Tralier Tyre Pressure

[Stemar]

I'll be towing my new (to me) Mirror 100 miles this Friday. It's been standing for a while, so I need to check the pressures but, apart from a vague memory that they should be quite high compared with the car's, I don't know what they should be. Can anyone help, please?

It's a pretty ordinary combi trailer.

 

[VicS]

I take it this is a Mirror 10 ,, not a Mirror 16

From my trailer book

For the common 8" diameter small trailer wheels
400 x 8, 2ply, max load per tyre 380lbs, max pressure 30psi

400 x 8, 4 ply, max load per tyre 600 lbs , max pressure 65 psi

The weight of a Mirror 10 plus trolley plus trailer must be well within the limits of the 2 ply tyres. I might go to 30 psi, but no more even with 4ply or 6 ply tyres.

Also so long since I trailed my Mirror I forget what pressure I did use

 

[sarabande]

no real weight, but I expect about 40 psi. The tyres will have the rating and max pressure printed on the outer wall.

You don't want them too hard, otherwise the dinghy may bounce around on the suspension, especially if your torsion rubber units have had the boat sitting on them all winter, and hardened.

 

[blackbeard]

If these are the usual 8" x 4" tyres, pressure should be quite high (about 50 psi) if you are towing a heavy-ish load but for a Mirror could be a lot less; I have found about 30 or 35 psi seems to work with a GP14 which will be heavier than a Mirror. Too much pressure will allow the trailer to hop about on cornering and also wear the centre of the tyre tread.

While you are at it, check that the wheels rotate freely without roughness or too much free play, and add some grease via the grease nipple on the hub.

 

[oGaryo]

I've always been told to inflate to the max pressure written on the tyre wall for trailer tyres... that's what I've done to date and had no problems.. underinflating tends to cause more blowouts and tyres coming off rims whilst drinving around corners than inflating to the max apparently

 

[Lakesailor]

Most trailers I've had have inner-tubed wheels.
I inflate them at as low a pressure as possible. It is the only real suspension the dinghy will benefit from. The little rubber block suspension units are rock hard.
I sold a Heron to someone who managed to punch two holes in the bottom where the dinghy sits on the pads.
One hole was through a brand new 6mm ply section.
If plod stops you and asks tell them your guage must be wrong or something. Don't damage your boat.
The trailer will follow the car, even with a low pressure in.

When I was rallying a lightweight Mini I used to put 12 psi in the back tyres. Otherwise it skipped all over the place.

This was the damage to the Heron. He punched a hole in one spot, so moved the boat and did it again, both sides. The bit that didn't break has a frame above it. You can see the marks from the trailer pads. This picture is of the 6mm marine ply I had just fitted a couple of months before.
He took one week to do this.

 

[oGaryo]

ah.. sorry, I was thinking more along the lines of larger boat's couple of ton jobs not a smaller dinghy trailer... no experience of those I'm afraid so will get back in me box on this one

 

[VicS]

I think LS is very right. No higher than necessary.

The problem with tyres coming off rims was largely/partly due to people putting tubeless tyres on caravan and trailer wheels intended for tubed tyres. Rims for tubeless tyres I think you will find have a recess in which the tyre bead locates while rims for tubed tyres do not ( or at least did not).

The solution was a band clamped round the rim (inside the tyre) to locate the tyre

My boat trailer has tubeless tyres but on car wheels. My dinghy trailer and camping trailer both have tubed tyres.

Reckon you have to be pretty reckless to corner hard enough to pull the tyres off the rims of a small dinghy trailer.

Note to Stemar
60mph is still the limit for trailers , 50mph on single carriageway roads

You are not allowed in the outside lane of motorways with 3 or more lanes

( I expect there are special concessions for glider trailers though )

 

[Stemar]

Note to Stemar
60mph is still the limit for trailers , 50mph on single carriageway roads

You are not allowed in the outside lane of motorways with 3 or more lanes

( I expect there are special concessions for glider trailers though )

Thanks Vic, I have some experience of towing, so am aware of the limits, including the minimum speed of 90 for trailers towed by BMWs...
(I drive a humble Focus, so will be sticking to 50 & 60 )

Thanks also to everyone else. I think I'll try 32.5 since that's what my pump's set to and see how I go. If it seems a bit bouncy, I'll let a bit out.

I wonder if Lakey's poor Heron was strapped down tightly enough - I'm shocked that a pothole could do that without some bounce to build up momentum.

 

[electrosys]

When I went to collect a Mirror 10 last summer (which came with a trailer), in the rear-view mirror I saw it leaping around all over the place. I stopped and deflated each tyre until a very slight bulge showed at the bottom. Dunno what the pressure was, but the ride from then on was a lot kinder on the hull - it's only around 100lbs after all !

I'd have thought 20lbs psi would be enough for such a light hull - if in doubt, do a similar visual check.

 

[Cymrogwyllt]

For what it's worth I had 25 psi on my trailer. Loads varied from one kayak+ extras to five sea kayaks + extras. Normal load was 18 ft sea kayak, 16 ft sea kayak, 13 ft plastic general purpose and 13 ft grp river boat. The box usually carried four sets of paddles, two wet suits+boots, three spray decks, buoyancy aid, flares etc, change of clothing, stove and basic provisions.

During experiments I found 20 psi to be 'lurchy' and 30 psi to be 'bouncy' so used the middle.

 

[Lakesailor]

I wonder if Lakey's poor Heron was strapped down tightly enough - I'm shocked that a pothole could do that without some bounce to build up momentum.

I don't know if he had it tied on well, but think SLEEPING POLICEMEN

I bought it back from him and repaired it, The repairs cost me nothing as I still had ply, epoxy and paint from the rebuild. He had no idea where to start. I don't know why he didn't but a Walker Bay or something tough.

I was quite pleased to get it back as I sold it too soon after the rebuild. I kept it a while longer and sailed it a bit more before selling it to a guy who arrived in a bih hire van to give it a nice ride to London.