Tire pressures

[colby]

Let me throw a real world example into the mix here.

Our 2018 212QB came with Goodyear Endurance tires stock (205/75R14). I always ran max PSI as stated on the sidewall (65PSI). We never load our trailer to max vehicle weight (5500#), every time I have weighed it, it is around 5000 pounds. And almost every time I pulled the trailer somewhere, things bounced around inside (in the cupboard above the sink) and things coming off of the shelf above the dinette.

This year when I replaced the tires, I went a bit bigger (215/75R14) which has a slightly higher load rating (2200 vs 2040) and I replaced the rims with ones that support that. I also looked up the suggested PSI based on the weight of the trailer. If I take my 5000 pounds and divide by 4, I get 1250 pounds per tire, which according to the Goodyear site (linked in a post above), which says 25PSI as the recommended pressure. Now I was a little uncomfortable with that, so I doubled that to 50PSI which is still well below the max PSI of 65 PSI (and will support 7480 pounds across the four tires so I should be covered if I really load the trailer incorrectly and one tire has more load). With that configuration, we went on a 3 week trip from Ontario to South Carolina, and even over the crappy section of I81 through Pennsylvania, construction zones, etc., things did not bounce around nearly as much and they stayed where they were. The TPMS reported consistent PSI across the tires and temperature was good. Tires also looked really good in terms of wear post trip.

Given that, with max PSI (65) for the old tires, that supported a trailer weight of 8160 pounds which is significantly higher than what my trailer weight historically has been, I feel that added to the "bounciness" of the trailer given there was not enough weight for the setup.

[Kevin Cooper]

Originally Posted by Bocafeet

Again ,, find me a sticker that lists hot pressure. you are just arguing with your self

Hot pressure can not be evaluated and suggested. Ambient temperature, distance driven, cold pressure when you started(low pressure, higher heat, higher pressure)
Cold tire pressure is the only thing to go by. If you do not have a compressor, this is the suggested thing to do. Measure pressure before you start. Note how much pressure you need in each tire. Drive to compressor location. Check pressure, and add the number of pounds you were low to that tire, and raise to the new pressure.

[Tireman9]

Originally Posted by El Chupacabra

I'm curious what you think of using sufficient load range truck tires (eg, an E-rated tire) on a trailer, instead of ST-rated trailer specific tires. Some trailers (usually smaller ones, it seems) actually come with LT tires instead of ST.

Apologies for the thread drift away from PSI...

My fundamental guideline for replacing tires is:


When replacing tires be sure that the new tires have equal or greater load capacity.


Sometimes there are LT type tires that can work i.e. have greater load capacity and physically fit the space available. i.e. no rubbing on any part of the vehicle. I guess there might be a case where a smaller tire can deliver equal or greater load capacity if the inflation in increased sufficiently. In that case you need to be sure you are not exceeding the max infl rating of the wheel.




See. even a simple question requires addressing all possibilities as sure as shooting someone will read the reply and not pay attention.

[Tireman9]

Originally Posted by Kevin Cooper

Hot pressure can not be evaluated and suggested. Ambient temperature, distance driven, cold pressure when you started(low pressure, higher heat, higher pressure)
Cold tire pressure is the only thing to go by. If you do not have a compressor, this is the suggested thing to do. Measure pressure before you start. Note how much pressure you need in each tire. Drive to compressor location. Check pressure, and add the number of pounds you were low to that tire, and raise to the new pressure.

Correct answer Coop

[Tireman9]

Originally Posted by Bocafeet

Again ,, find me a sticker that lists hot pressure. you are just arguing with your self

I don't know how to make this clearer.
You should only be adjusting tire inflation when the tires are "cold".


"Cold" means not in direct sunlight or having been driven on in the previous two hours.


The ONLY people who might be monitoring hot pressure are the tire engineers working on race tires when developing new tires or adjusting alignment and vehicle weight balance.


If you are driving a race car you can drop me a note and if I have the time we can discuss tire temperature. Be sure to know the brand and model of the Tire Pyrometer you are using.

[El Chupacabra]

Originally Posted by Tireman9

My fundamental guideline for replacing tires is:


When replacing tires be sure that the new tires have equal or greater load capacity.


Sometimes there are LT type tires that can work i.e. have greater load capacity and physically fit the space available. i.e. no rubbing on any part of the vehicle. I guess there might be a case where a smaller tire can deliver equal or greater load capacity if the inflation in increased sufficiently. In that case you need to be sure you are not exceeding the max infl rating of the wheel.




See. even a simple question requires addressing all possibilities as sure as shooting someone will read the reply and not pay attention.

