Trailer tyre pressures

lovezoo

lovezoo

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I've got a twin axle 2 tonne trailer (SBS 4/2000) with 165/80 R13 tyres on it. Anyone know what the tyre pressures should be?

At the moment they are all over the place (30-45psi) so was hoping someone on here might know as I don't really want to guess /forums/images/graemlins/confused.gif
 
The girl at SBS didn't sound too sure of what she was saying, which didn't give me confidence. On the Brian James link, they have two pressures for 4 or 8 ply, which could explain the different numbers:-

165 R13 4-ply 2000 36 2.5
165 R13 8-ply 2600 54 3.75

Next question, how to tell whether the tyre is 4 or 8 ply?
 
I'll have another look at the tyres tomorrow and see if I can find a max pressure rating or something that indicates what ply they are. Definitely looks like they only need be 4 ply for the weight of the trailer, which would suggest the lower tyre pressure values.
 
From another tyre website...

[ QUOTE ]
The correct pressure to inflate your vehicle's tyres to is the one recommended by the vehicle manufacturer, not the maximum pressure found on the tyre's sidewall.

[/ QUOTE ]

- it should also be noted that the Max Pressure and Max Load markings where present are only valid for the USA not UK/Europe /forums/images/graemlins/wink.gif
 
If I may post an anecdote re: trailer tyres........
Many moons ago my dad decided to retrieve a mirror dinghy that had been sitting abandoned (well it had been there for months and months) in the depths of the scottish countryside (and miles from any water).
Off we set with the trailer and duly lifted the boat on to the back of the trailer (we even left a note!) and started to trudle it home.
About twenty minutes into the journey, there was a massive bang as one of the trailer tyres blew out. With no spare we decided to remove the offending wheel and leave the trailer at the side of the road, then return the next day to carry on.
Dad popped into Kwik Fit or the like and explained that he wanted a replacement tyre as this one had exploded at speed. The guy from KwikFit looked a bit perplexed and asked "So exactly what speed were you travelling with your wheelbarrow?????" Needless to say 2 new trailer tyres were purchased and the boat arrived home later the next day.
 
Another site gives different and possibly more realistic pressures, based on the weight they are carrying around the 44-49 psi range. Thule

Personally I find that rubber bonded suspension units harden during periods when they aren't used (boat trailers especially) and a slightly lower tyre pressure give the load a much softer ride. I reduce pressure until the load stops crashing about.
 
Tyre pressure is largely about, what your trying to achieve.

The reverse of most thinking is true. Lets say, very hot weather, heavy load. Obviously dependant on what tyres can stand. But the more pressure the better. We used to struggle in Saudi, finding pumps that would give us 130 lbs or near.

It's the flexing that get tyres hot and blows them, so less flexing the better. Might be a bit bumpy tho...
 
I can see that. However the tyres would need to be at or near their limit to be effected by a bit of squirming.
Still, if you must have big, heavy boats........... /forums/images/graemlins/grin.gif
 
I have the next size up of SBS trailer, twin axle jobbie and I always tow with at least 50psi in the tyres when the boat's on, any lower and the tyres are clearly too soft which just makes them overheat. Also if they're too soft then the fuel economy takes an even bigger battering. A friend dragged it 200 miles for us last year and going from 50 to 60 psi made his journey easier and the fuel economy rise by the dizzying heights of an extra 2mpg /forums/images/graemlins/tongue.gif

Just remember to drop them down to ~30psi if towing the bare trailer as it'll bounce all over the shop if you're not careful.
 
4 ply 13" tyres usual have an axle load around 800 -900 kg, depending on manufacturer. Not enough for a twin axle 2 ton trailer. The 4ply sidewalls will be too thin, and even if they can take the weight, the loaded trailer will be a pigs ear to tow, as it will wallow all over the place.

8ply tyres - sometimes known as 'van tyres' for obvious reasons, will not only have a load rating something like 50% more, but the stiffer sidewalls will give a much more comfortable ride.

Pressures will depend largely on the actual load being carried, but they should be inflated enough so that the sidewalls are not flexing too much under the weight, and should look something similar to the rear tyres of your car in running trim. Maximum allowable pressure will be on the tyre somewhere - it has to be by law, together with maximum axle load, and maximum pressure. 13" 4 ply usually have a pressure maximum iro 35 - 38psi

As has been pointed out, over inflated tyres will make an empty trailer bounce around all over the place.
 
Thanks for the replies. I found the tyres have a max pressure of 44psi on them, so I will go with the 39psi suggested and see how the trailer feels.

I think these are the tyres on the trailer:

http://www.trailerpartswarehouse.co.uk/trailer_parts/Wheels_13__info_87.html

These ones say 4 ply and have an axle load of 1045kg, which is just enough for the trailer. I'll let you know if I make it.
 
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