What pressure in trailer tyres?

Timbow

Timbow

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Two tons of boat on a trailer, so say 2.2 - 2.5 tons total on two axles, four tyres in all. What tyre pressure should I give them (with the load on) before setting off down the motorway. Or how would I find out or calculate the recommended pressure?

I let down the tyres a bit when I bought this boat on a trailer 12 months ago because the coach roof was just scraping the lintel on the barn door when I was delivering her to storage. Now I want to launch her and will have to pump up the tyres again once I get outside but I can't remember what pressure was in the tyres. It might have been 100psi but it seems a lot. I have a compressor which I think will do the job.

Tim W
 
I don't know the direct answer to your question, but the tyre will almost certainly have marked on it the maximum pressure. I suspect this will be below 100psi. Having the tyre pressure too low will cause overheating, potentially damaging the tyre and causing premature failure, and uneven wear of the tread (on a car or bike it would also affect handling). Having it too high will lose you a little grip, but in the context of a trailer I would not have thought this too critical, and if it were me I would err on the high side and, in the absence of other info have it at or close to the manufacturer's maximum pressure.

You could search for the tyre manufacturer's recommendation for pressure for the weight each tyre is carrying, or use another manufacturer's recommendations as a rough guide.
 
Tyre pressure

I would suggest about 35PSI. ie what is normal for the tires on a vehicle plus a bit. If the tires are overloaded they will look a bit bulgy at the bottom so try to round them out a bit but beware too much pressure.
olewill
 
I previously owned a similar weight boat and often towed it on long journeys, over 2000Km ,in Australia, over some rough roads.
The pressures needed to be high for the tires to survive. From memory I ran them at 47psi. I suspect your requirements are less demanding, but rated tyer load goes up with pressure and your tire load is high. I would inflate them to a much higher pressure than your car tires.
 
Look at the tyre sidewall you will see something like 205 50 R 15 91 V E4


205 Width of the tyre in millimetres
50 Height of the tyre sidewall as a percentage of the width. In this case 50% of 205mm. Also know as the aspect ratio.

R Radial Construction
15 The diameter of the tyre's inner rim in inches

91 Load Capacity of Tyre (See Load Table). In this case its 615kg

V Speed Symbol. Indicates the max. speed for the tyre at full load. In this case 149.1mph.

E4 ECE type approval mark, which demonstrates the tyre has been tested as high quality by the European Regulatory Authorities

With that info you can find the max pressure on the WWW.

If the tyre is made to be sold in the USA the max pressure is also shown on the sidewall.
 
Look for the ply rating, you should be looking for up to 8 plies, with C in the description. You should be looking at about 55psi. 2.5 tonne is a lot to loose control of on the motorway.
 
With a boat that weight they should be at least 8ply van rated tyres. 4ply car tyres will be far too soft, and even at maximum rated pressure will cause the outfit to roll badly, even if they are within their rated load. Had a 1 ton boat with car tyres on the trailer, and anything over 30mph it became a total pig for handling. Soft tyres can seriously affect handling, and will cause the tyres to overheat and possibly burst. Over inflated tyres will give a very harsh bouncy ride with possible damage to the boat. The maximum pressure they are designed to take will be somewhere amongst all the information embossed on the tyrewall.

8ply van tyres usually run in the region of 50 - 60psi. Make sure the tyres fitted are rated as sufficient for the all up weight: if plod check you this is one of the things they look at. If the all up weight (i.e. with the outfit in running order is put on a weigh bridge) is over the tyre rating you will be taken off the road with a 'dangerous load' and given a 'stop notice' which means you cannot continue until the fault is rectified. Put the outfit on a public weighbridge to check you are not exceeding rated limits if there is any doubt - you might be surprised how much added weight there is with the gear on board! My 1 tonner on its trailer, with o/b engine and gear aboard came up 40% heavier! If stopped and they suspect you of exceeding weight limits you could have to go with them to have it all weighed.

I used to live near one of the official vehicle checking points on the M5, and regularly saw larger caravans, boats etc being pulled off the Mway for comprehensive and detailed checking for roadworthiness. Having said that, in 30 years of towing boats and caravans I was never once 'pulled'.
 
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It should state on the tyre, max load at certain tyre pressure. As you can see from Lakey's table the pressures vary. On my 3500kg plant trailer on 4 tyres which are 6.00X9 10 ply tyres the capacity is 2205lb (1000kg) each at 116psi. Garage pumps don't appear to go much above 50psi.

I shreded an almost new tyre which must have developed a slow punctue in a 15 mile journey, Do not attempt to drive with such a weight on tyres not correctly inflated.

This is the table I consult.
http://www.tyreline.com/trailer_caravan_wheels_tyres/hs_trailer_tyres.aspx?Page=1

This shows how you have to know the pressure for each specific tyre. Compare the data for my Michelin tyre above with the same size tyre and ply these people on the above table sell, namely 6.00X9 10 ply, 1402kg and 102psi, much different from mine!!
 
