Trailer Tyre Pressures

[Wezza]

Just wondering what pressure everyone keeps their tyre pressure at. I had mine on 32psi but found it was all over the road at 80kms. So I put it up to 38psi and now it seems to be fine. I have a 5.3 meter glass half cab on a single axel trailer, so it is a heavy load on the two wheels, I was just worried about blowing a tyre. ???

[billfisher]

The correct pressure (cold) will be printed on the sidewall and will vary according the model. Some makes require 60 psi. It sounds like you are just guessing what the pressure should be. Always fill to the recommended pressure as underinflation can lead to overheating and blow-outs.

[nisrol]

wezza
i keep mine at 28-32 psi but i have a duel axle trailer and this seems to ride fine behind the 4by

[klyons]

Tyre pressure will depend on the weight carried. Simple trial and error will soon reveal the best pressure. Too much and the trailer will bounce over every little bump, not enough and the trailer will be heavy to pull, tend to wander and the tyres will overheat. The pressure marked on the sidewall is the MAX pressure the tyre can be safely inflated to.
Put simply, more weight, more pressure.

Kev

[billfisher]

You should always inflate to the max or close to it, regardless of the weight of the trailer. The manufacturers tell you this by usually having a warning on the sidewall stating that under inflation can cause injury or death. If the trailer is then wandering or bouncing around it is because of some other problem with the trailer set up, not the tyre pressure.

[steve_n]

I tow my boat which is around the same size as yours to Rainbow Beach and set tyre pressure at 50psi. Max recommended is 64 cold. Tyres dont get hot and even with a small load it travels good at 100kph. Probably depends on what tyres you have though, mine are 185 X 13 Nankang? steel belted.
Cheers

[banshee]

I'm with Billfisher,Fueled and loaded to go fishing my boat/trailer comes in at a frag under 1400 kgs,I have a single axle trailer and run 60 psi,I would run 65 but can't find a pump around town that can get there.

[searaider]

I tow my boat which is around the same size as yours to Rainbow Beach and set tyre pressure at 50psi. #Max recommended is 64 cold. Tyres dont get hot and even with a small load it travels good at 100kph. Probably depends on what tyres you have though, mine are 185 X 13 Nankang? steel belted.
Cheers

Geday Wezza ,
I have the same tyres as steve_n (attached quote ) , on a dual axle trailer & an all up boat & trailer load of around 1900kg. I also run 50psi & check the pressures at home when the tyres are cold .
As stated by the other guys , check the pressure rating on the side of the tyre . Note how the maxium cold pressure is based on a maxium load rating on the tyre .
I'm pretty sure mine is something like 64psi cold on a maxium tyre load rating of something like 875kpa .

Even if I pumped the tyres up to the maxium of 64 psi , the 4 tyres combined could carry a maxium of 3,500kg .( this is well over the load rating of 2,000kg for the trailer )

I'm pretty sure that the maxium load rating of your trailer , would be well under the combined load rating of your tyres at the recommended maxium pressure .

TIME TO HAVE A LOOK AT THE WALLS ON YOUR TYRES AND SEE WHAT THEY ARE RATED AT .( Max Pressure & load )

Note they talk cold tyres for their maxium pressures .

Peter
Searaider 2

[billfisher]

I don't think some people realise that that load on your tyres is constantly changing. It is not a good idea to underinflate because you think you are well under the maximum load rating. In fact you are flirting with disaster. When you go around a bend the weight will shift from one side to the other, and a bend is not a good place to have a blow out.

[cooky]

this little post has been very helpful - I've been wondering what my tires should be at. I think I'll go out and pump the buggers up.

[steve_n]

Yes very informative.
So what do you reckon the best pressure would be? Should you start off at the max cold pressure and not worry about increase as tyres warm? ??? ???
Now I'm confused

[billfisher]

Yes, all you have to do is inflate to the max cold pressure (while the tyers are cold of course). The specification takes into account that the pressure will rise when the tyres are warm.

[klyons]

You should always inflate to the max or close to it, regardless of the weight of the trailer. The manufacturers tell you this by usually having a warning on the sidewall stating that under inflation can cause injury or death. If the trailer is then wandering or bouncing around it is because of some other problem with the trailer set up, not the tyre pressure.

I consider this advise dangerous in the extreme.
Over inflated tyres on a lightly loaded trailer can and will lead to potentially deadly bouncing and loss of control. A trailer carrying 1.5 t of boat requires more pressure than a trailer carrying a 12 foot tinny.
In the case of the original poster, he needs somewhere around 50 or 60 psi. My tinny runs fine and well and safely with 22psi. Pumped to 28psi causes it to attempt to change lanes with every bump! The tyres MAX pressure is 32psi.
There is no simple answer to what pressure should be used,. Different trailers, single/dual wheel/light or heavy boat, LT tyres or pass tyres all require different pressures within the manufacturers recommended range.



Kev

[billfisher]

Klyons,

It sounds like your reducing tyre pressure to compensate for some other problem. I also have a 12ft tinnie and run my tyres at 60 psi (max pressure) and hardly notice the tinnie is there. The max load rating is also way above the weight of the trailer/ boat combination. I have also had several other tinnies and have not encountered the "deadly bouncing" and "loss of control" you have described. I don't doubt you could get away with under inflating light rigs but I don't think you should have to, from my experience.

