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JRad

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Reply with quote  #1 
Ok so heading out to use the 345 for the second time, fingers crossed all goes well with the trailer.

So what's the standard road going tyre pressure?
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William the Conqueror

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Reply with quote  #2 
JRad

What is the weight of the trailer - loaded?

What size are the tyres?

Once known, I can work it out for you.

Cheers

Anthony

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JRad

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Reply with quote  #3 
Hi Anthony

Unloaded is 490kg max weight is 1,500kg, so I'll think once loaded 1,100kg? Can't be 100% on that.

Tyres are 245/70/16

JRad

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William the Conqueror

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Reply with quote  #4 
Sorry JRad

I gave you a bum steer.

I was using my load v pressure chart which considers the vehicle having four wheels. Caravan/trailer calculations are slightly different.

Can you have a look on the tyre and find the following information

Max tyre pressure (may say max inflation) and the Max load rating (will be in kg)

Use the following formula and you will get an approximate pressure.


max tyre pressure divided by max load rating times actual load per tyre (in your case it will be approx 550kg per tyre)

For example (450Kpa / 950kg) x 450kg = 213kpa

If you want to convert kpa to psi

kpa divided by 7.1 = ? psi

For example

213 kpa/7.1 = 30 psi

Hope this helps

Cheers

Anthony

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JRad

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Reply with quote  #5 
Hmmmm

360kpa / 975kg x 550kg = 203..08kpa

203.08kpa / 7.1 = 28.60 psi

Seems a bit flat doesn't it?

I was thinking they'd at least be around 36psi?
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TGoTS

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Reply with quote  #6 
Hi JRad,
I also have a 345, and I have always run mine at 36psi on the highway.
(fitted with Bridgestone Desert Duellers from factory - same size as yours)

Lower of course on sand/gravel depending on the particular conditions.
From memory we ran up the Birdsville track down around 26psi, but the track was in very good condition.

Not sure if that helps you, but we have not had any tyre issues - she is so light..!

Regards,
Ben


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Regards,
Ben
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JRad

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Reply with quote  #7 
Thank you Anthony and Ben, just a bit nervous using the trailer, things didn't go so great last time.

It's all good though, it'll be a new year and new adventures.
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Lightning2012

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Reply with quote  #8 
Hi Jarrad,

I trust everything finally got sorted for you so you can finally use the trailer as it is intended to be!

Same as Ben for tyre pressures but as Anthony says trailer weight is important. I go 36 on highway, 26 or so on dirt gravel and down to 15 on sand. Just a start point and vary accordingly as I go!

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Simon & Sharon (plus 2 kids somewhere....)
UEV 345 and New Toy! (2018 Toyota 79 Series Dual Cab)
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JRad

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Reply with quote  #9 
Hi Simon

Just opened it up to air out on the weekend, the canvas repairs look ok.

Will have to see how it all goes on hols..

Fingers crossed.

Merry Christmas to you and the family.
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William the Conqueror

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Reply with quote  #10 
Your right JRad

That is very low. Off the top of my head I would have been looking at around 36-38+ psi for highway running depending on load. I will have a chat with my tyre fitters and see where that formula has gone wrong.

I am presuming you are running the standard Desert Duellers 245/70r16  as supplied.

There is another method using the increase of 4 psi per tyre. This is what I use to work out all my tyre pressures.

  1. Inflate the tyres to the recommended pressure (as a cold pressure i.e dont move the trailer)  (start with 36 psi)

  2. Tow your trailer for approximatley 100Km, preferably on a highway at your normal tow speed (this will warm them up)

  3. Recheck the tyre pressures immediately after pulling over. Compare them with the the cold pressure you had at the start. If the pressures are right for the load carried, the hot readings should be 4 psi higher than the cold start readings. (no more than 4 psi increase)

  4. If there is more than 4psi difference between the hot and cold pressures, the cold start tyre pressure is too low and needs to be increased. (>4psi difference - increase the cold start pressure)

  5. If there is less than 4 psi difference, the cold start pressure is too high and needs to be lowered.(<4psi difference - decrease the cold start pressure)


    Cheers

    Anthony



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Kelvo

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Reply with quote  #11 
Quote:
Originally Posted by JRad
28.60 psi

Seems a bit flat doesn't it?

I was thinking they'd at least be around 36psi?


This is the reason trailers get damaged, people think the pressure looks too low and increase it to make it 'look' right. As an example my LR Discovery has front tyre pressures based on factory tyres as 28psi this has been calculated and tested by the factory at design stage.

Using the figures in your post the suggested cold pressure is 29.5psi or 203kPa.

I would then use the 4psi rule to fine tune the pressures as Anthony as explained. Being your max inflation pressure is only 360kPa I'll assume that they are 'Passenger' construction tyres and not LT (Light Truck) construction. If you have LT tyres you should use the 6psi rule.
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