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I had to get two new tyres for my 400/8 tyred trailer yesterday and asked the same question. The chap said the max pressure is set by the wheels, the ACTUAL pressure is set by YOU. If the boat bounces, make them softer, if it squashes the tyres make them harder. He said there ARE ways of calculating it scientifically, but at the end of the day its RIDE you are concerned with and thats all.

400/8 max press is 100psi.

HTH

David
 
don't forget that tyre pressures should be checked with the tyre at ambient temp ("cold"), not after a run. Height above sea level (probably not a factor in a boat trailer !) and the ambient air pressure will also affect the pressure you put in.

Max pressure is clearly stated on the tyre wall, in relation to the max tyre load - which may differ from the max wheel loading.
 
Timbow said:
Two tons of boat on a trailer, so say 2.2 - 2.5 tons total on two axles, four tyres in all. What tyre pressure should I give them (with the load on) before setting off down the motorway. Or how would I find out or calculate the recommended pressure?

Tim W
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57 psi for my 4-wheeled trailer with an all-up load of 3 tonnes.
 
BTW 250Kg for a trailer to carry 2 tonnes and having two axles is gross under estimation of both the all up weight and tare weight. I have not seen the trailer, but I would estimate, between 0.75 and 1 tonne. If it is much lighter, it's gonna flex, possibly catastrophically. So your all up weight is possibly closer to 3 tonnes
 
Bobobolinsky said:
BTW 250Kg for a trailer to carry 2 tonnes and having two axles is gross under estimation of both the all up weight and tare weight. I have not seen the trailer, but I would estimate, between 0.75 and 1 tonne. If it is much lighter, it's gonna flex, possibly catastrophically. So your all up weight is possibly closer to 3 tonnes
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I was thinking that too as it's way different from my combination. My boat is 1800kg. The boat sits on a trolley which sits on the trailer. Both trolley and trailer are pretty hefty. Trolley+trailer is 1200 kg, so all up is 3000kg.

Never been brave enough to tow it myself, got a professional to do it for me from Scandinavia. Don't fancy trying to get that mast round tight corners.

trans3.jpg
 
Bobobolinsky said:
BTW 250Kg for a trailer to carry 2 tonnes and having two axles is gross under estimation of both the all up weight and tare weight. I have not seen the trailer, but I would estimate, between 0.75 and 1 tonne. If it is much lighter, it's gonna flex, possibly catastrophically. So your all up weight is possibly closer to 3 tonnes
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U R right to point this out. I have not put it on a weighbridge. The previous owner told me he thought 2.2 tonnes which I think is an underestimate. Folkboats have a designed displacement of around 2 tonnes and I might estimate 500kg for the trailer. In any case the axles, tyres and hitch are all badged up to 3000kg and the car is rated to pull 2800kg so we will pump up the tyres to the correct pressure, leave very early in the morning and driving with great care we will be alright thanks. The 100mile trip from the vendor to my place 12 months ago was fine although done with a heavier towing vehicle.
 
Be very careful....

Tyre ratings eg

165/80/R13 common trailer tyre rated 487kgs at MAX pressure 35psi

165R13c tyre on same rim rated 670kgs at 54 psi MAX(commercial 8 ply)

Had to uprate our trailer to carry a supposed 1.5tonnes trailer sailer design weight.

Boat has got heavier with additions, modifications and age nearer 1.75 tonnes now:eek:

We are still on the limit and have to put as much kit as we can in the Tow vehicle eg o/bs, anchor and chain, warps,flubber dink,gas bottle.

Make sure fuel (25-30 litres) and water (50 litres) =80kg are empty or low.

It is easy to add another 200-400kgs of kit to the boat load.

Also take into consideration how well balanced load is as if boat COG is much forward of COG of trailer then your nose weight will be excessive and load on front axle will be much higher and vice versa.

If pulled plod will check weigh each axle if stopped and if you are too high for tyre rating you dont get home until load is adjusted or tyres uprated.


I would not have left the full load on those tyres after deflating. Very bad for side walls. You are supposed to jack up and take load off during storage even when fully inflated.

Black poly bag over tyres if left in sunlight helps stop uv degradation and sidewall cracking.
 
TSB240 said:
If pulled plod will check weigh each axle if stopped and if you are too high for tyre rating you dont get home until load is adjusted or tyres uprated.
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Only if plod is a real Construction and Use anorak - most unlikely nowadays. However if these boys stop you then it might just be a different story.

The Vehicle and Operator Services Agency (VOSA)

I used to carry a 22 foot hang glider on a Triumph Herald with significant front and rear overhangs and was stopped regularly by traffic police who only had the vaguest knowledge of what was legal BUT were sure I could not be legal. [ At that time it was 3'6" rear and 6' front different now. ] I used to know and quote the relevant para of the CU regs to them as a last resort.

Even senior plod did not know the overhang rules.
 
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