Thanks - to put a little finer point on my question, I was curious what you thought of the construction differences (if there indeed are any) between a ST and a LT tire. I've read tire company descriptions on ST tires, asserting the loads are different on trailer tires, therefore it was important to use ST tires, and LT tires couldn't/ wouldn't properly support trailer loads.

Which doesn't make sense to me, as I would expect a LT tire to have to put up with different and greater loads under, say, a truck that has to accelerate, turn, brake, and hold weight - vs a trailer tire, which mostly has to hold weight.

[Bocafeet]

Originally Posted by Tireman9

I don't know how to make this clearer.
You should only be adjusting tire inflation when the tires are "cold".


"Cold" means not in direct sunlight or having been driven on in the previous two hours.


The ONLY people who might be monitoring hot pressure are the tire engineers working on race tires when developing new tires or adjusting alignment and vehicle weight balance.


If you are driving a race car you can drop me a note and if I have the time we can discuss tire temperature. Be sure to know the brand and model of the Tire Pyrometer you are using.

ok so i don’t fill tires a a gas stop?

[Kevin Cooper]

Originally Posted by Bocafeet

ok so i don’t fill tires a a gas stop?

Read the comment he made just above the one you reference.

[jetlag]

I remember sometime back, on another tire pressure thread here, someone posted that he would actually stop down the road if his tire pressure exceeded the cold rated pressure, and take air out of his tires. he was lambasted by many here, but in the end he still thought he was correct!

[norty1]

Seems the question has been answered several or many times.

Cold pressure has been defined ad nauseum!

[Cincinnati Kid]

Yes, that means you don't add/subtract air when the tires are hot. Ever. (obviously, if one tire is showing out of whack numbers on your TPMS, check it out, fix it, let it cool down and air it up or put on the spare)
If I oversleep and the sun is already on my tires, I just wait until the next time they cool down to air them up.

Then nothing changes for weeks at a time.

If I go from Winter to Summer outside temps, and I plan to be in hotter weather for a while, (OH to Florida) then THE NEXT MORNING I adjust the cold temps.

[JB13502]

Originally Posted by Grumpy

Yes to both. Many will enjoy reading and following the correct information and yet others will continue to ignore it.

Grumpy hit the nail on the head. Tireman, thank you for sharing your expertise!

[Mr Bee]

I am certainly not an expert however, I believe the manufactures max pressure rating when " cold" is accounting for the tires heating up during use.

[wordsmyth]

Mine specify 65 psi.

[Tireman9]

Originally Posted by jetlag

I remember sometime back, on another tire pressure thread here, someone posted that he would actually stop down the road if his tire pressure exceeded the cold rated pressure, and take air out of his tires. he was lambasted by many here, but in the end he still thought he was correct!

I can't help it if some people choose to ignore proper advice. A friend had a saying "You can lead a horse to water but you can't make then drink"


Same goes for people and facts and knowledge. Once they have made their minds up no amount of discussion or presentation of facts seems to be able to get them to change their mind.

[Tireman9]

Originally Posted by Mr Bee

I am certainly not an expert however, I believe the manufactures max pressure rating when " cold" is accounting for the tires heating up during use.

When we design tires we specify a "cold" pressure and know the tire will heat up in use. We know that the pressure will increase in operation.



It might help if you think of the "MAX PSI" as an abbreviation for "The maximum load capacity for this tire is at this cold pressure"


When you look at the Load/Infl tables you can move along to the right and see ever increasing load capacity as the cold pressure at the top of the chart increases. Once you hit the pressure for that Load Range you stop and can not continue reading higher load capacities that are to the right of the psi for that Load Range

[Kevin Cooper]

Originally Posted by Tireman9

When we design tires we specify a "cold" pressure and know the tire will heat up in use. We know that the pressure will increase in operation.



It might help if you think of the "MAX PSI" as an abbreviation for "The maximum load capacity for this tire is at this cold pressure"


When you look at the Load/Infl tables you can move along to the right and see ever increasing load capacity as the cold pressure at the top of the chart increases. Once you hit the pressure for that Load Range you stop and can not continue reading higher load capacities that are to the right of the psi for that Load Range

Any insight on speed rating definition would be helpful too. Thanks for info from an expert.

[Cincinnati Kid]

I can't take it anymore. I'm going to be in line for these when available-

https://www.bridgestonetire.com/lear...concept-tires/

[Grumpy]

Originally Posted by Cincinnati Kid

I can't take it anymore. I'm going to be in line for these when available-

https://www.bridgestonetire.com/lear...concept-tires/

Michelin was working on a similar concept at their Lexington SC plant years ago. Don't know what ever happened to their research?

[Cincinnati Kid]

Originally Posted by Grumpy

Michelin was working on a similar concept at their Lexington SC plant years ago. Don't know what ever happened to their research?

It looks like next year for some passenger tires. A long way off for us, and very expensive.