Even if tires
are in date, look closely. If they have had "tire shine" put on them to make them look good, the shine will suck the oils out of the rubber and cause fine weather checking. You want tires
that are clean but not shiny/slick
Mine needs a good cleaning and recalking but I don't think it has leaked. I see no evidence of it and it has spent much of its life under cover or in a garage.
As already noted, things like propane
cylinders, and dates on detectors are important. Propane
bottles not so much, they only require a visual inspection and stamp applied at the 12 year point, so if not rusty, dented or have broken welds on the foot ring or handle, and they are the OPD type (triangular valve knob) then they are OK. If they have the old type knobs it is impossible to get them filled and not worth attempting to replace the valve. Cheapest price on 30 lb propane
tanks is about $60 off of Amazon for tanks made in Thailand (they look nice and meet all DOT specs, I bought a pair) and it will cost you $50 or $60 to get them filled. Manchester cylinder will cost a bunch more and are really not any better.
Flame King 30 lp cylinder, $60
Worthington 30 lb cylinder, $92
Manchester 30 lb cylinder, $75
I had to replace the LP gas detector, and didn't like the surface mount one Bigfoot
had installed. When I removed it, it looked crazy with all the holes in the wood behind the detector, it was original but someone poked about a dozen screw holes or larger in the wood to mount it, I installed a flush mount model that also had a CO detector in it, and was brown to blend with the wood. You can save a few bucks with the LP only detector and even save more buying the original style, ugly, protruding type detector, but I feel this is a worthwhile upgrade to have it flushed in and get the dual sensor.
Safe T Alert 35 dual LP/CO alarm $68
The ceiling mounted smoke/CO detector is battery
powered and I ordered the exact same unit from Amazon and installed it. You could get away with leaving the old base in place but the plastic had yellowed, so I carefully changed it out. Always use a hand screwdriver and NOT a power screwdriver to run screws. Power will strip them out in a heartbeat. Running by hand allows you to feel when the screw is tight.
First Alert battery powered smoke/CO detector
Carbon Monoxide is a neutral buoyancy gas so having a hard wired CO detector down low (and close to the air intake for the furnace
where there is air movement, and having one up high and battery
powered is a significant plus.
Important for the life of your battery
is the power converter. Generally I expect to replace it and if I were to stumble into one with a Progressive Dynamics 4 stage unit already installed, I consider it a bonus. The stock one in mine was a WFCO which stands for World Friendship Corporation, its a China firm. It was a model WF9845 which is supposed to be a 3 or 4 stage, but from reading on the RV forums, they seem to not switch stages and the one in my Thor trailer does not, and just stay stuck on the higher volt setting and will boil your battery. I bought a Progressive Dynamics 4600 upgrade kit from Best Converter and installed it. It comes with a new and better 12v fuse panel for the Parallax panel that gives you the ability to manually switch stages, which is useful if you want to bulk charge the battery while the generator
is running, even if the converter doesn't think its the thing to do.
I stuck with the 45 amp as I didn't feel like upgrading the wiring from 8 gauge to 6 for the 55 amp model, but I did get the one with the optional Lithium battery charge profile in case someone after me ever decided to install Lithium (I won't).
Progressive Dynamics converter upgrade kit, $207
Other things to look at are the propane hoses and regulator. If over 10 years old, I consider it all suspect. If it is a Fairview regulator, its junk. I replaced the tank pigtails with stainless braided variety as that is the part that gets the rough handling, and put a new high flow Marshall Excelsior regulator and a new regulator to hard plumbing hose in, all USA made Marshall Excelsior products, including the hose itself.
ME high flow regulator, be aware this is a bulk product so it is in a plastic bag and Amazon ships in a stupid padded envelope, first one was broken, $47
Protective cover for the vent on the two stage regulator. $7
ME 24 inch stainless braided tank pigtail, $25 and you need two of them.
