacity."
I disagree with this statement. The axles are quite capable of handling the trailer if not overloaded or used on extremely bad roads......


The bearings are specific to the spindles used on the various axles. I think the folks that upgraded axles retained the same springs, as they are designed with the gross weight of the trailer in mind.

Basically, when an axle is ordered, the width to wheel mounting surface, the center to center of the springs, the weight it is expected to carry so it can be cambered properly, brake style (std or self adjusting), spindle type (std, EZ-lube), etc, are specified and the axle is delivered ready to install. With a new trailer you really have no reason to replace the springs.

Side note, Hi-Spec wheels (owned by Dexter) or Sendel Weels, run from $160 to $210 per wheel for the six lug, 15 inch version, plus you need new hub caps, and probably a complete new set of lugnuts to get a match, PLUS a new spare wheel. I just bought 5 of the alloy wheels. At the time I bought in 2021, I got the wheels on sale for about $120 each and this was about the cost of having the original wheels refinished. One advantage of the 6 lug wheels is they are 6 inches wide, vs 5½ inch for the 5 lug wheels. The 225/75R15 tire is approved for either width but looks better and I believe runs with a flatter tread on the wider wheel.

I had to modify the spare tire holder with longer studs for the alloy wheel and used a Delrin block to retain it, to prevent marring the wheel.

Charles

[Scott and Bonny]

Charles,

Thank you for your detailed reply. I will consider all the information that you were able to share as I finalize the upgrades. Your spare tire mounting bracket advice is helpful. I also like the wheel design you chose and that happened to me my first choice as well.

Scott

[CharlesinGA]

The method to the madness on the spare tire is to use standard lugnuts to retain it. 1/2-20 thread, and I think it was 3/4 hex, same as the chrome ones. If you use standard hex nuts in 1/2-20 thread, they are a larger hex and require a different socket. You also have spare lugnuts should you need them, just throw the spare in your tow vehicle.

The lower nut is simply flipped backward and run down on a split lock washer and a flat washer.

The original bolts were retained by a internal star device but it will mar up the aluminum on the backside so the longer bolts need to be welded in place.

And I have seen several people remark that they have "6000 lb axles" simply because they have the 3 inch tubes, which is the same as the 5500 and light 6000 axles.

My real feeling is that you simply need to use the trailer and see what weight you are running at and go from there. You can easily get wrapped around the drive shaft worring about something that many dozens of people using these trailers never have an issue with.

Charles