What PSI to run?

[Daishi]

Hello all,

I recent purchased a 2019 FR XLR Boost 36DSX13. Everything looks good except for the Castle Rock tires which are factory original (235/80/16 @80 PSI E rated). I upgrade the tires to the Sailun s637's G rated (235/85/16) as well as metal fill stems and a TPMS system. On the tire placard it shows 80 PSI but the new tires are 110. The trailer dealer who suggested upgrading the tires/fill stems/tpms in the first place said running at 110 is not going to be a problem, but I am worried about the factory rims pressure cracking. There were no pressure markings anywhere on the rims.

Should I be running these at 110 PSI for my max load of 14k lbs? Ive done some googling and it ranges anywhere from people saying only use 80 PSI to 110 PSI to prevent over heating due to an underinflated tire. I have a 9 hour trip to bring the trailer home and I really want to make it in one piece.

 

[RobbieH]

See if your tire manufacturer has a chart for PSI based on load. I've run Michelins and Toyos on the Class A we used to own, and both had a chart to use. Otherwise, this is a pretty good SWAG way of determining the correct pressure.

https://www.youtube.com/results?search_query=tire+chalk+test

 

[NMWildcat]

I did the exact same thing on my 12k lb trailer. Rims also had no markings. Tire dealer said to run the LR G tires anywhere between 80psi and 90psi. I usually run at about 85psi.

I am on my second set of LR G tires and have had absolutely no problems.

To ease your mind check out the load charts for the size/brand of your tire. Take your loaded rig to a scale and verify correct psi on the chart.

 

[Chuck_S]

You don't need any more weight carrying capacity from the new tires than the original tires provided and that was at 80psi and only if the trailer was stuffed full to gross allowable weight. Filling an unnecessarily larger tire (which you just bought) to max sidewall pressure of 110psi is likely to pound the trailer to death on the road.

What weight is supported by the new tires at 110psi (it's on the sidewall) compared to the gross weight rating of the trailer? On line data (or guess) is 4400 pounds each or 17,600 and the on-line GVWR is only 14,333 and only about 12,000 of that is on the axles -- and that's unlikely since your "stuff" ain't in it.

Your current tires are rated at 3420 at 80psi (should be on the sidewall) the replacements are rated at 3640 at that same 80psi according to the Goodyear inflation chart (your tires will be identical or very close). You don't need more than 80.

110psi is safe for the tires but isn't doing anything beneficial for the trailer.

-- Chuck

 

[FlaNative]

We have G load rated tires on our 5'er (Hercules All Steel ST 235/80R16, made in Thailand) and run them at 95psi: with our TPMS we're seeing lower temps because of the higher psi, and a little better fuel mileage (not a whole lot better), but with fuel prices these days anything helps. We've had them for 3 1/2 years now and we're very pleased with them.

 

[jjscsix]

I would always go with the RV manufacturers recommendations. Tire companies build their tire to a max pressure for the tire, not the trailer because they cannot become experts on every trailers needs.

This is the conundrum of buying a tire that does meet the same exact specs as the OEM tire. You are on your own to decide what pressure to run.

 

[NMWildcat]

I would always go with the RV manufacturers recommendations. Tire companies build their tire to a max pressure for the tire, not the trailer because they cannot become experts on every trailers needs.

This is the conundrum of buying a tire that does meet the same exact specs as the OEM tire. You are on your own to decide what pressure to run.

Seems to me that the RV manufacturers go with the cheapest tire that will handle the empty weight and not much more, especially for towables. That is why a lot of us upgrade the tires immediately. Going up a LR greatly diminishes the OEM tire failure problem.

I trust RV manufacturer's recommendations even less than anything a politician might spout off about

 

[RobbieH]

Agreed. I'm certainly not going to put Chinese Castle Rock tires back on my trailer!

