Proper Tire Presure

There are at least 100 topics on this. It has to do with the weight on each axle and tire . . . Do a search

If your RV came with that size then the answer is use the MAX pressure marked on the tire.

ST tires are best run close to or at max psi as stated on sidewall. There should also be a white label, most often placed at the front corner of the trailer by the TT manufacturer that will indicate proper inflation psi. Every label I've ever seen at the dealers lot or RV shows always uses max psi of the ST tire installed on the trailer. Filling an ST tire to far below max psi will cause it to overheat, issues including tread separation and catastrophic failure are often times the end result.

If their close to the OEM capacity and close to the trailers OEM axle capacity I would run max pressures.
Close spaced axles toward the center of the trailer places tremendous side loads on the tires as they slide sideways while going around corners. Just one of many good reasons to use max pressures.

Max at stated on the tire.

Do NOT use the max pressure molded into the sidewall. That's the maximum the tire can take without blowing up (with a safety factor, of course). You need to weigh the load on the tires (when typically loaded for a trip), then consult the tire manufacturer's load/pressure chart.

As an example, the tires on my Kia minivan are rated to 45 psi by the molded # on the sidewall. The vehicle manufacturer recommends 34 in the front and 38 in the back. With our typical load (me, DW and our two Labradors) the weighbridge numbers suggest 31 front and 35 rear. The Toyos I have on the van are at about 55,000 miles (van has 120K) and are still in good shape, using those numbers.

I have yet to see a trailer with recommended pressure on a sticker, but every trailer tells you max pressure at max load.

Tire manufacturers publish load/inflation charts for a reason, proper pressure is the pressure at which the tire can support the load applied.

Overinflated isn't as bad as underinflated but still has drawbacks such as decreased traction, decreased tread life, increased susceptibility to road hazards, and transfer more road imperfections to the trailer.

The correct answer to weigh your axles and adjust accordingly. 5 psi over chart pressure is also recommended, up to sidewall max, if you will be driving 60-65 for a long ways. Until you can weigh your trailer run max pressure, but do weigh it.

Beerdawg wrote:
What should the proper tire pressure be on ST205/75R15 tires on a travel trailer? Thanks

Max psi per the sidewall, will allow your tires to perform their best. Low psi builds heat and heat kills tires.

Run them at exactly what the "maximum" on the sidewall says.

I posted this in another thread:

Tires should be cold inflated to the tire's max. sidewall pressure in the morning before heading off or after at least 3 hours of sitting in full shade. Don't go by the placard figure. The tires may have been upgraded by an owner or the factory. We have factory optional LRD tires that should be run at 65 psi however the factory used their standard placard for LRC tires (50 psi). Using the placard psi in our case would result in serious damage and a blowout(s).

The term "maximum" used on the sidewall tires creates confusion. It is actually the temp. that the tire should be cold inflated to in order to carry the load rating indicated on the sidewall. Lowering the pressure can result in overloaded tires (not good).

Cold inflation pressure is the inflation pressure taken with tires at the prevailing atmospheric temperatures. Tire pressure only changes about 2% for every 10F change in temp. Running your tires low will damage them from overheating and is a good invitation for an eventual blowout. You should never bleed them down when they are hot. Tires are designed and tested to be able to withstand up to around 3 times the sidewall pressure so no worries about exploding tires from running in high ambient temps.

For some tires (only a couple I think) such as GY Marathons, you can raise the psi by 10 psi and be able to run at 75 mph max.

Go and google "RVtiresafety" and you will find your answer there. Lots of reading on anything you ever wanted to know about RV tires. Remember, ST trailer tires are more "delicate" in comparison to other tire types and you want to take all the recommended measures to take care of them to minimize premature wear and reduce the chances of a blowout. Heat is the biggest enemy of ST tires by under-inflating and/or running above 65 mph.

Ranger Smith wrote:
There are at least 100 topics on this. It has to do with the weight on each axle and tire . . . Do a search

frankdamp wrote:
Do NOT use the max pressure molded into the sidewall. That's the maximum the tire can take without blowing up (with a safety factor, of course). You need to weigh the load on the tires (when typically loaded for a trip), then consult the tire manufacturer's load/pressure chart.

As an example, the tires on my Kia minivan are rated to 45 psi by the molded # on the sidewall. The vehicle manufacturer recommends 34 in the front and 38 in the back. With our typical load (me, DW and our two Labradors) the weighbridge numbers suggest 31 front and 35 rear. The Toyos I have on the van are at about 55,000 miles (van has 120K) and are still in good shape, using those numbers.

Both of the above quotes are IMO WRONG for ST tires which is what was asked about. While using pressures based on load inflation for normal vehicles has merit, tires on trailers and especially ST tires should be inflated to the max pressure listed on the sidewall as almost all of the other posts in this thread so far have recommended.

Larry