PSI in tyres

[Smelly]

Hi Team!

What should be the psi in 8-ply 13" tyres - carrying a Haines 5.3m fg boat (about 900kg)?

THanks

[PADDLES]

g'day smelly, i've got a 5.5 sig on a single axle trailer with 13 inch light truck tyres and chuck in about 45psi, they still look a bit flat though cos there's so much weight. :)

[whiteman]

If the sidewall says 60 max - pump em up real close to that. And don't forget the spare.

[PADDLES]

hey whiteman, my sidewalls say nothing about pressure but they definitely say light truck. do ya reckon i should be going higher than 45psi? they do still look fairly flat at 45 but i don't ever tow the thing real far cos the ramp is just around the corner.

[Mr__Bean]

I am a bit different to the concept of fillem righ tup.

Most boat trailers have light truck tyres as they are a far more durable tyre, they will withstand longer periods of no use without getting flat spots and they have a far superior side wall section that will take those gutter bangs that occur at times on tight turns etc.

But in their intended operation (light trucks) they are carrying a much heavier load that we have on our trailers and if pumped all the way up they can be very "bouncy" for the boat on trailer.

I prefer to run them at a pressure where the sidewall does still have the ability to absorb some road shock.

- Darren

[TOPAZ]

Hi All,
On the sidewall of most tyres, you will find printed the load bearing capacity of the tyre, and the maximum pressure which the manufacturer considers that the tyre should be inflated to.
The maximum load is generally only supportable at close to the maximum pressure.
Heat is the enemy of tyre durability, and heat is generated when the tyre flexes as it rotates. Flex is reduces with increasing pressure.
I used to have a trailer with those 6.00 x 9.00 alloy wheels, and was regularly having blowouts, until told by a tyre technician to run them at 60 (yes SIXTY) psi. That stopped my blowout problem and the tyres used to run quite cool, even at high speed and over long distances.
My current trailer is a Mackay tandem, and I run 55psi in the tyres, which are 13" light truck 10 ply radials.
As an aside, contrary to most popular opinion I think that crossply tyres are better than radials, particularly on a tandem trailer, as they don't grab hold of the road surface quite as hard.
I have a tandem box trailer with Kumho light truck crossplies, which look skinny, but carry weight like you wouldn't believe.

[Chimo]

Hi Smelly

On the trailer is there not a plate that as well as everything else indicates the inflation pressure for the specified tyre ?

Mine for eg is 420kp (about 62 psi) pressure with 205 X 14" 8 ply tyres

Cheers

Chimo

[Smelly]

I have brand new Hancook 8-ply tyres (light truck).

WHen boat sits, the tyres look pretty sad (don't know what psi is in them yet because when I find out what should go in, I will go to the sstation and go pumping.

I see no numbers on these tyres - have looked.

Topaz what weight do u carry on those tyres please?

If those tyres say around 60 psi - maybe this is their intended pressure - used on light trucks. But, we fisho use these tyres for our fiberglass boats which is exposed to potential damage if shock is not absorbed enough...

THoughts?

Smelly

[TOPAZ]

Smelly,

I don't know which trailer you were asking about (the current tandem boat trailer, or my tandem box trailer), but the boat trailer & boat is all-up 2.5 tonnes, and I have had up to 2 tonnes approx in my box trailer (eight full 44 gallon drums)

With respect to vibrations etc being transmitted to the boat - I don't travel on many roads with corrugations and potholes, so I am quite happy with how the boat rides. It is also VERY well supported on the trailer with ELEVEN keel rollers, as well as about 24 sets of wobble rollers (I say ABOUT, because I am not at present within reach of the rig to check!)

I do worry about multi-roller trailers with NO keel rollers to support the keel of the boat - the strongest part.

[Chimo]

Hey Smelly

The plate I was talking about was on the Tinka trailer and was set up to carry a FRP Seafarer Vag. On the Tinka Seafarer gives a 5 year warranty on the boat with ( 420 kpa / 62 psi) so I don't think you need worry about that.

The trailer suspension and the multiple rollers that carry the boat weight spead evenly are apparently what it about.

Too little air in tyres leads to too much flex and big bangs if you get them too hot and worn edges on the tyre as you use them, as you no doubt know.

I still reckon you should go by whatever the VIN plate on the traler states as the appropriate tyre pressure, assuming you have the tyres specified on the plate. If not why not asked the tyre people?

Cheers

Chimo

[dnej]

I think there is an obligation , to put the information on the wall of the tyre,but 45lbs,to 50 lbs,should be enough.

However, that should be when cold, at home,before you drive any where.
Why?
Well, as soon as you drive down the road with under inflated tyres, they heat up, and over inflate the tyre.

So as a result, when you go to the garage, the gauge shows, a heated tyre pressure.

That could mean, that you even let air out of the tyre, making the problem even worse, for the next time out.

Do yourself a favour, get a small compressor, the ones that run off the battery, and check the tyres at home, when cold.

Under inflated cold pressures, result in over inflated hot pressures, and this in turn also causes tyre wear,
Regards David

[Smelly]

well done people.

The tyre specs on mytrailer show those specs for the previous 10" wheels I used tohave before I changed over the 13" wheels just recently.

I think I will put the trialer on wheel stands and take the wheels in the boot of my car to the ssation instead..

THanks

[Smelly]

OK - My tyres say 65 psi.

What psi should my tyre be inflated to?

Smelly

[camsharkman]

Smelly - I had the same Hankook tyres on my previous trailer carrying a 6m Boat. 45-50psi, thousands of k's and no problem.

[dnej]

Yep, as I said previously
David

[whiteman]

Can't see any -ve to keeping the pressure as high as possible but there are plenty of -ve's if you go low. I've blown a few tyres and the dealer puts this down to storing the boat in a tropical shed which is always over 35C. He reckons I should only get 2-3 years out of a tyre in these conditions. When I leave shoes in the shed the soles peel off after a few months.

[BaysideMarine]

Most light truck tyres are rated to 60 or 65psi and generally speaking are best run at those pressure.

These are 8 ply tyres and are engineered to cope with the higher pressure which enables the higher load bearing capacity.

Run them at lower pressures and you are actually unduly loading the sidewalls instead of the tread area and you will reduce the tyres lifespan.

Many years ago I managed the workshop of a major tyre retailers store in Oakleigh, Melbourne and 8 ply tyres were always run at or very close to their maximum rated psi as technical discussion with the manufacturers suggested that max pressure in an 8 ply would ensure longevity.

Cheers,

Nicholas