 

[Aussieguy]

good tire companies will publish weight to pressure charts
see if the tires you use ... have a chart

a bushman tire gauge ... the flat part of the tire sitting on the road should be about 4 inches
width of average man's hand

if there is not a lot of contact area... you will have slipping sliding in the wet and poor braking performance
tires will also wear out in the center of the tread (crown)

too little pressure... side walls will bulge and get hot from flexing

 

[5picker]

Seems to me that the RV manufacturers go with the cheapest tire that will handle the empty weight and not much more, especially for towables. That is why a lot of us upgrade the tires immediately. Going up a LR greatly diminishes the OEM tire failure problem.

I trust RV manufacturer's recommendations even less than anything a politician might spout off about

Agreed. I'm certainly not going to put Chinese Castle Rock tires back on my trailer!

X3... trust and R/V manufacturer are not two things that go together or hold any weight. (see what I did there!) Otherwise, the poor decisions made by them wouldn't be the ongoing topics of conversation on this and other R/V forums day after day.

Tire companies have charts for inflation and all the ones I've ever looked for, were available online.
Find your loaded weight and adjust accordingly. Always inflating a tire to the MAX sidewall pressure is not my method of operation.

 

[5picker]

a bushman tire gauge ... the flat part of the tire sitting on the road should be about 4 inches
width of average man's hand

LOL... now you are going to have someone lay their hand on the road and have someone run their trailer tire across it to see if it measures.

What if it is a wide track tire like many of the No Boundaries trailers are coming with?... Put both hands under?

Of course I jest but I just don't believe tires and bush recommendations go together either when quality air gauges can be had for little money.

 

[DJ252]

The chalk test is probably pretty decent.

According to the charts, I should run 5psi less than I am.

Not sure I'm going to bother with it. I already installed a cushioned equalizer and reprogramming my TPMS is a hella pain. Don't know why. Possibly some sort of defect but when switched to the programming screen, it is really hard to see.

 

[ppine]

Trailer tires are made to carry weight. Check the recommendation on the sidewall. Keep your tires inflated close to that amount.

 

[NMWildcat]

Trailer tires are made to carry weight. Check the recommendation on the sidewall. Keep your tires inflated close to that amount.

????

Not the best advice to give. Too many variables.

Maybe you should advise to keep your trailer tires between the RV placard PSI and the max cold PSI on the tire as long as the tire is the same size as OEM.

 

[Aussieguy]

Chalk test on trailer????

we used chalk test to get the LOWEST tire pressure for track days
get absolute minimum pressure in tire .....
good for flat race tracks not for pothole streets and rocks


Ps when you do decide on a pressure... take note of the bulges / flats spots
your eyes can often spot a problem before you get on the road
I always look at tires , electical cords and chains..... after a pitstop

 

[DJ252]

Chalk test identifies over inflated, if it wears off in the middle, under inflated, on the sides, or perfect inflation for the load, evenly.

 

[Aussieguy]

I c npw
we would put the chalk on the side walls
if chalk rubs off sidewalls are rubbing on the road through the corners

Chalk on tread.... would work for a short period of time or the next puddle of water which ever comes first

 

[DJ252]

I c npw
we would put the chalk on the side walls
if chalk rubs off sidewalls are rubbing on the road through the corners

Chalk on tread.... would work for a short period of time of the next puddle of water which ever comes first

Correct but you don't have to, nor would you want to drive it far, before checking the results.

 

[DJ252]

And while the finer points of tire inflation ... Well, learning is never a loss but while slight over inflation, imparts more dynamics to the trailer than necessary, it can help with fuel econ and body roll, whereas underinflation, risks catastrophic failure.

The fact is, unless there is an alignment problem, or a road hazard, most people's trailer tires will age out, before they wear out.

 

[Daishi]

So this is the PSI chart for the 235/85.16's. Im a little confused as to what "Dual" and "Single" are referring to. I'm assuming my trailer is single? So at 80 PSI Id have 3640 lbs per tire? WHich would be 14,560lbs total which is the weight of the entire trailer loaded anyway.