PDA

View Full Version : How Much Air Pressure


nascar
04-14-2012, 09:31 PM
I have a 1994 Mastercraft single axle trailer for my ProStar 190 , the tire size is ST 215/75/14 , my question is how much air pressure to run ? The tires state 50 lbs max with weight 1870 . I have been running 40 lbs. Is this correct ? thanks in advance for your advice .

Jerseydave
04-14-2012, 10:00 PM
I have a tandem with the same size tires and run 46-48. I think you should run close to 50 cold psi on a single. If you have Goodyear Marathons check those babies close....some of them come apart (I had 3 go on me in less than 2 years)

jhall0711
04-14-2012, 10:06 PM
What are the signs that the GY Marathons are about to experience tread seperation... that is the problem right?

I ask because I have a set....:rolleyes:

I try to run 48PSI....

Jerseydave
04-14-2012, 10:12 PM
What are the signs that the GY Marathons are about to experience tread seperation... that is the problem right?

I ask because I have a set....:rolleyes:

I try to run 48PSI....

Look close at the shoulder of each tire, inside shoulder and outside shoulder. You can usually tell if the tread is starting to seperate from the sidewall. You can also jack up your trailer and spin each tire.....if it rotates like an "egg", it's going to give you trouble.

93Prostar190
04-14-2012, 10:19 PM
I run close to Max ... 48-50 psi is good ..... the air helps protect the tire sidewall ... and that is really important ........ especially on your single axle trailer ....

Footin
04-14-2012, 10:20 PM
I run my Marathons at 50.

CantRepeat
04-14-2012, 10:41 PM
It will say on the side wall of the tire.

Honkity Hank
04-15-2012, 08:08 AM
It will say on the side wall of the tire.

That is the max pressure for the tire. You can safely run less pressure. Higher pressure = less contact patch = less traction = less rolling resistance. Lower pressure = more contact patch = more traction = more rolling resistance. I think anything in the 32 to 42 range is going to be fine.

CantRepeat
04-15-2012, 08:24 AM
That is the max pressure for the tire. You can safely run less pressure. Higher pressure = less contact patch = less traction = less rolling resistance. Lower pressure = more contact patch = more traction = more rolling resistance. I think anything in the 32 to 42 range is going to be fine.

Yeah, max pressure for max load is what it says. Running less and you risk the chance of a "run flat". I'm no expert but going with what the manufacture has on the side wall wont be wrong. On the other hand, running 18 lbs under max isn't good.

OHpage21
04-15-2012, 08:49 AM
I replaced the marathons on my trailer last year. Guy at the shop said to run the new tires near full pressure. Running less will have them separate much quicker.

nascar
04-15-2012, 09:00 AM
thanks for all the replies , I will up my air pressure. I am only about 20 miles from the lake ( all country roads ) so my top speed is 55 mph , most of the time only 45-50 mph . I will also check my tires by inspection of side wall and jacking up my trailer and spinning the tire .

93Prostar190
04-15-2012, 09:20 AM
That is the max pressure for the tire. You can safely run less pressure. Higher pressure = less contact patch = less traction = less rolling resistance. Lower pressure = more contact patch = more traction = more rolling resistance. I think anything in the 32 to 42 range is going to be fine.

Very true but more applicable to cars vs. trailer loads. Where the loading is almost secondary to the other properties of the tire.

Less air also equals for sidewall flex which creates more temperature , not running at max psi actually reduces the load rating of the tire, on a single axle trailer you don't want the math in that direction.

My numbers below are for sample only but represent a lot of the numbers for typical inboard boat. Do your own math but here goes ...

For example 3000 lb boat + 800 lb trailer = 3800 load totally dry .... Add gear and fluids, etc.

Call it 4000 lbs ( some newer boats weigh 3300)

4000 lbs * .10 = 400 lbs of tongue weight if you are at 10 % tongue weight.

4000 -400 = 3600 lbs of weight left on the axle / 2 wheels = 1800 per wheel

Miss Rita
04-15-2012, 11:04 AM
DING DING DING! 93ProStar190 is right.

With the weight you're carrying you need to have the tires at max psi. Anything less will allow excessive sidewall flex, stress the tires more, leading to higher risk of tire failure. The trailer will be less stable, will sway more.

Tires are pretty tough, they won't complain about running at the maximum inflation pressure.

Running tires underinflated is probably the worst thing you could do; that's what led to the Explorer/Goodyear debacle.

There's a lot of talk about Goodyear Marathon tire failures. It's safe to say that they didn't fail because they were properly inflated.

MattsCraft
04-15-2012, 11:20 AM
If you are running Marathons - See service Bulletin - Running 65MPH to 75MPH, raise pressure to 60PSI. I run 55 minimum on mine.

CantRepeat
04-15-2012, 11:33 AM
If you are running Marathons - See service Bulletin - Running 65MPH to 75MPH, raise pressure to 60PSI. I run 55 minimum on mine.

Nice find!!

meg
04-16-2012, 11:05 AM
I have had 3 of my 4 Goodyear Mar. blow in the past 10 months (found the last one Sat. when i went to get the boat out of the shed for the first time since Sep.) They are 2006 tires which I assume is probably the shelf life- is that about right?

thatsmrmastercraft
04-16-2012, 11:12 AM
I have had 3 of my 4 Goodyear Mar. blow in the past 10 months (found the last one Sat. when i went to get the boat out of the shed for the first time since Sep.) They are 2006 tires which I assume is probably the shelf life- is that about right?

I never push trailer tires beyond five years from the DOT manufacture date on the sidewall. Marathons are a whole different can of worms.

MattsCraft
04-16-2012, 11:50 AM
Nice find!!

Can't take credit, found it here first:D

gatorguy
04-16-2012, 01:59 PM
I run all the tires I own at max PSI. The ride may suffer a bit, but I think my tires wear better, and you squeeze the last little MPG out of them too. Not to mention the added bonus of not blowing out a tire on an overloaded trailer because of heat, etc...