Tyre pressure

[Adam and Hayley]

I’m sorry to ask such a stupid question but im really not sure what pressure I should be running the trailer tyres at!

It’s a twin wheel trailer
Boat + trailer and sundries = 2000kg
13” rims
Tyre wall says max psi is 65

Any suggestions?

[beamishken]

Go with the 65psi tyres are only run lower on cars for comfort and even tyre wear neiter are much of a concern on a trailer keeping the flex out of the tyre helps them run cooler

[jonp]

I go 37 on mine so it doesn't shake the crap out of the trailer.

[jambo]

I go 45 on mine

[neil.mccrirrick]

65 on mine twin wheel

[Pikey Dave]

60 on my twin axle

[Adam and Hayley]

Thanks for that everyone

[treerat]

Have a look at this link, scroll down till you get to the tyre pressure bit

http://www.rib.net/forum/f49/trailer...cky-44849.html

[charliee]

I go 85-90 PSI with 195/60/12 Maxxmiler tyres on 5 x 6.5" rim so not very relevant but it show the range of options.

[jeffstevens763@g]

mine states 360kg at 70 psi

[beamishken]

Trailer manufacturers tend to spec tyres to the trailer load and not much more. Simple economics dictate that smaller lower rated tyres are cheaper the tyres achieve their max rating at max psi so unless your trailer is significantly over rated for the load then tyres should be close to the max stated on the sidewall
Running lower pressure means more flex in the sidewall causing heat and eventually failure

[jonp]

Originally Posted by beamishken

Trailer manufacturers tend to spec tyres to the trailer load and not much more. Simple economics dictate that smaller lower rated tyres are cheaper the tyres achieve their max rating at max psi so unless your trailer is significantly over rated for the load then tyres should be close to the max stated on the sidewall
Running lower pressure means more flex in the sidewall causing heat and eventually failure

Most manufacturers spec boat trailer tyres with heavy duty truck tyres this side of the pond, anyone who has cheap Chinese types on their rig should consider ditching them for light truck tyres.

[beamishken]

Originally Posted by jonp

Most manufacturers spec boat trailer tyres with heavy duty truck tyres this side of the pond, anyone who has cheap Chinese types on their rig should consider ditching them for light truck tyres.

But the majority of us who are not in Auz have trailers manufactured where the tyres are matched to the rated load. Not many if any European trailer manufacturers overspec trailer wheels and tyres hence most of us need to keep the pressures close to those printed on the sidewalls
Even premium brand tyres will fail if under inflated not just chinese tyres

[_monkey]

***Thread resurrect warning!

I'm trying to work out the correct pressure for the trailer tyres. It's a twin axle 2T rig with 155/13 84N tyres (kenda kargotrail 3g 155/80 r13 84N).

- tyre sidewall states max 50PSI.
- docs from the trailer maker - De Graaf - states 38PSI
- NTTA states 35PSI for 60MPH and 32PSI for 80MPH https://www.ntta.co.uk/law/trailers/load-pressure

The internet suggest stick with whats written on the tyre, but I'm concerned the trailer maker doesn't seem to agree!

Any tyre experts care to comment?

The NTTA site also states the axle load is 935 @60MPH and only 850 @ 80MPH - which is a bit of a worry.

[jeffstevens763@g]

80 MPH towing a trailer

[beamishken]

Whats the maximum load printed on the tyres? If the load is maxed out or close then you need to be at the max printed on the tyre. If the tyres are "over spec" for the load ie they can carry significantly more than the trailers capacity then go with the lower pressure reccomend by the manufacturer.

[The Black Pig]

Originally Posted by jonp

I go 37 on mine so it doesn't shake the crap out of the trailer.

If I ran miy empty trailer on 65 it would spend most of the time in the air down the lanes

[Striker]

If you run at the tyre maximum pressure you will in effect be assuming that the tyre is carrying its maximum designed load (load index stated 500kg each). If you’re not running at that weight you will have the tyres too hard and will be transmitting excessive shock into the trailer / boat. The tyre is a key part in the suspension. You will also wear the centre of the tyres out and reduce the contact area with the road (grip).
Given that the trailer manufacturer has specified a pressure I would run at that. Do the tyres look soft at that pressure? Sometimes you find either the front or rears look soft even though at the same pressure which can indicate your tow ball height is low or high, but so long as it’s not an excessive bulge it will be fine.

[_monkey]

Originally Posted by beamishken

Whats the maximum load printed on the tyres? If the load is maxed out or close then you need to be at the max printed on the tyre. If the tyres are "over spec" for the load ie they can carry significantly more than the trailers capacity then go with the lower pressure reccomend by the manufacturer.

Tyre load index is 84 or 500KG, which is correct for a 2T twin axle trailer.

The max PSI printed on the tyre sidewall is 50PSI which I assume is required when the tyre is supporting it's max load.

I can't understand why the trailer manuf. states 38PSI though.

[beamishken]

Originally Posted by _monkey

Tyre load index is 84 or 500KG, which is correct for a 2T twin axle trailer.



The max PSI printed on the tyre sidewall is 50PSI which I assume is required when the tyre is supporting it's max load.



I can't understand why the trailer manuf. states 38PSI though.

Yeh doesnt make sense the tyre is rated to carry its max load at max pressure. It usually states max pressure cold to take account of expansion when warm. Running under pressure risks overheating the tyres and causing damage to the tyre structure