The regulator to hard line hose will vary with the installation, mine was 30 inch but I went to 40 (really needed 36 or so) to get the hose out of the way of the "extra" battery area under the front storage locker. Bigfoot
also used a odd hose with a 3/8 male pipe thread on the regulator end but a male flare end for the hard line, which you will not find. I ended up with the female flare and a brass union to make the connection.
40 inxh regulator to hard line hose, $15, measure yours to get the correct length.
Its the simple things that bite you money wise. The tires
on my trailer are Hercules ST2, which is apparently a decent tire, I cannot find anyone badmouthing it on the RV forums, and they have 2018 date codes, but they were never balanced when installed. Many people think, "its just a trailer, why bother to balance the tires?" but its your stuff bouncing around in there, and the smoother the ride, the better for you towing, and for the trailer and the stuff in it. $40 while I had the tires off replacing the wheel bearings.
Speaking of tires and date codes, LOOK AT THE SPARE. Mine was original, a Goodyear Marathon (well known for failure) and was original with a 2007 date code. They have been know to even come apart just sitting on the spare tire bracket. Anyhow, I bought a new one, a Goodyear Endurance ST225/75-R15 (well endorsed by folks on the RV forums) and had the old spare swapped to a utility trailer rip in place of an old tire that had come apart just sitting in the yard. (I only use the trailer within a few miles of home, so its not a big deal) Cost of all of that was $184 at my favorite family owned tire store nearby.
Which brings us to the last point and I'll quit.
Wheel bearings.......... A lot or a little can be said about them, but if you read this forum, you will find a couple of examples of NEW trailers which, straight from the axle
manufacturer, did not have (or not enough) grease in the bearings, and they failed, destroying the axle/spindle, stranding them.
Up until the advent of the sealed hug/bearing assembly's used on cars now days, all automobiles and trucks used tapered roller bearings on the non-driven wheels (and the front axles of 4x4 setups). Rear hubs on full floating rear axles still use tapered roller bearings. The only bearing I have ever had fail, was one I installed in haste that I bought from an auto parts store, with CHINA printed on it. Otherwise I have always used bearings made in the Free World, USA, UK, Mexico, Japan, and never had any problems with them.
Every trailer you look at will have CHINA brand bearings in them, and so first thing, I pull the hubs, knock out the races (cups) and ditch all the CHINA parts and install USA manufactured Timken bearings (SKF mostly made in Mexico and Toyo Koyo made in Japan are also fine bearings). If you are repacking the bearings anyhow, this is extra money, but little extra work, adds ten minutes or so to each hub to replace the races and actually is easier as you don't have to clean the old bearings (Yes, I blow out all of the old grease, then wash them in mineral spirits thoroughly, and then blow them dry and re pack them, same way I was taught to do it on airplanes).
Second point of failure on bearings is improper tightening of the axle
nut. This is partly why I will never pay someone to do my bearings, I insist on proper torque of the axle
nut, which is to tighten 20 to 25 lb/feet (no you really don't need a torque wrench, just make it good and tight) and spin the hub/drum to seat the bearings and work excess grease out of the bearing so it is fully seated, then loosen it a quarter turn or so and re tighten, after several tries you will find that sweet spot where it is just touching and not actually exerting any pressure on the bearings beyond being seated, this is the point where the hub will be more difficult to turn if you continue to tighten. Roller bearings don't mind being loose, but fail easily if too tight, so back off till you can insert the cotter pin or lock keeper used on Lippert axles. I only wished they use the system Ford used that had a plain nut and a stamped metal keeper that had many teeth on it so you could get a perfect adjustment before inserting the cotter pin.
All of this goes out the door if you encounter a set of the sealed hubs which are used on some travel trailers now.
Here is a PDF that has a breakdown of the hub and drum and parts. Look on PDF page 7 of 21 which is page 25 if you look at the numbers on the bottom of each page.
Dexter 2300-4000 lb hub drum parts