Trailer tyre pressures

[Drumster]

Not sure if this is a daft question or not, but you'll soon tell me......

I recently upgraded my tyres to 8 ply on my twin axle trailer and noted that the the tyre wall said max psi was 65 and the load rating is 84 i.e 500kg per tyre. As I purchased the tyres and wheels together they were already inflated to 60 and i left them at that.

On the way to Curborough this weekend I could feel the firmness of the tyres through the tow car especially on the old part of the SW section of the M25 which is still largely concreted sections where the joins have long since lost there 'stuffing' to the point where the journey was fairly uncomfortable.

Anyway, by the time I'd got to Curborough one of the wheels was too hot to touch as the brakes were binding. On Saturday evening Mike Cocker kindly had a look for me and removed the hub ans we were pretty sure that the reason for the brakes binding was that one shoe had jumped out of its retaining slot at the top causing the brakes to self-adjust to the extent we could replace the hub. We then removed the brakes shoes for the return journey. 

So if the tyre pressures were too high and the trailer was 'bouncing' over bumps could this have caused the shoe to dislocate?

Having spent a bit of time searching the internet tonight and finding that there is a wealth of misinformation from one forum to another regarding trailer tyre pressures, I wondered what peoples thought were here.

I did find this tyre pressure calculator which was suggesting that for my given situation the pressures should be as low as 36psi , which is pretty similar to what I was running on my old Brian James supplied tyres.

Grateful for any advice as always....

[bosshogg]

I think everything you have said in your post is correct. I tow with different trailers regularly, and ride quality is severely compromised by over inflated tyres. They should be adjusted to the load being carried. That calculator you have found seems a good source to use. The worst trailer I have is an ifor williams with low profile tyres (to reduce the loading height), and even though it has suspension, it has a high load capacity, so the tyre pressures are high, and when towed with no load on it jars and bounces over every lump in the road.

Alastair

[anthonym]

I run my BJ Minno Shuttles with 2.4 bar (36psi) as per the "plate".. Never occurred to me to change that for 8 ply tyres.

[Paul Richards]

36psi. 

[Guy Lowe]

I have a twin axle PRG Mini Sport with a MGW OF 1500Kgs. The tyres are 10" 8 ply with a load rating of 79 and I run them at 38psi. Using Chris's link to the calculator it comes out at 39 so about right & it tows well, but I do tow it with a brick 

[elie boone]

I have a Fountain single axle with 13" wheels and the tyre pressure i use is 2.8 bar that is 40.5 in old money

[ECR]

The tyre pressure calculator in the first post is very useful ...

The only reference to tyre pressure that I had was on the trailer serial number plate and given that the maximum pressure marked on the tyre was 65psi the plate figure of 65psi seemed way too high. I've been running at around 50 but the trailer can be very "bouncy" at that. The calculated pressure using the link above, and given the all up weight of the trailer, is actually 36psi.

This seems a lot more sensible and I shall be interested in the results.

Thanks for the link (perhaps this should be included in the guides section ....)

[Shaun_E]

Guide added here.

[ECR]

Thanks Shaun, I'm sure this will help others