Anyway my comments were mainly directed at heavier rigs where you usually have little leeway with regard to maximum load. Bear in mind that your rig should be 20% lighter than the maximum load for the tyres due to the weight transfer effect I have descibed. #

Also weight is just one factor. Speed and ambient temperatures are the other two. If you are doing prolonged#high speed runs, particularly on a hot day, it is critical not to underinflate.

[klyons]

My tyres are NOT underinflated.
This is the whole point I'm trying to make. In 23 years of being a mechanic I've seen most things and the damage caused to vehicles by running grossly overinflated tyres is very real and dangerous. Why, do you think, do manufacturers have 2 recommended tyre pressures for vehicles like utilities- -1 for light loads, one for heavy loads. The sidewall of a tyre is designed to flex to help absorb road irregularities. Inflating a lightly loaded vehicle/trailer tyre will transfer a far greater amount of shock to the vehicle.
The max pressure of most car tyres is around 45psi. Now, go pump your pass car front tyres to that pressure and go for a drive. I would not recommend you do this for long . I've seen broken lower control arms/ ball joints/ collapsed wheel bearings as a result.

Kev

[billfisher]

Klyons,

Where did you get the 45 psi front tyre pressure from ? My Ford (not an uncommon car) manual states 30 psi for normal load and 30 psi for maximum load and add 4 psi for consistent high speed operation. This would suggest tyres are designed to operate at a narrow range of pressures. I take it you are recommending a large % drop in pressure. What about the fact that lighter trailers also have lighter springs ? This is where your car analogy falls down. Also I havent seen a safe minium pressure on a trailer tyre.

Anway the original post and my reply refered to a much heavier rig than a 12 foot tinnie. If you get away with the lower pressure well and good but there is a world of difference compared to larger rigs, nearly all of which have little leeway with regard to maximum load. In this case you have no choice but to inflate to the maximum.

[klyons]

The correct pressure (cold) will be printed on the sidewall and will vary according the model. Some makes require 60 psi. It sounds like you are just guessing what the pressure should be. Always fill to the recommended pressure as underinflation can lead to overheating and blow-outs.


Now your reading the manual and not the sidewall .Good move. Check the sidewall on your car tyres and you will see the difference between the Max tyre pressure and the Ford recommended pressure.

Kev

[billfisher]

The tyre says 44 psi max so you have a point, but it doesn't really change the thrust of what I have been saying. You can't just transfer this to any boat trailer.
The NRMA site has advice for trailers and towing and it states that underinflation is the main cause of misahaps and blowouts. Boat trailers don't come with a manual recommending pressures. And most of them are far closer to the limit than car tyres. If you want to optimise the tyre pressure then always start with the maximum load pressure. Then drive for one hour at the maximum recommended speed (usually 100 kph). Now check the pressure, it should have risen by 4 psi due to the increase in temperature. If it has risen by less than 4 psi you have room to deflate. If it has risen by more than 4 psi they are showing signs of overheating and may not be up to the job.

[macca]

Geez Guys

I think we need to call in a Tyre Expert from the trade. ;D

So we can settle you two down!!! ::)

Who can we call?

Macca

[Woody]

Will I catch more fish with under inflated tyres than I will with over inflated tyres cause I'll try it .
Wade ;D ;D ;D

[joeT]

I agree with Klyons, the pressure you inflate your tyres to should be in accordance with the prevailing conditions: weight of trailer, tyres, trailer and towing conditions. Just as an example, passenger cars usually inflate to 28-35psi, commercial vehicles (utes, vans) between 40-55psi, pushbikes and hand trolleys usually 50-60psi. The pressure required is all proportional to the size (and design) of the tyre, and the weight on it. But you also need to take into account the conditions such as speed.

There is no hard or fast rules, the max pressure the tyre is rated at is a good guide, but remember it is the MAXIMUM pressure, don't exceed it. The maximum pressure is usually only needed where the tyre is put under its maximum rated weight.

Heavy rigs of close or over 1 tonne will definitely need higher tyre pressures (perhaps 50-60psi) than a tinnie weighing 300kg (perhaps 20-30psi), but it will really depend on the factors mentioned above. Its a shame that trailer manufacturers don't have recommended pressures for certain weights.

[Fishinmishin]

OK. Here's how it is. After 3 pages of slightly correct babble I'm gonna tell you the right way. It takes a bit more time originally, but calculates the correct pressure taking into consideration the load and all other factors. Do this test with your usual load carried.
Check thecold pressure and note.
Drive several KMs to bring to operating temp and check again.
Ideally they should be about 4psi above the cold pressure.
If pressure is above 4psi over cold pressure you need more air.(due to too much wall friction)
If they are less than 4psi above cold pressure, the cold pressure is too high.
If the end result is above recommended max tyre pressure noted on the sidewall(NEVER exceed that reading), then your tyres are not correct and a larger model or thicker walled model or just duel axils or duel fittings are required. Check treads regularly as if tread is wearing on the outsides then pressure may be too low and vice versa if wearing in the center of the tread.
From your ex-mechanic, and with help from mate(tyre fitter).
Safe driving to you. Jay :)

[billfisher]

Fishinmisin,

Isn't that almost exactly what I said in my last post? I think your wrong on one detail, you have to drive for more than a few kms to warm them up fully. The NRMA recommends one hour, preferable at highway speeds. #

[Wezza]

Well, it seems their is a differance of opinion. Well what I ended up doing is inflating the tyres to 40psi and drove to Hervey Bay and back with no dramas at all. The trailer rode beautifully at 100kms. Thanks guys, I will however check next time after I have done some driving to see how much the tyre pressure has gone up. ;)

Wez