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Open Roads Forum  >  Towing

 > Tire Pressure-Sidewall number, or number on trailer?

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jwblock

Sussex Wisconsin

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Posted: 04/06/12 11:05pm Link  |  Print  |  Notify Moderator

50 psi, for 30 plus years for me. 4 different trailers, never a blowout or flat.

Just remember, heat is a tires worst enemy. Please do not wait twenty years to figure that out.

Go camping!

mowermech

Billings, MT

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Posted: 04/07/12 08:07am Link  |  Print  |  Notify Moderator

Ideally, you want 100% tread contact with the road, for safety.
If the tires are under inflated or over inflated, you do not have 100% tread contact.
Inflate for best tread contact. In other words, inflate to match the load, no matter what size, tread pattern, or Load Range your tires are!
It really IS just that simple!


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wittmeba

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Posted: 04/07/12 09:28am Link  |  Print  |  Notify Moderator

What ever you decide be able to support your decision with some good reasoning. RV tires may be changed - then any sticker may not apply.

All tires provide a max load rating at a max pressure. My opinion is scale the pressure to the load on the tires.

Postings about tires usually yield 3 replies.

- those who guess
- those who use deflation tables based on loads
- those who run at max PSI

Goodyear suggests running max pressure for trailers as they are subject to varying loads and sidewall pressures due to winds, tow conditions and loads.

Personally I use my own load table. This method will yield a PSI somewhere between a mfgs load table and the max pressure for the specific tire.





* This post was last edited 04/07/12 09:47am by wittmeba *   View edit history


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bryanl

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Posted: 04/07/12 09:53am Link  |  Print  |  Notify Moderator

re: "I've always understood the correct inflation for a tire requires weighing the axle and then looking up the correct inflation in the manufactures data." -- that's an inference based on the effect that weight has on the tire. Better than nothing, maybe, but there are better ways.

The weight on a tire makes it flex on the road which causes heat. Tire pressure stiffens it and reduces the heat buildup. As noted above, heat is one of the biggest enemies of tires.

re: "If the tires are under inflated or over inflated, you do not have 100% tread contact." -- the thing is, though, that the traction depends upon both the contact area and the weight on that area so worrying about contact area is not a matter of traction. It is a matter of wear but, for most RV purposes, tires are replace by age, not wear so a bit of extra wear in the center is no big deal.

The general recommendation I have seen every now and then from manufacturers is to run TT tires at max sidewall pressure. The downsides are usually minor and the upsides are reduced risk of tire failure.

It is a good idea, I think, to get an IR thermometer so you can do a go-around at breaks to check tire and hub temperatures. If your tires start getting hotter than 120F after a half hour or more on the road, they likely need more air. They shouldn't go over 140F even on desert afternoon driving. If they run at below 100F, you might be able to get away with less air. If you seen any differences more than 10F to 20F, you might want to see if you can figure out what is going on.

The 'speed rating' for TT tires is, essentially, a heat rating. One way to keep tires from overheating is to slow down (less flex). Some manufacturers have recommended that you should exceed max sidewall by 5 psi or so if running at freeway speeds all the time but I think a bit of restraint on the speed is a better idea.


Bryan

Jim Cindy

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Posted: 04/07/12 06:01pm Link  |  Print  |  Notify Moderator

I cannot help myself on this, does everyone who recommends adjusting the tire pressure to the load weigh each wheel before each trip? How? Where do you do it? What does it cost?


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goducks10

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Posted: 04/07/12 08:48am Link  |  Print  |  Notify Moderator

Are the tires the origial tires? And correct size? Could be that the sticker is for a different tire, and either the factory or if used someone upgraded tires.

wittmeba

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Posted: 04/08/12 12:05am Link  |  Print  |  Notify Moderator

Jim Cindy wrote:

I cannot help myself on this, does everyone who recommends adjusting the tire pressure to the load weigh each wheel before each trip? How? Where do you do it? What does it cost?

I dont think that is the meaning. Those who adjust for load weigh their rig and assume that unless there is some major adjustment to the contents they leave the pressures per the ratio - or as some suggest a little higher.

We pretty much had a second set of all the "household goods" in our trailer and they didnt get removed. So the weight almost never changed more than a handful of clothes - depending on the season.

Even when taking more friends/family we already had extra lawn chairs and bedding for guests.

JIMNLIN

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Posted: 04/08/12 08:14am Link  |  Print  |  Notify Moderator

AV8R 130 wrote:

Sorry, don't have all the info handy, camper is at it's storage location. It's a 2010 KZ CL232SS. Was bought new. Tires are the stock cheap tires, Freestar ST205/75R14. Don't have the sticker listing the pressures handy, but it states all tires are to be nflated to 35PSI. Sidewall states max inflation is 50. I think I'm going to run them at the sidewall pressure, makes a lot more sense to me, 35 just seems low.

Wise choice when it comes to tires on a trailer as they need all the help their owners can give them for a cooler longer lasting tire.


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JBarca

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Posted: 04/08/12 08:53am Link  |  Print  |  Notify Moderator

AV8R 130 wrote:

Sorry, don't have all the info handy, camper is at it's storage location. It's a 2010 KZ CL232SS. Was bought new. Tires are the stock cheap tires, Freestar ST205/75R14. Don't have the sticker listing the pressures handy, but it states all tires are to be nflated to 35PSI. Sidewall states max inflation is 50. I think I'm going to run them at the sidewall pressure, makes a lot more sense to me, 35 just seems low.


Hi AV,

OK I "think" I may have figured this out. There is one key piece of info missing. What load range tire, B or C did the factory declare was suppose to be on the camper?

I looked up your camper. Unfortunately I do not know how to go back in the archive of 2010 but in 2012 they still make that same model.

A 2012 Coyote CL232SS. Is this this correct model? I backed into the Coyote by the model number.

For the 2012 version the GVWR of the camper is 5,500# and they list 14" tires but not the load range. Is yours also a 5,500# GVWR camper?

http://kz-rv.com/brochures_2012/KZ12_Coyote_Bro4pg.pdf

Backing into this, load range B ST205/75R14 at max cold pressure of 35 psi is 1,430# each tire. So 4 of these holds 5,720# of camper against a 5,500# GVWR. And part of this is held by the truck.

Load range C ST205/75R14 at max cold pressure of 50 psi is 1,760# each tire. Or 7,040# worth.

It may well be that they figured on installing B load range tires which is where the tire placard came from and some how Load range C ended up there. Maye they found a cheaper deal on the C's. Now is this a bad thing? Not really. In the days of tire failures on ST tires having excess reserve captivity is a good thing.

I myself would run them at Max cold pressure.

Here is the Tireco site. They really did not show a tire inflation table. Nor a tire size table. http://www.freestartire.com/GuideLines/4.htm

So I used the Maxxis site which has one. I have found that "most" ST tires use the same table ratings. However not all so check your own manufacture if you are going less the max side wall.
http://www.maxxis.com/Repository/Files/m8008load.pdf

Hope this helps

John


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AV8R 130

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Posted: 04/07/12 08:15pm Link  |  Print  |  Notify Moderator

Sorry, don't have all the info handy, camper is at it's storage location. It's a 2010 KZ CL232SS. Was bought new. Tires are the stock cheap tires, Freestar ST205/75R14. Don't have the sticker listing the pressures handy, but it states all tires are to be nflated to 35PSI. Sidewall states max inflation is 50. I think I'm going to run them at the sidewall pressure, makes a lot more sense to me, 35 just seems low.

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